Exploration Architecture – RFI White Paper Response MIT Space Systems Architecture Group 20 May, 2004

The Massachusetts Institute of Technology Department of Aeronautics and Astronautics has for much of the past year been carrying out research for NASA’s Space Architect Office, aimed at applying modern techniques of systems architecting to the problem of developing a new space transportation system to support the Space Exploration Vision. During the spring of 2004, the Graduate Space Systems Design course was devoted to this endeavor. The class, composed of 19 students from the Aero/Astro, Mechanical and Electrical Engineering Departments and the Engineering Systems Division, produced a substantial report on this subject, entitled, “Paradigm Shift in Design for NASA’s New Exploration Initiative”.

This report addressed in considerable detail many “Focus Areas” mentioned in the Request for Information recently issued by NASA’s Office of Exploration Systems (Code T). We feel that the report, containing over 250 pages, is too long to constitute an appropriate direct response to the RFI. However, believing that the work done by the class has significant value in the search for an appropriate architecture in which to frame the design of individual exploration hardware elements, we have taken several steps to make the results accessible.

First, we are submitting as a formal white paper the 25-page executive summary of the document. The first part of this summary deals with the two elements we feel are the most significant contributions to the overall conception of the problem: an examination of the nature of sustainability and a recasting of the exploration paradigm as the creation and transmission of new knowledge. We believe that using sustainability and knowledge creation/transmission as evaluation criteria gives us powerful tools to compare the effectiveness of alternative architectures. The second part of the summary presents details of a baseline systems architecture which we developed to evaluate individual architectural elements and search for commonality among in-space, lunar and Mars missions. The interplay of an architectural system with its component parts is an iterative process, but in the confines of a single semester we only had time to go through a single iteration. Therefore the actual descriptions of the hardware are less significant at this point than the explanations of the design processes and tools which we used for the analysis, which are described in the last part of the summary.

In addition to submitting the executive summary, we have posted the entire report on the web (http://web.mit.edu/spacearchitects/1689report.htm). We have developed a table showing the correlation of various parts of the report with the focus areas and sub-areas listed in the RFI, so that anyone interesting in looking more closely at this work can easily navigate the document to find areas of specific interest. The table is included as part of this white paper.

In closing this cover letter, we want to emphasize the importance of designing all the hardware elements of the new space exploration system in the context of a sustainable, overreaching architecture, always taking into account how the system will support the ability to generate and transmit new knowledge as exploration proceeds. We believe that continued research into space systems architecture must accompany the development of new hardware if the space exploration vision is to be realized.

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Correlation Table for Full Report

Focus Area Subtopic Description LinkDesign Principles, Objectives and Guidelines

Sustainability Sustainability described, along with types. Extensibility described, operators explained as method for describing system evolution over time. Antarctic exploration as an example of sustainability. Design process presented for sustainable systems.

Chapter 2: Intro to Sustainability

Effectiveness The key to an effective exploration system is the identification and fulfillment of the system’s primary purpose, knowledge delivery. Knowledge delivery is discussed in terms of types, carriers and drivers. Data from the Apollo program is presented.

Chapter 3: Knowledge Delivery

Crosscutting Design Drivers and Architecture Elements

Mission Model/Utilization Assumptions

A potential mission strategy is staged deployment. Short duration Moon missions lead to intermediate and longer-stay missions with increasingly ambitious objectives. A similar strategy is proposed for Mars. A manned Phobos mission could serve to decouple long duration spaceflight technology from Martian landing.

Chapter 4: Baseline Mission Designs

Commonality:

In-Space and Lunar Surface

Mars and Lunar Missions

Commonality has been addressed through separation of the in-space transport function from launch and landing. Initial Moon, Mars and LEO requirements were understood and then compared across missions.

Direct Discussion:Chapter 5: Commonality

Supporting information:Chapter 4: Baseline Mission DesignsSection 6.4: Trades

Payloads A brief discussion of the benefits of separation of human and cargo transport is provided. Pre-positioning of cargo using low thrust/high ISP propulsion will be a key strategy, leading to mass reduction.

Section 4.4: Transport

Additional information:

Section 6.4: TradesCEV and Other System Concept Options and Variations

Important considerations for CEV architecture include entry-descent-landing (EDL) and interfacing with lunar propulsion stages. The trade space includes capsules, blunt bodies and lifting bodies. Provides high-level inputs into CEV studies.

Section 6.4: Trades

Additional Information in the Appendix:Section 9.1.1:CEVModel

Program Management, Acquisition, and Interfaces

Requirements Formulation and Evolution

There are two important points to be made regarding requirements definition:1. Requirements must come from knowledge delivery, not mass transport requirements alone. 2. Flexibility must explicitly be accommodated in order to track changing needs.

Chapter 3: Knowledge Delivery

Public Outreach and Engagement

Public outreach cannot be an afterthought, but must be considered as the main mechanism that delivers value to the public. We distinguish between news and knowledge.

Chapter 3: Knowledge Delivery

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Contact Information:

All investigators are members of MIT’s Department of Aeronautics and Astronautics and Engineering Systems Division.Address: MIT; 77 Massachusetts Avenue; Cambridge, MA 02139

Principal Investigator:Professor Edward F. Crawley 33-413; 617-253-7510; crawley@mit.edu

Co-Investigators:Professor Oliver L. de Weck 33-410; 617-253-0255; deweck@mit.eduProfessor Jeffrey A. Hoffman 37-227; 617-452-2353; jhoffma1@mit.eduProfessor Dava J. Newman 37-307; 617-258-8799; dnewman@mit.edu

16.89/ESD.352 Graduate Space Systems Design Class:Sophie Adenot, Julie Arnold, Ryan Boas, David Broniatowski, Sandro Catanzaro, Jessica Edmonds, Alexa Figgess, Rikin Ghandi, Chris Hynes, Dan Kwon, Andrew Long, José Lopez-Urdiales, Devon Manz, Bill Nadir, Geoffrey Reber, Matt Richards, Matt Silver, Ben Solish, Christine Taylor

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PARADIGM SHIFT IN DESIGN FOR NASA’S NEW SPACE EXPLORATION VISION

16.89 Space Systems Engineering Final ReportMassachusetts Institute of Technology, May 12, 2004

Executive Summary

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Table of Contents

Introduction..........................................................................................................................6Sustainability.......................................................................................................................6Knowledge...........................................................................................................................8Proposed Design Process...................................................................................................11Application of the Design Process.....................................................................................13Lunar Mission Baselines....................................................................................................15Mars Mission Baselines.....................................................................................................17Form/Function Mapping and Commonality......................................................................19Analysis.............................................................................................................................21Integrated Baseline............................................................................................................23Strategy Development Tools – Scenario Planning............................................................26Conclusions........................................................................................................................30Appendix: Table of Acronyms..........................................................................................31

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Introduction

On January 14, 2004, President George W. Bush presented the nation with a bold new space exploration initiative. NASA has been given the task of developing the program, which will take humans back to the Moon by 2020, to Mars, and beyond. The directive raises two important questions for space systems design: First, given the extended life cycle of the project, how can one architect a space exploration system to accomplish the directive in a sustainable fashion? Second, what measures should be used to evaluate the performance and effectiveness of a sustainable exploration system? The following report, based on the work of the 2004 MIT spring graduate course in Space Systems Design, addresses these questions. It presents a method for taking sustainability into account during the conceptual design of a space system, and uses it to design a preliminary exploration system architecture. In answering the second question, the report argues that the primary purpose of an exploration system is the delivery of knowledge to the stakeholders. Effectiveness and performance are thus intimately related with the acquisition, synthesis and delivery of knowledge both in space and on the Earth.

Sustainability

What is a sustainable exploration program? To “sustain” means literally: to maintain in existence, to provide for, to support from below. At the programmatic level, an exploration system will be maintained in existence so long as it is funded, and it will be funded provided it meets the needs of key stakeholders, members of Congress, the Administration, and ultimately the American people. Realistically, however, system designers must recognize that these needs themselves will change. A multi-year, multi-billion dollar program in the US Government must expect to face a great deal of uncertainty with respect to objectives, budget allocations, and technical performance.

In order for an exploration system to be sustainable, then, it must be able to operate in an environment of considerable uncertainty throughout its life cycle. Traditional engineering definitions of sustainability are often limited to the physical and technical realms, defining sustainability in terms of physical operation over a long period of time. Space systems, however, are subject to influences from several realms, including policy decisions, budgetary uncertainty, organizational changes and the more traditional technical and supply chain issues that are incorporated into most engineering definitions of sustainability. It is important to recognize that threats to the sustained operation of a space system may not only come from these realms, but from the interactions between them. For example, a policy decision change may mandate a technical change that is responsible for the system’s ultimate failure to survive. Thus, different forms of sustainability may interact with one another and form a cyclic relationship between the policy, organizational, technical and operational realms.

Designing for sustainability thus implies identifying various sources of uncertainty, and managing them through up-front system attributes. Various terms have been used to describe such system attributes, including: flexibility, robustness, and extensibility.

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While a large complex system must react to changing environments in order to be sustainable, technological aspects of systems can themselves impact the environment. Once in development and operation, a multi-billion-dollar system will mediate political interests, organizational decisions, and technical alternatives, creating potential sources of stability and positive feedback loops, as well as sources of uncertainty. Early decisions that create high switching costs or large infrastructure sites, can “lock-in” architectural configurations and influence the objectives and development path of later systems. A sustainable design will be one in which, to the greatest extent possible, the dynamics behind political, technical, and financial sources of stability support, rather than hinder, system development and operations.

There are two different sustainability design concepts that may be used to increase the length of a system’s lifecycle. At one extreme is robustness. A robust system is one that is designed to be able to withstand changes in its environment with minimal redesign. Unfortunately, this method is limited when designing for extreme uncertainties, since one may never know what factors it may be required to be robust to. At the other extreme lies flexibility. This design methodology encourages changes within a system so that it may adapt and evolve to meet the constraints imposed by the different environments in which it will operate. One element of flexibility that is particularly relevant to the creation of a long-term space exploration infrastructure is extensibility. Extensibility is the capability of a system to evolve or adapt through time such that it is better able to meet the needs of the key stakeholders. Unlike a point design, which is optimal for one point in time only, an extensible system is created such that it is able to change and evolve in the face of future environmental uncertainty. Often, creating an extensible system will require some additional up-front cost so as to reduce expected cost over the system’s life cycle. An extensible space exploration system is one that will continue to deliver knowledge to the stakeholders, even in the face of unfavorable policy, organizational and budgetary changes, while also successfully incorporating most of the benefits of changes in these and breakthroughs in the technical realm. Extensible systems are therefore sustainable by their very nature, because of their ability to evolve through time, thus increasing the chances that such systems will not become useless or prohibitively expensive to operate.

Examples of space systems architectures that are not sustainable include the Apollo program, which was not able to successfully scale down operations following budget cuts in 1972, and the Space Transportation System’s Space Shuttle, which is both costly and difficult to upgrade and refurbish due to its inflexibility in the face of new technologies. Neither of these systems were designed with extensibility in mind; a design decision that led to the Apollo program’s eventual demise. On the other hand, an example of a sustainable program may be found in the Antarctic exploration program, even though it was never designed with sustainability explicitly in mind.

The successful evolution of Antarctic exploration may be attributed to the fortuitous interplay of many factors, which converged to begin the Modern Age of Antarctic exploration in 1928. Previous to this time period, the Heroic Age of Antarctic exploration occurred, in which most exploration was limited to the coastal areas of the continent and was severely limited by inclement weather patterns and the numerous ice floes and pack ice, which limited naval access to interesting sites. Although the invention of steel-hulled ships and icebreakers helped somewhat, exploration was still very limited. The Modern Age of Antarctic exploration began upon the widespread use of the airplane and the radio, both inventions that had been extant for

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about 25 years prior to the commencement of the Modern Age. Another major enabler for Antarctic exploration was the political support from numerous countries, many of which wanted to use the new capabilities delivered by the airplane and the radio to stake a claim to Antarctic territory before other countries could. Thus, the true commencement of the Modern Age may be attributed to interplay between technological, political and geo-political factors. With recent events, including the President’s speech on January 14th, 2004, the recent discovery of the previous existence of Martian water, and the commencement of China’s new human space flight program, the political, organizational, scientific and technological environments are now ripe for a paradigm shift in the approach to sustainable space exploration. This paradigm shift comes in the form of recognition that the primary purpose of exploration is knowledge return.

Knowledge

While there are myriad motivations behind exploration, such as national prestige, sovereignty, technical leadership, and inspiration, the primary purpose of any exploration system is knowledge acquisition. While mass transport enables exploration, the ultimate success of an expedition depends on the acquisition, communication, and synthesis of visual imagery, scientific data, and human experience to various stakeholders. Scientific knowledge benefits scientists; technical and operational knowledge benefits explorers, technologists, and third parties such as the military; resource knowledge benefits commercial enterprises; “human-experiential” knowledge inspires and makes the American public proud. As this knowledge is returned, and is perceived as valuable by these stakeholders, it generates support for further exploration. Support may come in many forms such as funding or votes. Figure 1 illustrates how such a system can form a positive feedback loop resulting in sustainable exploration.

Figure 1: Positive feedback loop of knowledge, technology, and support for exploration

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This suggests revaluing traditional space system characteristics and trades to account for the demands of knowledge acquisition and delivery. Further, in order to make clear decisions about system capabilities and mission goals, attributes of knowledge must be categorized and valued in accordance with stakeholder needs. System designers must have a firm grasp of the knowledge delivery process, and establish how it will occur at each point in the system’s lifecycle.

This report defines five specific types of knowledge:

1. Scientific knowledge may be said to focus on the description of the universe and the world in which we live. This knowledge will ultimately generate a better understanding of past and present life, and its existence criteria. Scientific knowledge is of primary interest to the scientific community but in many cases also excites the public at large.

2. Resource knowledge relates to the existence, location and amount of materials on a celestial body or in outer space that may be used for in-situ resource utilization, such as the production of propellants and life-supporting substances. Resource knowledge is of primary interest to the government, private explorers, and those who would wish to take advantage of the resources identified.

3. Operational knowledge relates to the performance of maneuvers and activities while accomplishing a mission. Examples of operational knowledge include docking, drilling for resources, pre-positioning, and long-term survivability and human factors concerns. Operational knowledge is of primary value to NASA and other space faring agencies, and to individuals and corporations who may be performing activities in outer space in the future.

4. Technical knowledge relates to the development, testing and operation of new technologies, which will be used in the exploration process. Examples of technical knowledge to be gained include cryogenic storage capabilities, development of pressurized rovers, new modes of propulsion, and energy generation facilities. Technical knowledge is of primary interest to technologists and all those who would see the benefits of these technologies applied.

5. Experiential knowledge may only be gained from sending humans on exploration missions. It is the human experience which lies at the intersection of all other types of knowledge, and which is most instrumental in the inspiration of the public and of future generations. Experiential knowledge is of primary interest to the American people, and indeed, to all humanity, who are able to identify with the heroic acts performed by past, present and future NASA astronauts.

The goal of a knowledge transportation system is to allow for knowledge creation, transfer and transportation. Knowledge may be transported through three basic types of knowledge carriers, which we refer to as “bits”, “atoms” and human experience. These may be further divided into several categories, including:

1. Passive bits: This transportation scheme does not allow for direct interaction of the knowledge carrier with the environment. Rather, it relies on remote collection. An example of passive bits is photography, where bits carry digital images.

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2. Active bits: This transportation scheme requires direct interaction of the knowledge carrier with the environment. An example of active bits are those which result from taking a measurement, such as the use of a Rock Abrasion Tool to determine the composition of a Martian rock.

3. Implied discovery: This transportation scheme requires the return of a physical sample (atoms), which allows for a conclusion to be reached in terrestrial laboratories with respect to a specific hypothesis. An example of an implied discovery is the analysis of a rock with erosion patterns to confirm the prior evidence of water at the rock’s location or the radioactive dating of a sample to determine its place in geological history.

4. Direct proof: This transportation scheme is perhaps the most straightforward, as it requires the transport of a physical sample which directly verifies or refutes a hypothesis. An example of direct proof would be the discovery of liquid, flowing water on Mars.

5. Human experience: This transportation scheme is particularly important, since it does not rely on the delivery of knowledge to the human. Rather, the human directly interacts with that which provides the knowledge. An example of human experiential knowledge would be the experience of the first Martian astronaut upon landing on Mars and seeing, feeling and perhaps even tasting liquid water in person. Human experience is that which may be directly perceived through the basic senses. The sharing of human experience of new environments is at the core of exploration.

The process by which knowledge is delivered may be defined as a cycle, in which one piece of knowledge fuels a concept for a new exploration mission. This mission is then designed and executed, and if all goes well, data is returned for analysis. This data is

Figure 2: Hubble Space Telescope knowledge throughput, (Beckwith 2003)

then processed, and the relevant knowledge is extracted, which in turn fuels another exploration mission. It is worth noting that this cycle is far from instantaneous. Rather, the net cycle time may be defined as the amount of time that it takes for a mission to be conceived, designed, implemented and executed, in addition to the amount of time that it takes for knowledge to be successfully extracted from data. This research latency, referred to as the Knowledge Delivery Time, must be factored into the design of new missions and is thus an important factor in the overall mission design time.

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A sustainable knowledge delivery system must recognize that, although news is often instantaneous, net knowledge delivery often takes time on the order of years. For example the Hubble Space Telescope did not peak in knowledge delivery (as measured by the publication of papers in scientific journals) for 8 years after launch (See Figure 2). Thus, some amount of time must be allotted between missions if one mission is to take full advantage of its precursor’s achievements. On the other hand, if too much time is allotted between missions, the public will lose interest in space exploration. The public must be reminded as often as possible that feats of exploration are being achieved. Initially, the media will serve this function. However, as exploration activities become routine, the media, which concerns itself mostly with news, will divert its attention to other stories. This trend may be found in major breakthroughs and disasters, both of which have significant news value. One proposed way to decouple the public interest from the media is in the establishment of personal connections between those who perform exploration activities and the key stakeholders on Earth. For example, if one has family members or friends who are actively participating in exploration, the likelihood of maintained interest is increased. Also, the ability to share the results of exploration on a personal basis, such as through the Internet, allows the public access to exploration beyond what is available through commercial media. Thus, it is important to recognize that the establishment of a successfully sustainable knowledge delivery-based exploration system must extend into the realms of socio-political engineering as well as into the more traditional realm of technical engineering.

Proposed Design Process

The President laid out two major milestones for the new space exploration vision. The nation will first return humans to the Moon. Lunar missions will be used as a test bed for the second milestone, eventual Martian exploration. This high-level outline suggests a “stepping-stone” strategy, which NASA may use to reach the Moon, and then to proceed to Mars and beyond. An important aspect of the vision is its extended timeline. Any system designed to meet its objectives must operate through political change, budgetary uncertainty, and technical uncertainty. An underlying goal of a sustainable design process is thus to develop an integrated strategy that can quantify how the system reacted to changes in the environment. Rather than create a point design to accomplish a Moon or Mars expedition, various scenarios can be anticipated and addressed during conceptual design and, as importantly, the elements designed (which will likely make the system sub-optimal from a point-design perspective) can be justified quantitatively.

The first step in this strategy will be to regain capabilities originally demonstrated by the Apollo program by returning to the Moon for a short period of time. A following step will utilize the infrastructure generated by these shorter missions to perform in-depth scientific and technology test-bed missions on the Moon. The last phase of Moon missions will build upon the scientific and technological capabilities generated through previous missions to establish a long-term lunar habitation capability. Once the lunar test-bed missions have been completed, NASA’s exploration program will shift focus to Mars. The evolutionary mission path for Martian missions will be similar to that used by the lunar missions, in that the preliminary missions will focus on staying for short periods of time, and as experience progresses, staying for increasingly extended periods of time. These

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missions may culminate in the establishment of Martian infrastructure and possible habitation technology and capability. This report also considers the option of a mission to the Martian moons, which could de-couple Martian transport technology demonstration from Martian landing and habitation technology demonstration while still providing a mission with a significant exploration goal. This report uses this preliminary strategy to lay out the components for a sustainable system to carry humans to the Moon, to Mars, and beyond.

The design process established to create a sustainable space exploration system has five distinct steps:

1. Creation and refinement of individual staged missions, collection of existing studies and evaluation of the capabilities of legacy hardware.

2. Identifying required capabilities (“functional requirements”) for each of the staged missions and existing studies into a matrix aimed at identifying common elements between these missions.

3. Mapping common functional requirements between missions, while also identifying the capabilities (“functions”) provided by each piece of legacy hardware.

4. Analyzing each of the individual staged missions for key trades and options, that may make these missions more extensible and sustainable in the face of an uncertain environment.

5. Creation and refinement of an integrated baseline strategy that will map the progression of staged missions through time in an extensible, sustainable manner.

Figure 3: Design Process

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The process is iterative, and the baseline strategy must be re-evaluated in the face of deviations from the expected environmental conditions.

Application of the Design Process

In our work, we have attempted to separate analysis of the required functions necessary for an exploration system to achieve its goals from the actual forms, the hardware that will provide these functions. The delivery of knowledge to stakeholders requires the existence of a mass transportation system that will allow astronauts, as well as robotic precursor missions, to go from the Earth to the Moon, to Mars and beyond. In doing so, these astronauts will set up systems that transmit bits back to Earth, and to the key stakeholders. Astronauts will also be charged with transporting physical samples back to the Earth’s surface for further, in-depth analysis, which may be used to gain even more knowledge from one mission. Thus, a set of functions, and their associated forms, must be created to enable knowledge return. The design process outlined above provides a means to this end. Therefore, the first step in designing these functions and forms would be to examine existing studies and legacy hardware to determine if a desired functionality is already in existence.

The prime example in which existing legacy hardware may be used is in the delivery of mass to Low Earth Orbit (LEO). The current Space Transportation System (STS) architecture, including the Space Shuttle, provides an adequate opportunity to take advantage of the heavy-lift capability provided by the shuttle’s External Tank (ET) and Solid Rocket Boosters (SRBs). Several different configurations of legacy hardware were considered, including STS-derived launchers (a shuttle stack in which the shuttle is replaced with a cargo carrier), SRB derived launchers (an SRB with a large Saturn-derived cryogenic second stage on top), foreign launchers (such as the heavy versions of the Ariane 5), the Evolved Expendable Launch Vehicle (EELV) families (the Lockheed Atlas V and Boeing Delta IV families), EELV derived approaches, and completely new systems. After calculating the capabilities that could be achieved with different configurations of legacy hardware, the conclusion has been reached that the most technically attractive and cost effective architecture should be built around two launchers. A heavy launcher would be used to transport cargo, based only on the STS and possessing the capability to lift at least 100 metric tons to LEO (A. Cohen, 1989). Although we chose to use a human-rated heavy EELV such as the Delta IV Heavy for transporting crew, further study of an SRB-derived human launch system is recommended. Similar analyses may be performed upon other sets of legacy hardware to determine how their unique capabilities may be used to augment the extensibility of the space exploration system.

In order to develop an extensible space exploration system, an infrastructure must be set in place to provide for the transport of bits and of atoms. Another use of legacy hardware may be seen in the proposed communications infrastructure. Transportation of bits will occur through the use of a communications architecture consisting of a set of satellites, which will augment the capabilities of the existing Deep Space Network (DSN). The DSN will also be upgraded as necessary to allow for an as-needed communications capability. This communications system

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will aid in knowledge return and will support in extensible system operations. Transportation of atoms, on the other hand, will occur through an extensible set of baseline forms whose purpose is to deliver mass to and from the Earth. The bulk of this paper will focus on the operations of these forms. Following the description of the forms and their operations, individual staged mission profiles will be presented for the Moon and for Mars, thus completing the first step of the design process. Missions to the Moon and to Mars are separated into classes of three types of missions for each location, although it is important to recognize that these missions are not discrete. Rather, each of these classes of missions represents waypoints in an evolvable continuum of missions that may be attempted while exploring space. Lunar missions are divided into Short Stay, Medium Stay, and Extended Stay categories, whereas Mars missions are divided into Short Stay, Extended Stay, and Extended Stay + Infrastructure categories. Another mission to the Martian Moon, Phobos, is also considered as a potential intermediate step between the Moon and Mars.

Before mission profiles are described in detail, the forms used to execute these missions must be presented. These forms are as follows: The Crew Operations Vehicle (COV) is functionally similar to the Apollo Command Module, capable of transporting a crew of three to and from LEO and supporting the crew for a short duration mission. The Habitation Module (HM) is an extensible habitable volume, made up of separable modules. This module can sustain life for long duration missions. When the COV docks with the HM, they form the Crew Exploration System (CES), which can leave LEO and support human life and useful activity for extended periods. The Service Module (SM) is capable of providing propulsion for transporting the crew from Earth to the crew’s destination or from that destination back to Earth. In combination with the COV and HM, this module is defined as the Moon/Mars Transfer Vehicle (MTV). The Mars Landers (ML) or the Lunar Landers (LL) are functionally similar to the Apollo lander (slightly different forms for Moon and Mars) and capable of transporting three crewmembers from orbit to the surface and back into orbit. The Modern Command Module (MCM) is functionally similar to the COV in terms of transporting crew back and forth from Earth to LEO and transferring crewmembers to the HM in LEO, but the MCM is not intended to go beyond LEO.

Now that the forms have been defined, it is important to outline some of the assumptions that have been used in mission design. The primary assumptions used in developing the individual staged mission descriptions are as follows:

The capability to pre-position cargo using solar-electric propulsion systems is extant and available for use.

Technologies have been developed for the long-term storage of cryogenic chemical fuel. Countermeasures exist which may counteract the effects of high doses of radiation. Countermeasures exist which may counteract the effects of long-term exposure to a low-

gravity environment. Advanced space suits are available, which provide astronauts with increased locomotive

capability, and allow for increased exposure time to the space environment.

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Lunar Mission Baselines

Lunar missions assume the ability to successfully land humans and cargo on the lunar poles and on the far side of the Moon, as well as the ability to land cargo and humans within walking distance of one another.

Lunar mission descriptions are as follows:

Short-stay Mission: These missions deliver a crew of three astronauts, and spend approximately two days on the lunar surface. They are primarily aimed at re-establishing the lunar transit capability of the Apollo era, and will serve as scouts for future lunar missions. In this mission profile, a crew operations vehicle (COV) containing the three astronauts is launched into low Earth orbit. A Lunar Lander (LL) is launched into LEO separately. The COV and LL dock in LEO and transit to lunar orbit together using cryogenic chemical propellant. Once in lunar orbit, two crewmembers transfer to the LL, undock from the COV and descend to an equatorial landing site on the near side of the Moon using cryogenic chemical propellant. One crewmember remains in the COV in lunar orbit. The astronauts on the lunar surface will live in the LL for approximately two days and explore the landing site on foot. EVA will have minimal science capabilities since the purpose of this type of mission is a basic technology demonstration. Upon the conclusion of the surface stay, the two astronauts ascend to lunar orbit in the LL using cryogenic chemical propellant and dock with the COV. One person is left in the COV as a safety measure for the basic technology demonstration; in case the LL fails to dock with the COV, the astronaut in the COV can manually maneuver to dock with the LL. Then, the astronauts transfer to the COV, undock with the LL, and initiate the return trip using cryogenic chemical propellant. The COV performs a ballistic re-entry, returning the astronauts to Earth.

Medium-stay Mission: These missions have a crew of three astronauts and use the same spacecraft forms as in the Short Stay Lunar Missions. Their primary purpose is to perform technological and scientific tests, with the eventual goal of extending these practices to the Martian environment. There are three differences between the Short and Medium Stay Missions: the LL is pre-positioned in lunar orbit using electric propulsion, all astronauts transfer to the LL to descend to the lunar surface, and the astronauts stay on the lunar surface for one week. The mission will proceed as follows: First, a LL is launched into LEO alone. Electric propulsion is then used to preposition the LL in lunar orbit. Later, a COV containing the three astronauts is launched into LEO. The COV transits to lunar orbit using cryogenic chemical propellant. Once in lunar orbit, the COV docks with the pre-positioned LL, the three crew members transfer to the LL, undock from the COV and descend to non-equatorial landing sites on the near side of the Moon using cryogenic chemical propellant. No crewmembers remain in the COV in lunar orbit; it is assumed LL ascent was proven to be reliable during the Short Stay Lunar Missions. The astronauts on the lunar surface will live in the LL for approximately one week and explore the landing site using an unpressurized rover to aid mobility within walking distance from the LL; EVA will have increased science capabilities. Upon the conclusion

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of the surface stay, the three astronauts ascend to lunar orbit in the LL using cryogenic chemical propellant and dock with the COV. The astronauts transfer the COV, undock from the LL, and initiate the return trip using cryogenic chemical propellant. The COV performs a ballistic re-entry, returning the astronauts to Earth.

Extended-stay Mission: These missions have a crew of six astronauts and require a pre-positioned surface habitat for the crew to live in for up to six months. Their primary purpose is to establish semi-permanent habitation capability upon the lunar surface. The mission proceeds as follows:

First, a surface habitation module (SHM) is launched into LEO. The SHM is then pre-positioned on the lunar surface, using electric propulsion for the transit to lunar orbit, and cryogenic chemical propulsion for the descent. Second, two Moon landers are launched into LEO separately. Electric propulsion is then used to pre-position the Moon landers in lunar orbit. A HM is launched into LEO using one of the lunar landers. Third, a COV and a MCM each containing three astronauts, are launched into LEO. The COV docks with the HM and MCM, the crew of the MCM transfers to the HM, and the MCM undocks. The docked COV and HM then transits to lunar orbit together using cryogenic chemical propellant. Once in lunar orbit, the pre-positioned Lunar Lander 1 (LL1) docks with the COV and HM, the three crewmembers transfer to the LL1, undock from the COV and descend to the pre-positioned SHM on the far side or pole of the Moon using cryogenic chemical propellant. Likewise, the second pre-positioned lander, LL2, then docks with the COV and HM and transfers the crew to the SHM. No crewmembers remain in the COV in lunar orbit. The astronauts on the lunar surface will transfer from the Moon landers to the SHM for a surface stay of approximately six months. Upon the conclusion of the surface stay, the six astronauts ascend to lunar orbit in the two LL’s using cryogenic chemical propellant. They then dock with the COV and HM one at a time. The astronauts transfer to the COV, undock with the lunar landers, and initiate the return trip using cryogenic chemical propellant. The COV and HM aerobrake to establish Earth orbit and then dock with the MCM. Three astronauts transfer to the MCM to return to Earth. The other three astronauts remain in the COV, undock from the HM, and return to Earth.

The semi-permanent base allows for extensive science capabilities, possibly including but not limited to Moon-based observatories, greenhouse technology demonstrations for closed-loop life support, and nuclear power production. A habitable, pressurized rover for overnight field trips will aid surface mobility.

Individual staged lunar missions are aimed at the eventual establishment of a lunar habitation capability and the use of in-situ resources. In attempting lunar missions, valuable knowledge will be gained that may be applied to the eventual accomplishment of successful Mars missions. Thus, the Moon is used to reach Mars in what is commonly referred to as a “stepping-stone” approach. The Martian individual staged missions are aimed at exploiting this similarity.

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Mars Mission Baselines

Assumptions made in performing the Martian missions include a crew size of six people, the use of solar-electric propulsion for pre-positioning, the existence of life-support and radiation-shielding technologies, and the use of a Martian Orbital Rendezvous (MOR) mission strategy, similar to the Lunar Orbital Rendezvous strategy used by the Apollo missions.

It is important to realize that a Martian mission is significantly different from a lunar mission, if only for the disparity in the time scales and distances involved. Furthermore, Mars has an atmosphere, implying that lunar landing and habitation technologies will not be directly transferable to Mars. It is primarily for this reason, that a mission to one of the Martian moons, Phobos or Deimos, is proposed. This mission would effectively serve to de-couple the test of Martian transfer technologies from the Martian landing and surface habitation technologies. In addition, landing on a Martian moon would have significant knowledge return-related benefits. For example, inspection of the Martian moons could provide information on planetary science and evolution and potential sources of water ice (Ball, 2004). Significant operational knowledge is to be gained from performing operations with a Martian moon. Since they are asteroid-sized, and hypothesized to be captured asteroids, these missions would prove invaluable in providing asteroid rendezvous experience that could be extended to other asteroid missions. More generally, the ability to rendezvous with a planet’s moon may prove to be advantageous in future missions to the outer planets, whose moons are locations of interest. The ability to establish a human presence on a Martian moon implies that a telerobotic presence may be established on Mars with a minimal communications delay. Finally, a landing upon a Martian moon will serve to build the public’s confidence in NASA’s Mars exploration activities, since it will demonstrate a successful extension of lunar mission technology to another celestial body.

Even if a mission to the Martian moons is not undertaken, Martian missions will proceed in a three-tiered structure similar to that used for the Moon missions. The Mars mission descriptions are as follows:

Short-stay Mission: This mission is the shortest Mars mission possible in terms of total mission duration; it is composed of approximately 600 days transit time and 60 days surface stay (Walberg, 1993). The crew travels to Mars via an opposition class free-return trajectory with a Venus fly-by in the Mars Transfer Vehicle (MTV), which is composed of a habitation module (HM) and a crew operations vehicle (COV). Upon arrival at Mars, the MTV aerocaptures into Martian orbit and performs a rendezvous with two pre-positioned Mars landing vehicles (LM1 and LM2). Three crewmembers descend to the Martian surface in each lander, and this allows flexible timing for each landing, with the second being contingent on the success of the first. The landing is achieved using a heat shield for atmospheric entry after which parachutes are deployed to slow the spacecraft. The final stage of the landing is a powered touchdown that gives the crew as much control as possible over the landing so as to minimize risk of damage to the landing vehicle. The crew remains on the surface for approximately 60 days and during this time, lives in a pre-positioned surface habitat that could be extended by an inflatable module if more volume is required. At the end of the surface stay, the crew returns to Mars orbit in the two landing modules and docks with the MTV. The MTV docks with the pre-

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positioned return propellant module (SM2) and executes a trans-Earth injection maneuver. Entry back into low Earth orbit (LEO) is achieved via aerocapture, and the MTV docks with the two Modern Command Modules (MCM1 and MCM2) in succession allowing the crew to transfer into their Earth reentry vehicles. During the surface stay, the crew will explore the Martian surface within close range of their landing site using EVA suits in conjunction with an un-pressurized rover. To facilitate the short-stay mission, pre-positioning of mission elements is employed. In addition to the pre-positioned Martian landers, surface habitat, and return fuel, surface equipment, such as an un-pressurized rover and scientific payloads will be pre-positioned on the surface.

Extended-stay Mission: The extended-stay mission offers the advantage of a longer surface stay with only a small increase in the total mission duration over the short-stay mission. It is also less complex from a trajectory perspective since it does not require a Venus flyby to provide the required delta V. Instead, for this mission, the crew travels to Mars in the MTV via a fast transfer conjunction class trajectory. In most respects the mission architecture is taken directly from the short-stay mission, and assuming the short-stay mission precedes the extended-stay, the required operational knowledge to carry out the mission should be almost complete. One of the main differences between the extended and short-stay missions is the ascent to Mars orbit in the landing modules. Assuming the option of in-situ propellant production (ISPP) during a short-stay mission is employed, and successfully demonstrated, the ascent propellant for the landers will be provided in-situ using the Sabatier process. The functional test of ISPP at this stage will act as a stepping-stone towards the eventual goal of using ISPP to fuel the entire return journey to Earth. Another principal distinction between extended and short-stay missions is the length of surface stay. For an extended-stay, the crew surface habitation module will need to be considerably larger than that of a short-stay mission. To this end, an inflatable module or an additional habitation module will be pre-positioned. Besides the obvious extensive life support requirements for a mission of this duration, the crew will require an extended means of exploration equipment for this mission. Along with EVA suits, a transport vehicle, open or pressurized, will be pre-positioned, to enhance surface mobility. An open, un-pressurized, rover is limited to ranges of 10km, such that the crew is always within walking distance of the surface habitat. However, this safety requirement highly constrains the amount of exploration that can be accomplished during this long duration mission. Therefore, although not a requirement, a pressurized rover capable of ranges on the order of 500km is a recommended option for the long-stay mission. This will allow the crew to explore a large area, searching for water and life, collecting samples to return to Earth, and taking various measurements.

In addition to the large-scale physical exploration of the Martian surface, the crew will have the opportunity to conduct more advanced scientific experiments including experiments that may require a longer duration, such as small-scale agriculture development. The construction of an inflatable greenhouse prototype is one option for the extended-stay mission. This could supplement the crew’s food supply for both the surface stay and Earth return trip.

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Extended-stay + Infrastructure Mission: The idea behind this mission type is that if, after previous short and extended-stay missions, Mars remains an interesting destination either from a science or operations perspective, or even as a testing ground for the next exploration target, then subsequent Mars missions will develop infrastructure to facilitate surface stays, and exploration and to minimize mass that has to be transported from Earth. In this case, the aim of the mission is to use in-situ resources as much as possible – to provide return fuel, to generate power, to develop sustainable agriculture, to enable closed loop life support and so on. Missions to Mars will take place more frequently, possibly with one crew traveling at each launch opportunity. The initial architecture will follow the proven MOR scheme for a long-stay conjunction class mission, but assuming previous attempts at ISPP generation and fuelled ascent have been successful, it is likely that the architecture will move towards something similar in style to Mars Direct (Zubrin, 1996). The eventual outcome of this transition would be that the MTV would travel directly to the surface of Mars without orbital rendezvous, and would ascend from the Martian surface using ISPP fuel directly into a trans-Earth injection. The result of a move towards this architecture would be a significant reduction in Initial Mass in LEO. For these extended-stay missions, pressurized transport vehicles will be pre-positioned allowing the crew to have significant surface mobility on the order of 500km. Two pressurized rovers will be necessary to provide a rescue capability. The crew will conduct science experiments as described above, and the scientific payloads will be chosen to explore whichever areas have proven most interesting in previous missions as well as any new areas of interest. The Environmental Control and Life Support System will be designed to achieve as close to 100% closure as possible, and the crew will derive most of their power from ISPP. Agricultural facilities such as inflatable greenhouses will be installed to provide or supplement the crew’s food supply. The crew habitat will take the form of multiple inflatable modules as well as pre-positioned Habitat modules sent direct from Earth. The extended-stay mission with infrastructure will provide a test bed for further exploration technology development, and it is also possible that the ISPP facilities will allow Mars to serve as a way station for vehicles traveling to more remote destinations.

Form/Function Mapping and Commonality

Following the definition of individual staged missions, the next step in the design process is to map the functional commonality between these missions using a functional mapping matrix. The goal of this mapping is to enhance system sustainability through the development of extensible elements between missions. This is a process that consists of three steps, namely the identification of required functions for each mission, the mapping of these required functions to specific forms, and finally, identification of opportunities to maintain commonality across missions.

Requirements were specified for the three Moon missions and the four Mars Missions. Basic forms were selected and the functions were discussed for each form. Each mission was considered independently. For example, if an Extended-stay + Infrastructure Mars mission requires that the COV be equipped with an aeroshield, while the other three Mars missions do

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not, the Mars set of missions are assumed to require an aeroshield. This method of analysis allows functional traits of a form to be easily evaluated and compared to the other functions in terms of importance across the entire set of mission objectives. When the form does not capture a function, a decision must be made as to whether or not extending the functionality of a form to include higher-level requirements is justified or whether an additional form should be developed to serve the functional requirements flow down from the Mars and Moon mission objectives.

An example of the application of this method may be found in the lander design process. Table 1 demonstrates common lander functional requirements between mission profiles.

For comparison purposes, it is clear that common functions are shared. When common functions exist, extensibility will benefit the overall group of missions to the Moon and Mars. In the above example, the lander must dock with the COV or the COV/HM in both lunar and Martian orbit. The lander must also deliver a crew of 6 to the surface for all of the Mars missions and some of the Moon missions. If two identical landers are chosen instead of a single, larger lander, the impact of this decision can be observed by evaluating whether or not the new option satisfies the functional requirements. If all of the functions are deemed satisfied, only then was the impact of the decision not critical. As can be expected, a wide range of requirements exists for the landers, but many of these requirements are specified by only one of the seven missions, making it difficult to justify changing the baseline form. Indeed, the landers are a mission critical piece of hardware and must be highly reliable. Therefore, when considering extensibility of such a device, it may be beneficial to target the lander design for the most difficult landing mission, thereby ensuring a robust, if over-designed, form for the other missions. This has the effect of increasing net reliability while still maintaining an extensible form. The idea of designing a non-optimal form now, such that it may be optimal when used in a different manner or location, stands as one of the cornerstones of extensibility.

Once common functional elements have been identified, the next step in the design process is to maximize commonality between forms. When considering and comparing multiple forms, three degrees of commonality between components may be observed; components may be common, similar or different. In the lander example presented above, an example of a common component is the crew compartment, which will remain the same between missions and serve to demonstrate components that may be used as legacy hardware. Similar components are the propulsion modules, which must be adaptable and operable both in the Martian and lunar environments. Particular attention must be paid to these components to be sure that they are adaptable or extensible between environments. Finally, different components, such as the parachute,

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Table 1: Lander Form/Function Mapping

deployable landing structure or heat shield, in the Martian example, are examples of those components that should be modularized such that they may be added or removed as needed.

Although many simplifying assumptions were required to analyze a transportation system in this framework, the advantage of this method is evident when considering the impacts of a decision to exclude a certain function from an element of form. The Venn diagram in Figure 4 highlights the functions that were not captured by the baseline mission architecture for the lander. Thus, pains must be taken to integrate these functionalities into the eventual design for the missions that require them. In doing so, it is important to recognize a fundamental engineering tension that exists between point-design optimality and extensibility. A form that is designed purely with optimality in mind is restricted to the point design for which it was originally conceived. This makes the creative use and extension of such technology difficult. On the other hand, a form designed with only extensibility in mind will become “spread thin”, and unable to perform the functions required of it at certain stages or missions. Thus, a compromise must be struck between these two extremes.

Analysis

Once commonality has been identified between missions, key trades may be identified within different mission architectures, so that these trades may be exploited depending upon the needs of the stakeholders. One such trade to be considered is the use of a reusable system. In theory, a reusable system requires a larger initial cost than the associated expendable system, but savings may be gained from not having to fully rebuild the system after each use. Opportunities for reusability within the space exploration infrastructure include reusable landers and planetary cyclers. This approach generally works if more missions are to be accomplished within a given period of time. The Space Shuttle provides an example of a reusable system, which, due to under-estimations of its turn-around time between flights and its maintenance and re-verification costs, cost significantly more per flight than originally intended. Thus, when designing for reusability, it is necessary to consider the effects of environmental change upon the system. In the case of the Shuttle, changes in policy and unanticipated technical and operational problems undermined the value of a reusable system.

Another trade to be considered is the use of the Earth Moon Lagrangian Libration Point 1 (L1) as a trans-lunar stopping point. The benefits of stopping at L1 include the ability to reach a landing site at any lunar latitude, although there is an associated delta-V cost of about 11%. On the other hand, a mission may go directly into a lunar equatorial orbit and then execute a burn to create an orbital inclination change. Orbital inclination changes also have an associated cost in delta-V.

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MOON

Ability to Land Unmanned

Crew of 3 or 6

Life support

Dock with ISPP-SHM on surface

Crew of 6

Life support

Aeromaneuvering

Dock with COV/HM in orbit

Transfer crew of 6 from orbit to surface

Support EVA

MARSMOON

Ability to Land Unmanned

Crew of 3 or 6

Life support

Dock with ISPP-SHM on surface

Crew of 6

Life support

Aeromaneuvering

Dock with COV/HM in orbit

Transfer crew of 6 from orbit to surface

Support EVA

MARS

Figure 4: Lander Venn Diagram

This Trade studies indicate that more delta-V is spent executing this inclination change than is spent stopping at L1, if the desired inclination is greater than 39 degrees from the equatorial plane.

One of the most important design decisions that may be found in each of the individual staged

missions is the use of orbital rendezvous as means to reduce initial mass in LEO, especially for Mars missions. Figure 5 demonstrates the significant mass savings to be gained from using the Mars Orbital Rendezvous (MOR) mission architecture over a mission that goes directly to the Martian surface and the returns. The addition of pre-positioned elements may further reduce the initial mass in LEO to less than 500,000 kg.

Integrated Baseline

Once individual staged missions have been designed, compared and elaborated upon, an integrated baseline may be generated. This baseline combines all the individual missions and utilizes their common elements to form a strategy by which sustained space exploration may be achieved.

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Figure 5: Comparison of Mission Architectures

0

0.5

1

1.5

2

2.5

3

3.5

Direct to Surface Mars Orbit Rendezvous(MOR)

MOR w/ pre-positionedlanders

MOR w/ pre-positionedlanders and return fuel

Comparison of Mission Architectures

Initial mass in LEO (millions of kg) )

Human flight

Pre-positioned mass

is a schematic for this baseline.

Short-Stay Lunar Mission

Medium-StayLunar Mission

Long-StayLunar Mission

Phobos Mission

Short-Stay Mars Mission

Extended-StayMars Mission

Extended-Stay + InfrastructureMars Mission

Beyond

Site selection, resource information

Science & ISPP test, open rover, EVA, life-support

Lunar habitation technologies

Asteroid rendezvous tech., lunar interception tech., Venus flyby tech.

Fast transfer tech

Working ISPP, pressurized- rover, space-suit, life-support

Radio-control for probes

Large ISPP, pressurized-rover, excavation, habitat, infrastructure, Mars Direct

Pre-positioning

Short-Stay Lunar Mission

Medium-StayLunar Mission

Long-StayLunar Mission

Phobos Mission

Short-Stay Mars Mission

Extended-StayMars Mission

Extended-Stay + InfrastructureMars Mission

Beyond

Site selection, resource information

Science & ISPP test, open rover, EVA, life-support

Lunar habitation technologies

Asteroid rendezvous tech., lunar interception tech., Venus flyby tech.

Fast transfer tech

Working ISPP, pressurized- rover, space-suit, life-support

Radio-control for probes

Large ISPP, pressurized-rover, excavation, habitat, infrastructure, Mars Direct

Pre-positioning

Figure 6: Integrated Baseline

The baseline strategy presented by this report is as follows:

Lunar missions may be expected to occur in the near future. The primary purpose of these missions is to re-establish the capability of the Apollo missions and to serve as lunar “scouts”, which will search primarily for location information, perhaps regarding possible resources that may be exploited on the moon. Prior to the first of these missions, unmanned robotic probes may be sent to a number of promising landing sites. These missions will occur, each time in a different location, until a decision is made to study particular locations in more depth and for a longer period of time.

Initial missions will evolve towards larger endeavors aimed at the generation of scientific and technical knowledge, including resource evaluation of the more promising sites found on the short-stay missions. Astronauts participating in these new missions will be tasked with operating larger scale scientific apparatus and the scientific precursors to the first in-situ propellant production facilities. These will be small scale at first, serving primarily as technology demonstrators, but may be scaled up in future missions to allow for some basic functionality. Enablers, such as an un-pressurized rover that is designed to carry astronauts to locations beyond their operational walking radius, will eventually be introduced.

Assuming usable in-situ resources are available for extraction, one primary site will eventually be chosen for a future semi-permanent lunar base. This base will be aimed at establishing semi-permanent lunar habitation technology, and will also generate the capability to search the far side of the moon in more detail. It is important to note that the presence of semi-permanent

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infrastructure does not imply a permanent human presence. Rather, humans will be able to leave the semi-permanent base un-manned, if necessary, without a total loss of infrastructure. This report assumes that in-situ resources are present and usable. Over time, the number of astronauts on the moon during a given mission will increase from three to six. These astronauts may gain experience in living in non-Earth environments for increasingly long periods of time. Since these latest missions will all be aimed at the construction of one habitat, some pre-positioning will take place by necessity through drops from unmanned probes and previous moon missions. Therefore, this suite of missions will allow for the buildup of accurate pre-positioning operational knowledge. Astronauts participating in the later missions will be tasked with operating larger-scale in-situ propellant production facilities. The eventual goal will be to create a largely self-sustained semi-permanent base. Some potential capabilities to be added include a rescue vehicle stored in an easily accessible location so that astronauts may escape to Earth in case of unforeseen circumstances. Included with a semi-permanent base will be habitat modules in which astronauts may live for increasing lengths of time. These missions will occur until the first Mars mission is undertaken, at which point the semi-permanent base may be turned over to international partners or the commercial sector for further development. These missions will have the capability to survive throughout the lunar night, and will therefore require an independent source of power, at least during the night. The next step beyond the extended-stay missions is the Martian Short Stay set of missions. These will be the first expansion of humans beyond the bounds of Earth orbit.

The primary purpose of the first Martian missions is to demonstrate the ability of mankind to survive on the surface of Mars for short periods of time. These missions nominally require pre-positioning of cargo on the Martian surface, although the first such mission may not utilize this capability simply because of the complexity of the maneuvers involved. If pre-positioning has previously been accomplished successfully on the Moon, the technology used may be extensible to the Martian environment. Prior to the first missions, unmanned robotic probes may be sent to a number of promising landing sites. These probes may also be used to practice the accuracy of pre-positioning technology. Like an extended-stay lunar mission, all Mars missions possess habitat modules. In the event that no in-situ resources exist to be exploited on the Moon, the habitat capability must be developed for this mission alone with no extensibility from a previous mission. Like some of the lunar missions, Martian missions will possess un-pressurized rovers that may be used to explore over a relatively large range. They will also be used to test and verify in-situ resource production and utilization facilities for use on Mars. These first Martian missions will occur, usually in different locations, until a decision is made to study particular locations in more depth and for a longer period of time.

Upon finding an ideal long-term site, Martian exploration may continue with longer term, shorter-transfer missions to minimize the effect of microgravity and to take advantage of the resources expected to be found on Mars. Later missions may include testing of longer-term habitation facilities, testing of new space-suit concepts, and alternative propulsion and in-situ propellant production concepts. The primary purpose of later Martian missions is to demonstrate the ability of mankind to survive on the surface of Mars for an increased duration. In the long term, humans will establish a semi-permanent infrastructure on Mars to be used for science, operations research, or as a test bed for the next destination. These missions nominally require pre-positioning of cargo on the Martian surface, and therefore require the performance of

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previous successful shorter-term missions to ensure that pre-positioning technology is well enough developed. Initial Mars missions will have identified promising resource excavation sites, and resource processing activities. One of the purposes of the later Mars missions is to take advantage of these capabilities for refueling, for life-support & agriculture, and to explore Mars in a more comprehensive manner and over a longer period of time. Eventually, missions will have the capability to be self-sustained based upon in-situ resource production, thus reducing mass in LEO as much as possible. To this end, the transit characteristics of these missions will evolve from a MOR class mission to a Mars Direct mission. All later Mars missions will take advantage of knowledge gained from habitat technology used for the initial Martian missions, including upgraded rovers that may be used to explore over a relatively large range. These rovers may be pressurized in the later missions, and will certainly be pressurized if a decision is made to build a permanent Martian infrastructure. These missions may also make use of inflatable structures and other innovative semi-permanent construction materials in the establishment of a Martian base.

Upon successful completion of a semi-permanent Martian base, NASA will have gained unparalleled experience in the field of manned space exploration. This exploration will continue throughout the solar system. A mission to the Martian moons is just one way to start this expansion. The primary purpose of Martian moons missions is to demonstrate extensibility on multiple levels. Beyond the Martian system, there are three places that NASA may choose to explore. These include:

The inner solar-system The asteroid belt The moons of the outer solar-system

A Martian moon mission is an ideal technology demonstrator for any of these destinations. The suggested time for this mission is before the first manned Mars missions, when resources are not heavily invested in a semi-permanent Martian base. This will give NASA operational experience in navigating to Mars orbit, similar to how Apollo 8 achieved lunar orbit before the landing of Apollo 11.

Although this report only focuses on the Moon and on Mars as locations to be explored, the new NASA vision unequivocally states that the program does not stop there. Exploration is an activity that will never cease and whose potential to educate and to inspire will never run dry. Although the next location to be visited by human astronauts is not yet certain, there is no shortage of secrets to be unlocked and mysteries to be discovered. It is for this reason that the President’s vision is entitled Moon, Mars and Beyond, for beyond is the ultimate destination of mankind.

Strategy Development Tools – Scenario Planning

It is important to recognize that each design, including the baseline presented in this report, carries with it implicit assumptions about the state of the present and future environment. These assumptions about the environment constitute a de facto scenario in which the system is designed

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to operate nominally. Due to the high degree of uncertainty, and associated high probability of change surrounding these assumptions, it is necessary that the system be able to adapt to changing environmental factors. Seven extreme changes in the system’s operating environment were selected as scenarios against which the baseline system’s performance could be evaluated. Scenario planning is primarily used in this fashion to identify architectural options and trades. In doing so, the system may be made adaptable or robust in the face of changing environmental conditions. In this section, the baseline strategy was evaluated using each of the following scenarios. Where possible, options were exercised that allowed for significant adaptability or robustness to the constraints imposed by the scenario’s parameters. The performance of the baseline strategy upon the use of these options serves to demonstrate the degree to which this strategy is sustainable and extensible in the face of drastic change.

The seven scenarios, and their associated trades, are listed below:1. Space Race II: A foreign power challenges American leadership in space by making

public feasible claims of the establishment of a lunar base and a Martian human mission. NASA budget receives a resultant increase:

Trade: To what degree should extensibility be designed into the space exploration system at the cost of optimality or schedule?

2. Launch System Failure: NASA’s primary launch vehicle is destroyed during operation. All usage of that particular vehicle ceases. American astronauts are required to find another method to leave and return to Earth as soon as possible.

Trade: Should a second launch vehicle be designed as a preventative measure? If so, will it be done internationally or within a competitive structure?

3. Dawn of the Nuclear Propulsion Age: Nuclear propulsion technology emerges as a viable replacement to chemical propulsion.

Trade: To what degree should a subsystem in the space exploration architecture be modular?

4. Asteroid Strike: A Near Earth Asteroid impacts the Earth’s atmosphere. The US government allocates approximately 4% of the total yearly US budget between NASA and the DoD for the development of an early warning system, and to explore the possibilities of destroying or diverting asteroids on Earth impact trajectories.

Trade: Should a mission to the Martian moons be attempted for developing asteroid operational knowledge?

5. Lunar Water World: An American expedition to the moon discovers reserves of resources at the Lunar Poles, allowing for the large-scale extraction of hydrogen, oxygen, and water ice.

Trade: Should L1 be used to access the lunar poles?

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6. Following discoveries of microbial fossils on Mars, unmanned probes find strong evidence of one-celled life currently existing in the Martian subsurface soil.

Trade: To what degree should the Moon be used as a test bed for Mars?

7. NASA Policy Change: NASA is directed to cease all exploration activities. The exploration budget is cut due to lack of public interest.

Trade: To what degree should NASA maintain public awareness activities?

In order to be able to evaluate these trades, it is useful to develop a rigorous method by which one may evaluate one architectural choice over another. This report presents several econometric tools to do this. Two approaches are available; either a closed “best design” that attempts to take into account each and every possible change, or a strategy that will change and evolve to accommodate the unforeseen. The former option is restricted to current projections of future events, whereas the latter option is dynamic and adaptable in the face of uncertainty. This report proposes the latter approach as a way to adapt to changing environmental conditions, and to choose the best way to proceed in the future, while preserving as many open options as possible. Decisions, which would otherwise have to be made at the outset, are delayed such that, when the final choice is required, it is made in an environment of decreased uncertainty.

The bulk of this report focuses on the creation of a baseline strategy to go to the moon, to Mars and beyond. This baseline was designed with a set of implicit assumptions regarding the state of the system’s operating environment through time. Ideally, the baseline is the strategy that is most likely to succeed given present knowledge of future events.

An alternative set of extreme environmental changes that would impact the baseline design (either positively or negatively) was identified through brainstorming. These changes constitute scenario descriptions. A set of responses to those scenario descriptions was then developed. These responses constitute alternative paths that may be taken in designing the system. Using this framework, one may also think of the baseline as one of these scenario descriptions, developed in response to the most likely state of the environment. The way in which the scenario descriptions differed from the baseline identified a set of architectural trades or options, and ultimately, decisions, which were deemed to be critical, and worthy of a deeper analysis. Every potential architecture may be fully described by a vector of the different decisions that have to be taken in order to implement it. The meaning of the word architecture in this case is not restricted to the physical form of the objects, but instead to the whole system design, including forms, points in the space through which the system will transit, amount of money available, the political landscape, etc. It is possible to apply Utility Theory to analyze each of these vectors, and more specifically, the scenarios and associated trades. In doing so, one must first explore how the present baseline reacts to a change in the operating environment, and how appropriate decisions taken at points throughout the system’s lifecycle could buy some insurance against negative scenarios, or increased payoffs in case of positives ones. By investing some cost (in the sense of a slightly lower expected utility) one could decrease risk, in the sense of reducing the dispersion by neutralizing negative outcomes. Similarly, one could increase the payoffs by taking

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real advantage of optimistic outcomes. This analysis is the basis of Real Options theory. The problem of acquiring utility is complex; however, and in its complexity lays its value. The utility is not an absolute number; rather it is a scaled numerical representation that reflects a synthesis of the opinions of a group of stakeholders around an issue. The tool proposed to make this synthesis is called the Analytical Deliberative Process, and is a formal framework that helps a group of people to argue and discuss a set of measures that may sometimes be in opposition. In doing so, utility values may be determined such that the analysis can proceed. By assessing the different performance metrics that each of the architecture vectors presents, it would be possible to get a measure of the net utility that each architecture holds for the stakeholders.

As time passes, both decision points and chance points are encountered. Some of these chance points may have been predicted through previous analyses, and thus the baseline would remain unchanged, but others may not have been anticipated and thus, the architecture would take, at that point, an out-of-baseline approach. It is central to the purpose of this work to understand each of these possible branching points, and to study them through a conceptual scenario analysis, such as the one described above, in order to be able to apply the real options approach and to provide a thoughtful way to decide where, when, and how much to pay for risk reduction and benefit magnification

One defining attribute of a sustainable system is its long expected life cycle. Thus, predicting the circumstances under which the system will operate throughout its life cycle becomes difficult as uncertainty increases with time. Such systems must also incorporate subsystems that operate throughout the architectural domain, from the mechanical to the political, to the commercial. Again, significant uncertainty is present in the system’s operating environment. As a result, the system must be prepared to adapt to unexpected situations, should they arise, without significantly reducing the system’s operational utility. The value of many of these analysis tools is that they allow for the design of a system in an environment of high uncertainty.

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Conclusions

Current design methods are likely not sufficient to meet the goals of the new space exploration initiative. A new design methodology must be developed. The new methodology accounts for sustainability and evaluates designs based on knowledge. While the proposed design method is certainly not the only solution, it is intended to be a starting point for further improvement, and ultimately, a catalyst that enables NASA and the nation to move into the next era of space exploration in a sustained and consistent fashion. In conclusion, the following two recommendations are made to NASA:

Sustainability must be incorporated into the conceptual design of a space exploration system architecture. One way to do this involves using an iterative process that identifies and maximizes commonality across multiple mission scenarios. While resulting architectures will likely be sub-optimal from a point design perspective, tools such as real options, scenario planning, and decision analysis can be used to justify sub-optimality based on over-all life-cycle considerations.

The most important value-added deliverable for an exploration system is knowledge. NASA must view the acquisition, transfer, synthesis, and communication of knowledge as the primary product its exploration program, and include valuation of attribute of knowledge in important system trades.

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Appendix: Table of Acronyms

LEO Low Earth OrbitSTS Space Transportation SystemSRB Solid Rocket BoosterET External TankEELV Evolved Expendable Launch VehicleDSN Deep Space NetworkCOV Crew Operations VehicleHM Habitation ModuleCES Crew Exploration SystemSM Service ModuleMTV Moon/Mars Transport VehicleML Mars LanderLL Lunar LanderMCM Modern Command ModuleSHM Surface Habitation ModuleLL1 Lunar Lander 1LL2 Lunar Lander 2L1 Earth-Moon Lagrangian Libration Point 1MOR Mars Orbital Rendezvous

Table 2: Table of Acronyms

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