Contents

1 Abstract 1

2 Mission Overview 1

3 Design Objectives 2

4 Mars Deployable Greenhouse Overview 2

5 Concept of Operations 4

6 MDG Design Methodology 10

7 Greenhouse Design 11

8 MDG Arrangement 19

9 Biology Systems 24

10 Environmental Controls 34

11 Power System 43

12 Materials Handling 48

13 Communication Systems 51

14 Thermal Analysis 54

15 Conclusion 56

A Mission Timeline 62

B Landing Sites 62

C Compilation of Assumptions 64

D Lighting Program 66

E Elastomer-Seal Trade Study 66

F Nomenclature 66

G Outreach Status Report 68

H Team Biographies 76

I Co Investigators 79

J Consulting Members 81

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1 Abstract

Food will always represent a vital and challenging pri-ority for manned space flights. Given the limitationsof payload storage and weight, long-term voyages willundoubtedly rely upon the crew’s ability to producefood onboard the spacecraft.

The relatively short duration of Mars missions en-ables crews to carry a full stock of rations. Althougha Martian greenhouse would not replace pre-packagedrations, it would augment the diet of the astronautsand greatly improve their quality of life. This clas-sifies the Mars mission as an excellent candidate foran initial extraterrestrial greenhouse.

The Franklin W. Olin College of Engineering Mars-Port Team has created a preliminary design for an au-tonomous Mars Deployable Greenhouse. This green-house supplements the diet for a crew of six astro-nauts by up to 25%, and contributes to the scientificvalue of the Mars mission. Under ideal operatingconditions it will not consume any other mission re-sources, including the valuable resource of crew time.

The Mars Deployable Greenhouse uses robots toseed crops, grow them in a hypobaric environmentusing the highly effective hydroponic Nutrient FlowTechnique, and then harvest them. Robots also pro-cess the harvested crops in the MDG and load theminto a rover for delivery to the astronauts in theirhabitat.

The solution proposed is a two-level octagonalprism. The upper level features a transparent ex-terior that allows natural light to reach the plants.This transparent exterior is exposed by the Deploy-ment of two solar arrays exposes the transparent exte-rior. The upper level houses the plant growth struc-tures, water and nutrient delivery systems, supple-mental lighting, and autonomous harvesting systems.A vertical partition subdivides the upper level to helpcontrol pathogenic outbreaks. This upper level canfacilitate MDG operations at one-half capacity.

The lower level serves as an “equipment room” thathouses power generation equipment (RadioisotopeThermoelectric Generators (RTGs) and fuel cells), aSabatier electrolyzer for water production, comput-ing and communication equipment, crop processors,and additional water and nutrient delivery equip-

ment. Environmental sensors and controls are dis-tributed between the two levels.

Additionally, a small, deployable experimental sec-tion contributes to the mission’s scientific and prac-tical objectives. This system will attempt to growcrops in Martian regolith in a near-Martian environ-ment.

The MDG is designed with the primary crops asthe priority. After a tentative crop selection wasmade, the MDG was designed to create an environ-ment ideal for these crops. Redundancy for reliabilityand safety over the 20 year lifespan of the greenhouseare present in the design.

Figure 1: Mars Deployable Greenhouse

2 Mission Overview

Most current mission outlines for human explorationof Mars use a series of launches to distribute the largepayload requirements, and designate a long crew stay(∼ 500 days), to make the transit time (130-180 dayseach way) worthwhile[68]. The Mars Design Refer-ence Mission (DRM) 3.0 is one outline for the firsthuman mission to Mars. The DRM requires severallaunches over a period of two years to establish a basefor a crew of six on the Martian surface.

The first launch will place an Earth Return Vehicle(ERV) into orbit around Mars. A Mars Ascent Ve-

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hicle (MAV) / In-Situ Resource Utilization (ISRU)propellant and life-support production plant combi-nation will then be landed on the surface. Over thecourse of eighteen months, the ISRU plant will pro-duce all the propellants required for the MAV as wellas a large supply of crew consumables, such as waterand oxygen. At the conclusion of the 18 months,the readiness of the ISRU products will be evalu-ated, and, if sufficient propellant and consumableshave been produced, the launch of the first crew willbe given the green-light.

The first crew will launch two years after first ERV,MAV, and ISRU launch. A second ISRU/MAV willbe concurrently launched to serve as the primaryhardware for the second crewed mission, as well asa back-up for the first crew.

The DRM includes elements that are essentialto the initial deployment of long-lived outposts onMars. The extent to which additional elements areincluded in early colonization activities will dependupon whether the added value compensates for anyrisk or expense that may be entailed in their deploy-ment. The Olin College MarsPort team has designeda Mars Deployable Greenhouse (MDG) that will pro-vide this value.

3 Design Objectives

The MDG’s primary objective is to supplement thediet (up to 25%) for the crew of six astronauts. Ad-ditionally, the MDG must:

• contribute to the scientific value of the missionas much as possible without adding significantadditional costs or risk

• land within ±15◦ of the equator [1]

• have a design life of 20 years [1]

• have a leakage rate of < 1% of the volume perday at normal operating pressure [1]

• light crops using incident solar radiation, withor without supplemental electric lighting [1]

• communicate its status to controllers on Earth

• maintain environmental conditions within spec-ified ranges (Table 1)

• be self-sufficient under normal operating condi-tions such that the MDG will not consume othermission element resources, including

• either recover or dispose all waste associatedwith the functioning of the MDG

Parameter ConditionTemperature 10 to 30◦CRelative Humidity 40 to 90%CO2 Partial Pressure 0.1 to 3 kPaO2 Partial Pressure > 5 kPaInert Gas Composition OptionalEthylene Gas < 50 ppb equivalent at

100 kPa total pressure

Table 1: Specified Environmental Conditions[1]

4 Mars Deployable GreenhouseOverview

The MDG houses eleven main subsystems: water andnutrient delivery, plant growth structures, harvest-ing, crop processing, environmental controls, wastemanagement, crop delivery, experimental section,computing and communication, and power. Thesesystems collectively and autonomously satisfy the de-sign objectives. The astronauts’ only MDG-relatedresponsibility under normal operating conditions isremoval (and consumption!) of the crops from thedelivery rover. Astronauts might also serve as a re-pair team if unanticipated system damage occurs.

Diet Augmentation & Crop Growth is the pri-mary function of the Greenhouse, and all subsystemseither actively participate in this MDG activity orsupport the subsystems that do. Plant growth traysare complex and designed to facilitate growth andeasy harvesting. These trays primarily use the Nu-trient Flow hydroponic Technique (NFT), except for

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MDG Subsystem Diet Aug. Sci. Light Comun- Env. Self- WasteCrop Grth Cont. Crops icate Cond. Sufficient Rec/Disp

H2O & Nutrient Delivery√

Plant Growth Structures√ √ √

Harvesters√ √ √

Crop Processors√ √

Environmental Controls√ √

Waste Management√

Crop Delivery√ √

Experimental Section√

Computing & Communication√ √

Power√ √ √ √ √ √

Table 2: Subsystems achieve Design Objectives. “Self Sufficient” indicates that the design of this subsystemeliminates reliance on another DRM resource or human interaction

small aeroponic sections designed to start plants thatreproduce from tubers.

A battery of mobile and stationary harvestingrobots seed, harvest, and remove the plants. Har-vested crops are then either processed in equipmentlocated near the MDG’s airlock or (in the case ofcrops that do not need harvesting) delivered directlyto the crop delivery rover.

The rover makes semiweekly crop deliveries and isstored in the airlock when not in use.

Scientific Contribution is primarily made by theexperimental section, which is deployed external tothe MDG by the crop delivery rover. This sectionseeks to develop plants that are better suited for anear-Martian environment through simple natural se-lection. It has a design life of five years.

Crop lighting is achieved primarily through am-bient lighting, as the upper hull of the MDG is trans-parent. Research demonstrates that the ambientMartian lighting is sufficient for crop growth in un-shaded plants. To increase growing space, severalplant growth trays will be located in shadowed ar-eas. To light these crops, and to artificially extendthe photoperiod for all crops that would benefit fromincreased daylight hours, LEDs offer supplementallighting.

Communication is handled through a transmitterlinked to an assumed communication satellite constel-lation that provides global coverage. This solutionrequires little power and will not be obscured duringnighttime hours.

Environmental controls will maintain an inter-nal hypobaric environment with a pressure of 200-210 millibars, with partial pressures of O2 at 50-60millibars and CO2 at about one millibar (equivalentto 5000ppm). Average temperature will be 22.75◦Cand average relative humidity will be held around70% (19.48 millibars H2O).

Waste Recovery / Disposal proved to be a chal-lenge. While recycling or composting dead plant mat-ter seemed to be technically elegant and more in thespirit of the mission, it was unclear what value itwould provide. After removing the waste recoveryequipment’s additional mass and volume, it was de-termined that it was actually more efficient to bringmore nutrients and dispose of waste.

Self Sufficiency substantially decreases the cost ofthe mission. While the MDG is more expensive as aresult of the level of automation included and thenumber of systems required to operate independentof other mission elements, it saves the critical cost

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of astronaut time. The crew can to focus on theirscientific mission and not on the chores associatedwith tending a greenhouse.

Planetary Protection is another important con-straint of the mission. Much of the scientific work forearly Martian missions may focus on the search forlife, past or present, on Mars. Particularly during theearliest missions, it is critical that the environmentnot be contaminated with life from Earth and thatother features of Mars not be damaged. As a result,the MDG is sealed off as much as possible from theMartian environment. All elements entering or leav-ing the system – including gasses used in the powersystems and the crop delivery rover – are sterilizedto the extent possible.

While this team acknowledges the vital short-term importance of Martian planetary protection, theteam also looks forward to a day when planetary pro-tection requirements will be lessened. It is for thisday that the experimental section has been included.Large-scale Martian farming may someday occur, andfor this to be feasible, crops grown in open systemsconsisting of materials brought from Earth and thoseon Mars will be required. The experimental sectionattempts to grow plants in Martian regolith, with anatmosphere close to that of Mars, and with only sim-ple temperature controls.

5 Concept of Operations

5.1 MDG Delivery

5.1.1 Launch

The selection of a launch vehicle for the MDG is oneof the driving forces in the design; both the volumeavailable for the payload and the maximum mass aredetermined by the fairing dimensions of the selectedlaunch vehicle. Because the design guidelines allowthe design a 30 ton vehicle, this figure was used as aguideline for launch vehicle selection. Although thegreenhouse may end up being much lighter (the de-sired outcome), a vehicle capable of lifting the maxi-mum mass was baselined.

Figure 2: Wireframe view of MDG with PlantGrowth Structures highlighted

Except for the Energia rocket, no current heavylaunch vehicle allows 30 tons to be delivered to Mars.The Energia rocket alone claims able to deliver upto 100 tons to LEO; however, this project has beenmothballed since 1993 and does not appear to be vi-able at this point. The next largest vehicles are theTitan IV and the Space Shuttle, which can carry 24tons to LEO; however this translates to only approx-imately 15 tons to Mars orbit. Based on this data,the team concluded that no existing launch vehiclemeets our requirements, so the team then looked atlaunch vehicles currently under development.

On-orbit construction / assembly was also consid-ered to minimize the size of the launch vehicle re-quired. This option was rejected because of the costand complexity it would entail, as well as the unnec-essary risk to the astronauts that orbital constructionjobs may require.

The most promising of these proposals is the Mag-num launch vehicle. Although it is not yet developedand tested, the team feels it is reasonable to assumethat it will be available at the time of the mission,given that all other Reference Mission elements de-pend on the existence of a vehicle capable of deliver-

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ing 30 tons of payload to Mars. If the heavy launcherultimately used is not the Magnum, the MDG can bedelivered in any vehicle of comparable payload sizeand mass.

As with all other Magnum launches described inthe reference mission, the MDG and “other signifi-cant payload” assumed to be included will be deliv-ered to LEO, where they will rendezvous with theNuclear Thermal Rocket (NTR) stage that has beenlaunched by another Magnum. For the purpose ofplanning and payload packaging, it was assumed thatthe “other significant payload” is also Mars-destined.

Using a common launch vehicle as all other DRMelements, there should be a savings in mission eco-nomics. Additional savings on a per kilogram ba-sis, as the Magnum will benefit from RLV and ELVtechnology advances, with an expected launch cost ofapproximately $2,200/kg [68].

5.1.2 Trans-Mars Injection

Because the MDG is not carrying any time-sensitivepayload (plant seedlings, astronauts) the time spentin transit is not a crucial variable. Instead, given thetight mass budget and cost per pound of launchedpayload, the mass of propellant needed to launch thespacecraft on a given trajectory is the critical vari-able. While theoretically, the most energy-efficienttrajectory is a Hohmann transfer, the fact that theorbital planes of Earth and Mars are inclined at 1.85◦

to each other forces the trajectory to deviate some-what from this ideal. With these criteria in mind,the team looked at the trajectories NASA has alreadydeveloped for he Reference Mission, because our in-tention is to coordinate the launch of our MDG withthe other components of the Reference Mission. Ofthe trajectories that were presented, the long-stay,minimum energy trajectory fits our criteria the best.It is the most energy-efficient of the three, being theclosest to a Hohmann transfer, and allows the MDGto arrive at Mars at the same time as the other Refer-ence Mission components, regardless of the trajectorythey follow.

As with the launch vehicle selection, here the teamagain relies on technology yet to be developed byNASA for the Reference Mission. The TMI stage

will be powered by Nuclear Thermal Rocket (NTR)engines as specified by the Reference Mission Adden-dum. The reason for this choice is that an investi-gation into current methods of propulsion has shownthat no technology available today can deliver 30 tonsinto Mars orbit. In order to accommodate the vari-ous systems the MDG requires for plant production,the payload mass must necessarily exceed the capa-bilities of current technology. We feel that it is safeto assume that NTR technology will become a viableoption, given the tests that have already been con-ducted, and especially because it is a mission criticaltechnology. As with the launch vehicle, if NTR doesnot turn out to be usable, the team will rely on themethod that the other Reference Mission componentsuse.

The NTR engines will be used for the initial burnfrom LEO, as well as subsequent course adjustmentson the way to Mars. Once the MDG enters orbitaround Mars, it will begin aerobraking, using theNTR engine to initiate the deorbit burn and helpseparate the cruise stage aeroshell before entry.

During TMI, attitude will be controlled with 3-axiscontrol. This system is the standard proven on pastMars missions, versatile and reliable.

It should be noted that the Reference Mission Ad-dendum 3.0 discusses the potential of Solar ElectricPropulsion (SEP), particularly as it would allow a“Three Magnum Mission.” If the mission architec-ture is adjusted to use SEP instead of NTR, theMDG’s TMI stage will switch to use the SEP stage aswell, in order to reduce the number of launch vehiclesrequired. This also has the benefit of launching lessfissionable material into space, which will benefit thepublic perception of the mission.

5.1.3 Entry, Decent, and Landing

The team’s approach to landing and deployment wasto combine technology proven on Mars with smallpayloads and experience gained landing large pay-loads on the moon. The goal is to use proven meth-ods in a novel application, minimizing the risk to themission and reducing development time and cost.

The first EDL stage will be an aerobraking ma-neuver around Mars, starting with a very elliptical

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orbit and using friction with the Mars atmosphere toslow the spacecraft and circularize the orbit. Thisapproach is a somewhat risky maneuver, given thatan error in the spacecraft’s velocity and/or trajectorycan send it to burn up in the atmosphere or becomelost in deep space. However, this method has beensuccessful in Mars missions in the past and it is a verygood means of slowing the spacecraft down, requir-ing no additional mass and fuel volume. Because theMDG is not carrying any time-sensitive payload (theplants are all transported as seeds), the aerobrakingprocedure can be lengthy, allowing for a more gradualprocess. This will in turn reduce the thermal stresseson the spacecraft, protecting the more fragile subsys-tems.

EDL processes will be controlled by the onboardcomputer. Radar and various accelerometers will beused to guide the MDG to its landing location andprovide input to the guidance systems. Upon com-pleting the aerobraking maneuver, the mission man-agers will evaluate Martian weather and determineif it is suitable to initiate atmospheric entry. If thelanding site is currently engulfed in a dust storm, at-mospheric entry will be delayed until more amenableconditions are present. There were several optionsreviewed for the thermal protection system duringatmospheric entry:

Radiative cooling: in this system, the spacecraftis covered with an excellent insulator. During entry,this insulator is allowed to become red-hot and thusdissipate heat to protect the spacecraft. This is thesystem employed on the Space Shuttle, and has theadvantage of allowing for a reusable entry vehicle andconsiderable mass savings over other methods. How-ever, this cooling method is only suited to lengthy,gliding descent, where the rate of surface heating isequal to the rate of heat dissipated through the insu-lating layer. The other complication with this systemis that during a lengthy descent, some heat will reachthe inside of the spacecraft, no matter how effectivethe insulator. This can be a very serious problem onMars, if no other method exists to dissipate the heat.

Heat sinking technique: this method employsa large mass of material with a high melting point toabsorb the heat of entry. While this method allowsfor a reusable entry vehicle, it requires a fairly high

amount of mass and because of this becomes whollyimpractical for missions with significant entry heatloads.

Ablative cooling: this is so far the most com-mon method of heat protection. Instead of providinga mass of material to absorb the heat of entry, thismethod uses a shield that sublimes away and thuscools the spacecraft. While this has the disadvantageof preventing entry vehicle reusability, the cooling ef-fect is significantly better than with heat sinking (onthe order of 107 J/kg) and allows for a very flexibledescent trajectory. Because of the high-energy dissi-pation, this method provides the most cooling per kgof heatshield.

Based on a review of the above cooling methods,ablative cooling is the best choice. Entry vehiclereusability is not a consideration in this case and theballistic entry trajectory precludes the use of radia-tive cooling.

Once the MDG has slowed down to 350-450m/s,the heatshield and outer shell will separate from thespacecraft and the parachutes will deploy. Basedon the successful Mars Pathfinder mission, theseparachutes will slow down the MDG to the terminalvelocity 63 m/s. Because the atmosphere on Marsis only about 1

10 of Earth’s, the size of parachutesneeded to completely slow down the MDG would beprohibitive in terms of both mass and stowed volume.Instead, the parachutes will be used in conjunctionwith retro rockets to reduce the size of each.

After considering the various types of parachutesavailable, the design chosen is a disk-gap-bandparachute. This was the type of parachute used in theViking mission. It was developed specially for high-altitude, supersonic speed, and low dynamic pressureapplications, like the very sparse Mars atmosphere,still allowing for high drag and ease of construction.The parachutes will be made of Dacron, which isstrong enough to withstand the force of descent andalso sterilization and stowage.

The overall parachute system will include the threemain parachutes, which will be extracted by threesmaller pilot parachutes, in turn ejected by a mor-tar. Two smaller parachutes will also be deployed tohelp separate the outer shell and heatshield follow-ing atmospheric entry, before the main parachutes

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are deployed. This system is intended to have sev-eral layers of redundancy to ensure reliability; therationale for the excess weight and complication ofseveral deployed parachutes is ensuring that in caseof a single parachute failure, the mission can still goforward.

Once the spacecraft reaches terminal velocity, theretro rockets will fire and the main parachutes willseparate from the spacecraft. The MDG will in-clude four Pratt & Whitney RL-10 engines, burningLOX/CH4. These engines will be used not only forthe descent stage, but also for the de-orbit burn andany course changes during TMI. The descent enginesare gimballed and throttleable to give control overthe landing and correct for off vertical entry. In ad-dition to these, small rockets will be mounted on thesides of the greenhouse to control the vertical lean.

The greenhouse will land vertically, retro enginesdown. In order to function, it must be lying on itsside, such that as much surface area is perpendicularto the sun as possible. In order to change the ori-entation, in effect to tip the greenhouse over, a safeand controlled mechanism is needed. Because of theemphasis on low mass and volume of mission compo-nents and the similarity of function, the team decidedto use the same mechanisms for both landing and tip-ping the greenhouse. Both during landing and dur-ing final positioning the MDG will encounter impactstresses, so the mechanisms for reducing the result-ing loads on the structure can also be the same. Indesigning the landing mechanisms, the team investi-gated both traditional means used on many prior mis-sions (compressible lander legs) and relatively new,but proven technologies (airbags). In the end, bothsystems were used.

Airbags have been successfully used on prior Marsmissions, so the team opted to use the same basicairbag design as was used on the Mars Pathfindermission. The airbags will be arranged along the bot-tom of the MDG, around the descent engine skirtnext to the landing legs, and also along the bottomhemisphere of the top face of the MDG. The bottom-mounted airbags will cushion the greenhouse directlyduring landing and assist in deployment, while thetop set is used to cushion the MDG as it is tippedover. Both sets of airbags are inflated using Thiokol

gas generators when the MDG is about 300m abovethe Martian surface. The deflation of each set ofairbags is controlled by the onboard processor; eachsmall airbag can be individually deflated and re-tracted to assist in moving the MDG to a horizontalposition. The airbags will be made out of an innerbladder made of Vectran fabric and four more outerlayers of Vectran to ensure wear resistance.

In addition to the airbags, compressible landinglegs will be deployed. These provide an extra mea-sure of redundancy, and allow the greenhouse to landperpendicular to the surface, preventing prematurefalling of the greenhouse. Because they can be con-trolled with more precision, they will be also usedto slowly lower the greenhouse to its lying position,again preventing it from falling. Three landing legswill be deployed from the base of the MDG, and inaddition, two legs will extend from the other face ofthe MDG, attached to the bottom hemisphere. Thelanding legs will be arranged to form an equilateraltriangle around the base when viewed from above,with a vertex of the triangle located at the apex ofthe upper greenhouse hemisphere, such that whenthe MDG is tipped over, it is supported by two legsmounted on each face.

Each leg will consist of a large round landing padat the end of a telescoping tube which has a crush-able aluminum honeycomb insert, so that upon land-ing, some of the shock is dissipated by compressingthe insert. The legs themselves will be made of alu-minum alloy, with several supporting struts aroundthe main telescoping tube. The landing legs will bedeployed by means of explosive bolts. An extendingmechanism will also be attached to the upper hemi-sphere leg, which will be used to tip the MDG intoits final position. All of the other legs will be freepivoting, but with the ability to lock them, once theMDG is fully deployed. The legs will be 1.5m longto allow the MDG to stand approximately 1m abovethe ground (the exact number depends on how deepthe landing pads bury themselves in the Martian re-golith), and the landing pads will be 0.5m in diameterto provide stability. Instead of being solid, the padswill consist of aluminum alloy ribs, which will foldout using explosive bolts as soon as the landing legsdeploy. As the MDG lands, the pads will bite into

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the regolith to help anchor the greenhouse.

5.2 Pre-Crew Arrival Operations

5.2.1 Deployment

In order to finish deployment, the greenhouse willneed to be tipped on its side. This will be accom-plished using the landing legs and the airbags; theextendable leg will extend and the airbags will de-flate on one side to help push the greenhouse over.The non-extendable landing legs will pivot freely tohelp the process. On the top of the greenhouse (theface opposite the descent engine face), another twolanding legs and several airbags will have been al-ready deployed, and these will cushion the MDG as ittips over into its final position. Once the greenhouseis horizontal, the landing legs will lock into positionand the remaining airbags will deflate. The entireprocess will be executed several hours after landing,giving the spacecraft time to cool and perform sys-tems checks.

All systems will be checked to ensure that theyarrived on Mars in working order between the con-clusion of the deployment phase and the launch of thefirst crew. With this strategy, it may be possible forastronauts to bring a replacement if a piece of equip-ment has been damaged, as their payload capacitypermits.

The MDG will then activate its Sabatier Elec-trolyzer to begin in-situ production of water for thefuel cells and crops.

5.2.2 Startup

The MDG startup process will begin 130 days be-fore the astronauts arrive (A-130). At this point, theairlock will be cycled once to verify its functionality.Following the test of the airlock, atmospheric controls(temperature, pressure, humidity, and composition)will be activated to gradually achieve the target en-vironment for the greenhouse. 128 days before thearrival of the astronauts, the LEDs and their sensorswill be be checked and cycled.

The biology water and nutrient delivery systemswill be activated on A-125. This includes pumps, nu-

trient control, and filtration/purification. The mov-ing systems of the plant trays will also be activatedand tested. The MDG will then be ready for plant-ing, as scheduled by the average time-until-harvest ofeach plant.

On A-120 days before the astronauts are scheduledto arrive, the MDG will automatically plant the firstpotatoes, which have an expected time until harvestof 132 days. Other plantings continue on the scheduleshown in Table 3, with their first harvests scheduledtwelve days after the scheduled arrival of the astro-nauts.

Day CropA-120 PotatoA-108 StrawberryA-107 Sweet PotatoA-100 PeanutsA-85 SoybeansA-68 RiceA-67 WheatA-33 TomatoA-12 Lettuce

Table 3: Initial Crop Planting Schedule

During the time between planting and harvesting,the MDG will continue to maintain a proper environ-ment and monitor the growth of the plants. Shouldany plants mature faster than expected, they will beharvested, processed, and stored until the astronautsarrive. Tomatoes and lettuce are an exception andwould have to be discarded if premature, as they donot store well.

5.3 Post-Crew Arrival Operations

The MDG is designed to be as autonomous as possi-ble, as astronaut time is dedicated to exploration,sample collection, and analysis[16] and the MDGshould not interfere with their scientific objectives.Under ideal conditions, the MDG design is com-pletely self-sufficient, requiring no crew interaction,save to eat the food that the greenhouse produces anddelivers . Even under non-ideal conditions, however,

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the need for human intervention has been minimized.

5.3.1 Daily Operations

Daily operations include harvesting crops that aremature, removal of non-producing plants, reseeding,and crop delivery as necessary. This will be accom-plished autonomously.

5.3.2 Harvesting

Harvesting will be accomplished autonomously by avariety of harvesters, some of which are built into thegrowth tray while others are mobile. CCD cameraswill monitor the growth trays, and the computingsystems will select plants for harvesting at the ap-propriate time.

Harvested plants will be transported to a sectionnear the airlock for processing, storage, and delivery.Delivery will be accomplished by a rover that willmake a trip to the habitat on command from theastronauts (if they are running low on fresh produce)or when it is fully loaded. It is anticipated that thesetrips will occur roughly twice a week.

5.3.3 Replanting

Of the crops in the MDG, potatoes and sweet pota-toes can be cloned from tubers, tomatoes can becloned using cuttings, and strawberries use vegeta-tive propagation. By aeroponically growing tomatoesfrom cuttings instead of seeds, the germination time,normally longer than most of the other greenhousecrops’, is eliminated. Though cloning is a convenientmethod of reproduction for both types of potatoesand quick method for starting tomatoes, there areadvantages to occasionally starting plants from seed.Clones are generally not desirable in that a diseasewould more easily be able to wipe out the entirecrop[57]. Since the interior of our greenhouse willhave been sterilized, disease is a smaller factor thanit would be in a terrestrial garden.

More than enough seeds for the first three yearscan easily be brought in the MDG. Lettuce seeds areabout 881 seeds per gram and have a typical life offive years in storage. Only about 80-90% of all seeds

actually germinate, and that number decreases withtime. If the MDG is dormant for two years, the seedswill retain virtually the same germination rate. Tomaximize storage life, seeds will be stored in airtight,light-proof containers at temperatures between 2◦Cand 10◦C[43].

5.3.4 Maintenance

The MDG is designed to operate with minimal main-tenance requirements and no scheduled human main-tenance. Waste processing is completely automated,from collection of dead plants by the harvester robotto storage.

Dust-removal, a concern in the Martian environ-ment, is accomplished with electrostatic repulsion.Dust should never build up on the surface of thegreenhouse.

In the event that human access is required, it ispossible to use the airlock and two accessways in theupper level. The lower level is accessible by lift-outflooring. Astronauts will need to wear their EVA forany unexpected maintenance.

5.3.5 Shutdown

The shutdown procedure is timed such that astro-nauts will receive their last food delivery four to sixdays before they leave the Martian surface.

The first step in the shutdown procedure is to stopplanting. The time for this varies for each plant, andwill be date of departure minus one week, minus thegrowth period of the plant in question.

Crops will then be harvested as usual until the con-clusion of the final crop. However, because the seedswill eventually become “stale,” a small percentage ofthe last harvest will be collected for subsequent re-starting of the MDG. Any plants still alive six daysbefore astronaut departure will be removed by theharvester and destroyed as waste.

Once the last plants have been terminated, all sup-plemental LED lighting will be turned off. Concur-rently, the final food processing cycle will occur, andonce complete, the final crops will be delivered to theMDG not less than four days prior to MAV liftoff.

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At this point, the biology portion of the water sys-tem will be shutdown as well as the nutrient deliverysystem (though the system will have already stoppedadding nutrients to the solution two days before thelast harvest).

The atmosphere control system will then be re-duced to the minimum levels needed to keep theMDG structures in good condition. Atmosphericcomposition will no longer be regulated, but temper-ature, humidity, and pressure will still be controlled.

Some fuel cells will also be turned off to conservefuel. RTGs cannot be turned off and will be used toprovide the primary power necessary for systems thatremain powered during hibernation.

5.3.6 Hibernation

While in hibernation, the only systems running willbe the experimental section, communication at re-duced capacity (beacon-monitoring using four signalsto communicate the state of the greenhouse), dataprocessing at reduced capacity, temperature control,and the condenser.

Leaving the condenser on to reclaim water duringhibernation will keep the inside of the MDG as dryas possible. Excessive humidity can lead to corrosionof materials, degradation of electronics, and growthof harmful organisms.

Pressure is controlled minimally to limit outgassingfrom materials. Aside from this limiting factor, re-duced pressure on the inside is beneficial, as it reducesstructural stress and leakage. The pressure will lessenslightly on its own due to leakage, anyway. While it ispossible to actively reduce internal pressure as part ofthe shutdown procedure, separating and storing thegases would use more power and equipment, which isnot worth the few benefits.

6 MDG Design Methodology

A philosophy that emphasized the simplest solutionpossible was utilized in designing the MDG. When-ever possible, all MDG-critical systems are redun-dant, and if not possible, designed to fail gracefully(with adequate safety margins). However, in order

to push the cutting edge, it was decided that not allrisks could be eliminated. This decision is valid as itallows for a more capable greenhouse and does notendanger the astronauts, as the MDG is not criticalto the overall mission.

Mission economics were regarded as important,though they were not treated as a bottom line, butinstead as a tradeoff. The question “is this extramass/cost/volume important to the success of themission and/or does it add something of value?” wasfrequently asked. The team believes that this methodencourages the design of a greenhouse that is bothmore functional and less costly than might otherwisebe achieved. One such example is in the automa-tion of the greenhouse. While automated harvest-ing, planting, and crop processing, and the associatedpower supplies do add to the mission cost, this costis less than what it would cost in astronaut time ifgreenhouse operations were added to their duties.

Reviews of major subsystems or subsystem groups(example: environmental control - biology) were con-ducted frequently to ensure sufficient communication,though the the team found that the complexity of theproblem made higher amounts of communication nec-essary. Additional reviews within entire design teamwere conducted approximately every month. Theteam has learned that more frequent, brief reviews,on the order of once every two weeks would have beenmore appropriate and this method was used in theperiod between the PDR and DDR.

Near the conclusion of the preliminary design pro-cess, two other review teams were brought in. Thefirst was a Blue Team which included members ofthe Outreach team and the project’s co-investigators.The Blue Team’s review was primarily to ensure thatthe design was properly described so that those un-familiar with the project could understand it.

The second review team, the Red Team, waschaired by Dr. Daniel Frey. It also includes Dr. PeteYoung of MIT and Dr. Jeff Hoffman, a former as-tronaut. This team was charged with reviewing thePDR and the subsequent DDR, with a slant towardsbeing as critical is necessary.

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6.1 Functions of the MDG

The MDG’s primary function is to provide diet aug-mentation, up to 25% for a crew of six astronautsduring their stay on Mars. The crew will, however,bring enough food to ensure their survival should theMDG fail, and therefore it is not seen as mission crit-ical but instead as an additional, beneficial missionelement.

Additional functions required to accomplish theprimary function include crop planting, crop harvest-ing, crop delivery, waste management, environmentalcontrol, and power generation. After reviewing thegreenhouse elements, the Olin team also decided toadd the functions of scientific research to the MDG’scapabilities.

6.2 Method of Design

Any system designed to support life requires solv-ing many problems, often in parallel. To reducethe complexity of this highly parallel design chal-lenge, the team chose to first select the planned cropsand the estimated quantity required to achieve thecaloric requirements. After the crops were known, theteam developed the simplest greenhouse that wouldboth support them and achieve the team’s other de-sign goals. This ensured that the greenhouse wouldachieve its design objectives with a solution thatwould not include costly and unnecessary features.The method of design is outlined in Figure 3.

7 Greenhouse Design

During preparation of the Conceptual Design Report,the team drew heavily upon the model outlined byJenkins, Khanna, and Roylance in Linking Designwith Structural Mechanics and Materials, a materialsselection guide in which structure was driven moreby availability of materials than in other models. Inthe design’s continuation for this second phase, theselection of a reliable “tin can” model has allowedstructural decisions to be made more independentlyof materials selection than was previously possible.

The structure of the greenhouse is the overall sup-port system for the different subsystems of the green-

house, affording protection from shocks and stresses,the environments of Mars and space, and providingmounts for each component. In addition, the struc-ture must provide for redundancy and protection incase of a system failure or crop disease. The struc-ture determines the configuration of the various com-ponents both inside and outside the greenhouse. Be-cause of this, the structure is both dependent uponand determines the placement and maximum size,shape, and mass of each individual component.

7.1 Structure Criteria

Launch Vehicle Volume: The first criterion ofthe structure is the volume enclosed within it; weplan to fully utilize all the payload volume we areafforded by the launch vehicle. Therefore, the outsideshell has to be as large and thin as possible, takingaway the least space from the crop growing areas andsupport systems.

Location of Center of Mass: In addition to thevolume specification, the MDG structure and layoutmust also satisfy the center of mass constraint of thelaunch vehicle. The MDG must be arranged to havethe center of mass as close to the center of the space-craft as possible. This is given by the need to reducethe moment on the payload adapter and fairing dur-ing launch, and for attitude control during TMI.

Structural Loads and Stresses:

• Pre-launch Activities: Though the MDG will bedesigned to function for the majority of its lifes-pan in a Martian environment of low gravity andpressure, the design need also take into accountthe duration of its stay upon earth. Examples ofnon-service “function” include its handling, pro-tracted subjection to terrestrial gravity and pres-sure during construction, and pre-launch treat-ments such as baking/thermal sterilization, inaddition, incidental jerking and other stressesduring pre-launch operations need also be as-sumed.

• Launch: During launch, the MDG will be ex-posed to high levels of structural vibration and

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Figure 3: MDG Design Methodology

12

shock from the firing and cutoff of the main en-gines. Especially during the first few seconds oflaunch, the MDG must also contend with audi-tory vibration due to the reflection of the rocketengine noise off the launch platform.

• Interplanetary Transit: During transport toMars, stiffness is required to aid in maintainingthe attitude and control of the spacecraft. Thereduced need for corrective maneuvers will im-prove both fuel economy and the simplicity ofnavigation. All loads during this phase will bedue to acceleration, and should be negligible inrelation to those experienced during liftoff anddescent.

Thermal stresses must also be taken into consid-eration. One side of the MDG will always facethe sun, and will thus become much hotter thanthe side facing deep space, straining and distort-ing the outer structure.

• Planetary Deployment Operations: Upon plane-tary landing, the performance characteristics de-manded of the MDG undergo a dramatic shift.Assuming that the payload is delivered intactand without significant structural damage, thechief design parameter is reliable performance.Key factors contributing to reliability that areinfluenced by materials selection include effec-tive management of thermal, optical, mechani-cal, and all other types of materials performancedegradation. Damage due to UV radiation andcorrosion should be considered at all points inmaterials selection. A moderate degree of di-mensional stability on interior structures is alsorequisite for effective automation of harvestingand other tasks.

General Design Conditions and Parameters:To accommodate and balance the requirements forvarious phases of the mission, a dichotomous ap-proach to the design of the structure was chosen.The outer shell and the interior panel componentsserve to improve the stiffness of the MDG and main-tain pressure differentials. A heavier frame skeletonwill serve to absorb and distribute both static and

dynamic loads from lift off, EDL, and mounting ofequipment.

Due to the thin atmosphere in the Martian environ-ment and almost complete lack of atmospheric shield-ing, the levels of UV radiation to which the MDGwill be exposed are higher than those on earth. Theexterior structure must therefore be designed for ser-vice at these levels, and adequate shielding will beincorporated into the transparent panes of the upperhemisphere to shield the materials and plants of theinterior.

Resulting from the 20-year requisite service life ofthe greenhouse, it is necessary that all materials cho-sen for close tolerance applications have relatively lowrates of creep. For this reason certain classes of mate-rials, such as thermoplastics, may be less well suitedfor more dimensionally exacting applications.

Though only the exterior shell will be subjectedto the hard vacuum conditions of space, the interiorcomponents of the greenhouse will also be subject toaccelerated out-gassing due to the hypobaric atmo-sphere maintained in the interior of the MDG.

As in all space missions, mass is to be minimizedwhen and wherever possible. For this mission, theestimated costs of $2200 per kilogram for lifting apayload into orbit using the Magnum launch vehi-cle is more than doubled by the additional need forfuel in Martian landing and the cost of having putthis fuel into orbit initially. This mandates the useof lightweight, high strength alloys, polymers, andcomposites whenever feasible.

Incorporating a ±10◦C margin of error in peak,unsustained temperature, and a ±20◦C margin forsustained service temperatures, a temperature rangefrom -100◦C to 100◦C is anticipated for the exteriorstructure. For the interior of the MDG, the fluctu-ations will be less extreme-particularly in the lowerrange, where temperatures will not be allowed to fallmuch below 0◦C, and a greater degree of freedom isallowed in materials selection. This broad tempera-ture range requires effective management of stressesassociated with thermal expansion and contraction.

Facilitation of MDG Functions: To accommo-date and balance the requirements for various phases

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of the mission, a dichotomous approach to the designof the structure was chosen. The outer shell servesto contain and maintain the internal pressure duringall phases of the mission and to create a torque boxto assist in the resistance of torsional forces. Dur-ing transport, all stresses and shocks associated withlaunch, landing, and general movement of the green-house are to be absorbed and distributed primarilyby a skeleton that will also serve as the load bear-ing members in the deployed greenhouse; supportinglighting, shelving, the MDG hull and translucent pan-els, and as contact points for ground supports. Thisskeleton will also provide axial rigidity to the green-house.

Because hydroponics will be used, the structuremust allow for easy mounting of and access to wa-ter/nutrient solution pipes, lighting systems, andsome means to allow harvesting robots to movearound the greenhouse. To ensure redundancy, theinterior design must allow the greenhouse to be eas-ily separated into isolated sections, so that a growingarea where the plants have become diseased can besealed away to prevent the spread of the disease. Thegreenhouse must be as airtight as possible, in orderto minimize leakage to the Martian environment, butalso provide for some way by which the harvestedproduce can exit the greenhouse and reach the astro-nauts on Mars.

7.2 MDG Geometry

Several options for the MDG’s geometry were dis-cussed in the CDR. At that time, the team had ten-tatively selected a hybrid rigid/inflatable structurefor the additional volume it offered. However, afterthe crop research was completed, it was found thatthe design objectives could be met within the dimen-sion constraints of a rigid, “tin-can” structure. Afterthis discovery, the team chose to reconsider the MDGstructure, and ultimately settled on the simpler “tin-can” structure. A re-cap of the options presentedin the CDR and the factors that led to this decisionfollow.

At first, the team investigated the possibility of aninflatable greenhouse, this design would offer greatmass and volume reductions, allowing us to use a

smaller launch vehicle or grow more crops. However,this design proved to be impractical, due to the dif-ficulty in designing a material that would fulfill allthe functions we require: flexibility, UV protection,transparency, etc. A multi-layered material was alsoconsidered, but again, a suitable material could notbe found. In addition to material concerns, an in-flatable greenhouse also makes mounting the growthstructures and other systems very difficult.

A hybrid rigid-inflatable was then considered. Intheory, this combination of the two extremes wouldmitigate the shortcomings of each while taking atleast partial advantage of the strengths of both, theprimary advantage being increased volume availablefor plant growth and systems with a minimal com-mitment of available volume and weight in the mis-sion payload. The union of this design with a rigidunit would alleviate many of the issues related to in-frastructure and mounting of equipment created bypursuing a strictly inflatable platform for develop-ment. Thus, the stability and robustness required formore delicate and essential systems would, in theory,be achieved without wholly forgoing the potential of-fered by an inflatable. A more detailed study, how-ever, revealed that the hybrid concept did more tounite the disadvantages of rigid and inflatable struc-tures than it did to unite the advantages.

Wishing to retain the expanding feature of theinflatable section, with its associated payload vol-ume savings, the team next considered an extend-able greenhouse, where one section of the greenhousewould telescope out to provide extra growing spacefor the plants. This design, however, was abandonedbecause the costs did not outweigh the benefits. Anextendable greenhouse would have significant addi-tional mass, in requiring two exterior, rigid structuresand the telescoping mechanism. By improving thevolume estimates, the team found that there wouldbe no significant advantage to telescoping the green-house, because the stowed volume of the plant grow-ing structures is essentially the same as the deployed.Furthermore, the complexity involved in extendingthe various nutrient delivery pipes, lights, and otherplant growth structures greatly reduces the reliabilityof the greenhouse.

The final design is a rigid “tin can” model. The

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greatest factor in selecting this model was that thereis simply no need for an expandable greenhouse. Thepotential mass reduction and additional, unnecessaryvolume offered do not outweigh the risks and difficul-ties associated with the other geometries. Specificdifficulties with the other models include: fabrica-tion, testing, deployment, growth structures, leakage,durability in the Martian environment, and prece-dent. While the team agrees with that inflatableand expandable structures should be tested in space,a manned-mission is not a suitable venue for theirfirst use. The “tin can” is a mature, proven de-sign that has been used in decades of manned spaceflight. Perhaps the greatest advantage of the rigidplatform design for the MDG is the inherent robust-ness of the module. The rigid platform derives itsgreatest strengths from a far more perfect isolationof the MDG’s interior from the Martian environment.The lack of interaction with external elements allowsa greater degree of internal control and reliability.Leakage, UV shielding, and infrastructure supportissues associated with the other models are all buteliminated in the rigid module.

The selected concept can be described as a “tincan” with a nose cone covering the parachute sys-tem, and the retro rockets, fuel, airbags, and landinglegs located on the bottom. The remainder of the vol-ume will be the actual greenhouse, including powersupply systems, water generation, and crop growingareas. Before entry, the MDG will have an outer shell,which will release as the parachutes are deployed, sothe final landed structure will have a single thick-ness wall. The top section of the MDG wall will bemade of transparent polycarbonate to allow light toilluminate the plants below, with hinged panels ofPVC’s covering it during flight. Inside, the green-house is divided into two hemispheres by a floor. Thetop hemisphere contains the plants and their associ-ated growth structures, while the lower hemispherecontains the power, water and gas maintenance, andcontrol systems. To ensure redundancy, the green-house is also divided into a right and left half, eachof which will be sealed off in case of an outbreak ofplant disease. The MDG is domed at the rear end forstrength greater strength in launch and landing.

7.3 Launch

As has been mentioned above, the launch phase,while relatively short, puts a great deal of stress onthe payload. The first step towards protecting theMDG is to use the fairing and the rocket itself toconcentrate the stresses, and then attach the MDGin such a way as to isolate it from the fairing. Thiswill be done by means of kinematic mounts. Theseattachments resist the movement of the payload inall six directions, while isolating it from the vibra-tion due to the rocket. The MDG also has a resonantfrequency different from the resonant frequency of thelaunch vehicle, again reducing the loads. The mate-rials for the MDG structure are also chosen such thatonly a very minimal amount of galling can occur, andthe structure itself is not over-constrained.

7.4 TMI

During TMI, the most significant loads on the struc-ture will come from thermal stress due to the differ-ences in surface temperature of the sunny and darksides of the spacecraft. This problem will be allevi-ated by spinning the spacecraft, to expose both sidesto sunlight. This will be further assisted by paintcoatings to reflect sunlight, and by careful choice ofmaterials to avoid high coefficients of thermal expan-sion.

7.5 Landing

To counteract the thermal loads imposed by entry,the greenhouse will be protected by the heatshield, aswell as a second outer shell, which will be ejected onceparachutes deploy. The components inside the green-house are mounted similarly to the way the MDG ismounted inside the launch vehicle. This is again toisolate them from vibration, especially in the caseof precision equipment. The shock of landing willbe absorbed by the landing legs and airbags, whichwill also cushion the MDG during deployment. Inthis way, the stresses are again minimized. In ad-dition to these measures, the interior compartmentsare reinforced to further strengthen the structure andthe materials are chosen to increase the strength and

15

stiffness of the structure.

7.6 Solar Panels

The solar panels that will be used to protect the up-per hemisphere of the MDG during transit to Marsand landing will be deployed to expose both solarpanels and the upper hemisphere of the MDG to thesun after the greenhouse has cooled sufficiently torelieve residual thermal stresses from landing. Oneof the central questions to be addressed in the de-ployment of these panels is the decision to allow forthe panels to be closed again as a protective measure.Therefore, an analysis of the costs and benefits of sev-eral operational scenarios was performed. The firstoption considered was permanent deployment usinghighly reliable pyrotechnic actuators.

The primary advantage of this one time deploy-ment is its high reliability. However, it leaves the up-per half of the greenhouse exposed and provides lessthermal insulation to the greenhouse, though thermalanalysis suggests that the use of RTGs will renderthis a non-issue. The primary concern therefore, isincreased exposure of the greenhouse to the abrasiveeffects of the Martian atmosphere and high levels ofradiation.

Deployment only during active growing phases wasalso evaluated. Under this method, the solar panelswould be deployed by redundant, single-use actuators(electric motors, hydraulics, or pneumatics) approx-imately 130 days before each crew is scheduled toarrive and closed with their departure. Closed solarpanels during hibernation prevent unnecessary wearand protracted environmental exposure and offersgreater thermal insulation during hibernation. How-ever, it also requires larger space, mass, and powerinvestments, a loss of solar power during hiberna-tion, and a lower degree of reliability than one-timedeployment.

The third option studied was daily opening andnightly closing of the solar panels during MDG oper-ation. This would be accomplished with pneumatics,electric motors, or hydraulics and is the least reliableoption considered. It does aid in night/day thermalcycling and prevents unnecessary wear and thermalloss during hibernation. Its high complexity and risk

requires substantial and robust deployment mecha-nisms, and more power.

Upon the basis of this study, it was decided to in-corporate into the design the ability to close the pan-els between periods of production. This will allowincreased thermal efficiency and reduce wear and en-vironmental exposure of components. UnnecessaryUV degradation and abrasion will thus be avoidedduring hibernation. This will also forgo the powerproduction of the solar panels, increase the mass ofthe deployment actuators, and compromise reliabilityslightly.

After analysis, it was decided that thermal buffer-ing of the night and day cycle through the use ofthe third option was inadvisable. The first option,implemented in tandem with auxiliary thermal con-trol measures will therefore be utilized as the secondoffers little mass savings over the third option.

Explosive bolts will be used to secure the panelstogether during transit to Mars. After landing andprovision of a sufficient cool-down time for the MDG,the bolts will fire, allowing the two halves to separate.Pyrotechnic actuators will then fire to deploy the so-lar panels. The panels shall remain deployed for thelife of the mission.

7.7 Transparent Upper Hemisphere

No single material met or fulfilled the many specifica-tions and requirements demanded of this portion ofthe structure. Therefore, a layering technique simi-lar to those employed in the design of the walls of theTransHab module was used. As with all space appli-cations, the use of multiple panes for redundancy andstrength was assumed. For the upper hemisphere, thefollowing functions were identified as critical to thesuccess of the mission:

Hardness/Abrasion Resistance and Durabil-ity: Hard coating is necessary due to abrasion fromdust storms and micrometeorites that could degradeoptical quality of polymer windows-particularly inlight of the “always open” model chosen for the PVCpanels. Ribbon grown sapphire, Zirconia, and Alu-mina were identified as candidate materials for thisapplication.

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UV Absorption/Filtration: Protection must besufficient to protect the interior and reduce usage con-straints upon interior materials. This function maybe fulfilled incidentally as a secondary effect of an-other material selection. Particularly, filtration ofwavelengths below 300nm is sought to avoid unfa-vorable genetic mutations in the plant/seed stock ofthe MDG.

Dust Removal: The deposition of atmosphericdust on Mars and the dust storms that periodi-cally occur on the planet result in a .3% per dayloss in solar array performance due to dust obscu-ration. This problem will affect both the solar ar-rays used in the MDG, and the solar flux throughthe transparent upper hemisphere. Previous studieshave been performed at John Glenn Research Centerupon the effectiveness of wind-cleaning and verticalorientation of solar panels in preventing dust accu-mulation. Wind cleaning has previously been demon-strated to be ineffective in experiments, while the ge-ometry of the proposed MDG design prohibits depen-dence upon vertical orientation. Electrostatic dustremoval techniques, which were to be tested on thecancelled 2001 Mars Surveyor Lander [102], shouldbe suitable for use on both the solar arrays and up-per hemisphere of the MDG. The incorporation of aconductive outer layer near the surface of the green-house will enable the use of electrostatic dust repul-sion techniques, simplify maintenance, and minimizedamage to the surface from cleaning via mechanicalmethods. Indium-Tin-Oxide (ITO) has been chosenfor this application upon the basis of its extensive pre-vious use in the space program in such applicationsas dissipation of static electricity in thermal blankets.Thinly layered noble metals sandwiched between di-electric layers were also considered as an alternative,but disqualified upon the basis of reduced light trans-mission.

Structure and Strength: This layer will serve asthe substrate for other layers and bear the majority ofthe load from the pressure differential. The identifi-cation of a suitable, light-weight transparent materialfor structural use in the MDG and other “window”

applications in a Martian environment has yet to beaccomplished though. The importance of this designchallenge and its universal applicability to all futureefforts toward Martian settlement merit funding ofresearch and development of a material or compos-ite material suited to this application. Therefore itis recommended that some portion of DRM fund-ing be utilized to support related research. Shouldsuch research prove unproductive, the following op-tions were also considered: conventional glass, fusedsilica glass, and polymeric materials such as polycar-bonate (PC), or acrylics. The low temperatures ofthe service environment and the UV blocking effectof glasses suggest their use for the exterior pane, asdo the thermal shock resistance of both 96% silicaand fused silica glasses. Mass considerations and thereduced thermal considerations also suggest the useof polycarbonate for the interior pane.

Leakage Control: The overall design must becompatible with the less than 1% per day atmo-spheric leakage guidelines stipulated by the mission.Achievement of this goal will be dependent chieflyupon the composition and quality of the seals aroundthe windows. The desired minimization of loading ofwindows however, dictates the use of flexible, imper-fect seals.

The low surface temperature of Mars complicatesthe use of elastomers, a traditional material for suchsituations. Methyl phenyl silicone – a radiation resis-tant elastomer whose low temperature performanceextends as low as −93◦C – will be used for the outergasket, where the impact of its poor tear resistanceand high moisture permeability [103] will be mini-mized. For the inner, higher temperature and mois-ture seals, fluorosilicone rubber was selected in thetrade study due to its excellent gas and moisture per-meability characteristics, low temperature properties,and moderate radiation resistance.

Due to the general brittle nature of candidate ma-terials at service temperatures, and the vulnerabilityof layered materials in shear, the translucent panelswill bear minimal loads within the greenhouse. Thepanels will be secured using flexible rubber gasketsaffixed to the “ribs” of the MDG skeleton. Small

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compression pumps whose only function is the recla-mation of leaked gasses will be incorporated into thegap between the first and second pane.

7.8 Exterior Hull

The hull/skin of the MDG will consist of two whollyindependent walls, the space between which will becompartmented by the skeleton to isolate hull in-tegrity failure and leakage. Each wall will thereforebe required to independently fulfill the mechanicalneeds of the overall structure.

This portion of the MDG’s construction is derivedfrom the design of a basic pressure vessel. Upon thebasis of this model and the available payload, thetheoretical optimal design for dispersion of hoop andaxial pressure is cylindrical with semi spherical endcaps. The low pressures involved and the need formaximal utilization of available volume has led theteam to discard this model, while compensating foradditional stress with reinforcement at problematicangular joins.

It is assumed that any material capable of provid-ing the required stiffness will also be capable of sup-plying the necessary strength to contain the minorpressure differential needed. A composite honeycombcore material will be used for this application due tothe high elastic modulus to density ratio achieved bythis class of materials. Polycyanate resin core will beused for the majority of the structure, however, alu-minum honeycomb core will be utilized on the twolowermost sections of the octagonal structure to ef-fect greater heat transfer away from the RTG unitsstowed immediately inside the hull.

7.9 Skeleton

The length of the octagonal prism portion of thegreenhouse will be divided into four equally spacedspans of approximately 3 meters in length by four oc-tagonal ribs positioned between the two hulls of themodule. A fifth, smaller ring will cap the beveled endof the structure. These will be used for the mount-ing of shelving and equipment, and will bear bothnatural and manufactured hoop loads, in addition toproviding non-axial rigidity.

The axial component of the skeleton is dictatedwholly by the needs to seal off various sections of thegreenhouse, and for structural symmetry and evendistribution of loads. In cross-section, necessary lo-cations for such ribs were identified at 0, 90, 180,225-240, and 300-315 degrees. Therefore, an octag-onal skeleton was chosen with eight axial membersat each of the vertices, and in the center of the fig-ure. The figure was then strengthened in side loadingby two perpendicular support braces oriented to thevertical and horizontal within the octagonal ribs.

While not intended for structural purposes, butinstead for isolation and redundancy of various vol-umes, the composite core sheeting sealing sections offalong the 0, 90, 180, 225, and 315 degree radials willalso augment and stiffen the overall structure.

As one of the larger elements in the mass bud-get, the structure is one in which reductions frommarginally increased efficiencies represent potentiallysignificant savings. Asymmetric structural construc-tion techniques are one such opportunity for dras-tic reductions in weight. As the loading during cer-tain phases of the mission - specifically that of land-ing and entry - is experienced primarily from theaft (thruster) end of the module, it is here thatskeletal strength is of greatest import. At the morelightly loaded fore end, significant reductions in theweight and strength of the skeleton may be accommo-dated without reducing the performance of the MDG.Therefore, diagonal supporting braces and other aug-mentations of the basic symmetrical skeleton will beused at the aft end, while not at the fore.

Material Choice Given the high-strength and lowmass design objectives for the skeleton, early materi-als selection efforts focused primarily upon compositematerials based upon fiber reinforced polymer andresin matrices with high strength and low density.Graphite-epoxy and other similar composites provedunsuitable due to their poor performance and rapidmechanical degradation after sustaining “barely vis-ible impact damage” and in shear. Their water ab-sorption and accompanying degradation of mechani-cal properties in the event of interior hull failure alsocontributed to their disqualification for this applica-

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tion [104].

Traditional aerospace alloys of aluminum and tita-nium were considered subsequently for their past suc-cessful use in aerospace applications and widespreadavailability. Aluminum generally offers a lower man-ufacturing cost index, a higher elastic modulus for itsdensity, and better wear characteristics. Titanium of-fers greater yield strength by density, greater impactstrength, reduced thermal conductivity, and greatercorrosion resistance.

To achieve the strength and impact toughness re-quirements necessitated by this application, the ma-terials selection process focused upon identificationof specific alloys and series of alloys possessing amajority of the desired characteristics. As neitheraluminum nor titanium are particularly noted fortheir low temperature and impact applications, it wasdeemed advisable to focus particularly upon annealedalloys not fully hardened. For aluminum alloys, the2000 and 7000 series were both identified as strongcandidates upon the basis of their engineering for andextensive use in aerospace applications.

Alcoa’s recommendations were heeded in consider-ation of Alloys 2024 and 7075 for their use in “highlystressed structural parts” [100]. Among Titaniumalloys, Ti-5Al-2.5Sn ELI Annealed, a high purity an-nealed alpha alloy was particularly noted for retain-ing “ductility and toughness at cryogenic tempera-tures... 5Al-2.5Sn-ELI has been used extensively insuch applications” [105].

A materials selection trade study was then per-formed upon the identified alloys. The trade studysuggested the selection of either Aluminum alloy 2048or Ti-5Al-2.5Sn ELI Annealed, both of which offeredsimilar modulus of elasticity and yield strength todensity ratios. Aluminum 2048 was further recom-mended by its ease of fabrication and low cost. Bet-ter corrosion resistance, lower volume, and substan-tially higher impact strength favored the use of Ti-5Al-2.5Sn. Ultimately, it was the improved impactstrength and known successful use in cryogenic con-ditions that resulted in the selection of Ti-5Al-2.5Snfor the skeleton of the greenhouse.

7.10 Interior Structural Materials

In the design of the MDG interior, countless materialselection decisions need be made in each and everysubsystem. Many of these, however, have alreadybeen made in the design of off-the-shelf technologiesthat have been identified for use, or have been inher-ent to the needs of other missions, and have alreadybeen addressed in the past. Certain other decisionsrelating to the support structure and infrastructuremust, however, be made independently. Major, sys-tem independent decisions are outlined here, whilesystem-specific decisions will be covered in the ap-propriate section.

8 MDG Arrangement

The MDG will be primarily divided into two majorsections: a plant growth section in the top half of theoctagonal prism and an equipment/machinery sec-tion in the bottom half of the octagonal prism.

8.1 Upper Level

Figure 4: MDG Upper Level

8.1.1 Greenhouse Access

The plant growth area in the MDG will be accessibleby two accessways 0.75 meters wide by 2 meters tallthat will run from the airlock in the forward end al-most the entire distance to the rear end. The floor ofthe accessways will have hatches in it that will allowaccess into the lower service section. There will beno crew access into the central sodium borohydratestorage area.

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Density Strength Stiffness Impact CTE Thermal CorrosionStrength Cond. Resistance

Alloy g/cc MPa/g/cc GPa/g/cc J µ/m−◦C W/m-KTi-5Al-2.5Sn ELI 4.48 160.7 24.6 44 9.4 7.8 highAluminum 7075-O 2.81 33.8 25.6 23.6 173 medium (C)Aluminum 2048 2.75 150.9 25.5 10.3 23.5 159 lowAluminum 2024-O 2.78 27.0 26.0 23.2 193 low (D)Aluminum 2219-O 2.84 24.6 25.4 22.3 170 low

Table 4: Skeletal Material Options. “Strength” is effective tensile yield strength, “Stiffness”’ is the effectivemodulus of elasticity, and “Impact Strength” is Charpy impact strength

. [100],

In order to preserve structural integrity and to sim-plify design, there shall be only one external accessairlock. The airlock will be located in the center ofthe forward end of the greenhouse above the equatorand will measure 1m square at the base and be 2mtall. Another meter of depth has been allotted forthe rover docking station and harvesters.

The airlock will be used in case crew access is re-quired for repair purposes. The airlock will also bethe area in which the produce delivery rover will dockto the greenhouse and the space in which the exper-imental greenhouse will be stowed on the voyage toMars. Because the base of the door will be 3-5mabove the ground (depending on the terrain of thelanding site) the airlock will be accessible to crew andthe rover by a telescoping ramp that will be spring-loaded to extend to its full length. The ramp will bestowed beneath the nose cone and deployed by ex-plosive bolts before the airlock is used for the firsttime.

The airlock will have three access hatches largeenough for an astronaut to walk through with min-imal ducking. One outward-opening hatch will beused to access the outside while the other two out-ward opening (from the airlock’s perspective) willeach open onto one of the accessways. Solenoid valveswill open to allow pressure to flow from either com-partment the greenhouse into the airlock and equal-ize the pressure. Two compressor pumps will allowthe pressure from the airlock to be returned to thegreenhouse. A minute amount of pressure will be

left inside the airlock to blow out any foreign matterbrought inside the greenhouse by the astronaut orrover. It will be unnecessary for the airlock to pres-surize in order for the rover to dock. Every time theairlock is pressurized it will be bombarded by highintensity 1620 Watt UV lights to prevent the move-ment of pathogens from one side to the other or toeliminate any foreign pathogens that may otherwiseenter the greenhouse with the astronaut. The air-lock must also be sterilized before the external dooris opened to reduce the risk of environmental contam-ination of the Martian environment. The astronautwill be protected by her space suit.

Seals used in the construction of the access hatchwill have similar performance demands to thoseplaced upon the window seals, and upon aircraftdoors. For the outer of the two airlock doors, lowservice temperatures dictate the use of phenyl methylsilicone, while fluorosilicone rubber will again be usedfor the interior seal.

Since the airlock will be very infrequently pres-surized, depressurized, or sterilized, all airlock sys-tems (compressor pumps, sterilization and illumina-tion lights) will get their energy by diverting elec-tricity from the growing LEDs for a short period oftime.

8.1.2 Vertical Partition

The vertical partition between growing areas, whichprovides similar functionality to that of the floorplane

20

partition, will be constructed of similar polycyanatehoneycomb core material.

8.1.3 Plants, Processors, and Harvesters

The greenhouse must be divided by a vertical par-tition into two completely isolated sections, in orderto protect one side from a potential problem in theother. Therefore, all biology systems must be dupli-cated on each side. This will also allow for MDG op-erations to easily be reduced to half-capacity, shoulda situation ever arise that would make this desirable.Also, the airlock will be centrally located at the frontof the greenhouse, and will open to the exterior rampthat will be deployed upon landing, and will have twoother doors, each opening to one side of the green-house.

The plant structures will be arranged in such away to maximize growing area, while still providingenough room for other space-consuming necessities.Since it is important to have built-in space for astro-nauts to maneuver around the greenhouse in case ofa problem, each half of the greenhouse will containtwo plant growing structures, 1m wide each, with a0.75m wide accessways between them. A harvester,programmed to collect the plants on the bottom shelflevels, will also inhabit this accessway. There will alsobe a harvesting system on the ceiling to gather plantsfrom the top layers of the shelves. Both harvesterswill deliver their goods to the chute at the front thatleads to the food processing systems. This layoutwill be identical on both sides, such that there willbe two accessways and four plant structures (one oneither end of the greenhouse, and two in the middle,separated by the vertical partition).

The plants will be divided into the side of thegreenhouse which will have the best suited environ-ment for their growth. The left side of the MDG willbe heated less than the right side, and this will housewheat, potatoes, strawberries, and lettuce. Wheatwill be on the central structure, which will have fourshelves approximately 8m long. Potatoes will be onthe upper shelving unit, divided into two shelves ofabout 7.5m in length. The other 1.5m of shelvingwill be dedicated to strawberries. Lettuce will growin structures attached to the ceiling above the access-

way.The other, warmer, side of the greenhouse will hold

lettuce, peanuts, rice, tomatoes, sweet potatoes, andsoy. Similar to the cooler side, the right side will havelettuce growing in structures above the accessway.The central shelving (8m) will have three shelves.The top shelf will grow peanuts, the middle will con-tain rice, and the bottom will be divided betweentomatoes and sweet potatoes. The peripheral shelfwill be entirely soy. Also on the right side will be thealgae section. This will be located in the area be-tween the peripheral shelf and the greenhouse wall,and will stretch the entire 8.75m of the wall.

8.1.4 Communications System

After landing on Mars, it is essential that the green-house have an exterior antenna system in order tocommunicate with Mission Control on Earth. A con-stellation of communication satellites with global cov-erage has been assumed to exist, and only a small an-tenna necessary to connect to these. Therefore, thecommunications system will be located underneaththe solar panels during transit. Once the greenhousehas been deployed, and the solar panels open, thesmall, spring-loaded antenna will extend 180◦ andlock into position, enabling communication with thesatellite constellation. This satellite constellation willrelay communications traffic to Earth through a sin-gle, high-throughput satellite. Subsequent closings ofthe solar panels will not block the deployed antennaas it will extend past the end of the greenhouse.

8.1.5 Flooring

The division between the lower and upper hemi-spheres of the MDG will be marked in part by thenetwork of trusses, an isolating floor between the twohemispheres is still needed to prevent disruptive in-trusion of water and biological matter into the sup-port systems, and to provide a usable walking surfacefor astronauts in the eventuality of needed mainte-nance. As sufficient and evenly distributed contactpoints with the underlying trusses may be incorpo-rated into the design to account for the majority ofthe required strength, the chief demands placed upon

21

this materials will be a high elastic modulus and lowweight. A polycyanate ester core material has there-fore been chosen for this application due to its highelastic modulus to density ratio. The lowered mois-ture absorption-as low as 0.3% at saturation versusthat of 2.5% for traditional epoxies-allows fiber rein-forced polymers to be used for this application [104].

8.2 Lower Level

Figure 5: Lower Level Layout

8.2.1 Support Structures

The lower hemisphere of the MDG is divided intofour congruent triangles by the various structural el-ements in the lower hemisphere. These include theisolating walls at 225 and 315◦ separating power fromother subsystems, and the vertical along the centervertical axis, which are not marked by the same di-vision, but remain as a skeletal framework. A widthof 0.20m has been allotted to each of these structuralelements along the entire axis of the MDG. It is ex-pected that this full allotment will not be used, andmay instead be used for storage of backup equipmentand supplies if so desired.

8.2.2 Power

In order to prevent one side of the biology from beingcontaminated by the other side, the bottom sectionof the greenhouse must continue the isolation estab-lished in the upper level. Furthermore, if each half ofthe greenhouse needs to be self-sufficient, power mustbe divided in such a way that would allow one half tobe shut down, while the other half is in full operation.In order to do this, the natural divisions created bythe support structures will be utilized, dividing thebottom into three entirely secluded sections.

Although it is possible to access the bottom sec-tions on the far left and right through the floorhatches, the center section must be entirely inacces-sible to maintain seclusion. Therefore, it was deter-mined that this section will be occupied entirely bypower systems. The four RTG stacks in the centersection were positioned as close to the center and in-terior of the hull as possible to both isolate them ther-mally from heat-sensitive subsystems, and to maxi-mize transfer of heat to the MDG exterior. Aroundthem, over 40m3 of Sodium Borohydride has been po-sitioned both for proximity to the fuel cells located inthe aft end of the lower quadrant, and as a thermalbarrier and heat sink between the RTGs and all othersubsystems.

8.2.3 Biology

Most of the systems necessary for biology nutrientdelivery and storage will be located in the bottomhemisphere at the front of the greenhouse. Five me-ters of depth (measured from the front of the MDG,towards the center) on each side have been allottedfor systems such as: food processing, nutrient mea-surement instrumentation, nutrient storage systems,seed storage, a water reservoir, water purification,and water pumps. As the design calls for each sideof the greenhouse to be self sufficient, each of thesesystems must be duplicated on either half. Biologicalsystems have been allotted approximately 35m3 oftotal space, divided symmetrically between the twosides of the MDG.

In establishing a preliminary layout, certain con-siderations were made in placement of biological sub-

22

systems. Nutrient Delivery was centrally locatedalong the axis to maximize pump efficiency in thehydroponics system by minimizing maximum pipelength. This, in turn, must connect to the H2O reser-voir and purification systems, which are located justforward of center, and then to both fuel cells and theRTG water jackets. Likewise, atmospheric control,the other non-electrical distribution system, need alsobe afforded necessary ventilation. Finally, food pro-cessing equipment must be located in close proxim-ity to the airlock. It is these needs for connectivity,in addition to thermal isolation, that motivated theplacement of power systems in the lowest quadrantof the greenhouse.

8.2.4 Food Processing

Since the rover will never enter the biology sectionand will remain in the airlock when not deliveringfood, the harvested and processed plants must bedelivered to the rover inside the airlock. In orderto minimize food transportation systems, the pro-cessors will be located directly beneath the airlockin the front of the greenhouse. Food will enter theprocessors by a trapdoor activated by the harvester.Once the food is processed, it will be transported tothe rover in the airlock. Immediately following foodtransportation, the airlock will be purified and de-contaminated, before food from the other section isallowed to enter the airlock.

8.2.5 Computers and Backup Systems

Since the operating computers and interior commu-nications systems will take up less than 2m3 for eachside, a minimal amount of space must be allotted tothese systems. The reliability and connectivity needsof these systems are also low, though sensor interfac-ing would be facilitated by proximity to the upperhemisphere and central location. Extreme shock andvibration conditions were also considered unfavorablein their placement.

8.2.6 Storage

As noted in the volume budget, a projected 30.5m3 ofsurplus volume exist within the lower hemisphere of

the MDG. This volume has intentionally been con-centrated at the aft end of the landing module tomaximize utility in one of its two potential functions.The first is to serve as a buffer for unexpected vol-ume overruns and unbudgeted equipment. This spacecould also be used to store the following supplies: wa-ter, hydrogen, rocket fuel, and sodium borohydride.In addition, it is possible that the hydrolysis systemused for water creation will generate fuel, in the formof methane, as a waste product. Several of the biolog-ical systems have similar potential. Empty tanks forsuch by-products could also be stored in this surplusspace.

8.3 Mass Allocations

From the Mars Reference Mission, it was found thata total of 30 metric tons was allotted for the MDG.Furthermore, the engines, retrorockets and takeofffuel do not count in this mass allowance. Althoughthere has not been enough information gathered tohave specific mass measurements, estimations havebeen calculated for each major system, and mass al-lotments have been made based on these estimations.The following chart shows such mass allotments. Theallotments represent the maximum each set of sys-tems could use, final numbers are still being refined.

In the current arrangement, 60% of the budgetedmass of the MDG is located in the lower hemisphere.Further research must be conducted to determine ifmass must be more balanced in order to decrease thisratio. If the mass balance must be changed, somemassive systems in the bottom hemisphere, such asRTGs and water storage, may be moved to the tophemisphere and the partition between the two maythen be adjusted accordingly.

System Allotment (kg)Structure & Support 14,000Power 5,000Biology & Envi Ctrl. 7,000Computer & Comms 4,000Total 30,000

Table 5: Mass Allocations

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9 Biology Systems

9.1 Crop Selection

The well-developed crops of wheat, potatoes, sweetpotatoes, soybeans, rice, tomatoes, and lettuce andthe lesser-developed crops of peanuts and strawber-ries are planned as the MDG crops. Factors in select-ing these crops included their appeal to many people,the variety of ways in which they may be prepared,their growth rate, and the feasibility of growth in theMDG.

9.1.1 Nutritional Analysis

Although the primary purpose of the greenhouse isto provide fresh food for the astronauts to enjoy,an additional benefit will be the calories it provides.The precise nutrient composition was considered sec-ondary during crop choice because the greenhouseprovides only a portion of the calories consumed bythe astronauts and any essential nutrients may beprovided by prepackaged meals. Still, when soybeanswere evaluated, their abundance of amino acids was adecisive advantage. The team attempted to includecrops that provide a range of nutrients so that theastronauts will not rely on the greenhouse for all ofany particular nutrient. This assortment of crops willalso be more relevant to future, longer-term, Marsmissions that will have limited deliveries from Earth.

It is important to evaluate the nutritional valueof the crops when including them in meals; a briefsummary appears below each crop described.

9.1.2 Primary Crops

Brown Rice. Rice is also desirable for its abilityto produce a high amount of energy within a smallspace. Since its roots do not require oxygen, its pro-duction could be expanded temporarily if oxygena-tion methods were to fail. The Super Dwarf cultivaris the best choice.

Current food preparation within the space programis limited to rehydration and heating to serving tem-perature; additional equipment would be needed tocook the rice[35]. Regardless of its disadvantages, itsversatility is best of all the cereal grains[38].

ProximatesWater 72.96gEnergy 112.00kcalProtein 2.32gTotal Lipid 0.83gCarbohydrate 23.51gFiber, total dietary 1.80gNutrientsCalcium 10.00mgIron 0.53mgMagnesium 44.00mgPhosphorus 77.00mgPotassium 79.00mgSodium 1.00mgZinc 0.62mgCopper 0.08mgManganese 1.10mgSelenium 0.00mcg

Table 6: Nutritional Value of Brown Rice (100g)

Sweet Potatoes. Despite requiring one of thelongest growing periods, sweet potatoes have a highproduction rate and harvest index. In addition to thetubers, sweet potato leaves are edible. This is theonly crop that does not have increased levels of pro-tein when grown in controlled environments[39], andis an excellent source of vitamin A[40]. In CELSS- related tests at Tuskegee University, cultivars TI-155 and Georgia Jet were successfully grown in NFThydroponic system[41]; TU-155 was selected.

Strawberries. Fresh strawberries are desirableprimarily for their psychological value, since they willsignificantly contribute to the variety of food in thegreenhouse. An additional benefit is that their pro-ductive life is approximately twice as long as the timeneeded for them to grow to maturity, increasing theirefficiency.

Strawberries have been targeted as a potentialCELSS crop and grown hydroponically on a commer-cial scale. While they have not been used as exten-sively in CELSS testing as staple crops, the use ofa sensitive harvester will greatly increase their suit-

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ProximatesWater 87.96gEnergy 35.00kcalProtein 4.00 gTotal Lipid 0.30gCarbohydrate 6.38gFiber, total dietary 2.00gNutrientsCalcium 37.00mgIron 1.01mgMagnesium 61.00mgPhosphorus 94.00mgPotassium 518.00mgSodium 9.00mgZinc 0.29mgCopper 0.04mgManganese 0.26mgSelenium 0.90mcg

Table 7: Nutritional Value of Sweet Potato Leaves(100g)

ability for inclusion in the MDG. Strawberries havebeen grown successfully in troughs with the berrieshanging down in plain view, a layout that will be ex-tremely accessible to the harvester during the lifespanof the plant.

120 days before astronaut arrival, strawberry seedsare moistened and germinate at a fairly stable 15-18◦C. They then produce runners, some of which aretrimmed off and some of which are allowed to root.Using runners instead of seeds for subsequent plant-ings saves approximately 1.5-2 months of each straw-berry cycle. When the original plants are 9 monthsold, they are removed, and thereafter, plants will beremoved after 7.5 months.

Peanuts Peanuts were chosen for their high caloriccontent and ability to provide variety. They may bepressed for oil, eaten as a snack with minimal prepa-ration, or used to flavor a meal.

Peanuts have been grown experimentally at KSC,where a unique hydroponics system was used.Peanuts require a substrate above root level but be-

ProximatesWater 72.85gEnergy 103.00kcalProtein 1.72gTotal Lipid 0.11gCarbohydrate 24.27gFiber, total dietary 3.00gNutrientsCalcium 28.00mgIron 0.45mgMagnesium 20.00mgPhosphorus 55.00mgPotassium 348.00mgSodium 10.00mgZinc 0.29mgCopper 0.21mgManganese 0.56mgSelenium 0.70mcg

Table 8: Nutritional Value of Sweet Potato (100g)

low “ground” for the development of the nuts, whichgrow on pegs that grow down from the plant. Thepegs need to be in complete darkness and surroundedby media, which will cause them to be a more chal-lenging crop to maintain than most. Special atten-tion is necessary to ensure proper positioning of thesubstrate with respect to the plant in order to createa suitable environment for growth of the peanuts.

Wheat. A staple crop high in calories, wheat canutilize light 24 hours of the day and is not negativelyaffected by growth under low pressure conditions.[30]The crew is likely to feel more comfortable using afamiliar food item, which may increase its positivepsychological impact.

Varieties are available that make production in lim-ited space more efficient. One of the first to be devel-oped was Super Dwarf, which was only 30 cm tall buthad low yields. The USU-Apogee cultivar has beenselected, as it combines high production with full-dwarf height. While it is not as compact as SuperDwarf wheat, it has been specifically tailored to theconditions found in ALS systems. Other, more com-

25

ProximatesWater 91.57gEnergy 30.00kcalProtein 0.37gTotal Lipid 0.11gCarbohydrate 7.02gFiber, total dietary 2.30gNutrientsCalcium 14.00mgIron 0.38mgMagnesium 10.00mgPhosphorus 19.00mgPotassium 166.00mgSodium 1.00mgZinc 0.13mgCopper 0.05mgManganese 0.29mgSelenium 0.70mcg

Table 9: Nutritional Value of Strawberry (100g)

pact varieties are being produced as well, and someas short as 30-40cm may be available soon [31].

Tomatoes. Tomato is certainly one of the leadingcrops in CELSS research. Numerical optimizationplaced it in the top four crops for energy produc-tion; tomato would be one of the most versatile cropsand simplest to prepare for consumption, but auto-mated harvesting is more difficult to implement forthis growth pattern than for that of crops such aswheat. Several miniaturized varieties are available,ranging in height from “Micro-Tom” (15 cm) and“Red Robin” (20 cm) to “Microtina” (20-25 cm).

Soy. While soybean has a lower harvest index, it isan essential component of an ALS because it containsall 20 amino acids and is high in calories, protein, andfat. A greater variety of products can be made fromsoy than most crops; soymilk could be a substitutefor dairy products, and if soybeans are pressed for oil,the remaining soybean meal may be included in breador used for texture. Processing will require additionalequipment, which will be included as feasible.

ProximatesWater 6.50gEnergy 567.00kcalProtein 25.80gTotal Lipid 49.24gCarbohydrate 16.14gFiber, total dietary 8.50gNutrientsCalcium 92.00mgIron 4.58mgMagnesium 168.00mgPhosphorus 376.00mgPotassium 705.00mgSodium 18.00mgZinc 3.27mgCopper 1.14mgManganese 1.93mgSelenium 7.20mcg

Table 10: Nutritional Value of Peanut (100g, raw)

Lettuce. Lettuce has been grown in ALS studiesfor decades[33]. Though it has few calories, it growsquickly and is a source of leafy greens. It can ac-cept PPF levels ranging from 400 to 800[34] andcan tolerate higher levels of sodium in the nutri-ent solution[19]. In the team’s literature searches,“Waldmann’s Green” seemed to be the most com-monly grown variety of lettuce, which outperformed“Grand Rapids,” “Bibb,” and “Buttercrunch” in pro-ductivity in a recent study. Consequently, this is thevariety that will be grown in the MDG.

Potatoes. Potato has also been extensively stud-ied because it is high in digestible starch and pro-tein and has a high proportion of edible biomass. Itis characterized by ease of preparation and propaga-tion. Small tubers would be used to start the stock,but once grown, plants could provide leaves to startthe next generation of crops[32].

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ProximatesWater 12.76gEnergy 329.00kcalProtein 15.40gTotal Lipid 1.92gCarbohydrate 68.03gFiber, total dietary 12.20gNutrientsCalcium 25.00mgIron 3.60mgMagnesium 124.00mgPhosphorus 332.00mgPotassium 340.00mgSodium 2.00mgZinc 2.78mgCopper 0.41mgManganese 4.06mgSelenium 70.70mcg

Table 11: Nutritional Value of Wheat (100g)

9.1.3 Algae

Algae was the earliest form of life support, studiedin the 1950s for its ability to replenish oxygen[19]. Itwill be included in an exploratory role for food pro-duction, since it can offer lipids, protein, all essen-tial amino acids, and nearly all essential vitamins.The vitamin B12 is not produced by plants, butmany types of cyanobacteria can make it[38]. Har-vesting methods could use simple machinery, and al-gae may be produced rapidly, making it useful in anemergency[38]. Though not appealing in its currentform, advances in processing could make it more ac-ceptable for consumption.

Algae will not be considered a food product of thegreenhouse under normal conditions; current process-ing methods fail to make it palatable in large quan-tities. It is used as an additive in some items, but itis unlikely that it may be used in combination withthe other greenhouse crops, and the remainder of thefood will be pre-prepared. As an experimental crop,it will be present in small quantities in a section ofthe greenhouse that does not have the correct dimen-sions to be used for other plants. A 18m long tube

ProximatesWater 93.76gEnergy 21.00kcalProtein 4.00gTotal Lipid 0.33gCarbohydrate 4.64gFiber, total dietary 1.10gNutrientsCalcium 5.00mgIron 0.45mgMagnesium 11.00mgPhosphorus 24.00mgPotassium 222.00mgSodium 9.00mgZinc 0.09mgCopper 0.07mgManganese 0.11mgSelenium 0.40mcg

Table 12: Nutritional Value of Tomato (100g)

doubled back on itself will be located in one of theseareas.

New ways of using algae may come into being dur-ing the lifespan of the greenhouse.

9.2 Plant Growth Structures

All crops in the MDG will be supported in growthstructures consisting of shelves with supports con-necting to the MDG’s overhead structural skeletonand extending down through the floor to either thecentral A-frame support or the lower outside wall it-self. The lighting system will share these supports.

All growth structures will be able to support upto 40kg per square meter and consist of a slanted,stationary tray for the water to flow from a source atthe top to a drain that returns it to the reservoir.

wheat, rice, peanuts, tomatoes, lettuce and soywill grow on shelves equipped with an upper supportlid with multiple holes through which the plants willgrow. The upper lid will be a mobile continuous loopto slowly move plants from the end where they areplanted toward the harvesters at the other end with

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ProximatesWater 68.60gEnergy 141.00kcalProtein 12.35gTotal Lipid 6.40gCarbohydrate 11.05gFiber, total dietary 4.20gNutrientsCalcium 145.00mgIron 2.50mgMagnesium 60.00mgPhosphorus 1.58mgPotassium 539.00mgSodium 14.00mgZinc 0.91mgCopper 0.12mgManganese 0.50mgSelenium 1.40mcg

Table 13: Nutritional Value of Soy (100g)

an electric motor. After the plants have been har-vested, the lid will circulate back to the top whereanother plant may be planted. These crops will bestarted at the top of the slope where they may ben-efit from the light intensity near the LEDs. As theplants mature they will move down the slope wherethey will have more vertical growth room.

The early growth of tomatoes will be in growthtrays that feature aeroponic misting jets to facilitatequick early root growth. Peanuts will be grown be-neath a covering that will keep light off the roots.Lettuce and soy will be grown on a conveyor beltthat has divots in which the roots will be contained.The divots will be smooth so that the roots of soy andlettuce will easily come free when they are dumpedinto the storage trays at harvesting.

Strawberries, potatoes, and sweet potatoes will begrown in stationary trays and will be harvested bymobile harvesters with manipulator arms that willpick the fruits off of the plants. The plants will beplanted and removed after death by the manipulatorarms.

Algae will be grown in an 18m pipe which is dou-

ProximatesWater 94.00gEnergy 18.00kcalProtein 1.30gTotal Lipid 0.30gCarbohydrate 3.50gFiber, total dietary 1.90gNutrientsCalcium 68.00mgIron 1.40mgMagnesium 11.00mgPhosphorus 25.00mgPotassium 264.00mgSodium 9.00mgZinc 0.29mgCopper 0.04mgManganese 0.75mgSelenium 0.20mcg

Table 14: Nutritional Value of Lettuce (100g)

bled back on itself so that the overall length is 9m. Itwill be harvested by placing a mesh basket into theflow of the water/Algae and then removing it fromthe stream where it may be dried.

All shelves will be angled 15◦ from normal to theMartian gravitational field in order to facilitate watermovement. The landing legs must stabilize the green-house so that this angle is not more than 5◦ above orbelow the intended 15◦.

Figure 6: MDG Upper Level with Plant GrowthStructures Highlighted

The size and shape of any particular growth tray,and the amount of plants growing within any partic-

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ProximatesWater 71.20gEnergy 109.00kcalProtein 2.30gTotal Lipid 0.10gCarbohydrate 25.23gFiber, total dietary 2.40gNutrientsCalcium 10.00mgIron 1.36mgMagnesium 27.00 mgPhosphorus 57.00mgPotassium 418.00mgSodium 8.00mgZinc 0.32mgCopper 0.31mgManganese 0.23mgSelenium 0.80mcg

Table 15: Nutritional Value of Potato (100g)

ular tray, depend on what kind of crop is being grownwithin the tray. There will be three tiers of shelvesin the center of the greenhouse. This will decrease totwo as the shelves approach the side walls.

The support frame for the hydroponics system de-mands balanced rigidity and strength. The length-oriented stresses associated with landing render ter-restrial shelving structure models designed only for“vertical” loading and compressive strength impracti-cal. Attachment points with the skeleton of the MDGalong the height of the units will assist in this task.In addition, dimensional stability for compatibilitywith automated harvesting and bio and operation in amoist environment are also required of the structures.Square Aluminum tubing has been chosen for thisapplication due to its high strength, low weight, andready machinability. Its tubular construction servesto increase rigidity and reduce weight.

9.3 Water & Nutrient Delivery Sys-tem

Water is an essential element to plant growth, es-pecially in hypobaric conditions. Water mixed withnutrients will make up the nutrient solution whichwill be the source of nutrition for the crops. A blockdiagram of the water flow in the greenhouse is shownin Figure 7.

De-ionized water will enter the nutrient solutionsystem reservoir from the fuel cells. Nutrient levelswill be monitored electronically. When more nutri-ents of a given type are needed, de-ionized water willenter into the tank in which the nutrients were storedin dry form for the journey to Mars. A valve will opento allow the super-concentrated solution to flow intothe reservoir until the correct amount has been addedand nutrient levels are restored to nominal.

To reliably provide water to all of the plants, everygrowth tray will have a separate pump. The “mag-drive” pumps will have one moving part, a mag-netized ceramic impeller, and will be immersed inthe reservoir tank to save space[91]. The water willflow down the angled growth trays, due to gravity,through the roots of the plants and be pumped intothe sand filter to remove any large particles and to bethe first screen for bacteria. A sand filtration systemwas chosen over other mechanical, ionic, or reverseosmosis filters because it does not require any addi-tional electricity or replacement over the duration ofthe mission. From the sand filter, the water will passunder a UV lamp or high intensity light to removeany other bacteria in the water before it is returnedto the reservoir. This system will be duplicated inboth halves of the MDG.

For the sand filter, the water will return to thereservoir where a computer controlled UV lamp willact upon all bacteria in the water and either kill themor disrupt their DNA enough to render them sterile.The commercially available electronic control will beequipped with sensors to monitor bacteria levels inthe water and optimize power use while ensuring theproper dose of radiation is delivered. Multiple lampswill serve as a redundancy mechanism in case a bulbmalfunctions or burns out. The bulbs will be outsideof the tank to allow them to operate at their highest

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Figure 7: MDG Water Flow

efficiency temperature of 40◦C without heating thewater. Normal glass is opaque to UV radiation andtherefore the window that allows light to flow intothe reservoir will be made of quartz.

A number of hydroponic and aeroponic techniques,including the Static Aerated Technique (SAT), Ebband Flow Technique (EFT), Nutrient Film Technique(NFT), Aerated Flow Technique (AFT), Root MistTechnique (RMT), and Fog Feed Technique (FFT)[23][24], were considered for the MDG. Hybrid aero-hydroponic systems were determined to be impracti-cal and will not be discussed. The combined disad-vantages of using the two systems together outweighthe advantages. Having two nutrient delivery sys-tems where one would suffice would be unnecessarilyexpensive and complex. However, this does not ruleout using both methods separately in the event thateach is better suited to growing plants of differentspecies or growth stages.

In order to quickly produce crops of high quality,the rootzone needs adequate aeration. Hydroponicsallow for this by pumping air into the water (SATand AFT), periodically draining the water (EFT), orexposing a section of the roots to air (NFT) [24]. TheStatic Aerated Technique seems to be the least ad-

vantageous because of the static water, which needsto be changed every two weeks. For some plants,such as tomatoes, having the roots constantly sub-merged can be detrimental. One of the most commoncauses of houseplant death is overwatering [25]. Pe-riodic drainage of water is not as effective a methodof aerating roots because the oxygen is provided ata different time from the nutrient solution. Continu-ously circulating systems provide more benefit for theplants while being more efficient in water usage. Theaeroponic methods RMT and FFT provide oxygen tothe roots by growing the plants in the air and spray-ing a water/nutrient solution over them at regularintervals. The two techniques differ by the size of thedroplets sprayed – RMT uses water droplets from 30to 100 microns in diameter, while FFT droplets areless than 30 microns. Since vegetables more readilyabsorb larger droplets, RMT would be a better choicethan FFT[27]. The above conclusions show RMT andNFT to be the most viable growing methods. Of allthese options, the RMT has the best potential pro-duction rates because it uses the least water, morethan an order of magnitude less water and nutrientsthan hydroponic systems, and causes plants to growfaster[28].

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Tomato Production Data Hydroponics AeroponicsDays to germinate 14 immediateDays to first flower 28 immediateDays to first harvest 68-95 10-30Last day of harvest 105-120 47Crops/year 3.4 7.7

Table 16: Comparison of hydroponics and aeroponics. Hydroponics from seed, aeroponics from cuttings.Data from Colorado Power Partners, Denver, CO.

Accordingly, aeroponics also uses more than an or-der of magnitude less fertilizer and nutrients thanNFT. Although seeds and equipment will have beensterilized, any diseases will be less likely to spreadbecause the plants are individually sprayed insteadof sharing a common trough of water. However, thenecessary mechanical equipment is a disadvantage foraeroponics. In NFT, one pump could be used to cir-culate water for an entire tray of plants, but one spraynozzle for an RMT system could only service a fewplants. This translates to higher costs for AFT, whichis reflected by the lower number of commercial aero-ponic farms[55].

Recommended especially for growing fruits andvegetables, NFT is the best hydroponic techniqueavailable[29]. The great advantage it has over otherhydroponic methods is that a depth of as little as twomillimeters of solution can be used.

With the exception of the early tomato growth, allother plants in the MDG will get their water andnutrients through NFT, or nutrient film technology,where the roots are immersed in a few millimeters ofwater. The close proximity of the roots to the sur-face and the flow of the water allows the roots to getan ample amount of oxygen. This system was cho-sen over a conventional hydroponics system becauseof its lower water volume requirements and superioroxygenation abilities. It was also chosen over conven-tional soil because it is significantly more productivewith far less mass.

System Failure. A system failure could be themost damaging to plants grown without the benefitof a water trough. In aeroponics, clogged nozzles or

a power outage would leave the plants with no watersource. A complete loss of the crop can be avoided,but the plants would still need to recover. As long assprayings are spaced at intervals rather than contin-uous, the plants will not be as dependent upon a con-tinual water supply. Experiments by Aeroponics In-ternational have shown that plants can survive with-out being sprayed for a week or more under speciallow-temperature, low-light, and high-humidity condi-tions. [28]. Plants in a gravity-drained NFT systemare acclimated to the continual water supply. A lowerwater level due to a pump failure could have dramaticeffects, especially because the roots are only partiallyimmersed. A lack of regulation could cause a waterlevel that is too high and would decrease the benefitof exposure to oxygen.[26]

Hypogravity. Testing of aeroponic systems underhypogravity conditions has uncovered possible prob-lems. The lessened effect of gravity increased theeffect of other forces such as surface tension on thebehavior of water droplets. As a result, the dropletstended to hang onto the roots and apparatus, form-ing suspended bubbles of water. This phenomenonposes potential problems in regards to aeration of theroots and circulation of the nutrient solution. A pos-sible solution is to spray air through the nozzles afterspraying water. Experimentation with droplet sizesand speeds under simulated Martian gravity couldimprove results[28].

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9.3.1 Nutrient Control

A computer will monitor the concentrations of atleast the following nutrients: NO3, K, Mg, SO4, NH4,PO4, SO4, Ca, Mn, Fe, Zn, Cu, Mo, C, B, and Cl.The elements essential to plants are C, H, O, N, P,K, Ca, S, Mg, Fe, Cl, Mn, B, Zn, Cu, and Mo. Threeof these, C, H, and O, make up 90-95% of a plant’sdry weight. Since water and carbon dioxide in the airsupply those three elements, the other thirteen will bediscussed, divided into the categories of primary andsecondary elements. The primary elements, those re-quired in high concentrations, are C, H, O, N, P, K,Ca, S, and Mg. Secondary elements, found in lowerconcentrations but still thought to be essential, in-clude Fe, Cl, Mn, B, Zn, Cu, Mo, Si, Ni, and Co.

Solid-state, ion specific electrodes will monitor con-centrations of important nutrients. More durablethan membrane types, solid-state electrodes will lastlonger in the running stream of solution. Manycompanies, including Jenway, Sentek, Hanna Instru-ments, and Omega Engineering, produce ion specificelectrodes, mainly for water quality analysis. All op-erate in temperature ranges from 0 to 50◦C and thepH range from 4.5 to 6 [25]. Target parameters areshown in Table 17

Nitrogen is the element representing the largestpercentage in plant matter after carbon, hydrogen,and oxygen, and it is a major component in fertiliz-ers and nutrient solutions. A part of the chlorophyllmolecule as well as amino acids, nitrogen seems toaffect plant development more other elements [110].A nitrogen deficiency can cause leaves to turn yel-low and die. On the other hand, excess nitrogenmay cause more damage than a nitrogen deficiency.Most nutrient formulas provide nitrogen in two forms,NO3

− and NH4+, which also helps to balance the

pH. The ideal ratio of NH4+ to NO3

− appears to bebetween 1 to 3 and 1 to 4. Less ammonium is usedin order to avoid ammonium toxicity [109].

Phosphorus deficiency can considerably slowgrowth. Phosphorus content in excess of 1.00%should be avoided because too much phosphorus caninterfere with the functions of other elements [109].

Low High AverageNO3 150.00 1000.00 185.00NH4 40.00 120.00 65.00SO4 200.00 1000.00 400.00K 100.00 400.00 300.00Ca 100.00 500.00 200.00Cl 50.00 170.00 100.00PO3 50.00 100.00 80.00Mg 50.00 100.00 75.00Fe 2.00 10.00 5.00Mn 0.50 5.00 2.00B 0.50 5.00 1.00Zn 0.50 1.00 0.50Cu 0.10 0.50 0.50Mo 0.01 0.05 0.02

Table 17: Concentration of Nutrients in Solution(ppm)

Potassium is necessary for a healthy rate ofgrowth and is especially essential to the developmentof fruit. An excess of potassium is not a real prob-lem, other than that it can cause a deficiency in otherelements. Ideally, potassium, calcium, and magne-sium should achieve a balance. Potassium is usuallyin the form of KNO3, K2SO4, or KCl at about 200ppm [109].

Calcium exists in plants primarily in the cell walls.Calcium deficiency manifests itself in leaves that havebrown or black tips and a torn appearance. An excessdoes not have any direct negative effects, the indirecteffect being a disruption of the balance between theK+, Mg2

+, and Ca2+ cations. Some nutrient so-

lutions have a reduced concentration of calcium be-cause relatively little is necessary and commonly, cal-cium already exists in tap water. The water in theMDG, since it is being produced on site, will not havethat extra calcium. The nutrient solution will supplythe proper, unreduced amount [109].

Magnesium is also a component of chlorophylland a lack of magnesium can have a great im-pact [110]. Plants lacking in magnesium exhibit in-

32

terveinal chlorosis and increased susceptibility to dis-ease. Excess buildup of magnesium is unlikely, butonce again, the cation balance must be considered.The MDG’s nutrient solution will include more Mgbecause the water will not already have magnesiumin it [109].

Sulfur is a part of two plant amino acids, and istherefore another essential element even though it’sa small percentage of plant matter. Less is knownabout the role of sulfur compared to that of otherelements. Sulfur deficiency is somewhat rare, andsymptoms are very similar to those of nitrogen de-ficiency. Scientists currently believe that plants canhandle relatively high concentrations of sulfate ionswithout deleterious effects [109].

Various parts of a plant, such as the stem, leaves,seeds, and roots, have different proportions of eachelement (Table 18). Because of this uneven distribu-tion, different types of crops require different propor-tions of nutrients. In general, leafy crops, for exam-ple, need more N[25]. A plant’s needs also vary as itgoes through each of three main growth stages. Earlyvegetative growth mostly consists of leaf tissue. Dur-ing this stage the nutrient solution is more concen-trated because leaves have higher percentages of mar-cro elements and younger plants tend more towardsnutrient deficiency than toxicity. During late vegeta-tive growth, leaf and stem tissue grow about evenly.In the reproductive growth stage, nutrients are redi-rected to fruit and seed formation while other growthslows down[50]. Tailoring the solution for each plantand stage would be ideal but much more complicatedthan having a single nutrient system.

Plants take in NO3, NH4, P, K, and Mn relativelyquickly; Mg, S, Fe, Zn, Cu, Mo, and C at a mediumrate; and Ca and B more slowly. Contrary to whatwould seem to be a good way to provide the rightamount of nutrients, many nutrients should not re-main at a constant concentration with the initial lev-els by continuously replenishing the same amount ab-sorbed. Those taken in more quickly could be highin the starter solution and soon drop to near zero. Inthe case of phosphorus, feeding in more as a plant ab-sorbs it could allow the amount in the plant to rise as

% Leaves Stem Seeds RootsN 5.00 2.00 3.00 3.00P 0.30 0.20 0.50 0.20K 2.50 2.30 0.70 2.00Ca 1.20 0.30 0.10 0.20Mg 0.50 0.05 0.20 0.05S 0.50 0.30 0.20 0.20mg/kg Leaves Stem Seeds RootsFe 100.00 40.00 100.00 800Mn 75.00 20.00 50.00 25.00B 5.00 3.00 0.50 5.00Zn 50.00 20.00 50.00 30.00Cu 10.00 1.00 5.00 10.00Mo 2.00 1.00 1.00 1.00Cl 1.00 1.00 1.00 1.00

Table 18: Approximate Nutrient Concentrations invarious Parts of Wheat Plant[50]

high as three times more than the optimal level. Ex-cessive intake of one element leads to deficiencies inothers. Instead, those nutrients likely to accumulatein excess should be kept at very low concentrations.Frequent “topping off” in small quantities keeps thelevels much more even and stable[50].

Concentrated solution will be stored in a smalltank. Macronutrients will each be stored individu-ally, and micronutrients will be stored in one con-tainer in pre-measured proportions. Each of the twowater systems in the warm and cold section will havea separate nutrient/water supply. A stretch no longerthan 10-15 meters can be adequately supplied by onefeed point[51]. Either way, the solution flowing outwill be recirculated by a pump.

A possible alternative or supplement to monitor-ing nutrient concentrations in the water is monitoringnutrient concentrations in the plants. The concentra-tions in the plant are what really matters, and a tissuesampling give more accurate results. ICP-emissionspectrophotometry, nitrate-N analysis, Kjeldahl orLECO Total Nitrogen analysis[50], and electrical con-ductivity are other methods to help determine if plantuptake of nutrients are at optimal levels[25].

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9.4 Experimental Section

The experimental section will be a 0.75 meter cubewith a clear top panel and a operational life of upto five years. Its purpose will be to determine if thesimple addition of water can change Martian regolithto be less hostile to life. When deployed from therover with a spring-loaded mechanism triggered byan electric servo, a clamshell door at the bottom ofthe experimental section will spring closed, scoopingup Martian regolith and sealing the experimental sec-tion shut to avoid contamination. A box filled withseeds from multiple plant species will be dumped ontothe regolith and a canister filled with water and com-pressed gas will be mechanically opened to providewater to the regolith. (Figure 8).

Figure 8: Experimental Section

A simple atmospheric composition sensor willcheck at intervals of one day for changes in com-position from the previous day. If any changes arerecorded it will transmit its findings to the green-house to be transmitted back to Earth. The rovermay also periodically point its camera into the win-dow to check for signs of life. In the event thatthe oxygen level in the experimental section exceedshealthy levels for the plants, a UV lamp will sterilize

the internal atmosphere to avoid contamination tothe martian surface by bacteria and a solenoid valvewill open to change the atmosphere, the UV lamp willturn on to sterilize the inside of the experimental sec-tion regardless of instrumentation readings after fiveyears. Dust and other debris will be cleared from thewindow by a simple electric windshield wiper onceevery five days. All instrumentation systems in thegreenhouse will only be turned on once a day to con-serve power so that the entire section may be pow-ered by a lithium ion battery with a small solar cellfor recharging.

10 Environmental Controls

10.1 Internal Pressure

A hypobaric environment is one in which the pres-sure is lower than the standard condition; the MDGwill have an interior pressure in the range of 200-210millibars, significantly less than standard Earth pres-sure.

The primary advantages of a non-hypobaric green-house would be the ability to give the crew full access,without requiring them to wear EVA suits, and theability to provide a measure of redundancy in casethe life support systems fail in the laboratory/habitatmodules. While requiring the crew to wear an EVAsuit inside the greenhouse is a disadvantage of a hy-pobaric environment, it is not as severe as it wouldappear; modern technology has made significant im-provements in the thinness and flexibility of suits. Inaddition, the crew does not need to withstand condi-tions as extreme as floating freely in space, meaningthat their Mars EVA suits can be thinner and lighterthan even modern spacesuits. The energy requiredto power six EVA suits (assuming all the crew workin the greenhouse simultaneously) for eight hours aday is much less than the amount needed to keepthe entire greenhouse constantly at Earth pressure.If there were to be a failure of life support systemsin the habitat module, the interior pressure of thegreenhouse could be rapidly increased to allow theastronauts to temporarily seek refuge.

A lower pressure also requires less energy to main-

34

tain, and reduces the rate of leakage to the atmo-sphere. Lower pressure in a constant volume requiresfewer moles of a gas, which is especially significantin terms of water vapor. Fewer moles will saturatethe air to the proper relative humidity. Given thatthere exists need to manufacture water in-situ fromhydrogen brought from Earth, any savings that canbe made in terms of water usage will reduce over-all launch weight and the energy needed to producewater for the greenhouse.

There may also be advantages to growing plantsunder hypobaric conditions. Research on the growthof plants in hypobaric conditions shows that yield canincrease by as much as 76% at lower pressures andhigh humidity [30]. As pressure decreases, the rates oftranspiration and photosynthesis increase, so plantsare able to mature and produce faster[20]. However,to date, research on this subject has been inconclu-sive as to the advantages, but there is agreement thatthere are no disadvantages. While higher yields couldbe of value, the MDG design presented assumes andrate of growth equivalent to that on Earth. If thecrop yield is higher than expected, the MDG caneasily adapt by planting less frequently or in lowerquantities, to ensure that there is not a surplus offood and that the resources brought along are notdepleted ahead of schedule.

The specific conditions for the greenhouse will de-pend largely on the final crop selection. From theperspective of plant growth, a pressure of 100 mil-libars is the most promising. The goal is to reducethe pressure as much as possible while still retain-ing robustness in the system. Were the pressure tobe much lower, crop failure becomes a much greaterrisk; at 25 millibars, interrupting the water supplyfor more than several minutes can result in completecrop failure[20]. The increased rate of transpirationassociated with lower atmospheric pressures causes agreater dependence upon a constant supply of water.

To meet atmospheric composition and safety re-quirements, however, the initial target pressure willbe 200 millibars. The minimum O2 partial pressureis 50 millibars (or 5 kPa)[1]. In order to maintainan environment with safe flammability levels, thispressure must constitute 30% or less of the totalpressure[45]. Therefore, the total pressure must be

a minimum of 167 millibars. The target pressure of200 millibars gives an adequate cushion for the oxy-gen partial pressure, which can then be as high as 60millibars without compromising flammability consid-erations. MDG atmospheric composition is shown inTable 19.

Partial PercentagePressure

O2 ≥50.00 25.00%CO2 ≥1.00 50.00%H2O ≈19.48 9.74%Inert Gas(N2, Ar) 129.52 64.76%C2H4 0.00001 0.00%Total 200.00001 100.00%

Table 19: MDG Atmospheric Composition

10.2 Carbon Dioxide Enrichment

A common practice in commercial greenhouses is el-evating the carbon dioxide concentration to manytimes the Earth’s normal level of 300ppm [47], ef-fectively increasing the rate of photosynthesis. Car-bon dioxide must be present in a range of 1 to 30millibars (0.1 to 3 kPa)[1]. In a total pressure of 200millibars, 1 millibar of carbon dioxide gives a concen-tration of 5000 parts per million (ppm). Many sci-entists and commercial growers have noted increasedphotosynthetic rates and crop yields in experimentswhere greenhouses have achieved concentrations of5000ppm[49].

A very high concentration of carbon dioxide willalso make the plants more water-efficient; when car-bon dioxide is so readily available, the plants’ stom-ata can shrink, allowing less water out, and still cap-ture the same amount of carbon dioxide[48]. There-fore, the elevated transpiration rate caused by the lowpressure will be counteracted by the carbon dioxideenrichment. Although 5000ppm is a bit on the highside, some studies suggest that the ratio between oxy-gen and carbon dioxide is more important than theactual concentration of carbon dioxide alone. Be-

35

cause the MDG will have a greater concentration ofoxygen as compared to Earth, any disadvantage cre-ated by an abundance of CO2 will be counteracted.

10.3 Other Atmospheric Components

The other important constituents of the MDG’s at-mosphere are water vapor and an inert gas. The rela-tive humidity will be regulated at about 70%. Undera pressure of 200 millibars and an average tempera-ture of 22.75◦C, a relative humidity of 70% would beachieved with 19.48 millibars of water vapor[16].

When the greenhouse is initially filled on Earth, itwill have the aforementioned amounts of oxygen, car-bon dioxide, water vapor, and an inert gas. The gasused here would be nitrogen because of its abundanceon Earth.

10.4 Atmospheric Revitalization

To make up for lost gas due to airlock usage andleakage, gas will primarily be taken in-situ from theMartian atmosphere, with a backup supply broughtfrom Earth. Using 1% of the internal volume per dayas the maximum leakage rate, the MDG will lose itsentire contents 73.05 times over 20 years. Althoughthe estimated leakage will be significantly less, thefollowing section will account for the maximum rate.

10.4.1 Oxygen

According to the chemical equation for photosynthe-sis, the amount (in moles) of oxygen produced bythe plants is equal to the amount of carbon dioxideconsumed.

6CO2 + 12H2O + light → C6H12O6 + 6O2 + 6H2O

If a leakage rate of 1% per day were assumed, the rateof oxygen leakage would be less than the rate of pro-duction by the plants. Since the leakage rate is lessthan 1% per day, it can be assumed that under nor-mal operation of the greenhouse, no oxygen will needto be resupplied. When oxygen levels rise past 27%,the computer will start the oxygen removal process.

Figure 9: MDG Gas Cycle

Oxygen will be stored in tanks until they reach maxi-mum capacity. Oxygen produced after storage tanksare filled will be vented to the atmosphere. Whenthe percentage reaches 24.4% (50 millibars), oxygenremoval will stop.

10.4.2 Carbon Dioxide

With 95% carbon dioxide, the atmosphere on Marscan more than adequately supply enough carbondioxide for the plants. The power system and at-mosphere revitalization system can share equipmentfor capturing purified carbon dioxide from the envi-ronment. Because carbon dioxide has the narrowestmargin, it will be the most carefully monitored andcontrolled.

10.4.3 Ethylene

Ethylene is a naturally occurring plant product thataffects the rate of ripening in fruits. Too much ethy-lene causes fruits to rot. To control the amount ofEthylene in the greenhouse a product known as bio-KES will be utilized[92]. Within the assembly, tita-nium dioxide composes a photocatylitic coating onborasilica glass beads that remove ethylene from the

36

system when exposed to UV light.

10.4.4 Other Gases

Enough water will be brought to account for leak-age of water vapor. In-situ collection of water vaporwould not yield much, since water vapor is availableat a mere 0.03% of the surrounding atmosphere. Hu-midity will be kept near 70% by the condenser andthe computer-controlled humidifier.

The remainder of the internal pressure will be re-filled with inert gases. To refill a volume of 60 m3

at 200 millibars and 22.75◦C 73.05 times would re-quire 23071 moles of inert gas. Compressed to 3000psi, this amount translates to 189.2 m3 and a massof 646.0 kg. Liquid nitrogen would take up only 0.8m3, but it would need to be cooled to -196◦C. Giventhat carbon dioxide already needs to be extractedfrom the Martian atmosphere, the less costly (andvoluminous) answer would be to also collect nitrogenand argon from the Martian atmosphere, these gasesexist at levels 2.7% and 1.6%, respectively (see Ta-ble 20). The external atmosphere can be processedto remove other gases and leave behind nitrogen andargon in that ratio to make up the remaining internalpressure. As a backup measure, enough pressurizednitrogen and argon to fill the greenhouse once will bebrought from Earth.

Gas PercentCarbon dioxide 95.32%Nitrogen 2.7%Argon 1.6%Oxygen 0.13%Water vapor 0.03%Neon 0.00025%Krypton 0.00003%Xenon 0.000008%Ozone 0.000004%

Table 20: Main component gases of Martianatmosphere[46]

10.4.5 ISRU Process

One of the greatest limitations on a 20-year mannedmission to Mars is the capacity to bring an adequatesupply of consumables. To account for worst-casescenarios and functionality over 6 years, the MDGwill require at least 602 L of H2O, 7556 kg of CO2,and 46141.5 moles of inert gas.

Options for supplying consumables can be catego-rized by level of reliance upon Mars. The option re-quiring least reliance is to bring a 20-year supply ofwater, or the necessary components, and all othergases entirely from Earth. The sheer amount of massand volume required immediately eliminates this op-tion. Therefore, at least partial reliance is essentialto the mission.

The opposite extreme would be to gather all wa-ter and gases in-situ. This would be possible forthe gases, but water poses a problem. Two possiblesources are vapor in the atmosphere or frozen wa-ter in the permafrost. Using water vapor as the solesource is not at all feasible because water vapor isonly 0.3% of the atmosphere. Since oxygen is readilyavailable by breaking down the carbon dioxide, thebest option is to bring the hydrogen from Earth andextract oxygen from the air on Mars.

Enormous mass savings are gained through ISRU.The MDG’s ISRU equipment utilizes the local atmo-spheric gases CO2, N, and Ar. Since ISRU equip-ment has never been run in outer space, no trulyproven technologies exist. Such technology has, how-ever, been successfully tested under simulated Mar-tian conditions in NASA laboratories, and the can-celled Mars 2001 Surveyor Lander was to carry theMars ISPP Precursor (MIP) to be tested on the sur-face. It is assumed that since the DRM uses ISRUtechnology, the technology will have developed to ahigh level of reliability by the time of the MDG’slaunch.

The MIP has the ability to adsorb carbon dioxide,compress it, and convert it into oxygen. However,the oxygen generation system uses zirconia basedsolid oxide electrolyzer instead of the more efficientSabatier process. The would like to use the MIP’s re-liable carbon dioxide adsorption process and temper-ature swing utilization and incorporate that with the

37

Sabatier process for oxygen production. Not all of thecarbon dioxide captured would be processed to makeoxygen. As needed, a portion of the carbon dioxidewill pass through a 30-micron filter and replenish theinternal atmosphere of the greenhouse. Nitrogen andargon will be separated using similar absorption tech-nology from the Mars In-situ Carrier Gas Generator(MICAGG) developed at NASA Ames Research Cen-ter. This device is also unique for its independenceof power systems; it relies upon the diurnal energycycles of Mars for all power [108].

10.4.6 Backup Gas Storage

Although carbon dioxide, argon, and nitrogen will becollected from the atmosphere, enough gas to refillthe MDG two times will be brought along in storagetanks as a backup. At a pressure 200 millibars andan average temperature of 22.75◦C, the volume ofthe MDG could be filled twice with 406.5 moles ofO2, 8.129 moles of CO2, 158.36 moles of H2O, 1052.9moles of inert gas. The gases will be compressed to3000psi in tanks made of filament-wound Kevlar fiberwith a titanium liner. They can be stored safely atroom temperature. Although this storage methodrequires more volume than cryogenics, it eliminatesthe problem of continuously cooling the tanks.

10.5 Emergency Astronaut Environ-ment

The design team considered the ability of altering thepressure and composition of the MDG atmosphere tosupport human life in the event of of a catastrophichabitat module malfunction (Table 21).

In order to increase the oxygen pressure to theminimal amount required for humans, the greenhousewould need 144 more millibars of oxygen. To bringthe overall pressure up to an acceptable level, an ad-ditional 635 millibars of other gas needed. The teamfound that altering the atmosphere would be easilyaccomplished using the already planned environmen-tal equipment. However, the additional requirementssupporting a higher internal pressure (with safetymargins required for human occupation) – more thanfive times what they would otherwise be – would

Parameter RequirementTotal Pressure, kPa 97.9-102.7O2 Partial Pressure, kPa 19.5-23.1CO2 Partial Pressure, kPa < 707Oxygen 0.13%Temperature, K 291.5-302.6Relative Humidity, % 25-70

Table 21: Respirable Atmosphere Requirements (Op-erational) International Space Station, 1996[45]

place on the MDG structure were regarded unfavor-ably. The cost of launching the additional mass wasdetermined not to be worth the cost of providing thisadditional mission service, and so the feature was notincluded.

10.5.1 Air Circulation

The greenhouse will require an air circulation systemto ensure that gases are evenly distributed and to pol-linate plants. The first reason, continuously mixingthe air, serves many purposes. In stagnant air, anenvelope of CO2-depleted air would develop immedi-ately around the leaves as they use the CO2 directlyin contact. Adequate air circulation will keep a freshsupply of CO2 constantly available. One experimentin the Netherlands increased the photosynthesis rateup to 40% by increasing wind speed from 0.10 to 1.0m/s. Since plants primarily take in air during theday, the fans will not need to serve that purpose atnight[49]. Instead, the fans will operate infrequentlyduring that period. The only purpose they will servethen is to make the gas composition and heat sen-sors’ readings more accurate by mixing any areas ofconcentrated heat, cold, or component atmosphericgas.

Of the plants chosen for the MDG, strawber-ries, potatoes, and sweet potatoes can propagatethrough asexual reproduction. Lettuce, soybeans,and peanuts, have a high degree of self-pollinationwithout external help[56]. Wheat, tomatoes, and riceneed to an agent to help with pollination. Theseplants need gentle shaking or wind currents at 6-7m/s

38

for an adequate rate of pollination. In addition, cross-pollination is desirable whenever possible so that notevery plant will have the exact same genetic make-up and thus be susceptible to complete annihilationby a single disease[57]. The speed necessary is muchhigher than the speed needed for air circulation and ispossibly harmful to the plants if applied continually.In the interest of energy conservation and the plants’well-being, only crops that need wind pollination willhave a fan with a higher speed setting. The fans willswitch between off, low speed, and high speed at pre-programmed intervals throughout the day and night.Conventionally, greenhouse circulation fans are ratedby cubic feet per minute (CFM). The recommendedCFM value is 0.75 times the volume[58].

10.6 Lighting

Lighting technology has made rapid advances in re-cent years. For example, Light Emitting Diodes(LEDs) have historically increased in performance bynearly 30 percent per decade since they were createdin the 1960s [53]. This provides several options forthe lighting of the MDG.

10.6.1 Ambient Lighting

To facilitate the use of natural lighting, the growtharea of the greenhouse features a transparent exteriorwall constructed of polycarbonate. On clear days,the incident radiation on Mars is sufficient to pro-vide lighting for the plants [60], as polycarbonate hasa hazing effect of only 1%, which is relatively low[100]. However, Mars receives only 50% of the solarradiation that is received on Earth. The Martian dayis 24.62 Earth-hours long. In the equatorial latitudes,approximately 12 hours of daylight exists throughoutthe Martian year. However many of the plants thatwill be grown in the MDG would benefit from morethan 12 hours of light [19]. In addition, dust storms,which block out much natural light (increasing op-tical depth to 6), are frequent and unavoidable[59].This means that incident solar radiation cannot pro-vide all the lighting that is required for the MDG tofunction optimally.

Therefore, it is necessary to include an artificial

lighting system, despite any problems that mighthave to be overcome. Due to the power demands ofartificial lighting, it is advisable to use natural light-ing to the extent permitted by the optimal exteriorstructure. Electrical lighting will primarily be usedto light shadowed growth areas, to artificially extendthe daylight hours, and to supplement natural lightduring dust storms.

10.6.2 Efficiency

Given that electrical power on Mars will be a veryprecious commodity, efficiency is a primary factor indeciding which lighting system to use. Several op-tions exist that may be applicable to the MDG; theseinclude low-pressure sodium, metal halide, incandes-cent, fluorescent, mercury vapor, and high-pressuresodium lamps[54]. Recently, LEDs and microwavesulfur lamps have been developing into extremelycompetitive products[61]. Lighting efficiency is gen-erally measured in lumens/watt. For the purposes ofthe MDG, it is assumed that efficient lighting is moredesirable than lighting that generates excess heat andheating can be provided in a more efficient mannerthan by lights.

The majority of less modern lighting methods havemaximum efficiencies that are significantly less than100 lumens/watt[62]. In addition, such lights gen-erally produce light at more wavelengths than justthose necessary to grow plants. For plants to behealthy and grow, they require only the wavelengthsof maximum chlorophyll and cartenoid absorption[66]and those at which the rate of photosynthesis is high-est.

An additional measure of efficiency is the ratio ofusable wavelengths to unusable wavelengths gener-ated. For example, low-pressure sodium is very “ef-ficient” at 150 lumens/watt, but the majority of thelight it produces is in the yellow range, renderingit useless to plants, which primarily require wave-lengths in the red and blue ranges[67]. High-pressuresodium undergoes spectral shift as the input wattageis changed[73]. LEDs can provide high efficiencies,around 100 lumens/watt in the red spectrum andaround 25 lumens/watt in the blue[53]. The effi-ciency of microwave sulfur lighting ranges from 100-

39

150 lumens/watt[70]. Microwave sulfur light providesroughly the spectrum of the sun, but concentratesmore in the visible portion of the spectrum than theinvisible portion.[70].

10.6.3 Lamp Life

Lamp life is a very important issue; frequent resupplywill not be an option on the Martian surface. Manyolder lighting methods have lifetimes around 20,000hours or less[54]. In contrast, LEDs can last around100,000 hours, which translates into almost 11.5 yearsof continuous use[54]. As only four to six years of oc-cupancy are planned, the lights will not need to bereplaced. Microwave sulfur lamps have an unknownlifetime and as technological advances allow their ef-ficiency to increase, it is possible that they will neverneed replacement[62]. This is drastically better thanthe 2.5 years that conventional lighting sources mightlast.

The efficiency of most lamps degrades throughouttheir lifetime. This can influence not only the straightlumens/watt efficiency, but also the light spectrumproduced. Specifically, metal halide lamps have beenknown to undergo spectral shifts as they age [63].In contrast, LEDs and microwave sulfur lights ex-perience no degradation of either efficiency or lightspectrum produced.

10.6.4 Reliability & Safety

Reliability is also a critical issue. The landing is notexpected to be very soft and it is imperative thatthe lighting sources remain functional after landing.The bulbs used by most conventional lighting sourcestend to be fragile. In contrast, LEDs are solid-statelighting devices, which makes them very shock andvibration resistant[72].

Safety to both the plants and astronauts is an im-portant factor in deciding which lighting source touse. Mercury, an environmentally toxic substance, isused in most efficient conventional sources[71]. Nei-ther sulfur lamps nor LEDs contain mercury. Ifdamaged or broken, mercury vapor and metal halidelamps may also emit harmful ultraviolet radiationinto the growing area[64]. Microwave sulfur lamps re-

quire a radio frequency screen to protect plants fromthe microwaves. However, it is unknown what thedangers would be if a microwave sulfur lamp were tobe damaged[73].

All of these traits suggest that a successful MDGwould require the usage of either LEDs or microwavelamps as the primary lighting source.

10.6.5 Primary Lighting

Microwave sulfur lighting is not practical for appli-cations in the MDG as a primary lighting source.Though it has a very high efficiency, it is a pointsource which would kill any plant within a few feetand must be placed to allow for diffusion of bothlight and heat, unless light piping is used[73]. Thedisadvantage of current piping technology is that itcauses the light to lose approximately 50% of itsefficiency[70], eliminating the most significant advan-tage of this system. By the time the MDG launches,piping technology may have improved enough for mi-crowave lighting to be a practical primary light sourcefor the MDG, but at this point one cannot say forcertain [73].

LEDs have been selected for the MDG’s primarylighting system. LEDs are commonly used in arrays,which are placed above each growing area due to avery low level of heat produced. This conserves agreat deal of space and maximizes growth area. An-other advantage of LEDs over other lighting sourceswith comparable lumens/watt ratios is that all of thelight produced is of the specific wavelength neededfor the plant to use it. Unfortunately, blue LEDsdo not have very substantial efficiency at this time,so it could be advisable to use an alternative lightingsource to provide the blue light. Blue fluorescents area more electrically efficient source for this supplemen-tary light, though blue LEDs are still more practicalfor several reasons. Fluorescent lights will not last aslong and emit significantly more heat in the directionof the plants as compared with LEDs. From a de-sign perspective, it is more efficient to use blue LEDsbecause their use allows for the space managementbenefits of LEDs to be maximized, while supplemen-tal fluorescent lighting would significantly limit thesebenefits. [67]. However, blue LEDs have only been

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Incandescent LED Microwave Sulfur Low Prs SodiumWeight Score Wtd Score Wtd Score Wtd Score Wtd

Efficiency 0.35 0.5 0.2 4.3 1.5 2.5 0.9 5.0 1.8Life time 0.20 0.5 0.1 4.5 0.9 5.0 1.0 3.0 0.6Durability 0.10 1.0 0.1 5.0 0.5 3.5 0.4 2.5 0.3Safety 0.25 2.0 0.5 5.0 1.3 4.5 1.1 2.0 0.5Usable wavelengths 0.10 3.0 0.3 5.0 0.5 3.5 0.4 0.5 0.1Total 1.00 7.0 1.2 23.8 4.6 19.0 3.7 13.0 3.2

Metal Halide Hg Vapor Lamps High Prs. Sodium FluorescentEfficiency 0.35 3.3 1.1 2.0 0.7 4.3 1.5 2.5 0.9Life time 0.20 2.5 0.5 2.8 0.6 2.5 0.5 1.5 0.3Durability 0.10 2.5 0.3 2.5 0.3 2.5 0.3 2.5 0.3Safety 0.25 2.0 0.5 2.0 0.5 2.0 0.5 2.0 0.5Usable wavelengths 0.10 4.0 0.4 2.5 0.3 3.5 0.4 4.0 0.4Total 1.00 14.3 2.8 11.8 2.3 14.8 3.1 12.5 2.3

Table 22: Lighting comparison matrix. Microwave sulfur listed is assumes light piping required. Scale: 1 -5; 5 is best

around for a few years and their efficiency is skyrock-eting. By the time of MDG launch, it is probable thatthe efficiency of blue LEDs will be high enough to useexclusively LEDs as the primary lighting source.

One common belief about LEDs is that they arenot capable of producing adequate levels of light in-tensity. This is not accurate. The MDG guidelinesrequire a midday light intensity of 500µmol/m2/sec,and a minimum of 200µmol/m2/sec [1]. QuantumDevices Inc, which provides the majority of the LEDlamps currently used by NASA[73], has two new com-mercial LED products that meet the light intensityrequirements for plants. Their new SNAP-LITE LEDlamp can produce an irradiance output of up to 400µmol/m2 /sec[65]. This directly corresponds to thelight intensity that is needed for successful potatogrowth[54]. Quantum also manufactures the Q-Beamlamp, which has a maximum light intensity of at least1500 µmol/m2 /sec[65].

LEDs are generally more directional than otherlight sources[53], however use of reflective surfacesor another type of reflector would be a good way tomaximize light usage. Porcelain-coated reflectors areexcellent and require little maintenance[74]. It is veryimportant to ensure that reflectors are kept free of

any coating that obscures the light. Aluminum foilor white paint can be used beneath the growing areato help with the reflection of lighting.

10.6.6 Secondary Lighting

In order for astronauts to perform any necessarymaintenance on the interior of the MDG, a secondarylighting system was considered. This light is neces-sary because humans operate best with white light,which is not generated by the primary LED light-ing. After reviewing microwave sulfur, high-pressuresodium, fluorescent, and metal halide systems, it wasdecided that they posed too many additional design,power, and space requirements to be effective. In-stead, astronauts will use portable lights that arebrought to their work site.

10.7 Sensors

10.7.1 Atmospheric Composition

Concentrations of carbon dioxide, oxygen, nitrogen,argon, and ethylene will be monitored by two infraredgas analyzers.

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10.7.2 Temperature/Humidity

The warm section and the cool section of greenhousewill each be equipped with a wet and dry bulb tem-perature/humidity sensor. The dry bulb will providethe computer with temperature readings and the wetbulb will provide the comparison temperature, al-lowing the main computer to calculate relative hu-midity. A humidity sensor with electrical parts di-rectly exposed to the greenhouse environment willnot be used due to possible increased degradationof the equipment over time[87]. Ideally, the tempera-ture/humidity sensor will operate between the rangesof 5◦C to 35◦C and 40% to 80% relative humidity.The accuracy should be at most 2◦C or 4-5 percent-age points of relative humidity.

Environdata’s WT20 wet and dry humidity sensorcan measure temperatures to a calibration accuracyof plus or minus 0.2◦C. It has an operational accuracyof plus or minus 0.3◦C under operating conditionsof -10◦C to 50◦C and 0% to 100% relative humid-ity, which completely covers the range of greenhouseconditions[88]. Backup sensors would be brought, asthe average operational time is five years before a re-placement or overhaul is needed. Four extra units foreach side of the MDG will be brought. The runningsensor will be deactivated and a new one activated atfive-year intervals.

10.7.3 Pressure sensors

The MDG will utilize pressure sensors for boththe purposes of measuring atmospheric pressure and“wind” pressure created by circulation fans. Onetype of sensor at vertical and horizontal orientationswill be used for both applications because both havethe same environmental constraints. Also, in the veryextreme case of multiple sensor failures, the wind sen-sors can be turned horizontal for use as atmosphericpressure sensors. Silicon pressure sensors will be usedfor their proven dependability. These devices havebeen used successfully to detect changes of one mil-libar in airflow systems. Other common applicationsare in the harsh environment of an automobile as wellas in the human heart[98].

Honeywell silicon pressure sensors have the op-

erating range necessary for the MDG. The series24PC sensors are used to measure absolute pressurefrom 138 millibars to 1034 millibars. They have theruggedness to operate from -40◦C to 85◦C and havebeen shock tested to 150g. Small and lightweight,each has a mass of 2 grams[99]. A desirable char-acteristic this series does not include is temperaturecompensation. However, the temperature within theMDG will be carefully regulated, even during hiber-nation.

10.7.4 Light

Photosynthetically Active Radiation (PAR) will bemeasured throughout the growing area so that plantswill be ensured adequate light and artificial lightswill not be running needlessly. Readings from lightsensors will allow a computer to calculate how muchartificial lighting is necessary to reach the optimumamount of PAR. More or less artificial light will beautomatically put out to account for seasonal changesor unexpected dust storms.

The light sensor will have a photodiode to changelight energy into a small current and filters to blocklight outside of PAR range. One advantage to usinga photodiode is that it does not consume any power.

LI-COR Biosensors produces the LI-190 QuantumSensor, made specifically for measuring PAR andused in scientific photosynthesis studies. The operat-ing temperature is from -40◦C to 65◦C at 0% to 100%relative humidity[89]. Atmospheric pressure does notaffect the readings in any way. These sensors aremade to last for decades, but it is possible that somefactors could reduce accuracy over long periods oftime unless the sensor is recalibrated. Causes suchas high humidity and dust can give a measurementerror of up to ±2% per year[90]. Two sensors willbe brought for each section of crops for a total of 24sensors (3 wheat sections, 2 potato sections, 1 sweetpotato section, 2 soy sections, 2 strawberry/tomatosections, 1 rice section, 1 peanut/lettuce section).With this arrangement, LED output can be tai-lored to the varying light needs of the different plantspecies. Each sensor will hang down near the leavesof the plants on levels one and two. Sensors on thehighest level will be attached to the rim of the NFT

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trays. Sensors will have a slight tilt in the direction ofcirculation fans to prevent settling of excessive dustand pollen.

10.8 Ultraviolet Radiation

Although Mars is farther from the sun than Earth,its atmosphere is significantly less substantial, allow-ing UV radiation to sterilize the surface. Ozone inthe Martian atmosphere is about 2% that of Earth’sat best. As a result, Mars is subject to more radi-ation in the wavelengths from 300-360nm. However,carbon dioxide helps to absorb and scatter UV rays.For wavelengths shorter than 204nm, carbon diox-ide absorbs a significant amount of UV light, and forwavelengths shorter than 190nm, it provides an ef-fective shield. The effect of other gases in the criticalwavelengths is negligible[36].

Another factor in the amount of surface UV ra-diation is dust, which also absorbs and scattersrays, mostly in the wavelengths between 200 and220nm[37]. However, this effect is much more vari-able than the effect of atmospheric gases. Whilethere is always some dust in the air, dust storms andweather phenomena cause unpredictable changes.

Ultraviolet wavelengths from 330nm and less canbe potentially damaging to plants and humans. Ingeneral, plants have a higher tolerance to UV radia-tion than do humans. While a dose of 450 REM couldbe lethal for a human, a lethal dose for wheat is aboutnine times higher at 4022 REM. Potatoes, rice, andbeans have even higher tolerances. Plant seeds havesuccessfully been germinated and grown even aftersix years of exposure to cosmic radiation. There isno danger of plants becoming dangerous to the crewdue to cosmic radiation; the FDA has approved thepractice of irradiating foods[60]. Therefore, the re-striction on UV dosages inside the greenhouse is thatof crewmembers entering for maintenance purposesor a habitation module emergency.

The greatest amount of UV radiation not absorbedby atmospheric gases or dust is in the 300+ nm range,with less coming through between 200 and 300nm.The plants in the MDG can grow well with mini-mal filtration of UVC (200-280nm) and UVB (280-300 nm).

10.9 Microbe Management

There will be two separate environments within theMDG divided by the airlock and a barrier wall thatruns the length of the greenhouse.

The risk of pathogenic infection of the crops withinthe MDG will be minimized by chemical, radio, orthermal sterilization of the MDG prior to launch.Diversity of represented species will be the primarydefense against the rare chance of pathogenic attackbecause few pathogens can destroy a wide variety ofcrops. In the event of a catastrophic pathogen, lossof pressure or other catastrophic failure of one halfof the MDG, the barrier walls will protect the otherhalf.

Systems for the circulation of water and nutrients,generation and circulation of atmosphere, harvestingand storage of the plants and even the valves thatallow the flow of atmosphere from the growing areainto the airlock will all be separate for each side ofthe greenhouse. In order to go from one side of thegreenhouse to the other, the airlock must be depres-surized of the atmosphere from one side, sterilized byhigh intensity light, and repressurized with the atmo-sphere from the other side.

While efforts will be made to limit the spread ofmicrobes from one half of the MDG to the otherand through the water and nutrient delivery systems,there will be little controls within the two sectionsthemselves. Research has demonstrated the value ofhaving a healthy, beneficial microbe population. Ithas also shown the negative effects and the impracti-cality of attempting maintain a sterile environment.A beneficial population can prevent a small sample ofa harmful pathogen from becoming a problem. Theteam recommends that, before launch, a sample ofhealthy microbes be gathered from terrestrial hydro-ponics farms and be placed aboard the MDG.

11 Power System

Power for the Mars Deployable Greenhouse is basedupon the following precepts:

• Power is mission critical

• Diversification and redundancy are a necessity

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• Production of harmful byproducts should beavoided at all costs

• Heat production must be kept to a minimum toprevent damage to growing plants

• Integrating power systems with other systems tooptimize resources would be ideal

• Power system should reflect the needs of theMDG and the philosophies of the team andNASA

With these precepts in mind, the power team under-took a case study to investigate the options for powerproduction. The results are shown in Table 23.

Due to the conditions on Mars, the duration of themission, and the needs of the team, it is likely thatRTGs will be the primary power supply, with fuel andphotovoltaic cells as auxiliary and backup power.

The needs of the team are essential in designing thepower system for the MDG. Despite using the mostefficient systems available, the greenhouse requires anenormous amount of power. This is mostly due to thelighting system necessary to provide plants with suffi-cient energy to carry out photosynthesis. The break-down on energy needs for the greenhouse is shown inTable 24.

The total energy needs are, at maximum usagetimes, approximately 46kW. For guaranteed energyavailability, however, power production of at least50kW should be maintained at those peak times.Peak times of growth and harvesting directly precedeand coincide with times of astronaut occupation, fora total intermittent time of six years of habitation.

11.1 Transport, Landing and Deploy-ment

A one time power usage of 1kW is necessary for thelaunch, landing, and decent phase. Energy to be-gin production of water and communicate initially isalso needed before full operation begins. Therefore,some source of energy must be available before thegreenhouse has landed. Radioisotope Thermoelec-tric Generators produce a steady stream of energyfrom before the greenhouse leaves Earth, which can

be used to meet this need. As part of deployment,the doors on the top hemisphere will be opened toreveal solar panels on their interior while at the sametime exposing the windows to sunlight.

11.2 Initialization of Power Systems:Water Production

Water is essential to the function of the MDG. Whilethe obvious necessity of providing water for plantgrowth is important, the power for all the systemsof the MDG to run at full capacity are dependentupon H2O.

Several options have been examined for the pro-duction of water in-situ. The two most promising areZirconia electrolyzers (ZE) and Sabatier electrolyz-ers (SE). A trade study has been performed, and theresults are shown in Table 25

SE ZE (kW)O2 production 0.48kg/day 0.15kg/dayCH4 production 0.24kg/day 0.00kg/dayPower 0.12kW 0.25kW

Table 25: Water Production Options[97]

It is most likely that a Sabatier Electrolyzer willbe used, as it is more energy efficient, produces morewater per unit of energy, and does not require hightemperatures as with ZE. Each SE is cylindrical, andmeasures approximately 0.36m long, with a radiusof 0.05m. Mass is approximately 3kg. Three willbe included in the mission [111]. The reaction toproduce water is as follows:

4H2 + CO2 −→cat

CH4 + 2H2O

Therefore, it is only necessary to bring hydrogen[97],because carbon dioxide is easily obtained from theMartian atmosphere. There are several ways in whichthis might be done. Hydrogen can either be broughtin a liquid state, compressed gaseous state, or as acomponent of another compound, such as sodiumborohydride. Case study appears in Table 26.

Therefore, it is most feasible to transport a largequantity of sodium borohydride to Mars, as it is an

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Historical Uses Watts/kg Reliability Weaknesses AdvantagesRadioisotope 23 space missions, 5 to 7 no moving parts alpha particles extra heatThermoelectric including Mars expensiveGenerators landers(Plutonium 238)PEM Fuel Cells prototype autos, 50001 degradation of bring fuel clean

home generators, membranehospitals backups,and other systems

Photovoltaic Used terrestrially 40 moving parts to requires energy inexpensive,Cells and in space deploy; dust storage for no by-

storms and high night period productsOD2 on Mars

Scarlett Solar Deep space probes 5 to 7 moving parts to requires energy expensiveArrays deploy; dust storage for

storms and high night periodOD on Mars

Nuclear Fission On Earth and also 100-3000 moving parts alpha particles extra heatReactors a Reference expensive

Mission element

Table 23: Power Options

Landing Deployment Hibernation Growth HarvestingLanding 1.00 0.00 0.00 0.00 0.00Nutrient Delivery 0.00 0.00 0.00 0.60 0.60Waste 0.00 0.00 0.00 0.00 0.06Harvesting 0.00 0.00 0.00 1.30 1.30Misc. Bus 0.00 0.00 0.50 0.50 0.50Water Production 0.00 0.00 0.12 0.12 0.12Lighting 0.00 0.00 0.00 42.00 42.00Comp/Comm 1.00 1.00 1.00 1.00 1.00Total kW 2.00 2.00 1.62 45.52 45.58

Table 24: Power Needs

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Nuisance Factor Mission DangerGaseous High - large, Medium:

highly compressed flammabletanks

Liquid High - coolant Medium:system required flammable

Bonded Medium - requires Low:reaction to completelyrelease H2 innocuous

Table 26: Hydrogen Storage Options[96]

innocuous, unreactive powder. Once dissolved in wa-ter, it can be pumped over a catalyst to release purehydrogen. The reaction is as follows:

NaBH4 + 2H2O −→cat

4H2 + NaBO2

The result is hydrogen and dissolved sodium borate.Water can be distilled from the sodium borate andre-fed through the system. The hydrogen, after be-ing reacted with the CO2, will release more water andCH4. This water can be recycled back into the sys-tem to dissolve more NaBH4. Once a critical mass ofwater has been produced, fuel cells may be broughtonline.

11.3 Strength in Diversity: ThePower Triangle

Figure 10: Power Triangle

11.3.1 Radioisotope Thermoelectric Genera-tors

RTGs have powered every manned mission for NASA.As a passive way of harnessing the heat of atomic de-cay, they are incredibly reliable, generally all havean effective lifespan of 25 years. Most are poweredby Plutonium 238 and rely upon the Seebeck effectof non-uniform conductancies to produce electricityacross a temperature differential. However, in theMDG, Stirling Cycle Engines will be used insteadto harness this temperature differential, as minia-ture Stirling Engine Cycles are three times more ef-ficient than using the Seebeck effect to create elec-tricity. Considering the energy requirements of themission (highly biocentric) and the space constraints,use of non-uniform metal wires is not a viable op-tion. Furthermore, with the re-engineering of theStirling Engine by the DEKA Research and Develop-ment Center, despite a historical lack of robustnessand containing moving parts, it is a dependable andlong-lived option. With several hundred tiny Stir-lings within the RTG, connected in parallel, even ifmalfunctions occur, sufficient energy should be pro-ducible. Therefore, Stirling Cycle Engines will har-ness the heat produced by RTG cores to power theMDG.

Since NASA uses RTGs on such a regular basis,they have reached a point of modularization, whereeach system does not have to be individually designedfor a mission. The standard stack of 18 RTGs pro-duces 5.4 kW, measures 1.14m x .41m x 7.38m, andhas a mass of 1.008 metric tons. The size signifi-cantly limits the number of stacks – four stacks willbe used in the MDG. While this would not be suf-ficient energy to run the entire MDG in the case ofa massive fuel cell failure, it is possible that usingmini-Stirling engines would double the power outputto approximately 44kW, nearly enough to run theentire greenhouse.

11.3.2 Fuel Cells

Fuel cells will comprise a great deal of supplementaryand backup the power for the MDG. Their minimalsize, lack of harmful byproducts, and ability to be

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RTG Power Harness Property Used Relative Relative TotalEfficiency Robustness

Wires of Non-uniform conductivities Seebeck Effect 1 5 6Miniature Stirling Cycle Engines Ideal Gas Law 3 4 7

Table 27: RTG Power Harness Options Trade Study

linked with the biology system are great advantages.However, because significant quantities of fuel mustbe brought to run them for prolonged lengths of time,they do not make a good primary power source. Twotypes of fuel cells were investigated.

Direct Methanol Liquid-Feed Fuel Cell: Thiscell uses the following reaction:

CH3OH + H2O → 6H+ + CO2 + 6e−32O2 + 6H+ + 6e− → 3H20

CH3OH + 32O2 → CO2 + 2H2O

This produces six spare electrons which must com-plete the circuit of the greenhouse before being re-united with their hydrogen ions, which have jumpedthe membrane in the fuel cell[93].

The Direct Methanol Liquid-Feed Fuel Cell(DMLFFC) produces carbon dioxide, which is essen-tial to plants and water production, and which is alsovery common in the Martian atmosphere. Venting itout of the greenhouse would pose no harm to theastronauts, greenhouse or planet. Water producedwould be recycled through the plant nutrient deliv-ery system, and much would be recaptured with acondenser in the humid greenhouse.

Each 5kW DMLFFC measures 131 cubic centime-ters, and weighs less than one kilogram. It has alifespan of 2000 hours, which requires that they bechanged at least four times per year[93]. Therefore,for six years of habitation, 240 fuel cell stacks mustbe brought to meet all the power needs with onemethod. For the minimal power needs of hiberna-tion (the other 14 years), another 56 fuel cells wouldbe required. The total volume and mass is 4.625m3

and approximately 296 kilograms. Of course, thisdoes not include storage systems for bringing hydro-

gen, methanol and storing a constant supply of the3% methanol solution.

Sodium Borohydride Fuel Cell: While rela-tively similar in use to the DMLFFC, the SodiumBorohydride Fuel Cell (SBFC) has some marked ad-vantages. The reaction is as follows:

NaBH4 + 2H2O → 4H2 + NaBO2

With the hydrogen separated from the rest of thecompounds, it is passed through the fuel cell, whichseparates the positive hydrogen ions from their elec-trons, which must travel the MDG power grid be-fore being reunited with the hydrogen and oxygen toproduce an output of water. The only other resultsare heat and NaBO2 (sodium borate), which is theharmless substance most commonly known as boraxsoap[95].

The major advantage to using “Borax Cells” is thestability and storage properties of sodium borohy-dride. When bonded to borax, hydrogen produces awhite powder that is generally non-reactive and eas-ily maintained. Normal methods of transporting hy-drogen require massive pressurizers and/or coolingmechanisms - sodium borohydride can be kept in arelatively simple storage unit. It is only in the pres-ence of the catalyst that hydrogen is released, andwhen the catalyst is removed, the reaction ceases[96].

When in use, the sodium borohydride is dissolvedin water to a 44% solution. As such, it yields approxi-mately 5kWh/liter (kWatt hours per liter). Since themajority of the water will be produced upon reach-ing Mars, the amount of sodium borohydride to bringon the mission must be calculated based upon undis-solved powder. Each cubic meter of sodium boro-hydride powder stores 11,000kWh. Each kilogram ofsodium borohydride powder stores 9,300kWh. There-

47

fore, each kWh of fuel brought will require 9.09×10−5

cubic meters and 1.08 × 10−4 kilograms. In order toprovide the last required 6kW of power during peaktimes, 315,576kWh must be produced. Therefore,fuel cells will require another 28.7 cubic meters and33.9kg [106].

Furthermore, the property of DMLFFC whichcauses them to degrade so quickly is linked to thesignificant accumulation of carbon on the membrane.As a result, sodium borohydride fuel cells should notneed to be changed - simple water and hydrogen so-lutions will not damage the cells. Therefore, a mere40 fuel cells increase, decreasing the number of cellstacks necessary to power the mission.

Selection Sodium Borohydride fuel cells (SBFC)were chosen over the DLMFFC for a number of rea-sons. The first and foremost was cost, space, andmass savings that would come from the lower num-ber of fuel cells required for the SBFC, since theydo not generate membrane-degrading carbon. DLM-FCC also possessed a number of other disadvantages,including inefficient use of raw energy, high activationenergy, and a fuel source that is incompatible withthe water production systems. The SBFC disadvan-tages of lower raw energy concentration and relativelyyoung technology were considered, but its advantagesover DLMFCC were decisive.

11.3.3 Solar Array

Of all options considered, a solar array takes bestadvantage of natural resources afforded us. However,with the significant disadvantages inherent in solarenergy on Mars, the mission should not depend uponthem, nor should too much be invested in makingthem work.

Factors working against solar cells are significant.There is approximately half the ambient light onMars as there is on Earth. In general, solar panelswork best when angled towards the sun. The Mar-tian environment, however, mitigates the importanceof this: on clear days (OD of 0.4), indirect sunlightconstitutes 30% of the total light reaching Mars’ssurface; in a dust storm (OD of 6.0), 99% of thesunlight reaching the Martian surface is indirect[59].

This means that a large, planar array is better thana small array with a sophisticated light focussing orsun tracking system. Severe dust storms and night-time make power production unpredictable. Whilethey are very lightweight, expanding solar panels tocover sufficient surface area is difficult and not worththe effort.

However, advantage of spare surface area on theexterior of the MDG must be taken. When the hatchon the top of the MDG is opened to expose windowsthere to sunlight, the inside of those hatch doors areexposed skyward as well. There are 110 square me-ters available for the tiling of solar cells, which areapproximately 25mm thick. PVCs will not make ahuge impact on the power resources of the MDG –perhaps 1kW [68] with current technology – yet thiscould be critical in an unexpected situation.

12 Materials Handling

12.1 Harvesting Techniques

Each harvester will be specifically designed for thecrop grown in it’s tray. The MDG will incorporateboth stationary and mobile harvesters to handle thevarying harvesting needs of the crops. In most ofthe greenhouse, long, mobile trays of crops will beplanted at one end and mature by the time they reachthe harvesters at the other end. Wheat, rice, peanuts,tomatoes, soy and lettuce will be grown in this man-ner.

For mobile plants there will be a harvester at theend of each tray. These harvesters will run along hor-izontal tracks perpendicular to the trays remove ma-ture the plants at the end of the tray. The harvestersthemselves will not be large, but will be capable ofreaching all the plants on the meter-wide trays. Itwould have been possible to design harvesters thatalso moved up and down between trays, but one har-vester for an entire growth rack of trays in the green-house was not seen to have adequate redundancy.

Wheat and rice harvesters will be very similarwith slight modifications to accommodate the differ-ing heights. Both crops will be monitored electroni-cally for greenness in the heads and, once ready, the

48

top 4 cm of the stalks will be sheared off and takento the processor. The remaining stalks taken to theinedible biomass storage unit.

Peanuts will be challenging to harvest, as thepeanuts themselves grow between two layers of thetray in a light-shielded zone. The plants themselveswill be sliced off at the base by a simple moving blade,and a bar mounted on a second track will scoop themtoward a place where they can be collected.

Lettuce and soy will be delivered whole to the as-tronauts. Therefore they will simply fall out of thedivided tray in which they were grown and into acollection box where they can then be transportedto the rover for delivery to the astronauts. While itwould be preferable to harvest some of the soybeanswhile green to be eaten as edamame, Soybean podsare extremely similar in appearance to the leaves andwould be too difficult to distinguish without geneticengineering to change the color of the leaves or pods.Mechanisms, therefore, will be in place to harvest theentire bush when it reaches maturity.

Tomatoes will be harvested by a three-fingeredBarrett hand on a robotic arm that will be equippedwith an electronic color sensor to determine when thefruits are ready for harvesting. Because the lightsin the greenhouse will provide only a limited spec-trum of light which will change the appearance ofthe fruit’s color, the arm will also be equipped with asmall white light that will switch on while it is takinga reading.

Stationary crops (e.g. potatoes, sweet potatoes,and strawberries) will be grown on angled trays tofacilitate water flow but there will be no apparatusto move them toward the harvesters due to their ex-tended fruiting period or challenges associated withmoving them. Therefore the harvester must come tothe crops. Potatoes, sweet potatoes and Strawberrieswill be harvested by the same type of manipulatorarm used to harvest the tomatoes. The primary dif-ference between the tomato harvester and stationarycrop harvester is that the stationary crop harvesterwill be on a moving platform mounted to tracks inthe floor and ceiling. It will be able to move verticallyfrom the bottom to top of the greenhouse by use ofa worm screw.

The central body of the stationary plant harvest-

ing robot will have a central body housing controlsystems. Located opposite the arm on the upper sur-face of this body will be a compartment to providespace to transport harvested produce. In addition tothe Barrett grappling hand, the arm will support asmall camera to examine crops and recognize indi-vidual fruits. All grappling arms will have controlsallowing them to exert an extremely light force andavoid damage to the fruit. This harvester will also beable to place items into the processors and the roverwill have delicate enough control to shake tomatoesand aid in pollination by shaking them. It will alsobe able to place strawberry runners into the growthtrays.

Algae will grow in an 18m long clear tube to al-low light to enter. The algae will be harvested byinserting a screen collection basket into the flow ofthe water stream. Once the basket is filled, it will beremoved from the flow stream and be emptied so thatthe contents may be dried and sent to the astronauts.

An automated harvesting system consisting of a 2axis transporter and 5 axis manipulator and gripperhas been developed by Metrica for use in space facil-ities. Some of their advances may be used, such asthe sheathing for the robot arm. The robots in theMDG, however, will not be needed for heavy liftingand should be considerably smaller.

There will mechanisms similar to the peanut har-vester to clear roots and stalks from each growth tray.The growth belts will be smooth to prevent plantsfrom adhering to them. Any particles that remainin the growth belt would be dried by the heat of thelights below before they returned to the planting end,making them even easier to dislodge.

12.2 Crop Processing

All produce will be taken to the processing sectionat the end of each aisle next to the airlock. Some ofthe crops will merely be stored there in a refrigeratedsection, but there will also be machinery to grind thegrain.

Some space above the section with exposure tosunlight and space above the airlock will be used tosprout soy and wheat prior to planting.

None of the produce will be washed at this point.

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While the crew will wish to rinse them in a hydrogenperoxide solution, this will be most effective directlyprior to consumption.

Some storage space will be available especially forpotatoes, since they constitute the largest crop vol-ume that will be harvested at once. Otherwise, asmuch of the produce as possible will be placed di-rectly into the rover.

This section will have stored bags for shippinggrain and small food items to the habitat. With therisk of contamination, none of these will be returnedfor reuse, so a large number will be needed and theymust be small and light. The temperature of the in-terior of the rover will be controlled so there will beno need for insulating containers.

A grain dryer could be useful to extend the storagelife of grain or prepare it for grinding, but it is unnec-essary due to the high frequency of shipments to thecrew, It is inefficient to reserve space for a grain binfor the possibility that it will be necessary to have areserve. If delivery cannot proceed normally for anyreason, wheat can stay at moisture content levels ofas much as 22% for 3-5 days.

12.3 Crop Delivery Rover

The rover will be stored in the airlock during transit,upon arrival it will deploy the experimental sectionand radio navigation beacons. The rover will dockin the airlock whenever it is not in transit so that itmay be loaded as the produce is harvested. This willhave the secondary effect of protecting the rover fromexcess damage due to prolonged Martian exposure.2-3 deliveries will be made weekly to the astronauts.to lower development costs, many of the proven sys-tems, such as software and navigation controls, willbe adapted from the Sojourner and the 2003 rovers.

12.3.1 Power

For consistency with the rest of the greenhouse powerstructure and to utilize existing fuel, the rover willbe powered by two Sodium Borohydride Fuel Cells.Although The 8000 hours at 5kW that a fuel cellprovides will allow the rover to operate on a singlefuel cell for the entire length of the mission the second

is being carried for redundancy. The fuel for the thecells will be supplied when the rover docks with thegreenhouse.

Use of a fuel cell will allow the rover to have greatercomputing abilities for navigation and instrumenta-tion in addition to greater speeds and signal trans-mission than any previous Martian rover.

12.3.2 Navigation and Control

While much will be known about the general grad-ing and layout of the landing site, signal delays willrequire the rover to have a high degree of autonomyin order to properly place the experimental sectionand negotiate small obstacles and a highly probableindirect path to the habitat.

The rover will be equipped with the same combi-nation of five laser stripe projectors and two CCDcameras used on the earlier rovers. The cameras andlaser projectors will be mounted on the front of thevehicle at the upper edge of the cargo container. Theabundance of power, allows the use of a real-time,multitasking system architecture capable of monitor-ing the rover’s speed. Moveable cameras will allowthe rover to survey the near foreground while it ismoving slowly and look farther ahead while movingmore rapidly. Other obstacle detection mechanismswill include potentiometers and an contact sensitivebumper.

Once the optimal route has been found, the roverwill deposit transmitters to be used as waypoints,reducing the amount of computing power needed fornavigation and increasing the speed it is able to travelat. The rover dead reckoning will be used as a redun-dancy measure. An electronic memory of the routewill allow the rover to recall areas that are extremelyrough so that it may slow down.

In order to reduce the possibility of contaminationand prevent the loss of air into the non-pressurizedairlock, a close match with the hatches is needed,and the rover will need to be able to find its preciselocation within the airlock. While most of this can bedone with locators implanted in the walls, the rovermay also need to make use of its camera.

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12.3.3 Telecommunications

The rover will make use of the same radio modemand radio whip antenna as sojourner. This technol-ogy, proven on the surface of Mars, consumes smallamounts of power and requires minimal volume andmass. While this communication system has a lim-ited transmission range, continuous contact is notnecessary as the system will only be used to alertboth the greenhouse and the habitat of its approach.

Upon arrival at, or departure from the MDG thehabitat will be notified. If the Rover malfunctionsout of range and fails to arrive astronauts may bedispatched to recover/repair the rover.

12.3.4 Mechanics

The rover will utilize the rocker-bogie system fromthe Sojourner rover to maximize its mobility in un-even terrain.Each of its six wheels will be indepen-dently powered, and four will be independently con-trolled. With this arrangement, the rover will be ableto turn in place and surmount obstacles larger thanits wheels.

On the platform, there will be the box in which thefood will be placed during transit, fuel cells, and sens-ing equipment. This box will be shielded from radi-ation and insulated with aerogel so that it maintainsa nominal temperature between 4 and 10◦C. Remov-able compartments will be available to hold bags ofwheat or other processed crops, and small items suchas tomatoes. The compartment will have an interiorvolume of 0.15 cubic meters divided into two air-tightsections each with their own external door. The sec-tions will each serve only one side of the greenhouseto avoid contamination while loading.

The upper surface of the food compartment willbe flat, allowing the experimental section to be storedthere in transit. Spring-loaded arms will be activatedby an electric servo to push the experimental sectionclear of the rover after it has travelled a set distancefrom the habitat.

12.4 Resource Recovery

Due to contamination issues and the goal that theMDG be as self-sufficient as possible, neither liquid

nor solid astronaut waste will be used in the MDG.With all of the nutrients necessary for the missioneasily stored within a few square meters, there is verylittle reason to implement resource recycling.

Unused biomass cannot simply be tossed out of thegreenhouse because of the risk of environmental con-tamination. The use of a bioreactor in the MDG isalso improbable due to the high energy demands ofcurrent technology bioreactors. A bioreactor is alsoun-necessary to generate the CO2 required for thegreenhouse as it is abundant in the martian atmo-sphere. Large-scale composting is impractical in theMDG because it requires the addition of several dif-ferent kinds of bacteria which may escape into thegreenhouse and cause disease in the plants or maysimply not survive the trip to Mars. The concept of asmall experimental compost system in the MDG wasalso discarded because of the relatively large criticalmass necessary to initiate composting.

Most unused biomass from the crops, such as rootsor wheat stalks, will be put into a chamber along theoutside wall of the MDG. Once sealed, a compres-sor pump will remove all of the pressure to reclaimas much moisture as possible. The chamber will thenbe cooled by a piece of conductive material which willremove heat from the chamber to the Martian envi-ronment. The cold temperature and near zero pres-sure inside the chamber will prevent bacteria fromforming on the biomass.

13 Communication Systems

In the design of the radio communications systemthat will link the MDG to targets both as near as itsown rover and other elements of the reference mission,to communication with the ground team via NASA’sDeep Space Network, the fundamental goals of sim-plicity and reliability were established in the designof the CCDHS. Therefore, particularly in view of thestrong selection of commercial off-the-shelf (COTS)technologies available, it was decided that this sub-system would rely solely upon such less expensiveand proven COTS technologies. This affects costsavings in design, development, and testing of newtechnologies and mission-specific support systems, as

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well as assuring the pre-qualification and proof-of-technology of the components for space use.

13.1 Command and Data Subsystem

This consists of the central processing unit that re-ceives data from various external sources (i.e. subsys-tems, earth command, etc.) and controls all aspectsof greenhouse operations upon the basis of this infor-mation. It also formats data for downlink and pro-cesses digital uplink data. This subsystem containstwo primary components:

13.1.1 Data Logging

A solid-state data recorder developed and qualifiedfor space use will be used to eliminate the need forcontinuous real time communications. By storing andprocessing data internally during radio blackout pe-riods and between downlinks it is possible for themission to utilize the beacon-monitoring technologydemonstrated on Deep Space 1. Thus communica-tions expenses and load placed upon the DSN systemwill be minimized.

Three solid-state recorders were evaluated for com-patibility with the mission (Table 28). As it is de-sired to minimize the number of telemetry sessionswith DSN as much as possible, and as a large num-ber of complex sensors will be used in conjunctionwith a high degree of system automation, substantialstorage capacity upon which to store the sensor dataupon which the automation will depend is required.BAE Systems’ SU-214G was selected upon the ba-sis of its large storage capacity, internal redundancy,error correction, and reliability.

13.1.2 Computer

Due to the degree of automation desired in opera-tion of the MDG a fundamental goal of scalabilityand performance was established for this subsystem.Therefore, to accommodate proven automated con-trol technologies and such as Remote Agent and fu-ture iterations of this and similar software, it is ad-vised that only flight computers based upon chips op-erating at speeds over 100MHz be considered candi-

dates for the mission. The current primary drawbackof these chips is their unproven track record. How-ever, further testing and proof-of-technology shouldbe completed well in advance of the reference missionlaunch date, and allow the resolution of all issues withtheir use.

The harsh conditions of space require use of a ra-diation hardened (RH) processor qualified for andproven in space. Unfortunately, original developmentand adaptation of such processors from commercialproduction lines is slow, and radiation hardened pro-cessor speeds currently lag several years behind theircommercial counterparts. Other key factors in theselection of the flight computer are ease and diver-sity of interfacing for the acquisition of data from thelarge number and variety of sensors necessitated bythe target degree of automation. Software compati-bility with the Flight Linux project is also consideredto be desirable.

Several flight computers, some existing-others stillunder development based upon either the RAD750,Sandia Pentium, or PowerPC 603e were consideredfor use in the design of the MDG. The X2000 MissionData System (X2000 MDS) based upon the RAD750and currently under development at JPL, was ulti-mately selected. It was selected on the basis thatthe X2000 design goals of modular, powerful, andversatile space computing coincided with the needsand goals of the Olin Marsport Team, and the per-ceived high reliability of its development and deliveryin time for launch of the MDG. The X2000 MDS wascontracted for use in 5 missions, including the So-lar Probe, Mars Sample Return, Europa Orbiter, andPluto/Kuiper Express. As all missions were sched-uled for launch prior to the earliest possible Refer-ence Mission launch (2011), the full development ofthe technology in time has been deemed low-risk bythe team.

13.1.3 Software

To achieve the desired degree of automation in theMDG, and to most effectively exploit the advan-tages of beacon-monitoring technology, highly sophis-ticated automation software is required. The RemoteAgent software tested on Deep Space 1 is a prototype

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Manufacturer BAE Systems Alcatel CSEModel SU-214G SSR 120 EOS-AM SSRCapacity 214Gbits 120Gbits 160GbitsLife 5 yrs 7 yrs 5 yrsReliability .99 .98 .92Error Correction Yes No YesPower (W) 110/75/40/15 160/80/30/NA N/AMass 36Kg 25KgVolume .052m3 .22x.223Redundancy Full Hot/cold No single

interface & control point failures

Table 28: Data Logging Systems

of the sort of technology that is envisioned. Envi-ronmental controls, and day-to-day operation of allsubsystems will be entrusted to software controls.Unique emergency situations and initial deploymentwill reside in the hands of ground control.

Funding from the MDG mission should be used tofinance additional research into the area of automatedcontrol systems and into the development and testingof the specific software needed for the mission.

One of the primary issues in the design of theCCDHS was the relatively short service life of avail-able components. For solid-state data recorders, theproscribed service life ranged from 5 to 7 years. Dur-ing the course of a 20 plus year mission throughoutwhich parallel operation of a backup system must beassumed, this would necessitate the incorporation ofas many as 12 data recorders with 5 year operatinglives. This statement assumes negligible degradationin life expectancy in non-operating systems upon thebasis of the majority of degradation being linked topower and thermal cycling during use [101].

As the issue of component service life is of greatimport in all aspects of the reference mission, and toprevent unnecessary mass and fuel expenditures, it isadvised that research into the development of highlydurable CCDHS components be sponsored and bud-geted into the cost of the Reference Mission. Due tothe universality of the issue, the costs of this devel-opment will be distributed appropriately among thevarious mission elements, and should not constitute

a great portion of the MDG budget.

13.2 Telecommunications Subsystem

In the design of the TCSS, the availability of a Com-sat constellation providing global coverage of Mars,which will in turn interface with an aerostationary,high data rate communications satellite that will re-lay data to Earth was assumed [101]. This greatlysimplifies the design of the TCSS in relation to thepreviously assumed in need for independent commu-nication capacity.

As the operating frequencies and other specifica-tions of the Comsat constellation are currently un-known, an optimal configuration for the TCSS maynot be determined at this point. For the purposesof mass, power, and space estimates, certain assump-tions were, however, made. The system required isassumed to be comparable to other high-reliability,high data rate satellite communications systems onearth, such as that aboard Air Force One.

Due to the criticality of the communications sub-system, all components will be cross-linked and fullyredundant. Should the issue of technological servicelife arise, it will be addressed in an identical mannerto that used in the data handling system.

13.2.1 Beacon Monitoring

Reliance upon the beacon monitoring technologydemonstrated on Deep Space 1 will be used to mini-

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mize the load placed upon the Deep Space Network(DSN) while retaining a measure of safety compara-ble to that of more constant radio contact or lock. Itsuse is particularly well suited to the MDG during theextended periods of hibernation in the MDG’s oper-ation. With the cost of a 1-hour telemetry sessionwith the DSN peaking at over $1,000 per hour, theability to fully monitor the craft using smaller dishesat a cost of only $100 per day contributes substan-tially to the economy of long-term missions such asthis [107]. The signal protocol to be used in the bea-con monitoring of the MDG is described in Table 29.

Subcarrier Message ConveyedSignal1 All systems healthy2 Contact for data downlink

or minor error within2-4 weeks

3 Minor error-establish 2-waywithin 1-2 weeks

4 Critical error-establish2-way communication ASAP

Table 29: Beacon-Monitoring Protocol

14 Thermal Analysis

14.1 Requirements

The upper hemisphere of the MDG must maintain anambient temperature of between 22 and 25◦C dur-ing active periods. When in hibernation, the entiregreenhouse must be kept above 0◦C.

14.2 Thermal Condition

14.2.1 Environment

The low temperature and relatively high wind veloc-ities of the Martian environment create a favorablesituation for radiation of excess heat. The extremelylow pressure of the atmosphere, however, greatly re-duces the impact of this mode of heat transfer in the

overall thermal system. The low atmospheric pres-sure also contributes to another significant consider-ation in the dynamics of the system, that of signif-icant thermal cycling between night and day. Thelack of a substantial atmosphere or a greenhouse ef-fect results in great temperature fluctuations betweennight and day, which must be regulated to maintainfull productivity of the greenhouse. Extreme seasonalvariations in total daily solar radiation were also ob-served at the Viking lander sites, with total kW/m2

of sunlight varying a full order of magnitude from0.4kW/m2 to 4.0kW/m2.

Figure 11: Thermal Environment

14.2.2 Sources of Heat

Though operation of many of the individual com-ponents of the MDG results in the generation ofheat within the system, there are only two signifi-cant sources of heat. The first of these is the conver-sion and subsequent retention of solar radiation tothermal energy by the red shift of radiation enteringthrough the upper hemisphere. Infrared wavelengthreflective coating of the interior of the upper hemi-sphere allows the majority of this energy to be re-tained. The second is the heat generated by radioac-tive decay occurring within the on-board radioiso-

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topic thermoelectric generators (RTGs) which fulfillmuch of the MDG’s power requirements.

In the team’s analysis of heat generation, a worst-case scenario for heat generation was assumed withthe intention of designing a thermal management sys-tem capable of handling the projected extremes ofthe mission. Therefore, solar radiation levels wereassumed to be identical to those of a black body at5800◦C, and 100% transmissivity in, 0% out, wereassumed in the analysis. This situation, however, di-verges greatly from the norms that may be expectedduring the operation of the MDG. Analysis identifieda net generation of 50kW of energy from this source.In analysis of the RTGs, an efficiency of 20% in ther-mal to electrical energy conversion was used to derivethe generation of 160kW of heat by the four RTGs.

14.2.3 Heat out

In thermal analysis, there are three modes by whichheat may be transferred: conduction, convection,and radiation. In the thermal analysis, radiativeheat transfer through the transparent upper hemi-sphere was assumed to be negligible, as was heat lossthrough conduction and subsequent convection to alllander appendages (i.e. legs, solar panels, commu-nications antennas) the remaining idealized cylinderwas then analyzed in a cross-flow convection modelusing 15m/s wind velocity.

The results of the team’s analysis indicate a negli-gible heat loss through the upper hemisphere duringoperation as a result of the vacuum maintained be-tween the panes. This will allow for the interior paneto be maintained at a temperature of approximately15◦C. Therefore, as the humidity in the interior ofthe MDG will be maintained above 50%, the MDGdesign must incorporate and provide for reclamationof condensation upon the interior surface of the upperhemisphere.

Thermal loss through the lower hemisphere is a farless critical issue. The primary constraints in thisportion of the structure is prevention of frozen pipes,and maintenance of a temperature above 0◦C. Asheat generation occurs primarily in the lower hemi-sphere, it is here that thermal management effortswill be concentrated. The use of materials possess-

ing higher thermal conductivity in the two lowermostoctants will be used to promote radiative and dissipa-tive thermal transfer away from the MDG. Materialschoice for filler material between hulls may be usedto further regulate heat loss in this critical section ofthe MDG.

Figure 12: Diagram of thermal upper hemisphereheat loss used in determining radiative balance.

14.3 Issues Addressed

As identified in the team’s thermal analysis, the fol-lowing thermal issues must be addressed by the de-sign of the MDG:

• Dissipation of excess RTG heat

• Thermal isolation of the RTGs

• Buffering daily thermal cycling in the upperhemisphere

• Buffering seasonal fluctuations in solar radiationlevels.

• Reclamation of condensation

14.4 Solutions/Outcomes of Analysis

To address the aforementioned issues, a number ofthermal control mechanisms will be incorporated intothe final design of the MDG. Buffering of both dailyand seasonal fluctuations in radiation levels may beachieved through use of a deployable multi-layer insu-lating blanket over the upper hemisphere of the MDGduring periods of low solar flux, such as duststorms

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and Martian nights. Thermal isolation of the RTGswas achieved, in part by their placement in the lay-out, and by their encapsulation within the forty cubicmeters of stored sodium borohydride. Dissipation ofthe excess heat generated by the RTGs is promotedthrough selection of a high conductivity aluminumcore material for the lowermost quadrant of the hull.

As botanical considerations demand levels of hu-midity above the dewpoint, drains and gutters will beincorporated to collect any condensation that shouldform upon the interior of the panes. Improved con-vection, analogous to that effected by standard au-tomobile window defoggers, will also be incorporatedinto the design, possibly as a secondary function ofthe air circulation/ventilation fans.

15 Conclusion

The first generation Mars Deployable Greenhousepresented in this Preliminary Design Review is a keystep towards a Martian future. Technologically “sim-ple” and highly automated, the MDG augments thediet of the first crew to set foot on Mars with fresh,healthy produce while using no additional mission el-ements and requiring no crew time.

The team recognizes the existence of more techno-logically advanced ways to solve the MDG problem,which may allow reduced launch mass and volume.However, these solutions all depend on experimentaltechnologies that ready for use in a manned missionwith a requisite life span of 20 years. Consequently,the MDG proposal represents the best and reliablesystem for a first generation greenhouse.

The MDG will play a valuable role in the daily livesof the first crew. These six astronauts will benefitpsychologically and physically from fresh produce intheir diet. Technologies used in this greenhouse willalso inform future long-term space missions, as astro-nauts may one day venture out on long missions thatrender the transport of all necessary rations imprac-tical.

In addition, the results of the experimental green-house will pave the way for the next generation ofMartian greenhouses. These will prove essential forlarger-scale and longer-term Mars missions. Until

Figure 13: Mars Deployable Greenhouse (solar panelsnot shown for clarity)

such a time as these next generation greenhouses areready (at least 20 years), the MDG will continue pro-viding Martian explorers with fresh produce.

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[56] McGregor, S.E. Insect Pollination of Cul-tivated Crop Plants. http://gears.tucson.ars.ag.gov/book/.

[57] Sochaczewski, Paul Spencer. 23 Septem-ber 2001. “‘Miracle Rice’ Unwittingly De-stroys Bali’s Coral Reefs.” CNN Traveller,http://www.sochaczewski.com/ARTjika-miraclerice-july2001.htm.

[58] “How to Select the Correct Size of an ExhaustFan.” 2001. Charley’s Greenhouse, http://www.charleysgreenhouse.com/GdnTips/Fan-Shutter tips.htm.

[59] Landis, Geoffrey A., 1998. “Solar Cell SelectionFor Mars.” Proceedings of the Second WorldConference on Photovoltaic Energy Conver-sion, vol. III, p. 3695-3698.

[60] J.M. Clawson, A. Hoehn, L.S. Stodieck andP. Todd. 1999. “AG-Pod: The Integrationof Existing Technologies for Efficient, Afford-able Space Flight Agriculture,” BioServe SpaceTechnologies.

[61] Halvorson, Todd. September 25, 2001. “Lettuceand LEDs: Shedding New Light on Space,”http://www.space.com/businesstechnology/technology/light farming 010926.html.

[62] Sulfur Lamp, 2000. Innovative Lighting. http://www.sulfurlamp.com/slq&a1.htm.

[63] Langhans, R.W. and T.W. Tibbitts. 1996.PlantGrowth Chamber Handbook.

[64] “High-Intensity Discharge Lighting.” Inte-grated Publishing. http://www.tpub.com.

[65] “LED Products.” Quantum Dev.

[66] Vermaas, Wim. March 1998. “An Introductionto Photosynthesis and Its Applications,” TheWorld & I, p. 158-165.

[67] Yorio, Neil. July 7, 2000. “Lighting,” BiomassProduction at KSC-ALSGB, http://bioscience.ksc.nasa.gov/oldals/plant/lighting.htm.

[68] Hoffman, S.J. and D.L. Kaplan, eds. 1997.Human Exploration of Mars: The ReferenceMission of the NASA Mars Exploration StudyTeam, Johnson Space Center, Houston, TX.

[69] Drake, B.G., ed. 1998. Reference Mission Ver-sion 3.0: Addendum to the Human Explorationof Mars: The Reference Mission of the NASAMars Exploration Study Team, Johnson SpaceCenter, Houston, TX.

[70] Fusion Lighting Representative. November 6,2001. Phone interview.

[71] Rubinstein, Francis. 1995. “SulfurLamps–The Next Generation of Ef-ficient Light?” CBS Newsletter.http://eetd.lbl.gov/cbs/newsletter/ NL6/S-Lamp.html.

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[72] LEDtronics, Inc.. http://www.led.net/.

[73] Goins, Gregory D., Dynamac Corporation.2001. Phone Interviews.

[74] Trinklein, David H. April 1, 1999. “LightingIndoor Houseplants,” http://muextension. mis-souri.edu/xplor/agguides/hort/g06515.htm.

[75] Adams, Rod. April 2001. “Alternative NuclearPower,” The World & I.

[76] “Mini Nuclear Power Plant Pro-posals.” August 22, 2001. BBCNews, http://news.bbc.co.uk/hi/ en-glish/sci/tech/newsid 1504000/1504564.stm.

[77] McKay, Mary Fae, D.S. McKay, M.B. Duke.1992. “Space Resources: Energy, Power, andTransport.” NASA SP-509, vol. 2.

[78] Lando, Mordechai, J. Cagan, A. Baranga, J.Achiam. May 1996. “Development of Appli-cation Oriented Solar Pumped Lasers.” SunDay Symposium, Weizmann Institute of Sci-ence, Rehovot, Israel.

[79] American Stirling Co., 2001. http://www. stir-lingengine.com/.

[80] DSC Corp. http://www.dscsec.com/batteries/batteries.htm.

[81] Decker, Ed and C. Millsaps. March 2001.“Rechargeable Battery Cycle Life Issues,” Bat-tery Power Products & Technology, Motorola.

[82] “Energy Storage System.” 1996. NASA Sci-ence & Technical Information. http://www.sti.nasa.gov/tto/spinoff1996/32.html.

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[84] Plater, Brian B. and J.A. Andrews. 2001. “Ad-vances in Flywheel Energy-Storage Systems,”Power Pulse. Darnell Group.

[85] Mitlitsky, Fred. May 1997. “The UnitizedRegenerative Fuel Cell.” Lawrence LivermoreNational Laboratory, http://www.llnl.gov/str/Mitlit.html.

[86] Landis, Geoffrey A. January 1998. “MarsDust Removal Technology,” AIAA Jour-nal of Propulsion and Power, Vol. 14,No. 1, 126-128. http://powerweb.grc.nasa.gov/pvsee/publications/mars/removal.html.

[87] Nederhoff, Elly. 1998. “Humidity in Green-houses.” The Horticulture and Food ResearchInstitute of New Zealand, http://www.hortnet.co.nz/publications/science/n/neder/humid05.htm.

[88] Environdata. 2001. “Relative Humidity Sensorfor Environmental Monitoring.” http://www.environdata.com.au/relahumd.htm.

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[90] Claassen, Brent (Applications Analyst, LI-COR Biosciences). Personal contact (e-mail).

[91] GreenAir Products. 2002. www.greenair.com.

[92] Bio-KES. Gas Control Systems, Inc. http://www.storagecontrol.com/kes.htm.

[93] Hyder, Wiley, Halpert, Flood, Sabripour. 2000.Spacecraft Power Technologies. Imperial Col-lege Press: London.

[94] Carney, Dan. March 2002. “Detergent in theTank,” Popular Science.

[95] Millennium Cell. 2002. http://www. millenni-umcell.com.

[96] Evarts, Eric C. January 31, 2002. “‘Soap’may make clean fuel-cell cars feasible,”Christian Science Monitor. http://www.csmonitor.com/2002/0131/p13s01-stss.html.

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Gas Shift: Experiments and Mission Applica-tions. American Institute of Aeronautics andAstronautics.

[98] Hagen, Rick. 1998. “Choosing the Right LowPressure Sensor,” Sensors Online. http://www.sensorsmag.com/articles/0998/low0998/main.shtml.

[99] Honeywell. 2001. “24PCCFA6A Data Sheet.”http://catalog.sensing.honeywell.com/printfriendly.asp?FAM=Pressure&PN=24PCCFA6A.

[100] MatWeb, Online Materials Resource. 1997-2002. http://www.matweb.com.

[101] Mukherjee, Jaydeep. 2002. Personal Communi-cation.

[102] Landis, Geoffrey A., P. Jenkins, C. Baraona,D. Wilt, M. Krasowski, and L. Greer. 1998.“Dust Accumulation and Removal Technology(DART) Experiment on the Mars 2001 Sur-veyor Lander,” Proceedings of the 2nd WorldConference on Photovoltaic Energy Conver-sion, Vol. III, pp. 3699-3702.

[103] “The Chemistry of Silicon Rub-ber.” 2001. General Electric Tech-nical Libary. http://www. gesili-cones.com/silicones/americas/business/ port-folio/hce/workshops/paperpodhce02Part1.shtml

[104] Willis, Paul B. and Cheng Hsien Hsieh. “SpaceApplications of Polymeric Materials.” NASAJPL.

[105] Metals Handbook, 9th Ed, Volume 3. 1980.American Society for Metals.

[106] Amendola, Steven. December 28, 1995. Electro-conversion Cell. US Patent Number 5,804,329.

[107] Wyatt, Jay. 1998-2000. Beacon MonitorOperations. http://spacescience.nasa.gov/ os-stech/sec82.htm.

[108] “MICAGG,” NASA Ames Re-search Center. http://ares.ame. ari-zona.edu/micagg/micagg intro.html.

[109] Jones, J. Benton Jr. 1983. A Guide for the Hy-droponic & Soilless Culture Grower. Portland:Timber Press.

[110] McMahon, P. and Max Teplitski. 1999.Nutrient Deficiencies. http://hcs.osu.edu/hcs200/Defrme.html.

[111] Bootstrap Chemistry 101.

[112] Larminie and Dicks. 1999. Fuel Cell SystemsExplained. John Wiley and Sons: New York.

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A Mission Timeline

1 2 3 4 5 6 7 82011 •2012 •

•••

2013 ••••

2014 • •• • •• • •• • •

2015 • • •• • •

••

1. MDG Transit2. Crew Presence3. Initial Water Production4. System Startup5. Planting / Growth6. Harvesting7. Shutdown8. Hibernation

B Landing Sites

The team recognizes that considerations other thanthose most advantageous to the successful operationof a greenhouse will determine the location of earlyMars outposts. Nevertheless, in the spirit of totaloptimization, the team has devoted some attentionto site selection because some of the advantages fora greenhouse may also pertain to the program as awhole. A number of sites were considered for theMarsPort base, with three studied in detail. Fac-tors of the greatest weight were feasibility of landing,

scientific interest in the site, and, unique to a green-house, the availability of ambient light (i.e. no moun-tains that would obstruct sunlight). Sites with rela-tively smooth terrain also were important, so that asizeable base could be established without requiringsignificant levelling or grading of the surface. Thethree candidate sites are Gusev Crater, the VallesMarineris, and the Elysium Paleolake Basin.

B.1 Gusev Crater

The first potential landing site studied was GusevCrater, 13◦ S, 183◦ W (Figure 14), at the mouth ofthe Ma’adim Valis. The light here should be morethan adequate for plant growth due to its equato-rial proximity; the crater walls should not cause anysignificant additional shading of the greenhouse, asthe site would be a few kilometers from them. Sincethe Gusev Crater was formed from the impact of ameteorite, it can be safely assumed that the groundwill not collapse from under it. The crater’s 150 kilo-meter diameter allows for a great deal of error roomin landing, as just about anywhere within the crateris a safe place to touch down, though maintaining asafe distance from crater walls is important. Thecrater has a depth of 1600 meters[7], which offerssome shelter from weather occurrences outside of itsbounds. The ground is, however, slightly inclined,which could prove to be a difficulty in landing [5].The walls, though themselves of interest, also limitthe mission. Expeditions outside the crater (wellwithin the range of the rovers described in the Refer-ence Mission) would be hindered by this formidableobstacle. This crater is not yet an official landing sitefor any future Mars mission.

Researchers have created a theory of the historyof the Gusev Crater, suggesting that its location atthe mouth of the Ma’Adim Valley would have causedit to become the basin for many floods. From pre-liminary observations, scientists have also found in-dication that there exists sedimentation in the area.Scientists, intrigued by this evidence, are trying tofurther research it. Other research potentials at thissite include prospects in exobiology – if there wasonce life on Mars, it is a strong possibility that thesediments in Gusev Crater contain fossils. In 1995,

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NASA named Gusev Crater a high priority for bio-logical exploration [8].

Figure 14: NASA photo showing Gusev Crater andthe Ma’Adim Vallis

B.2 Candor Mensa / Vallis Marineris

The second outpost location studied was CandorMensa / Vallis Marineris, 5.5◦S; 74.5◦W (Figure 15).Again, due to equatorial proximity, lighting wouldbe excellent, but shadows from cliffs near the landingzone might cause shading of the greenhouse.

Although there exist some flat areas on which toland, there would be little room for error, as steepcliffs and dropoffs await. However, if landing weresuccessful, this site would provide the best protec-tion from dust storms as well as the greatest scientificvalue among sites considered.

The large chasms in Valles Marineris may be ofgreat scientific value. Since the walls of some of thetroughs reach as high as seven kilometers, a great dealof Martian history can be learned from studying thedifferent layers of rocks[6]. Specifically, the rocks inand near Candor Mensa are particularly young (mostlikely from the Late Amazonian age [9]), and prob-ably came from local volcanoes. Attaining samplesof these volcanic rocks, and studying their makeupand origins, may lead to the discovery of the ther-mal history of Mars. Furthermore, material fromnearby dunes could verify the existence of volcanicvents Mars. The extremely convenient location ofCandor Mensa would also allow most of these samplesto be obtained through the use of rovers and balloons,and would not require extensive resource-consuming

treks. The greatest disadvantage to Candor Mensa(and the rest of Valles Marineris) is clearly the dan-gers in landing a craft in or near the chasms. Anysmall mistake could translate to the crashing of a ve-hicle, and a devastating failure of the mission. Also,there is the slight possibility that a nearby volcanocould erupt, as recent studies indicate that Mars maystill be geologically active[13].

Figure 15: Map of the Valles Marineris

B.3 Elysium Paleolake Basin

The third and final site considered to date is the Ely-sium Paleolake Basin, 5◦N and 197◦W (Figure 16).Ambient lighting is adequate.

The basin is a moderately safe place to land, butprobably not a good location for a large building.Although it looks flat, the ground is most likelyfairly rough, and may include “platey” and flow-liketextures[11]. Since the area is relatively flat, compli-cations with hills should not be a problem. However,being in such an open location also leaves any vehicleor building in the basin fully open to any wrath theweather can unleash upon it.

The Elysium basin is the only place on Mars wherethere is clear evidence that an outflow of water ex-isted. Although the basin is one of the most recentlyformed on Mars, there is also evidence that showsthat this basin’s existence on Mars was intermittent.Such intermittency could lead to a great deal of dis-coveries about Martian climate and biology. It is pos-sible that this basin, and its neighboring lake system,could have been the ideal location for life on Mars[12].Also, since the basin was formed from volcanic activ-ity, some studies on Martian volcanoes can take place.Treks of distances greater than 100 kilometers would

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be required to fully explore the basin.

Figure 16: A picture of the general area around theElysium Basin and a blowup of the potential landingarea.

B.4 Role of Future Data

Information gathered by upcoming missions will con-tribute to the selection of a landing site for mannedmissions. The Mars Odyssey, currently in its aero-braking phase, carries a high resolution thermal emis-sion imagining system (THEMIS) capable of identify-ing previously undetectable Martian features. Theseinclude hydrothermal vents and hot spots, buried ice,and carbonate deposits. If located, these features arelikely be of high scientific priority for detailed explo-ration, as they are more likely to hold evidence of lifethan other areas may be. The Odyssey will also uti-lize a gamma ray spectrometer to measure distribu-tion and quantity of 20 elements [10]. One example ofthe benefits of this study is that measuring hydrogenin the upper meter of regolith will assist in estimatingthe amount of water available to future missions.

In 2003, the Mars Express and its lander, the Bea-gle 2, as well as two Mars Exploration Rovers willbe launched. The Mars Express mission includes aninstrument called Mars Advanced Radar for Subsur-face and Ionospheric Sounding (MARSIS), a ground-sounding radar used to locate subsurface water reser-voirs [14]. The 2005 Mars Reconnaissance Orbitercan be expected to contribute even further to landing

site selection with its 20-30 centimeter main camera[10]. The 2005 mission will be especially important inhelping to select as level a landing site as possible forthe MDG. A level, smooth landing site helps reducecomplexity of the landing system and supports thatare required.

C Compilation of Assumptions

There are a variety of assumptions that have beenmade in order to prepare this preliminary design re-view

1. The safety of the astronauts cannot be compro-mised.

2. Planetary protection is a high priority.

3. The primary contribution that an early green-house can make to the Mars program is to in-crease the quality of life of the colonists withfresh produce. The large fraction of their nutri-tion will be provided by pre-packaged rations.

4. Only proven technologies will be used in theearly greenhouse. The exception to this assump-tion is that any technology required for the Ref-erence Mission, developed or otherwise, is usablefor the MDG.

5. Opportunities for new technologies and agron-omy research that may provide more effectivenutritional delivery to colonists should be accom-modated in the evolutionary greenhouse.

6. Compatibility and interoperability with otherReference Mission elements is essential.

7. Systems should be multifunctional and of valueto other mission components whenever possible.

8. Failure should be graceful.

9. Everything is a potential resource.

10. A global communication satellite constellationwill be in place around Mars[101].

11. The “other significant payload” required if theMagnum launch vehicle is used[1] is also Mars-destined.

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Crop Time Area Needs Peak Photon Daytime Power Nighttime Power(hours) (m2) µmol/m2/s Flux Watts Watts

Low High W/m2 Min Max Min MaxPotato 12 4.0 150 250 63 0 0 0 0Soy 12 16.4 500 1000 250 656 8856 0 0Rice 12 9.2 600 1800 450 1288 12328 0 0Peanuts 12 8.0 900 225 3520 3520 0 0Sweetpotato 12 6.0 1000 250 3240 3240 0 0Strawberries 12 3.0 300 500 125 0 120 0 0Tomato 16 16.4 400 45 113 0 0 0 6560Lettuce 18 8.0 400 800 100 0 2720 0 3200Wheat 24 30.0 1200 1250 312.5 23700 23700 36000 36000

Table 30: Clear Day, 195W/m2 ambient light

Crop Time Area Needs Peak Photon Daytime Power Nighttime Power(hours) (m2) µmol/m2/s Flux Watts Watts

Low High W/m2 Min Max Min MaxPotato 12 4.0 150 250 62.5 0 0 0 0Soy 12 16.4 500 1000 250 656 8856 0 0Rice 12 9.2 600 1800 450 1288 12328 0 0Peanuts 12 8.0 900 225 3520 3520 0 0Sweetpotato 12 6.0 1000 250 3240 3240 0 0Strawberries 12 3.0 300 500 125 0 120 0 0Tomato 16 16.4 400 450 112.5 0 0 0 6560Lettuce 18 8.0 400 800 100 0 2720 0 3200Wheat 24 30.0 1200 1250 312.5 23700 23700 36000 36000

Table 31: Dust Storm, 115W/m2 ambient light

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D Lighting Program

Potatoes, having the lowest light requirements, canbe very productive on ambient light alone, even dur-ing a mild storm. During a large storm, they will notreceive the optimal amount of light, but will havemore than the minimum amount. No power is allot-ted for potatoes.

Tomatoes have the second lowest light require-ment, but they have an extended 16-hour photope-riod, so they will only consume power at night or dur-ing a large storm. The nighttime allotment for toma-toes is four hours after sundown at 400 µmol/m2/s,which consumes 6.56 kW. Like tomatoes, lettuce hasan extended photoperiod. Their nighttime allotmentis for 400 µmol/m2/s for six hours before sunrise.During the day, the peak intensity for lettuce will bea total of 800 µmol/m2/s. Wheat is a special case; itwill ideally be exposed to a constant supply of light.With both the largest growing area and the highestcapability to utilize light, wheat will need by far thegreatest amount of light. It is planned to have 1250µmol/m2/s for the twelve hours of daylight and 1200µmol/m2/s of artificial light at night.

Aside from the crops just mentioned, all othercrops will use light during the day only. Throughoutthe approximate twelve hours of daylight on Mars,each will have six hours of “peak” LED output (withthe exception of wheat). This six-hour period is thetime during which the LEDs will have enough of apower budget to run at their specified maximums.The first six daylight hours will be the peak time forrice and peanuts. The second six hours will be thepeak time for soy, sweet potatoes, strawberries, andlettuce. Staggering the peak times in such a way low-ers the maximum amount of power necessary by 11.7kW. Base values and peak values of photon flux den-sity are broken down by crop in Table 30. LED powerallotments are such that crops are somewhat depen-dent upon incident sunlight. However, in the case ofa complete blockage of incident light, the LEDs alonewill be able to meet minimum requirements.

Setting a maximum power limit on the LEDs anddepending upon sunlight means that light deprivationcould potentially occur if there is significant blockageof sunlight. The only plants completely dependent

upon sunlight are potatoes, which, because of theirextremely low light requirement, will still grow duringa global dust storm. All other crops will have supportby artificial lighting. Enough power will be availableat all times of the production cycle to meet minimumlight levels of 50 W/m2 on LEDs alone.

E Elastomer-Seal Trade Study

Please refer to Table 32.

F Nomenclature

A: Date of First Crew ArrivalALS: Advanced Life SupportAFT: Aerated Flow TechniqueCCD: Charged Coupled DeviceCDHSS: Command and Data Handling SubsystemCDR: Conceptual Design ReviewCELSS: Controlled Environment Life Support Sys-temCOTS: Commercial, Off-the-ShelfDDR: Detailed Design ReviewDRM: Design Reference MissionDSN: Deep Space NetworkEDL: Entry, Descent, and LandingEFT: Ebb and Flow TechniqueERV: Earth Return VehicleEVA: Extra Vehicular ActivityFFT: Fog Feed TechniqueITO: Indium-Tin-OxideISRU: In-Situ Research UtilizationLED: Light Emitting DiodeLEO: Low Earth OrbitMAV: Mars Ascent VehicleMDG: Mars Deployable GreenhouseMICAGG: Mars In-situ Carrier Gas GeneratorMIP: Mars In-Situ Propellant Production PrecursorNFT: Nutrient Film TechniqueNTR: Nuclear Thermal RocketOD: Optical DepthPAR: Photosynthetically Active RadiationPC: Polycarbonate PDR: Preliminary Design ReviewPPF: Peak Photon Flux

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Resistance to:Tears Abra- Gas H2O Ozone Sun- Radiation Temp. (◦C)

sion Perme- Absorb- light (25% Dam- Low Highability tion age Dose)

Natural 4 5 3 5 3 2 2.50e7 -55 90RubberStyrene 3 3 3 5 3 3 1.00e7 -50 100ButadieneEthylene 4 3 2 5 5 5 -50 150PropyleneNeoprene 4 5 4 4 5 5 6.00e6 -40 100Nitrile 3 4 3 4 3 4 7.00e6 -40 100Silicone 2 2 3 4 5 5 4.00e6 -60 100Urethane 5 5 3 3 5 4 4.30e7 -25 100RubberFluorocarbon 3 4 5 5 5 1.00e6 5 -20 200

Table 32: Elastomer Trade Study, (Scale 1-5, 5 is best)

RH: Radiation HardenedRMT: Root Mist TechniqueSAT: Static Aerated TechniqueSBFC: Sodium Borohydride Fuel CellSE: Sabatier ElectrolyzerTCSS: Telecommunications SubsystemTMI: Trans-Mars InjectionUV: UltravioletZE: Zirconia Electrolyzer.

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G Outreach Status Report

G.1 Olin College Outreach

As a new college, Olin is pursuing an aggressive andexpansive advertising campaign for its own purposethat was easily redirected to supporting the Outreachmission of Olin’s MarsPort team. It is in Olin’s bestinterests to advertise its successes in this type of na-tional competition. The fact that more than half ofOlin’s student body is participating in the MarsPortCompetition provides further incentives for Olin tosupport and publicize its MarsPort team with its ownresources. This effort has already born fruit and willcontinue to do so well past the end of this school year.

G.2 Community Outreach

Olin’s MarsPort team understands the importance ofoutreach both to the competition and to the college asa whole, and this is why roughly 7 members of Olin’steam is currently involved in the outreach componentof the project. Olin’s prospective and current stu-dents, faculty and staff are very connected to and in-terested in the space program. The external commu-nity is therefore the focus of Olin’s outreach program.The goal of this program is to excite people, who cur-rently hold limited interest in space, about the ideaof space exploration. Community outreach can bebroken down into two segments: youth-focused andat-large. The team’s website will serve as the focalpoint of its outreach efforts, though it is not the onlymethod of content delivery that will be used.

G.2.1 Youth Outreach

Erika Brown, a previous member of MIT’s NASAMeans Business Team and the educational coordina-tor for the New England Mars Society, and 5 mem-bers of Olin’s team who have experience in develop-ing engineering education materials for the JASONfoundation, facilitate the youth component of Olin’soutreach campaign.

The Olin MarsPort team’s website(projects.olin.edu/marsport) provides a meansof reaching students worldwide (though, in practice,

the team’s efforts will be limited to English speakingstudents). The website will soon include models ofthe greenhouse’s outer structure and interior createdwith CAD modeling software by members of theteam.

A Choose Your Own Adventure Story was addedto the website in December. This story is orientedtowards students in grades 6-8, and follows the modelof the popular book series by the same name. In thisstory, the reader discovers that he or she has awokenin a strange, and unfamiliar location, which turns outto be the surface of Mars. The reader is compelled tochoose the paths to be taken by the main characterand determine whether he or she will be rescued fromthe barren surface.

The primary focus of Olin’s youth outreach effortsis an educational kit for use in grades 4-8. The kitprovides assistance to teachers in teaching their stu-dents about space. It has two components: inter-active in-class learning activities and an online edu-cational resource nexus for teachers. The interactiveactivities are created by the team and are intended tobe run with low financial overhead. Currently theseactivities include a solar light demonstration as wellas planetary size and distance comparison activities.The activities allow students to learn through obser-vation instead of lecture. Other activities are cur-rently being developed, including a bingo game thatwill test students’ knowledge about space, the sun,and the planets in our solar system.

The educational resource network will be a multi-phased project. It provides “one-stop shopping” toteachers interested in teaching material relating toouter space. This information will be separated intoseveral categories including course syllabi, activities,and information. The information will also be cate-gorized by subject matter. The first phase involvedlocating a wealth of existing educational material on-line and adding links to this material on the team’swebsite. The team will then provide overview sum-maries of each source of online material as well ascritically evaluating the content for usefulness. Thiswill allow teachers to visit our website and get directaccess to quality materials that will help them withtheir instruction. Teachers will not have to wastetime searching for quality materials relevant to their

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subject matter. The focus of our project is to compilein-class activities into one site.

This kit will be refined throughout the summerwith regular checks on each set of online materi-als to note new additions or any change in qual-ity. These kits will be refined based on feedbackreceived from the science department of RooseveltMiddle School in Eugene, OR and with perhaps addi-tional feedback from Pollard Middle School in Need-ham, MA. Once the team is satisfied with the nexusand other materials, it will publicize these materi-als to a much larger educational community. Theteam has received support for this from Dr. IoannisMiaoulis, Dean of Engineering at Tufts University,who has championed the introduction of engineeringstandards into the Massachusetts K-12 CurriculumFrameworks Program. This support will be useful inpublicizing the team’s materials and resources to thelarger educational community. This increase in pub-licity will likely occur primarily during the summerand next fall as instructors prepare for their courses.

The team explored assisting the New EnglandMars Society in its Boy Scout Space Merit Badge pro-gram. The Mars Society has already developed mate-rials for this use, but the support of Olin’s MarsPortteam members would allow these materials to reachmore students than ever before. Unfortunately, thisprogram was rescheduled from its original date onMay 4th to May 29th by the Mars Society and noneof Olin’s MarsPort team members are able to partic-ipate. However, the Mars Society has given permis-sion for some of the materials used in this Space MeritBadge program to be displayed on our site providedthey were cited as the source. After a few small editsare made to content, these materials will be online.Expected date of posting is on or before May 8th.

Representatives from Olin’s MarsPort team hadthe opportunity to attend a discussion with JohnPickle, Program Manager for Global Systems Sci-ence at the Museum of Science in Boston, at MITon Thursday, April 18. This discussion focused ona proposed “Mars Classroom.” This “classroom”would be a series of educational programs or activitiesthat would be hosted by the Museum of Science foryoung children. The concept of the MarsPort compe-tition and a greenhouse on Mars intrigued Mr. Pickle

greatly. In reporting possible projects that the Mu-seum of Science could pursue for its classroom, Mr.Pickle specifically referenced both Olin’s team web-site and the main MarsPort site as locations to in-vestigate for the classes. The team was able to con-tribute valuable information to the discussion. An-other of the final projects that came from the ses-sion was a “Choose your own Adventure” activitythat would allow students to determine which inves-tigative exercises they wish to engage in. The teamis well positioned to assist the Museum of Scienceas its project progress, and help spread the name ofboth Olin and the MarsPort Competition to new au-diences. Mr. Pickle requested copies of our PDR andDDR reports, so that he could be up-to-date on theprogress of our design and project.

G.2.2 At-Large Outreach

The year: 2009.The place: Mars.The plotline: outrageous.This is The History and Mystery of Mars.(cue music)

The History and Mystery of Mars is a monthlyradio drama written, performed, directed, recorded,edited, produced, and broadcast by the Olin CollegeMarsPort Team. The idea is simple, the narrativeverbose, and the plagiarism apparent. The series hasmany purposes. First and foremost its purpose is toinspire interest in the stars above and the unknownworld still yearning to be explored. Second, and onlyslightly less foremost, it seeks to illustrate that OlinCollege is not just an engineering school; it is a schooldriven by creativity and innovative ways of approach-ing challenges. Third, it is meant to make peoplelaugh. Fourth, the series is meant to document thepersonal peeves of the authors, as any good parodywould. Fifth, and perhaps most shrewd, it was in-tended to add an extra incentive for the judges tochoose Olin College as a finalist, knowing that if theydidn’t, they would never hear the climatic series fi-nale that will be the topic of conversation for monthsto come.

The outrageous plot is as follows: it is assumedthat NASA actually plans to launch a deployable

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greenhouse, based on designs submitted to them ina student competition, to the planet Mars. It is alsoassumed that the planet Mars is inhabited by greenbug-eyed monsters with antennae who live below thesurface, and who have been aware of the existenceof Earthlings for some time. The Martians are asignificantly advanced race, but highly xenophobic.However, once they learn of Earth’s manned mis-sion attempt to Mars, they overcome their timidityand develop Operation Greeting, the Martian UnifiedGovernment’s plan of making first contact with theEarthlings. Of course, as in most stories, things arenot always what they seem.

The History and Mystery of Mars draws it’s in-spiration from great classics such as Douglas Adam’sThe Hitchhiker’s Guide to the Galaxy and OrsonWelles’ War of the Worlds, and draws its fans fromexotic places like New Jersey. It is hoped that by lis-tening to the series, interest in space projects and theMarsPort competition specifically will be spawned. Itis also hoped that a small glimpse into the world ofOlin College might be gained from the experience.

Currently, the first five installments of The Historyand Mystery of Mars are available from Olin’s Mars-Port website at http://projects.olin.edu/marsport.The shocking finale will be produced and online byMay 13th. A special educational episode, featuringthe stars of the show describing the Olin greenhouseconcept, is also in the works. Efforts are being madeto get college radio stations to play History and Mys-tery to their audiences. The radio stations of bothBabson College and Wellesley College have been con-tacted. Babson has given no response yet, but we re-main hopeful given the close natures between Babsonand Olin College. Wellesley has responded enthusias-tically, but has not yet given a concrete commitment.

Flower Show A key component of Olin’s outreachplan is to spread the benefits of space exploration tothose who may not necessarily appreciate the oppor-tunities presented by such exploration. The crux ofthis effort was the creation of a booth at the NewEngland Flower Show, which was attended by ap-proximately 175,000 visitors.

Exposing horticultural enthusiasts to the impor-

tance of Mars exploration is a very different outreachapproach. It is both worthwhile and important to ed-ucate the average individual about the prospects ofMars exploration and how useful such missions canbe. These horticultural enthusiasts are able to con-nect with the MDG due to their own interests andare therefore inspired to develop an interest in thespace program.

As part of the outreach efforts, Olin’s NASA de-sign team worked with juniors and seniors from Need-ham High School in Needham, Massachusetts, toplan and create a display booth at the New EnglandFlower Show, held at the Bayside Exposition Centerin Boston during March 16th - March 24th. One ofthe main goals of this project is to help create enthu-siasm for Mars exploration in high school students.Due to a high level of interest on the part of the stu-dents, they also contributed their skills as researchassistants to Olin’s team. The high school students’research included background research on launch ve-hicle payload mass and volume. Their participationin actual research for the project enabled them to bebetter-informed managers of the booth for the FlowerShow.

The high school students were designed and cre-ated the booth under the guidance of Olin’s MarsPortteam. A true understanding of all the important de-sign topics was expected from the students, as theystaffed the booth during the Flower Show in March,while the Olin’s students were in France for an inter-national experience.

The MarsPort booth at the Flower Show incorpo-rated a large variety of information in a visually pleas-ing format. It included three informational posters, acomputer slide show of the CAD models of the green-house, sample plants grown using a hydroponics sys-tem, a sample of Moon soil, and a sample of sim-ulated Martian regolith, along with handouts thatdescribed the design competition and Olin’s partici-pation therein. The posters included such informa-tion as crop selection, the hydroponics system, andthe nature of the competition and booth. There wasa computer at the display booth that allowed visitorsto observe a CAD animation. Olin team membersused 3D Studio Max to design these models.

In terms of press coverage, Chris McArdle, Olin’s

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Director of Communications, Joseph Hunter, andOlin’s Vice-President of External Relations, DuncanMurdoch promoted the MarsPort booth at the show.From Olin’s perspective, this outreach program as-sisted in the formation of a stronger bond betweenOlin College and the Needham community at large.Therefore, support from the College was very forth-coming. Olin College personnel staffed the boothwhen the high school participants were unavailable.

The following are excerpts from an out-brief of theFlower Show activity written by Vice President ofExternal Relations, Duncan Murdoch:“The New England Flower Show is the largest eventin New England. More than 175,000 guests visitedthe Bay Side Exposition Center between March 15and March 24. Olin Partners worked closely withthe show’s organizers to build a booth for displayingthe NASA MarsPort Design Project for the educa-tion and benefit of a wide range of audiences. Thebooth was strategically located just to the right ofthe Expo Center’s main lobby entrance adjacent tothe Flower Show’s information center for official pro-grams. I estimate that 80 percent of the guests no-ticed our booth, as we were the first exhibit they saw,and several thousand actually stopped to learn aboutthe project and the college.

“Booth design - the booth was “L” shaped in an 8’x 12’ space. A computer animation of the deployablegreenhouse and handout information were displayedon skirted tables along with hydroponic plants, grownby Needham High School students. Large four-colorposters explained in text and graphics the hydroponicsystem and the crops that were to be grown on Mars.A professionally produced 4’ x 8’ cloth banner, fea-turing the NASA logo, announced and advertised thebooth. Simply put, we had the best location in theshow and we could not be missed. Moreover, the “au-thentic” - “simulated” Martian and Moon Soils thatNASA provided were magnetic in attracting visitors- especially children.

“Media - News articles and photos about theproject appeared in the Needham Times and theproject was listed in the Flower Show program. Aphotographer took pictures of the Needham studentsstaffing the booth and greeting the President of theMassachusetts Horticulture Society...

“A wide range of guests visited the booth - fac-ulty from MIT and Tufts, CEOs of high tech compa-nies, high school and elementary teachers, televisionproducers and news broadcasters, scout troops, ele-mentary students and the general public. Most weredrawn to the booth by the MarsPort Project and werefascinated by the idea of pre-college students at a“college that doesn’t exist” successfully participatingin a NASA competition. Needham townsfolk wereespecially pleased to see their high school studentsparticipating in the program and staffing the booth.

“By encouraging middle school and elemen-tary school children to grow plants hydroponically,younger students could be introduced to the funda-mental aspects of designing engineering systems.

“Student Participants from Needham HighSchool: Zach Cicala *, Andy Dunn *, Sam Kesner,Sophia Kogan *, Dan Korsunsky, Alla Lazebnik *,Bobby Liu, Ben Mullican *, Adam Nir *, Evan Patey*, Laurel Powers *, Dan Schlauch, Brian Stam, LeifRehberg (* Denotes the students who staffed thebooth in evenings and on weekends.)

“Needham students grew the demonstration plantshydroponically, designed and produced parts of thedisplay (posters), helped set up the booth and staffedthe display. Needham faculty who were involved inthe project include, Mr. Hamblin, Ms. Frenkel andMr. Lockhart, who was especially helpful in locatingstudents during the school day and relayed impor-tant messages to and from the high school and thecollege.”

Upon their return from France, Olin’s MarsPortteam members began to create professional levelposters that advertise the competition and Olin’s par-ticipation in it. These posters include informationon the Martian atmosphere, Olin’s unique MDG de-sign, crop selection and plant support systems. An-thony M. Schilling, Operations Director, Unicco In-tegrated Facilities Services, has expressed significantinterest in hosting this display in at least one mall.This display might include information from otherSpace projects including TransLife. Unfortunately,due to construction at the mall this component ofthe project has been delayed. Nevertheless, it is ex-pected that these posters will be displayed in a varietyof locations during the summer.

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For both technical assistance and a possible out-reach venue, the team also contacted Disney Corpo-ration, which operates The Land greenhouse projectat EPCOT Center. They provided useful informa-tion, but could not make any commitment to displayour exhibit.

Culinary Schools Originally the team hadplanned to conduct a local competition among culi-nary experts as part of its outreach plan. The goalof this activity would be to inspire professional chefsto generate recipes using only ingredients that wouldbe available to the astronauts on Mars. The recipesconcocted in such a bake-off could be used to furtherincrease the quality of living for the astronauts onMars through creative and appetizing preparation ofthe MDG’s crops.

After much consideration, the team decided thatcompetition was not the best way to spread inter-est in the project among culinary schools across thenation. Therefore, Olin’s MarsPort team contactedover 200 culinary schools across the nation and re-quested assistance in generating recipes for astronautuse instead. The request for assistance included in-formation on foods currently available on the SpaceShuttle that might be similarly available on Mars, aswell as the cooking methods currently available to as-tronauts in space. Several of these schools respondedvery positively to our request for assistance. Unfor-tunately they report that they have not yet had suf-ficient time to perform their research. It is expectedthat recipes will be provided to the team soon andthey will be added to our website as they arrive.

Publications A key component of the Olin Mars-port team’s outreach has been external press cover-age. Chris McArdle, the professional journalist at-tached to the Olin team, is a freelance writer whosearticles have appeared in the Boston Globe. She hasmade contact with an editor at each of the student’shometown papers across the country and has sentout press releases and photographs. As a result, ar-ticles have appeared in the following papers: OakLeaves, Oak Park, IL, Rutland Tribune, VT, Char-lottesville Observer, VA, La Crosse Tribune, WI, Lee-

ward Courant, HI.Ms.McArdle has also arranged an in-depth inter-

view for Sean Munson, Olin’s Marsport Project Man-ager, with Pat McDaniel, Saturday People Editorat Asbury Park Press, NJ and for Jessica Andersonwith Ms. Archuleta of the Albuquerque Tribune, NM,when the students return home at the end of May.Both papers wanted photographs taken by their ownphotographers.

Editors have expressed interest in the project atthe following papers: Palo Alto Weekly, CA, Hon-olulu Advertiser, HI, Essex Reporter, VT, and ThePanatagraph, Bloomington, IL. Ms. McArdle is hope-ful that a story will appear in these papers in the nextweek.

Ms. McArdle also has stories out to the Albu-querque Journal, NM, The Register Guard, Eugene,OR, The Day, CT, La Jolla Light, CA, and San JoseMercury News but has yet to follow these up. Eachpublished article has been the result of several roundsof phone calls and emails!

To date, Ms. McArdle has concentrated on home-town papers across the country but will now turn herattention to the Boston papers - the Boston Globe,Boston Herald and Boston Phoenix. She hopes tointerest the Boston Globe in a story on the final pre-sentations.

Joseph Hunter, Olin’s Director of Communica-tions, has also been extremely instrumental in pro-moting the team’s outreach program. A news itemran on Olin’s success with the MarsPort project inthe Boston Globe and two stories ran inthe NeedhamTimes, MA.

A February 5 article on Olin College appeared inthe Christian Science Monitor and included a de-scription of the team’s participation in the MarsPortproject.

Olin College publishes a newsletter Innovations,distributed to prospective students as well as cor-porate and educational leaders, and the most recentedition included an article about Olin’s participationin the MarsPort competition. Similarly,the tabloidstyle O.V.A.L. is sent to any high-school student ex-pressing interest in Olin and its second issue includedan article on MarsPort. The Babson Free Press, thestudent newspaper of Babson College.

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Name of Publicity Direct Mention Expected Positive Awaiting PublicationResponse Response Date

Babson Free Press 2,500 OctO.V.A.L. 3,500 Nov/DecNew England Flower 175,000 March 16-24Show, Boston, MABoston Globe, MA 86,823 Jan 3Needham Times, MA 11,700 Jan 31Leeward Current, HI 20,000 FebNeedham Times, MA 11,700 Apr 4Innovations (Olin) 6,000 MayOlin MarsPort Site 1,015 as of 04/19Olin Website 187 as of 04/19Press ReleaseOak Leaves, IL 10,700 May 1Forest Leaves, IL 2,400 May 1Charlottesville Observer 31,000 May 1VirginiaRutland Tribune, VT 16,155 May 3Christian Science 400,000 Feb 5 (print)Monitor 95,000 Feb 5 (online)La Crosse Tribune, WI 33,000 Exp. May 4/5Asbury Park Press, NJ 160,000 Exp. May/JunAlbuquerque Tribune 23,000 ExpectedNew Mexico June/JulyHonolulu Advertiser 153,666 Exp. MayHawaiiPalo Alto Weekly, CA 50,000Essex Reporter, VT 7,500The Pantagraph 50,000Bloomington, ILAlbuquerque Journal 130,0000New MexicoThe Register Guard 75,000Eugene, OR 75,000The Day, CT 42,000La Jolla Light, CA 31,000San Jose Mercury 284,000Press, CASub totals: 372,680 495,000 369,666 107,500 562,000

Total: 1,906,846

Table 33: Outreach Exposure

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Figure 17: Needham Times Coverage

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G.3 Conclusion

The Outreach Program reached a high level of expo-sure, both in terms of quality (working closely overa multi-month period with high school students) andquantity (867,680 to date with 1.9 million plus possi-ble). In addition, the team has reached a geographi-cally diverse audience with a variety methods thatwill appeal to different demographics, such as thehigh school students and science fiction enthusiastsattracted by The History and Mystery of Mars andthe gardeners reached at the New England FlowerShow.

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H Team Biographies

Sean Munson, Project Manager. Since sub-mitting a crude battleship design to the Navy inkindergarten, Sean has had his sights set on engi-neering. Over time, he developed a strong inter-est in aerospace, and designed a replacement for thespace shuttle in seventh grade, the result of which hewas able to present to NASA engineers at MarshallSpace Flight Center. Sean attended High TechnologyHigh School in Lincroft, New Jersey. During his fouryears at High Tech, Sean participated in the FIRSTrobotics competition, completed a research project inmagnetic levitation and linear induction, and was anactive student leader. Also an accomplished web de-veloper, Sean has worked both as a consultant andat a medium-size video conferencing company. Seanis also an Eagle Scout and active as a Section Officerin the Order of the Arrow, Boy Scouting’s NationalHonor Society. At the present, Sean is one of 30 OlinPartners helping to develop the college’s academicprogram and student life before becoming part of theclass of 2006.

Joelle Arnold, Power Systems. Joelle comes toOlin College from Middletown Springs, Vermont. Co-captain and founder of her policy debate team atRutland Senior High School, she has trophied in sev-eral regional competitions. High school achievementsalso include Junior Engineers and Technicians Soci-ety President and lead trombonist in RHS’ state rec-ognized Jazz Band. She has also been employed bySSESCO/Sage Physics and Engineering of St. Paul,Minnesota, where she uses computational fluid dy-namics to model diesel engines. In the summer of2000, she researched for SSESCO investigating thestate of Acoustical Modeling software, a project forwhich she was recognized as and Intel Science TalentSearch Semi-Finalist and a Finalist at the NorthernNew England Junior Science and Humanities Sympo-sium. A staunch advocate of a “renewable” future,free time finds her listening to her favorite folk artistsof SolarFest, wrestling with her collies and playingbridge.

Katerina Blazek, Engineering. Kate is a grad-uate of Henry M. Gunn High School, Palo Alto, Cali-fornia, who originally hails from the Czech Republic.She was a member of the nationally ranked GunnFIRST Robotics Team, where her specialty was cre-ating pneumatic vice grips and devices to move balls.Kate also led the community outreach part of theteam and headed the video production group. Shespent her summer at Xerox Palo Alto Research Cen-ter (PARC) making a documentary about interns,doing production support, and learning about thevirtues of caffeine and Macintosh editing systems. Inher spare time, she translated a textbook about themethods of coloring glass and volunteered at Record-ing for the Blind and Dyslexic. Since coming to OlinCollege, Kate has concentrated on fielding questionsand comments about her dyed-red hair and not get-ting lost in Boston.

William Clayton, Outreach Coordinator.Will graduated from Henry D. Sheldon High School,Eugene, Oregon, at the top of his class with an Inter-national Baccalaureate Diploma as well as an Hon-ors Diploma. Will enjoys travelling and participatedin the People to People Student Ambassador pro-gram between his junior and senior year. He wasSheldon’s Outstanding Chemistry Student and Out-standing Mathematics Student during his senior year.Will was selected as one of the Franklin W. Olin Col-lege of Engineering’s first 30 students, the Olin Part-ners. Outside the classroom William is interested increative writing, reading, philosophy and computers.William is currently a founding member of the Need-ham Olin Technology Exchange, which refurbishescomputers and provides them to primary and sec-ondary school students in need, and is a staff writerfor the Babson Free Press. William’s interest in en-gineering can be traced back to his childhood whenhe spent much time building with LEGOs. He hasalways been interested in space and the concept ofspace travel. William is very interested in roboticsand hopes to work on cybernetics and robot/humaninteraction throughout his career.

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Susan Fredholm, Materials Science. Susan hasalways enjoyed math and science but recently be-came interested in materials science after attendingASM International’s first Materials Camp in August2000. When not doing academic work, she purses herlife long passion for dance by continuing to perform,study and teach. She graduated from Alvirne HighSchool in Hudson, New Hampshire, in 2001 and isvery excited to be an Olin Partner.

Matthew Hill, Materials Science & Structures.Matt is a graduate of Oak Park and River Forest HighSchool, where he was academically active as a mem-ber of both the Scholastic Bowl and Math teams.Outside of the classroom, he has also played var-sity volleyball and earned national recognition for hisartistic abilities as a potter. Currently, Matthew isone of thirty student partners at F.W. Olin College ofEngineering who is working with faculty to developthe curriculum and student life for the college’s open-ing in fall 2002. He continues to pursue his interestsin art and athletics, and is a founding member and co-director of the Needham Olin Technology Exchange,a volunteer student group that refurbishes computersfor needy area children.

Adam Horton, Botany & Engineering. Agraduate of Essex Junction High School from West-ford, Vermont, Adam was fascinated with advancedBiology and Botanical Science in high school. Adam’sdesire to tinker, build, and create have led him toundertake such tasks as designing and building theGeodesic dome he lives in with his family and restorea 1972 VW Beetle. Adam is also interested in sym-biotic relationships especially in biological systems.Outside interests include acting, singing and helpingto create Olin College.

Grant Hutchins, Outreach. Grant graduatedfrom Santa Fe High School in Edmond, Oklahoma.His interests include writing electronic music andlearning about anything he can, especially cryptog-raphy and the history of computing. He made hisfirst “animated movies” with a friend on his V-TECHVideo Painter that he received for Christmas in third

grade. He also enjoys playing many different musicalinstruments (none very well), and was the captain ofhis school’s nationally competitive academic team.Grant’s favorite experience was spending a monthin Japan with his best friend Souichirou. Grant en-joys working with the MarsPort team while produc-ing The History and Mystery of Mars.

Cheryl Inouye, Botany. Cheryl recently gradu-ated from Pearl City High School in her home stateof Hawaii. Her interest in the NASA competitionstems from early childhood books such as The MagicSchoolbus: Lost in the Solar System. Cheryl enjoysscience and helped to start her high school’s ScienceBowl Team. One of her first projects at Olin Col-lege, Biodiversity, sparked Cheryl’s devoted passionfor plants and ecology. When not studying, she likesto play music and practice martial arts.

Steven Krumholz, Outreach & Engineering.Steven graduated from Monticello High School, Char-lottesville, Virginia, where he was not only captain ofthe chess and academic teams, but also was the stu-dent ambassador to his school’s improvement team,representing the student body to the faculty andcounty Board of Education. He was on a state-ranking Odyssey of the Mind team, and was namedthe school’s most outstanding student in both mathand science. As a senior, he started a card gamecompany with a friend as an independent study, anddonated all of the company’s proceeds to his schoolas charity. This extroverted, playful dreamer is cur-rently one of the 30 Olin Partners. When not inschool, Steven is usually found playing games, admir-ing penguins, or watching sports (especially hockey).

Daniel Lindquist, Outreach / CAD. Dan is agraduate of the Porter-Gaud School in Charleston,South Carolina, where he was an active member ofthe Faraday’s Candle Science Club, Scholastic Bowl,and National Ocean Science Bowl Team. He also be-gan a computer club which focused on designing astudent run webpage for the student body. Dan’s loveof engineering, entrepreneurship, and all things com-puter related made Olin College, his current place of

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study, a perfect fit, and he is excited about contribut-ing to the NASA design project.

Que Anh Nguyen, Outreach. Que Anh gradu-ated from Andrew P. Hill High School in San Jose,California, where she was the battalion commander ofher high school JROTC unit. During her high schoolyears, she also held the office of class president, aswell as served as Supreme Court Chief Justice. QueAnh’s interests, besides leading and coordinating, in-cludes everything from robotics, astronomy to swim-ming, singing and tennis. Her primary interests how-ever lies in Engineering and Research. She spent hersummers doing thin film technology research at theAdvance Materials Laboratory in Albuquerque, NewMexico and working as an intern at IBM’s office inSan Jose. Que Anh is involved in the outreach efforts,focusing on coordinating the Mars display booth atthe New England Flower Show.

Joy Poisel, Outreach. Joy graduated fromBloomington High School in Bloomington, Illinois.There she was actively involved with the Environ-mental Club and Scholastic Bowl. She was a medal-list in the annual World Wide Youth in Science andEngineering (WYSE) and won multiple state medalsat Science Olympiad competitions. Joy’s interest inthe stars grew from her love of Science Fiction novelsand TV shows. Joy is currently an Olin Partner.

Nicholas Zola, Outreach Nick has wanted to bean astronaut ever since he was a kid, although origi-nally it was merely for the chance to float around infree fall. Since then, he has a developed a keen appre-ciation for the vastness and complexities of space. Hehopes one day to work for NASA; until then, he is re-signed to devoting his time to research projects likethis one, including an astrophysics research projecton supernovae centered at Harvard University. Al-though Nick often finds himself on other planets dur-ing design competition meeting, his ultimate goal isto actually land on Mars someday. Nick graduatedfrom La Jolla High School in San Diego, California,before coming to Olin College.

H.1 Phase I Team Members

Jessica Anderson, Outreach. Jessica, a gradu-ate of the Valley High School and Academy in Albu-querque, New Mexico, became interested in astron-omy and space while taking a basic Astronomy courseduring her senior year of high school. A dancer sincethe age of three, her passion for life spans a plethoraof areas. She is intrigued by knowledge and plans tofervently study all she is able to during her careerat Olin. The opportunity to be an Olin Partner isone she will feel gratitude for and dismay at forever,while acknowledging that without the support of herfamily and her faith in God she would not have beenable to achieve all she has.

Nicole Hori, Botany. Nicole is a resident ofHonolulu, Hawaii and a recent graduate of UpperColumbia Academy in Spangle, Washington, whereshe started a science club. Nicole is currently an OlinPartner. For Nicole, work on the MarsPort projecthas become a lifestyle, offering opportunities for in-side jokes and satisfying pure intellectual curiosity.Nicole is also a vegetarian who understands the chal-lenges in creating a nutritional and appealing dietfrom plants. Her other research interest is in celland molecular biology, and she intends to eventuallyfind a career in biotech. This summer she travelledthrough Lima, Peru and San Francisco to Seattle,where she began a cross-country road trip that even-tually brought her to Needham, Massachusetts. Inher spare time, Nicole plays the guitar and enjoysvisual arts.

Ann Marie Rynning, Materials. Ann Marie be-came interested in engineering, science, and spacetechnologies at a young age. This was mainly dueto the influence of her grandfather, an engineer, whohelped her work on various projects in these ar-eas. Ann Marie came to Olin after graduating fromMontville High School in Connecticut.

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I Co Investigators

Stephen S. Holt, Professor of Physics. Dr.Stephen Holt, an astrophysicist, was previously theDirector of Space Sciences at the NASA-GoddardSpace Flight Center in Greenbelt, Maryland.

Dr. Holt received a B.S. degree with honors in En-gineering Physics and a Ph.D. in Physics from NewYork University before joining the staff of the God-dard Space Flight Center. His primary research dis-cipline is high-energy astrophysics, the study of theuniverse via the detection and interpretation of celes-tial X-rays and gamma rays. He has been selected tobe Principal Investigator and/or Project Scientist oneight NASA scientific spacecraft, including joint mis-sions with Germany, Japan, Russia, and the UnitedKingdom. He has more than 200 refereed publica-tions in technical journals and scholarly books, andhas been awarded the NASA Distinguished ServiceMedal, the NASA Medal for Exceptional ScientificAchievement, and the John C. Lindsay MemorialAward for Outstanding Science. He is a Fellow ofboth the American Physical Society and the Ameri-can Association for the Advancement of Science.

Dr. Holt has served on numerous nationaland international committees such as the NationalAcademy of Sciences’ Space Science Board Commit-tee on Space Astronomy and Astrophysics, the Na-tional Academy of Sciences’ Panel on Science Policy,and the Executive Committee of the American Physi-cal Society. He has been elected Chair of a number ofscientific society venues, including the High EnergyAstrophysics Division of the American AstronomicalSociety and multi-national Joint Scientific ProgramCommittee of the World Space Congress.

An outstanding teacher and a lecturer, Dr. Holthas taught in both the physics and astronomy depart-ments at the University of Maryland, and has beeninvited to make more than 100 major presentationsat scientific society meetings and international sym-posia. Dr. Holt also serves as Director of Sciencesand Professor of Science at Babson College.

Erika Brown, Graduate Student, MIT. ErikaBrown is a graduate of Vanderbilt, where she receiveda BS in biomedical engineering. Erika is also a grad-

uate of the International Space University’s SummerSession program. She has worked for both Lockheed-Martin in Houston and Boeing in Huntsville, Al-abama. Last year, she was a member of MIT’s NASAMeans Business team, which produced a project ti-tled “2020 Vision.” At MIT, she works in the MITmanned-vehicle lab investigating adaptation to arti-ficial gravity systems for long duration space flight.She is the led for the MIT TransLife biosatelliteproject. She is the educational coordinator for theNew England Mars Society, where she organizes ed-ucational events. She is also the Outreach Coordi-nator for bioengineering education for the VaNTHconsortium. As Outreach Coordinator, she works onnational K-12 outreach for biomedical engineering,including the development of curriculum to be usedin grades K-12.

Woodie Flowers, Pappalardo Professor of Me-chanical Engineering, MIT. In addition to hisMIT position, Dr. Woodie Flowers is also a Dis-tinguished Olin Partner. He received a B.S. fromLouisiana Tech University and S.M., M.E., and Ph.D.degrees from MIT. His current research includes workon the creative design process and product develop-ment systems. He helped create MIT’s renownedcourse “Introduction to Design.” Dr. Flowers hasreceived national recognition in his role as host forthe PBS television series Scientific American Fron-tiers from 1990 to 1993 and received a New EnglandEMMY Award for a special PBS program on design.

He is a member of the National Academy of En-gineering, a Fellow of the American Association forthe Advancement of Science and recipient of an Hon-orary Doctor of Humane Letters from Daniel WebsterCollege. He was recently selected to receive a Pub-lic Service Medal from NASA and the Tower Medal-lion from Louisiana Tech University. At MIT, he isa MacVicar Faculty Fellow, an honor bestowed forextraordinary contributions to undergraduate edu-cation. He was also the inaugural recipient of theWoodie Flowers Award by FIRST, a national orga-nization that promotes youth involvement in scienceand technology.

Currently, Dr. Flowers is a director of four compa-

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nies and is on the board of Technology Review mag-azine. He is a member of the Lemelson-MIT PrizeBoard Executive Committee, is National Advisor andVice Chairman of the Executive Advisory Board forFIRST; and is a member of the Historical Commis-sion in Weston, Massachusetts where he lives with hiswife Margaret.

G. Duncan Himmelman, Director of Welles-ley College Botanical Gardens. Dr. G. DuncanHimmelman received a B.A. in Botany and Historyfrom Hobart and William Smith College. He receiveda M.Sc. in Ornamental Horticulture from the Uni-versity of Guelph in Ontario, Canada. In 1990, heearned a Ph.D. in Ornamental horticulture with mi-nors in plant ecology and landscape architecture fromCornell University.

For the previous 20 years, Dr. Himmelman hasworked at Olds College in Olds, Alberta, Canada. Hewas Horticulture Program Coordinator from 1991-1994. He has been the Lead Instructor in the Hor-ticulture Program from 1996-present. From 1978to 1981, he was Assistant Nursery Manager for theMetropolitan Toronto and Region Conservation Au-thority in Ontario, Canada.

Dr. Himmelman is a member of several profes-sional societies. Since 1977, he has been a member ofthe American Association of Botanical Gardens andArboreta. In 1982, he became a member of the Land-scape Alberta Nursery Trades Association. He is alsoa member of the International Society of Arboricul-ture, specifically the Prairie Chapter.

Christine McArdle, Journalist Dr. McArdleholds B.A. (Hons) and Ph.D. (Medicine), Glasgow,Scotland. In 1972, she served as Publications Direc-tor for the City of Edinburgh, Scotland. Dr. McArdlehas also worked as a medical researcher in Scotlandand as the Publications Director, for Project Softwareand Development Inc.. Currently a freelance writerwhose articles have appeared in The Boston Globeand The TAB., Dr. McArdle is known for her arti-cles on rail travel across America. She is also a guideat Arnold Arboretum in Boston and a naturalist forthe Appalachian Mountain Club.

Jonathan Stolk, Assistant Professor of Me-chanical Engineering and Materials Science.Dr. Jonathan Stolk joined Olin College from Buck-nell University, where he served as a Visiting Assis-tant Professor.

Dr. Stolk holds M.S. and Ph.D. degrees in Mate-rials Science and Engineering from the University ofTexas at Austin and a B.S. in Mechanical Engineer-ing from the University of Texas at Arlington. Be-fore joining Bucknell, Dr. Stolk was an Assistant In-structor and Graduate Teaching Assistant in the De-partment of Mechanical Engineering at UT Austin,where he taught the Materials Engineering lectureand laboratory courses. He received several teachingawards at UT Austin, including the Materials ScienceDepartment Exemplary Teaching Award, the Lock-heed Martin Teaching Excellence Award for Exem-plary Performance in Engineering Teaching, and theH. Grady Rylander Award for Excellence in Engi-neering Teaching.

Dr. Stolk’s Ph.D. research involved the devel-opment of new chemical synthesis techniques fornanocrystalline metallic and composite materialswith low thermal expansion and high conductivity.Dr. Stolk has research experience in corrosion fa-tigue behavior of carbon fiber-epoxy composites inhigh-pressure seawater, and he has many years of in-dustrial experience in the area of testing and failureanalysis of materials and components. Dr. Stolkalso worked as a Research Scientist at the Insti-tute for Advanced Technology, where he evaluatedthe performance of materials for use in electromag-netic launcher rail conductor applications. His cur-rent research is focused on the synthesis, processing,and characterization of novel metal alloys and metal-polymer nanocomposites with specialized mechani-cal, electrical, and thermal properties.

Dr. Stolk is passionate about engineering teach-ing and the development of new laboratory exper-iments, and he greatly enjoys working with under-graduate students on independent or group researchprojects. In two years at Bucknell, Dr. Stolk super-vised a dozen student projects. Several of his researchstudents have presented their work at national con-ferences, and he recently published the results of onestudent research project in a leading materials sci-

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ence journal. Dr. Stolk developed and taught a newAdvanced Materials lecture and laboratory course atBucknell, and was recently voted “Bucknell’s FavoriteProfessor” by first- and second-year students.

Mark H. Somerville, Assistant Professor ofElectrical Engineering and Physics. Dr. MarkSomerville joined Olin College from Vassar College,where he had been an Assistant Professor of Physicssince 1998. He holds M.S. and Ph.D. degrees inelectrical engineering from MIT, as well as an M.A.(first class honors) in physics from Oxford Univer-sity. He did his undergraduate work at the Univer-sity of Texas at Austin, where he earned a bachelorof science (highest honors) in electrical engineeringas well as a bachelor of arts (special honors) in lib-eral arts (English concentration). His academic hon-ors include the Joint Services Electronics ProgramDoctoral and Post Doctoral Fellowship, the Office ofNaval Research Graduate Fellowship, and the RhodesScholarship.

Dr. Somerville’s research focuses on the physics ofsemiconductor devices, with particular emphasis onhigh electron mobility transistors, which hold greatpromise for high-speed wireless and optical commu-nications. He is currently examining the use of lightemission to understand failure mechanisms in thesedevices; this work is supported by a Research at Un-dergraduate Institutions grant from the National Sci-ence Foundation.

Brian Storey, Assistant Professor of Mechani-cal Engineering. Before coming to the F.W. OlinCollege of Engineering, Dr. Storey was at the Uni-versity of California at Berkeley, where he completedhis Ph.D. in mechanical engineering in May 2000.

Dr. Storey holds an M.S. from the University ofIllinois at Urbana-Champaign, where he worked inexperimental heat and mass transfer, and a B.S. fromthe University of Texas at Austin. He has also workedin active sonar systems and underwater acoustics atUniversity of Texas Applied Research Labs.

Dr. Storey’s Ph.D. research involved detailed com-putational modelling of fluid dynamics, heat andmass transfer, and chemical kinetics in the study

of sonochemistry, an ultrasound-based chemical pro-cessing technique. His current research interests arefluid mechanics, computational science and engineer-ing, numerical methods, heat transfer, chemically re-acting flows, biomedical ultrasound, and geophysicalfluid dynamics. Dr. Storey is currently publishingin a leading journal the results of an undergraduateresearch project which he supervised at Berkeley.

Gill Pratt, Associate Professor of Electricaland Computer Engineering Before coming toOlin, Dr. Pratt was Associate Professor of ElectricalEngineering and Computer Science and a researcherin parallel computer hardware at the MassachusettsInstitute of Technology, where he received his Bach-elor’s, Master’s, and Doctorate degrees in ElectricalEngineering and Computer Science. As a member ofMIT’s AI Lab, he directed the MIT Leg Laboratory,focusing on the development of robots with legs anddevices for helping people walk. In his research Dr.Pratt and his students emphasized “series-elastic”actuators with more natural properties than indus-trial robots possess, and “virtual model” control lan-guages that allow natural dynamics and active con-trol to work synergistically. Dr. Pratt’s two-legged“dinosaur” robot was featured in a recent ScientificAmerican article.

Dr. Pratt received excellent reviews while teach-ing MIT’s core subject in computer architecture andhas served as both a member and a mentor to severalextracurricular student project groups. He is an en-thusiast of hands-on, “do-learn” education, and hasa strong interest in the societal aspects of technology,including “green” technologies like electric cars andlarger issues like the impact of robotics on the qualityof life.

J Consulting Members

Hillary Thompson Berbeco is an AssistantProfessor of Chemistry at Olin College. She receiveda National Science Foundation Graduate ResearchFellowship. As a Director’s Postdoctoral Fellowat Lost Alamos National Laboratory, Dr. Berbecoinvestigated the chemistry and thermodynamic

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properties of novel catalyst materials intended forfuel cell use. Dr. Berbeco is serving as a chemistryconsultant, especially in the area of fuel for powersystems.Jill Crisman is a Senior Olin Partner for Electricaland Computer Engineering at Olin College. Dr.Crisman’s research is focused in robotics, computervision, and graphic simulation. She is a consultantfor robotic systems, especially in reference to roboticvision.John Bourne is a Professor of Electrical andComputer Engineering at Olin College, Professorof Technology Entrepreneurship at Babson College,and the Director for the Sloan Center for OnlineEducation at Olin and Babson Colleges. ProfessorBourne’s research interests have included Quan-titative Electroencephalography, Visual EvokedResponse Studies, Syntactic Pattern Recognition,Applied Artificial Intelligence, and QuantitativeQuality Methodologies. He has also built his owngreenhouse and used hydroponics as a hobbyist. Heis a consultant for hydroponics, greenhouse sensors,and online education modules.George Fix is a Senior Principal Materials En-gineer at Raytheon Electronic Systems. His areasof specialty include: failure analysis of polymers,structural adhesive bonding systems and dielectricmaterials for both microwave transmission and highvoltage electronics. George has thirty years experi-ence in electronic, optic and structural applicationsof materials science.William H. Fossey, Jr. is a Senior PrincipalEngineer with the Raytheon Mechanical & MaterialsEngineering Laboratory in Lexington Massachusetts.He has 30 years experience in the design, analysis anddevelopment of composite hardware for numerousapplications including spacecraft, missiles, aircraft,and ground equipment. Components/assembliesinclude both primary and secondary structures, andradomes.Daniel Frey is an Assistant Professor of MechanicalEngineering at Olin College. Professor Frey holdsnumerous patents, and has published extensively inpeer-reviewed journals. He is a consultant in the areaof structural design and analysis and coordinatedthe Red Team review of the PDR.

Gregory Goins is a research scientist for DynamacCorporation in the Advanced Life Support/SpaceBiology laboratories at Kennedy Space Center. Hisresearch focuses on the testing of hardware to allowplants to grow in space. He is a consultant in theareas of lighting and nutrient delivery.John Graff is a graduate student at BostonUniversity. He worked on the development of aphoton recycling semiconductor light-emitting diode(PRS-LED). He is serving as an LED consultant.Merle Jensen is the Assistant Dean of College ofAgriculture at the University of Arizona in Tucson.Dean Jensen is an expert in hydroponics and isfrequently consulted for that field.David Kerns is the Provost and Franklin and MaryOlin Distinguished Professor of Electrical Engineer-ing at Olin College. Dr. Kerns was recently electedVice-President of the IEEE Education Society andserves on its AdCom. His research interests includeMEMS devices, analog circuit design, silicon-basedoptoelectronics, and radiation effects on microelec-tronics. He is primarily serving as a consultant onthe effects of radiation on integrated circuits.Sherra Kerns is the Vice President of Innova-tion and Research at Olin College and a VisitingProfessor of Electrical Engineering and ComputerScience at M.I.T. Dr. Kerns has received both theIEEE Millennium Medal and the 2000 ASEE ECEDistinguished Educator Award. Her research hasfocused on the reliability and information integrityof microelectronic circuits. She is a consultant onthe effects of radiation on computer systems and theelectrical environment of space.Jason Krumholz is a graduate of Lawrence Uni-versity in Appleton, Wisconsin, with a bachelorsdegree in biology. Krumholz has a passion for spacestudy and education, having taught space physicsat a Center for Talented Youth (CTY) summerprogram. He provided information and ideas foroutreach including suggestions for activities in theeducation kit.Robert Martello received his Ph.D. from MIT’sProgram in the History and Social Study of Scienceand Technology, a Master of Science degree fromMIT’s Department of Civil and Environmental Engi-neering, and a Bachelor of Science degree from MIT

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in the field of Earth, Atmospheric, and PlanetaryScience. His non-academic work includes consultingfor an online publishing company and several years’experience as a programmer and environmentalconsultant.Richard K. Miller is the President of Olin Collegeand a Professor of Mechanical Engineering. Dr.Miller has been a consultant to many companiesincluding the Aerospace Corporation, NASA’s JetPropulsion Laboratory, Hughes Aircraft Company,and Astro Aerospace Corporation (TRW), wherehe made significant contributions to the Heliogyro,Solares, Mast Flight Experiment, Milstar, MobileTransporter, and many other projects. His researchinterests revolve around structural dynamics andnonlinear mechanics with application to earthquakeengineering and spacecraft structural design. Heis serving as a consultant on external structure,atmospheric controls, and system dynamics andcontrols.James Philips is an Associate Professor of Scienceat Babson College. Professor Philips is a communityecologist and non-molecular biologist. He has pro-vided information about existing ecosystem projectsand will continue to serve as an advisor for thistopic.Joanne C. Pratt is an Assistant Professor ofBiological Sciences at Olin College. Professor Pratt’sresearch involves biochemistry, molecular biology,and DNA mutation. She is a consultant for radiationeffects and concepts involving genetically modifiedplants or microbes.Christopher D. Raleigh is a Microbial Matresearcher at NASA’s Ames Research Center. Heis a consultant in the usage of microbes within thegreenhouse and is serving as a link to other researchthat is being done at Ames.Brian Sauser is the Senior Program Coordinatorfor the New Jersey NASA Specialized Center ofResearch and Training (NJ-NSCORT) and NewJersey EcoComplex. Dr. Sauser offered to passquestions on to whomever of his researchers wouldbe the most appropriate.Richard Stoner is the CEO and founder of Agri-House, Inc. Mr. Stoner is the inventor of the Methodand Apparatus for Aeroponic Plant Growth (patent

#4,514,930) and principal-inventor of the Methodfor Organic Disease Control (Patent Pending, 1994)and most recently a Tuber Planting System #6,193,958. He has agreed to assist the team in any waypossible, primarily as a consultant on aeroponics.Andy Sugar is a researcher for Dynamac Corpo-ration, who works at Kennedy Space Center. Hisresearch focuses on growing plants in hypobaricconditions and the use of LED growth lights. Heis primarily a consultant with regard to hypobaricplant growth.Randy Tustison is the manager of the MaterialsEngineering Department of Raytheon ElectronicSystems. Materials Engineering addresses materialsresearch and development as well as design andproduction support for all of Raytheon locations,with emphasis in the Northeast. He joined RaytheonResearch Division in 1978. He is a member of theAmerican Vacuum Society, where he was Chairmanof the Vacuum Technology Division in 1990-91,a member of the American Physical Society andSigma Pi Sigma, Physics Honor Society. He is amember of SPIE Executive Program Committee andChairman of the SPIE Aerosense 2001 Window andDome Technologies and Materials VII Conference.He also serves as the Chair of Raytheon’s Materialsand Processes Technology Network. Dr. Tustisongraduated from Purdue University with a B.S.degree in Physics, and from the University of Illinois,receiving a M.S. and Ph.D. in Materials Scienceand Metallurgical Engineering. Prior to joiningRaytheon, he was a Research Associate in Physicsat the Massachusetts Institute of Technology.Neil Yorio is a Plant Physiologist for DynamacCorporation, who works at Kennedy Space Centerin the Advanced Life Support research group. Hisresearch focuses on plant physiology studies and wasconsulted for the influence of various light spectrumson plant growth.

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