Technology Focus Electronics/Computers...is contained in a TSP (see page 1). GSC-16184-1 Detecting...

Technology Focus

Electronics/Computers

Software

Materials

Mechanics/Machinery

Manufacturing

Bio-Medical

Physical Sciences

Information Sciences

Books and Reports

10-12 October 2012

https://ntrs.nasa.gov/search.jsp?R=20120016252 2020-06-11T16:21:18+00:00Z

NASA Tech Briefs, October 2012 1

INTRODUCTIONTech Briefs are short announcements of innovations originating from research and developmentactivities of the National Aeronautics and Space Administration. They emphasize information con-sidered likely to be transferable across industrial, regional, or disciplinary lines and are issued toencourage commercial application.

Additional Information on NASA Tech Briefs and TSPsAdditional information announced herein may be obtained from the NASA Technical Reports Server:http://ntrs.nasa.gov.

Please reference the control numbers appearing at the end of each Tech Brief. Infor mation on NASA’s Innovative Partnerships Program (IPP), its documents, and services is available on the World Wide Webat http://www.ipp.nasa.gov.

Innovative Partnerships Offices are located at NASA field centers to provide technology-transfer access toindustrial users. Inquiries can be made by contacting NASA field centers listed below.

Ames Research CenterDavid Morse(650) [email protected]

Dryden Flight Research CenterRon Young(661) [email protected]

Glenn Research CenterKimberly A. Dalgleish-Miller(216) [email protected]

Goddard Space Flight CenterNona Cheeks(301) [email protected]

Jet Propulsion LaboratoryIndrani Graczyk(818) [email protected]

Johnson Space CenterJohn E. James(281) [email protected]

Kennedy Space CenterDavid R. Makufka(321) [email protected]

Langley Research CenterMichelle Ferebee(757) [email protected]

Marshall Space Flight CenterTerry L. Taylor(256) [email protected]

Stennis Space CenterRamona Travis(228) [email protected]

NASA Headquarters

Daniel Lockney, Technology Transfer Program Executive(202) [email protected]

Small Business Innovation Research(SBIR) & Small Business TechnologyTransfer (STTR) ProgramsRich Leshner, Program Executive(202) [email protected]

NASA Field Centers and Program Offices

5 Technology Focus: Sensors5 Detection of Chemical Precursors of Explosives

5 Detecting Methane From Leaking Pipelines and as Greenhouse Gas in the Atmosphere

6 Onboard Sensor Data Qualification in Human-Rated Launch Vehicles

6 Rugged, Portable, Real-Time Optical GaseousAnalyzer for Hydrogen Fluoride

7 A Probabilistic Mass Estimation Algorithm for a Novel7-Channel Capacitive Sample Verification Sensor

7 Low-Power Architecture for an Optical Life Gas Analyzer

9 Electronics/Computers9 Online Cable Tester and Rerouter

9 A Three-Frequency Feed for Millimeter-Wave Radiometry

10 Capacitance Probe Resonator for Multichannel Electrometer

10 Inverted Three-Junction Tandem Thermophotovoltaic Modules

13 Manufacturing & Prototyping13 Fabrication of Single Crystal MgO Capsules

13 Inflatable Hangar for Assembly of Large Structures in Space

14 Mars Aqueous Processing System

15 Materials & Coatings15 Hybrid Filter Membrane

17 Mechanics/Machinery17 Design for the Structure and the Mechanics

of Moballs

18 Pressure Dome for High-Pressure Electrolyzer

19 Cascading Tesla Oscillating Flow Diode for StirlingEngine Gas Bearings

19 Compact, Low-Force, Low-Noise Linear Actuator

20 Ultra-Compact Motor Controller

21 Bio-Medical21 Extreme Ionizing-Radiation-Resistant Bacterium

21 Wideband Single-Crystal Transducer for Bone Characterization

22 Fluorescence-Activated Cell Sorting of Live VersusDead Bacterial Cells and Spores

23 Nonhazardous Urine Pretreatment Method

25 Physical Sciences25 Laser-Ranging Transponders for Science

Investigations of the Moon and Mars

25 Ka-Band Waveguide Three-Way Serial Combiner for MMIC Amplifiers

26 Structural Health Monitoring With Fiber BraggGrating and Piezo Arrays

27 Low-Gain Circularly Polarized Antenna With Torus-Shaped Pattern

29 Software29 Stereo and IMU- Assisted Visual Odometry for

Small Robots

29 Global Swath and Gridded Data Tiling

29 GOES-R: Satellite Insight

29 Aquarius iPhone Application

31 Information Technology31 Monitoring of International Space Station Telemetry

Using Shewhart Control Charts

31 Theory of a Traveling Wave Feed for a Planar Slot Array Antenna

32 Time Manager Software for a Flight Processor

32 Simulation of Oxygen Disintegration and MixingWith Hydrogen or Helium at Supercritical Pressure

35 Books & Reports35 A Superfluid Pulse Tube Refrigerator Without

Moving Parts for Sub-Kelvin Cooling

35 Sapphire Viewports for a Venus Probe

35 The Mobile Chamber

35 Electric Propulsion Induced Secondary Mass Spectroscopy

35 Radiation-Tolerant DC-DC Converters

10-12 October 2012


This document was prepared under the sponsorship of the National Aeronautics and Space Administration. Neither the United States Govern-ment nor any person acting on behalf of the United States Government assumes any liability resulting from the use of the information containedin this document, or warrants that such use will be free from privately owned rights.


Technology Focus: Sensors

Certain selected chemicals associatedwith terrorist activities are too unstable tobe prepared in final form. These chemi-cals are often prepared as precursor com-ponents, to be combined at a time imme-diately preceding the detonation. Oneexample is a liquid explosive, which usu-ally requires an oxidizer, an energysource, and a chemical or physical mech-anism to combine the other components.Detection of the oxidizer (e.g. H2O2) orthe energy source (e.g., nitromethane) isoften possible, but must be performed ina short time interval (e.g., 5–15 seconds)and in an environment with a very smallconcentration (e.g.,1–100 ppm), becausethe target chemical(s) is carried in asealed container.

These needs are met by this inven-tion, which provides a system and asso-

ciated method for detecting one ormore chemical precursors (compo-nents) of a multi-component explosivecompound. Different carbon nan-otubes (CNTs) are loaded (by doping,impregnation, coating, or other func-tionalization process) for detecting ofdifferent chemical substances that arethe chemical precursors, respectively, ifthese precursors are present in a gas towhich the CNTs are exposed. After ex-posure to the gas, a measured electricalparameter (e.g. voltage or current thatcorrelate to impedance, conductivity,capacitance, inductance, etc.) changeswith time and concentration in a pre-dictable manner if a selected chemicalprecursor is present, and will approachan asymptotic value promptly after ex-posure to the precursor.

The measured voltage or current arecompared with one or more sequencesof their reference values for one ormore known target precursor mole-cules, and a most probable concentra-tion value is estimated for each one,two, or more target molecules. Anerror value is computed, based on dif-ferences of voltage or current for themeasured and reference values, usingthe most probable concentration val-ues. Where the error value is less thana threshold, the system concludes thatthe target molecule is likely. Presenceof one, two, or more target moleculesin the gas can be sensed from a singleset of measurements.

This work was done by Jing Li of Ames Re-search Center. Further information is con-tained in a TSP (see page 1). ARC-15566-5

Detection of Chemical Precursors of ExplosivesPrecursors provide early warning.Ames Research Center, Moffett Field, California

Laser remote sensing measurementsof trace gases from orbit can provide un-precedented information about impor-tant planetary science and answer criti-cal questions about planetaryatmospheres. Methane (CH4) is the sec-ond most important anthropogenicallyproduced greenhouse gas. Though itsatmospheric abundance is much lessthan that of CO2 (1.78 ppm vs. 380ppm), it has much larger greenhouseheating potential. CH4 also contributesto pollution in the lower atmospherethrough chemical reactions, leading toozone production. Atmospheric CH4concentrations have been increasing asa result of increased fossil fuel produc-tion, rice farming, livestock, and land-fills. Natural sources of CH4 include wet-lands, wild fires, and termites, andperhaps other unknown sources. Impor-tant sinks for CH4 include non-saturated

soils and oxidation by hydroxyl radicalsin the atmosphere.

Remotely measuring CH4 and otherbiogenic molecules (such as ethaneand formaldehyde) on Mars also hasimportant implications on the exis-tence of life on Mars. Measuring CH4 atvery low (ppb) concentrations fromorbit will dramatically improve the sen-sitivity and spatial resolution in thesearch for CH4 vents and sub-surfacelife on other planets.

A capability has been developed usinglasers and spectroscopic detection tech-niques for the remote measurements oftrace gases in open paths. Detection ofCH4, CO2, H2O, and CO in absorptioncells and in open paths, both in the mid-IR and near-IR region, has been demon-strated using an Optical Parametric Am-plifier laser transmitter developed atGSFC. With this transmitter, it would be

possible to develop a remote sensingmethane instrument.

CH4 detection also has very importantcommercial applications. Pipeline leakdetection from an aircraft or a helicop-ter can significantly reduce cost, re-sponse time, and pinpoint the location.The main advantage is the ability to rap-idly detect CH4 leaks remotely. This isextremely important for the petrochem-ical industry. This capability can be usedin manned or unmanned airborne plat-forms for the detection of leaks inpipelines and other areas of interestwhere a CH4 leak is suspected.

This work was done by Haris Riris, KenjiNumata, Steve Li, Stewart Wu, Anand Ra-manathan, and Martha Dawsey of GoddardSpace Flight Center. Further information is contained in a TSP (see page 1). GSC-16184-1

Detecting Methane From Leaking Pipelines and as GreenhouseGas in the AtmosphereRemote detection will speed up response time. Goddard Space Flight Center, Greenbelt, Maryland

The avionics system software forhuman-rated launch vehicles requiresan implementation approach that is ro-bust to failures, especially the failure ofsensors used to monitor vehicle condi-tions that might result in an abort de-termination. Sensor measurements pro-vide the basis for operational decisionson human-rated launch vehicles. Thisdata is often used to assess the health ofsystem or subsystem components, toidentify failures, and to take correctiveaction. An incorrect conclusion and/orresponse may result if the sensor itselfprovides faulty data, or if the data pro-vided by the sensor has been corrupted.Operational decisions based on faultysensor data have the potential to be cat-astrophic, resulting in loss of mission orloss of crew. To prevent these later situ-ations from occurring, a Mod ular Arch -itecture and Generalized Meth od ologyfor Sensor Data Qual if ication inHuman-rated Launch Vehicles hasbeen developed.

Sensor Data Qualification (SDQ) is aset of algorithms that can be imple-mented in onboard flight software, andcan be used to qualify data obtainedfrom flight-critical sensors prior to thedata being used by other flight softwarealgorithms. Qualified data has been ana-lyzed by SDQ and is determined to be a

true representation of the sensed systemstate; that is, the sensor data is deter-mined not to be corrupted by sensorfaults or signal transmission faults. Sen-sor data can become corrupted by faultsat any point in the signal path betweenthe sensor and the flight computer.Qualifying the sensor data has the bene-fit of ensuring that erroneous data isidentified and flagged before otherwisebeing used for operational decisions,thus increasing confidence in the re-sponse of the other flight softwareprocesses using the qualified data, anddecreasing the probability of falsealarms or missed detections.

At a high level, SDQ is called by theflight computer, as required each cycle,to qualify a specific sensor or set of sen-sors. SDQ first determines the update-rate of the data, and obtains the speci-fied data from the sensor data table.SDQ then consults the data provided bythe Mission Manager Function to deter-mine the appropriate subset of pre-de-fined algorithms, thresholds, and pa-rameters to be used in qualifyingspecified sensor data. Next, appropriatealgorithms are applied to the data. If agiven algorithm determines that thedata is faulty, the associated data signalaccrues a strike from that algorithm forthe current flight computer cycle, and

the algorithm or algorithms that failedthe data are recorded. Having run all ap-plicable fault detection algorithms, thestrike counters for each of the applica-ble algorithm/sensor pairs are thentested for the persistence of any failures.Sensors associated with data that meetspersistence criteria are flagged as per-manently failed.

Alternate embodiments of some of thequalification algorithms used in the AresSDQ architecture have prior implemen-tations that were incorporated into com-mercial data qualification developmentand analysis tools under the SureSensetrademark. SureSense has been used todevelop and implement real-time dataqualification algorithms for ground-based nuclear power generation systems.

This work was done by Edmond Wong andKevin J. Melcher of Glenn Research Center;William A. Maul, Amy K. Chicatelli, ThomasS. Sowers, and Christopher Fulton of QinetiQNorth America; and Randall Bickford of Ex-pert Microsystems, Inc. Further information iscontained in a TSP (see page 1).

Inquiries concerning rights for the commer-cial use of this invention should be addressedto NASA Glenn Research Center, InnovativePartnerships Office, Attn: Steven Fedor, Mail Stop 4–8, 21000 Brookpark Road,Cleveland, Ohio 44135. Refer to LEW-18633-1.

6 NASA Tech Briefs, October 2012

Hydrogen fluoride (HF) is a primaryevolved combustion product of fluori-nated and perfluorinated hydrocarbons.HF is produced during combustion bythe presence of impurities and hydro-gen-containing polymers including poly-imides. This effect is especially danger-ous in closed occupied volumes likespacecraft and submarines. In these sys-

tems, combinations of perfluorinated hy-drocarbons and polyimides are used forinsulating wiring. HF is both highly toxicand short-lived in closed environmentsdue to its reactivity. The high reactivityalso makes HF sampling problematic.

An infrared optical sensor can detectpromptly evolving HF with minimal sam-pling requirements, while providing

both high sensitivity and high specificity.A rugged optical path length enhance-ment architecture enables both high HFsensitivity and rapid environmental sam-pling with minimal gaseous contact withthe low-reactivity sensor surfaces. Theinert optical sample cell, combined withinfrared semiconductor lasers, is joinedwith an analog and digital electronic

Rugged, Portable, Real-Time Optical Gaseous Analyzer forHydrogen FluorideApplications include trace gas sensor applications where rapid sampling is required, particularlyin human-occupied closed volumes.John H. Glenn Research Center, Cleveland, Ohio

Onboard Sensor Data Qualification in Human-Rated Launch Vehicles Applications include sensor data qualification and equipment condition monitoring incommercial power plants. John H. Glenn Research Center, Cleveland, Ohio


control architecture that allows forruggedness and compactness. The com-bination provides both portability andbattery operation on a simple cam-corder battery for up to eight hours.

Optical detection of gaseous HF isconfounded by the need for rapid sam-pling with minimal contact between thesensor and the environmental sample. Asensor is required that must simultane-ously provide the required sub-parts-per-million detection limits, but with thehigh specificity and selectivity expectedof optical absorption techniques. Itshould also be rugged and compact forcompatibility with operation onboardspacecraft and submarines.

A new optical cell has been developedfor which environmental sampling is ac-complished by simply traversing the few-mm-thick cell walls into an open volume

where the measurement is made. A small,low-power fan or vacuum pump may beused to push or pull the gaseous sampleinto the sample volume for a responsetime of a few seconds. The optical cell si-multaneously provides for an enhancedoptical interaction path length betweenthe environmental sample and the in-frared laser. Further, the optical cell itselfis comprised of inert materials that renderit immune to attack by HF. In some cases,the sensor may be configured so that theoptoelectronic devices themselves are pro-tected and isolated from HF by the opticalcell. The optical sample cell is combinedwith custom-developed analog and digitalcontrol electronics that provide rugged,compact operation on a platform that canrun on a camcorder battery.

The sensor is inert with respect toacidic gases like HF, while providing the

required sensitivity, selectivity, and re-sponse time. Certain types of combustionevents evolve copious amounts of HF, verylittle of other gases typically associatedwith combustion (e.g., carbon monox-ide), and very low levels of aerosols andparticulates (which confound traditionalsmoke detectors). The new sensor plat-form could warn occupants early enoughto take the necessary countermeasures.

This work was done by Jeffrey Pilgrim andPaula Gonzales of Vista Photonics, Inc. forGlenn Research Center. Further information iscontained in a TSP (see page 1).

Inquiries concerning rights for the commer-cial use of this invention should be addressed toNASA Glenn Research Center, InnovativePartnerships Office, Attn: Steven Fedor, MailStop 4–8, 21000 Brookpark Road, Cleveland,Ohio 44135. Refer to LEW-18892-1.

Analog and digital electronic controlarchitecture has been combined with anoperating methodology for an opticaltrace gas sensor platform that allows verylow power consumption while providingfour independent gas measurements inessentially real time, as well as a user in-

terface and digital data storage and out-put. The implemented design eliminatesthe cross-talk between the measurementchannels while maximizing the sensitiv-ity, selectivity, and dynamic range foreach measured gas. The combinationprovides for battery operation on a sim-

ple camcorder battery for as long aseight hours. The custom, compact,rugged, self-contained design specificallytargets applications of optical major con-stituent and trace gas detection for mul-tiple gases using multiple lasers and pho-todetectors in an integrated package.

Low-Power Architecture for an Optical Life Gas AnalyzerA simple camcorder battery can be used for as long as eight hours.John H. Glenn Research Center, Cleveland, Ohio

A Probabilistic Mass Estimation Algorithm for a Novel 7-Channel Capacitive Sample Verification SensorNASA’s Jet Propulsion Laboratory, Pasadena, California

A document describes an algorithmcreated to estimate the mass placed on asample verification sensor (SVS) de-signed for lunar or planetary roboticsample return missions. A novel SVSmeasures the capacitance between arigid bottom plate and an elastic topmembrane in seven locations. As addi-tional sample material (soil and/orsmall rocks) is placed on the top mem-brane, the deformation of the mem-brane increases the capacitance. Themass estimation algorithm addressesboth the calibration of each SVS chan-nel, and also addresses how to combinethe capacitances read from each of theseven channels into a single mass esti-

mate. The probabilistic approach com-bines the channels according to the vari-ance observed during the trainingphase, and provides not only the massestimate, but also a value for the cer-tainty of the estimate.

SVS capacitance data is collected forknown masses under a wide variety ofpossible loading scenarios, though in allcases, the distribution of sample withinthe canister is expected to be approxi-mately uniform. A capacitance-vs-masscurve is fitted to this data, and is subse-quently used to determine the mass esti-mate for the single channel’s capaci-tance reading during the measurementphase. This results in seven different

mass estimates, one for each SVS chan-nel. Moreover, the variance of the cali-bration data is used to place a Gaussianprobability distribution function (pdf)around this mass estimate. To blendthese seven estimates, the seven pdfs arecombined into a single Gaussian distri-bution function, providing the finalmean and variance of the estimate. Thisblending technique essentially takes thefinal estimate as an average of the esti-mates of the seven channels, weightedby the inverse of the channel’s variance.

This work was done by Michael Wolf ofCaltech for NASA’s Jet Propulsion Labora-tory. Further information is contained in aTSP (see page 1). NPO-48143


Commercial off-the-shelf digital elec-tronics including data acquisition cards(DAQs), complex programmable logicdevices (CPLDs), field programmablegate arrays (FPGAs), and microcon-trollers have been used to achieve thedesired outcome. The lowest-power inte-grated architecture achieved during theproject was realized in the prototypethat utilized a custom FPGA digitalboard (in combination with a custom-built, low-power analog electronicsboard) and a low-performance commer-cial microcontroller. The FPGA gener-ated all the necessary control signals forthe analog board, and performed data

acquisition and low-level, time-criticaldata processing. The microcontrollerwas used to implement high-level dataanalysis, the user interface, and datastorage and output. Further power sav-ings were realized by operating the fourlasers sequentially, rather than operatingthem in parallel. A several-Hz updaterate was achieved even with sequentialoperation, much faster than requiredfor gas measurement on the Interna-tional Space Station.

A rugged and flexible multiple gassensor platform was developed, whichinvolves laser diode-based optical ab-sorption spectroscopy coupled to an el-

egant optical path length enhancementsolution and advanced digital and ana-log electronic design. The optical ab-sorption cell is shared by multiple lasersand detectors, which minimizes thefootprint of the device. On the otherhand, the optical layout is simple andflexible: no precise alignment is re-quired. The laser diodes are easily in-terchangeable, which, in principle, al-lows reconfiguring the sensor tomeasure different sets of trace gases.Custom power-efficient analog and dig-ital electronic boards are designed tominimize the power consumption ofthe sensor. Further power savings arerealized by fast time-multiplexing themeasurements of different gases, ratherthan implementing them in parallel.This development allows a fully inte-grated multiple gas monitor to operateon simple camcorder batteries for a pe-riod of several hours.

This work was done by Jeffrey Pilgrim andAndrei Vakhtin of Vista Photonics, Inc. forGlenn Research Center. Further information iscontained in a TSP (see page 1).

Inquiries concerning rights for the commer-cial use of this invention should be addressed toNASA Glenn Research Center, InnovativePartnerships Office, Attn: Steven Fedor, MailStop 4–8, 21000 Brookpark Road, Cleveland,Ohio 44135. Refer to LEW-18894-1.

The Sensor Data Qualification (SDQ) system receives inputs from system messages and data acquisi-tion. The sensor data includes first-stage and upper-stage flight-critical sensors.

Data

Acquisition

System

Messages

Vehicle Higher-Level

Control and

Safety

Functons

SDQS Sensor

Data

SensorData

DataQuality

Flight Computer


Electronics/Computers

A three-frequency millimeter-wavefeed horn was developed as part of anadvanced component technology taskthat provides components necessary forhigher-frequency radiometers to meetthe needs of the Surface Water andOcean Topography (SWOT) mission.The primary objectives of SWOT are tocharacterize ocean sub-mesoscale proc -esses on 10-km and larger scales in theglobal oceans, and to measure the globalwater storage in inland surface waterbodies, including rivers, lakes, reser-voirs, and wetlands.

In this innovation, the feed providesthree separate output ports in the 87-to-

97-GHz, 125-to-135-GHz, and 161-to-183-GHz bands; WR10 for the 90-GHz chan-nel, WR8 for the 130-GHz channel, andWR5 for the 170-GHz channel. Theseports are in turn connected to individualradiometer channels that will alsodemonstrate component technology in-cluding new PIN-diode switches andnoise diodes for internal calibration inte-grated into each radiometer front end.For this application, a prime focus feed isrequired with an edge taper of approxi-mately 20 dB at an illumination angle of±40°. A single polarization is provided ineach band. Preliminary requirementscalled for a return loss of better than 15

dB, which is achieved across all threebands. Good pattern symmetry is also ob-tained throughout all three-frequencybands. This three-frequency broadbandmillimeter-wave feed also minimizesmass and provides a common focal pointfor all three millimeter-wave bands.

In order to achieve similar E and Hplane beam widths over the combined87-to-183-GHz band ring, loaded slotsare employed in the corrugated portionof the feed. The feed operates in a flare-angle limited condition, which gives ap-proximately constant beam width acrossthe entire band, and provides a com-mon phase center located near its apex.

A Three-Frequency Feed for Millimeter-Wave Radiometry This wave feed operates at frequencies approximately five times higher than current feeds andprovides greater bandwidth. NASA’s Jet Propulsion Laboratory, Pasadena, California

Hardware and algorithms have beendeveloped to transfer electrical powerand data connectivity safely, efficiently,and automatically from an identifieddamaged/defective wire in a cable to analternate wire path. The combination ofonline cable testing capabilities, alongwith intelligent signal rerouting algo-rithms, allows the user to overcome theinherent difficulty of maintaining systemintegrity and configuration control,while autonomously rerouting signalsand functions without introducing newfailure modes. The incorporation of thiscapability will increase the reliability ofsystems by ensuring system availabilityduring operations.

The operation of the innovation isbased on the injection of a low-level andshort-duration signal into a wire undertest. The cable router master unit con-sists of a pulse generator, a multiplexer,a switch matrix, and a detector circuit.The pulse generator provides a steppulse that is applied to the multiplexer.The multiplexer, in turn, routes the test

pulse to one of many wires. The signalthen propagates through the selectedwire until it reaches the cable routeslave circuit. The slave circuit monitorsthe wire, and once it receives the signal,it routes it back to the master unitthrough a communication wire. The de-tector circuit in the master unit then de-termines the presence of the signal toindicate that a good connection is inplace. The absence of the test pulse be-comes an indication of a faulty connec-tion. A plurality of communicationwires is used, so that the individual stateof health is not a determining factor forthe analysis of the health of the wire(s)under test.

The master unit sequentially scans allthe wires selected as “active” or “spares.”The current implementation of the on-line rerouter system can monitor up toeight wires. However, the circuit can beexpanded to monitor a larger numberof wires. The wires can be independentlyassigned to be “active” or to be “spares.”Once an active wire has been labeled as

failed, the master and the slave unitscommunicate with each other, and im-mediately route the signals that wereflowing through the failed wire to one ofthe spare wires. This allows for the sys-tem to maintain integrity with a disrup-tion shorter than one second in the cur-rent implementation.

The small amplitude of the test pulseinjected into the wires requires multiplesuccessive measurements to assess the in-tegrity of the wire. The test pulse levelhas to be maintained at a low level inorder not to interfere with signals beingcarried in the wire under test. This al-lows for discrimination between a large,non-correlated signal and a small, syn-chronous test pulse without interferingwith the operation of the wire.

This work was done by Mark Lewis ofKennedy Space Center and Pedro Medelius ofASRC Aerospace Corporation. For more infor-mation, contact the Kennedy Space Center In-novative Partnerships Office at 321-867-5033. KSC-13440

Online Cable Tester and RerouterThis technology enables proactive detection of impending cable failures, allowing for function rerouting.John F. Kennedy Space Center, Florida


The half-flare angle for the feed is ap-proximately 30°. Analysis and optimiza-tion of the overall feed design employeda combination of finite element andmode-matching tools.

The illumination requirements andrelative frequency spacing for this appli-cation are similar to those required forthe Scanning Multichannel MicrowaveRadiometer (SMMR) on Seasat, the(TOPEX)/Poseidon, and the Jason mis-sions. However, in this particular appli-cation the required fractional band-width is larger. Thus, while thethree-frequency feed horn describedhere shares many features in commonwith the feed previously developed forthe above missions, enhancements arenecessary in order to achieve broadband performance and manufacturabil-ity in the millimeter-wave bands.

This work was done by Daniel J. Hoppe,Behrouz Khayatian, John B. Sosnowski, AlanK. Johnson, and Peter J. Bruneau of Caltechfor NASA’s Jet Propulsion Laboratory. For moreinformation, contact [email protected]

The assembled prototype Three-Frequency Feed is shown, with the low-frequency combiner absent,along with a half-dollar coin for scale. The overall size of the feed, including the combiner block, isapproximately 1×1.25×1.5 in. (≈2.5×3.2×3.8 cm).

An InGaAs-based three-junction (3J)tandem thermophotovoltaic (TPV)cell has been investigated to utilizemore of the blackbody spectrum (froma 1,100 °C general purpose heatsource — GPHS) efficiently. The tan-dem consists of three vertically stackedsubcells, a 0.74-eV InGaAs cell, a 0.6-eV InGaAs cell, and a 0.55-eV InGaAs

cell, as well as two interconnecting tun-nel junctions.

A >20% TPV system efficiency wasachieved by another group with a 1,040°C blackbody using a single-bandgap 0.6-eV InGaAs cell MIM (monolithic inter-connected module) (30 lateral junc-tions) that delivered about 12 V/30 or0.4 V/junction. It is expected that a

three-bandgap tandem MIM will eventu-ally have about 3× this voltage (1.15 V)and about half the current. A 4 A/cm2

would be generated by a single-bandgap0.6-V InGaAs MIM, as opposed to the 2A/cm2 available from the same spec-trum when split among the three series-connected junctions in the tandemstack. This would then be about a 50%

A multichannel electrometer volt-meter has been developed that employsa mechanical resonator with voltage-sensing capacitance-probe elec t rodesthat en able high-impedance, high-volt-age, radiation-hardened measurement ofan In ternal Electrostatic Discharge Mon-itor (IESDM) sensor. The IESDM is newsensor technology targeted for integra-tion into a Space Environmental Moni-tor (SEM) subsystem used for the charac-terization and monitoring of deepdielectric charging on spacecraft.

The resonator solution relies on anon-contact, voltage-sensing, sinu-soidal-varying capacitor to achieveinput impedances as high as 10petaohms as determined by the res-onator materials, geometries, cleanli-ness, and construction. The resonatoris designed with one dominant me-chanical degree of freedom, so it res-onates as a simple harmonic oscillatorand because of the linearity of the vari-able sense capacitor to displacement,generates a pure sinusoidal current sig-

nal for a fixed input voltage undermeasurement. This enables the use ofan idealized phase-lock sensing schemefor optimal signal detection in the pres-ence of noise.

This work was done by Brent R. Blaes,Rembrandt T. Schaefer, and Robert J. Glaserof Caltech for NASA’s Jet Propulsion Labora-tory. Further information is contained in aTSP (see page 1). NPO-47335

Capacitance Probe Resonator for Multichannel ElectrometerNASA’s Jet Propulsion Laboratory, Pasadena, California

Inverted Three-Junction Tandem Thermophotovoltaic ModulesJohn H. Glenn Research Center, Cleveland, Ohio


increase (3×Voc, 0.5×Isc) in output powerif the proposed tandem replaced the sin-gle-bandgap MIM.

The advantage of the innovation, ifsuccessful, would be a 50% increase inpower conversion efficiency from ra-dioisotope heat sources using existingthermophotovoltaics. Up to 50% more

power would be generated for radioiso-tope GPHS deep space missions. Thistype of InGaAs multijunction stackcould be used with terrestrial concentra-tor solar cells to increase efficiency from41 to 45% or more.

This work was done by Steven Wojtczuk ofSpire Semiconductor for Glenn Research Cen-

ter. Further information is contained in aTSP (see page 1).

Inquiries concerning rights for the commer-cial use of this invention should be addressed to NASA Glenn Research Center, InnovativePartnerships Office, Attn: Steven Fedor, MailStop 4–8, 21000 Brookpark Road, Cleveland,Ohio 44135. Refer to LEW-18909-1.


Manufacturing & Prototyping

Fabrication of Single Crystal MgO CapsulesLyndon B. Johnson Space Center, Houston, Texas

A method has been developed for ma-chining MgO crystal blocks into formsfor containing metallic and silicate liq-uids at temperatures up to 2,400 ºC, andpressures up to at least 320 kilobars.Possible custom shapes include tubes,rods, insulators, capsules, and guides.Key differences in this innovativemethod include drilling along the crys-tallographic zone axes, use of a vibra-tion minimizing material to secure theworkpiece, and constant flushing of ma-terial swarf with a cooling medium/lu-bricant (water).

A single crystal MgO block is cut intoa section ≈5 mm thick, 1 cm on a side,using a low-speed saw with a 0.004 blade.The cut is made parallel to the directionof cleavage. The block may be cut to anythickness to achieve the desired lengthof the piece. To minimize drilling vibra-tions, the MgO block is mounted on apiece of adhesive putty in a vise. Theputty wad cradles the bottom half of theentire block. Diamond coring tools areused to drill the MgO to the desired cus-tom shape, with water used to wet andwash the surface of swarf. Compressed

air may also be used to remove swarfduring breaks in drilling. The MgOworkpiece must be kept cool at all timeswith water. After all the swarf is rinsedoff, the piece is left to dry overnight.

If the workpiece is still attached to thebase of the MgO block after drilling, itmay be cut off by using a diamond cut-off wheel on a rotary hand tool or byusing a low-speed saw.

This work was done by Lisa Danielson ofJacobs Technology for Johnson Space Center.Further information is contained in a TSP(see page 1). MSC-25052-1

Inflatable Hangar for Assembly of Large Structures in SpaceSuch hangars may greatly increase the dexterity and performance of astronauts by operating in ashirtsleeves environment during the assembly process.NASA’s Jet Propulsion Laboratory, Pasadena, California

The NASA Human Space Flight pro-gram is interested in projects where hu-mans, beyond low-Earth orbit (LEO),can make an important and unique con-tribution that cannot be reasonably ac-complished purely by robotic means,and is commensurate with the effort andcost associated with human spaceflight.

Robotic space telescope missionshave been conceived and launched ascompleted assemblies (e.g., Hubble) oras “jack-in-the-box” one-time deploy-ments (e.g., James Webb). If it werepossible to assemble components of avery large telescope from one or twolaunches into a telescope that was vastlygreater in light-gathering power andresolution, that would constitute abreakthrough. Large telescopes onEarth, like all one-off precision assem-bly tasks, are done by humans. Humansin shirtsleeves (or cleanroom “bunnysuits”) can perform tasks of remarkabledexterity and precision. Unfortunately,astronauts in pressure suits cannot per-form such dexterous and precise tasksbecause of the limitations of the pres-surized gloves.

If a large, inflatable “hangar” wereplaced in high orbit, along with all the

An artist’s rendering of the Shirtsleeves Assembly Hangar. At the lower right is a cutaway of the in-flated fabric sphere that houses astronauts in oxygen masks and backpacks. The humans would workwith a robot to accomplish the final telescope assembly.


components needed for a large assemblysuch as a large telescope, then humans inbunny suits could perform the same sortsof extremely precise and dexterous as-sembly that they could be expected toperform on Earth. Calculations showthat such an inflatable hangar, and thenecessary gas to make it safe to occupy byshirtsleeves humans wearing oxygenmasks, fits within the mass and volumelimitations of the proposed “SpaceLaunch System” heavy-lift rocket. A sec-ond launch could bring up all the com-

ponents of a ≈100-meter-diameter orlarger telescope.

A large [200 ft (≈61 m) in diameter] in-flated fabric sphere (or hangar) wouldcontain four humans in bunny suits. Thesphere would contain sufficient atmos-pheric pressure so that spacesuits wouldnot be necessary [about 3.2 psi (≈22kPa)]. The humans would require onlyoxygen masks and small backpacks simi-lar to SCUBA tanks. The oxygen contentof the gas would be about 35%, lowenough to reduce fire risk but high

enough to sustain life in the event of afailure of an oxygen mask. The bunny-suited astronauts could ride on long“cherry-picker” robots with foot restraintssomewhat similar to the arm on the Inter-national Space Station. Other astronautswould maneuver freely with small pro-peller fans on their backpacks to providethrust in the zero-g environment.

This work was done by Brian H. Wilcox ofCaltech for NASA’s Jet Propulsion Laboratory.Further information is contained in a TSP(see page 1). NPO-48441

Mars Aqueous Processing SystemThis technology can be used in treating soil contaminated with heavy metals and remediation ofacid mine drainage.Lyndon B. Johnson Space Center, Houston, Texas

The goal of the Mars Aqueous Pro-cessing System (MAPS) is to establish aflexible process that generates multi-ple products that are useful for humanhabitation. Selectively extracting use-ful components into an aqueous solu-tion, and then sequentially recoveringindividual constituents, can obtain asuite of refined or semi-refined prod-ucts. Similarities in the bulk composi-tion (although not necessarily of themineralogy) of Martian and Lunarsoils potentially make MAPS widely ap-plicable. Similar process steps can beconducted on both Mars and Lunarsoils while tailoring the reaction ex-tents and recoveries to the specifics ofeach location.

The MAPS closed-loop process selec-tively extracts, and then recovers, con-stituents from soils using acids andbases. The emphasis on Mars involvesthe production of useful materials suchas iron, silica, alumina, magnesia, andconcrete with recovery of oxygen as abyproduct. On the Moon, similar chem-istry is applied with emphasis on oxy-gen production.

This innovation has been demon-strated to produce high-grade materials,such as metallic iron, aluminum oxide,magnesium oxide, and calcium oxide,from lunar and Martian soil simulants.Most of the target products exhibitedpurities of 80 to 90 percent or more, al-lowing direct use for many potential ap-plications. Up to one-fourth of the feedsoil mass was converted to metal, metaloxide, and oxygen products. The soilresidue contained elevated silica con-tent, allowing for potential additional re-fining and extraction for recovery of ma-terials needed for photovoltaic,semiconductor, and glass applications.

A high-grade iron oxide concentratederived from lunar soil simulant wasused to produce a metallic iron compo-nent using a novel, combined hydrogenreduction/metal sintering technique.The part was subsequently machinedand found to be structurally sound. Thebehavior of the lunar-simulant-derivediron product was very similar to that pro-duced using the same methods on aMichigan iron ore concentrate, whichdemonstrates that lunar-derived mate-

rial can be used in a manner similar toconventional terrestrial iron. Metalliciron was also produced from the Marssoil simulant.

The aluminum and magnesium oxideproducts produced by MAPS from lunarand Mars soil simulants exhibited excel-lent thermal stability, and were shown tobe capable of use for refractory oxidestructural materials, or insulation at tem-peratures far in excess of what could beachieved using unrefined soils. Thesematerials exhibited the refractory char-acteristics needed to support iron cast-ing and forming operations, as well asother thermal processing needs.

Extraction residue samples containedup to 79 percent silica. Such sampleswere successfully fused into a glass thatexhibited high light transmittance.

This work was done by Mark Berggren,Cherie Wilson, Stacy Carrera, Heather Rose,Anthony Muscatello, James Kilgore, andRobert Zubrin of Pioneer Astronautics for John-son Space Center. Further information is con-tained in a TSP (see page 1). MSC-23885-1/4362-1


Hybrid Filter MembraneUses for this device include battle tanks, remote command centers, field hospitals, and nuclearpower plants. John H. Glenn Research Center, Cleveland, Ohio

Cabin environmental control is animportant issue for a successful Moonmission. Due to the unique environ-ment of the Moon, lunar dust controlis one of the main problems that sig-nificantly diminishes the air quality in-side spacecraft cabins. Therefore, thisinnovation was motivated by NASA’sneed to minimize the negative healthimpact that air-suspended lunar dustparticles have on astronauts in space-craft cabins.

It is based on fabrication of a hybridfilter comprising nanofiber nonwovenlayers coated on porous polymer mem-branes with uniform cylindrical pores.This design results in a high-efficiencygas particulate filter with low pressuredrop and the ability to be easily regener-ated to restore filtration performance.

A hybrid filter was developed consist-ing of a porous membrane with uni-form, micron-sized, cylindrical pore

channels coated with a thin nanofiberlayer. Compared to conventional filtermedia such as a high-efficiency particu-late air (HEPA) filter, this filter is de-signed to provide high particle effi-ciency, low pressure drop, and the abilityto be regenerated. These membraneshave well-defined micron-sized poresand can be used independently as air fil-ters with discreet particle size cut-off, orcoated with nanofiber layers for filtra-tion of ultrafine nanoscale particles. Thefilter consists of a thin design intendedto facilitate filter regeneration by local-ized air pulsing.

The two main features of this inven-tion are the concept of combining amicro-engineered straight-pore mem-brane with nanofibers. The micro-engi-neered straight pore membrane can beprepared with extremely high precision.Because the resulting membrane poresare straight and not tortuous like those

found in conventional filters, the pres-sure drop across the filter is significantlyreduced. The nanofiber layer is appliedas a very thin coating to enhance filtra-tion efficiency for fine nanoscale parti-cles. Additionally, the thin nanofibercoating is designed to promote captureof dust particles on the filter surface andto facilitate dust removal with pulse orback airflow.

This work was done by Castro Laicer, BrianRasimick, and Zachary Green of Giner Electro-chemical Systems, LLC for Glenn ResearchCenter. Further information is contained in aTSP (see page 1).

Inquiries concerning rights for the commer-cial use of this invention should be addressedto NASA Glenn Research Center, InnovativePartnerships Office, Attn: Steven Fedor, MailStop 4–8, 21000 Brookpark Road, Cleve-land, Ohio 44135. Refer to LEW-18922-1.

Materials & Coatings


Mechanics/Machinery

The moball is envisioned to be a round, self-powered, and wind-drivenmultifunctioning sensor used in theGone with the Wind ON-Mars(GOWON)[http://www.lpi.usra.edu/meetings/marsconcepts2012/pdf/4238.pdf]: AWind-Driven Networked System of Mo-bile sensors on Mars. The moballs wouldhave sensing, processing, and communi-cation capabilities. The moballs wouldperform in situ detection of key environ-mental elements such as vaporizedwater, trace gases, wind, dust, clouds,light and UV exposure, temperature, aswell as minerals of interest, possible bio-signatures, surface magnetic and elec-tric fields, etc. The embedded variouslow-power micro instruments could in-clude a Multispectral Microscopic Im-ager (to detect various minerals), a com-pact curved focal plane array camera(UV/Vis/NIR) with a large field of view,a compact UV/Visible spectrometer, amicro-weather station, etc. The moballscould communicate with each other andan orbiter. Their wind- or gravity-drivenrolling movement could be used to har-vest and store electric energy. Theycould also generate and store energyusing the sunlight, when available, andthe diurnal temperature variations onMars. The moballs would be self-awareof their (and their neighbors’) posi-tions, energy storage, and memory avail-ability; they would have processingpower and could intelligently cooperatewith neighboring moballs by distribut-ing tasks, sharing data, and fusing infor-mation. The major advantages of usingthe wind-driven and spherical moballnetwork over rovers or other fixed sen-sor webs to explore Mars would be: (1)moballs could explore a much larger ex-panse of Mars in a much faster fashion,(2) they could explore the difficult ter-rains such as steep slopes and sanddunes, and (3) they would be self-en-ergy-generating and could work to-gether and move around autonomously.

The challenge in designing the struc-ture and the mechanics of the moballwould be that it should be sturdy

enough to withstand the impact of itsinitial fall, as well as other impacts fromobstacles in its way. A mechanism wouldbe needed that could enable hundredsof moballs to be carried while theywould be deflated and compact, thenwould inflate them just after deployingthem to their drop site. Furthermore,the moballs should also be light enoughto allow them to move easily over obsta-

cles by force of the wind. They alsoshould have some kind of maneuveringmechanism in place to help them avoidvery hazardous sharp objects or events,and to enable them to get closer to theobjects of interest.

The structure of the moballs was de-signed so that they would have differentlayers. The outer layer should comprisea sturdy, yet light, polymer that could

Design for the Structure and the Mechanics of Moballs Moballs could be used to explore Mars and other windy bodies of the solar system such as Titan. NASA’s Jet Propulsion Laboratory, Pasadena, California

Moballs are able to recognize sharp objects as well as their speed and direction. Based on algorithmsalready provided in the controller, they can decide when and how to change weights in order to avoidobstacles or jump over them.


Pressure Dome for High-Pressure Electrolyzer External gas pressure permits higher pressure and more versatile electrolyzer. John H. Glenn Research Center, Cleveland, Ohio

A high-strength, low-weightpressure vessel dome was designedspecifically to house a high-pres-sure [2,000 psi (≈13.8 MPa)] elec-trolyzer. In operation, the dome isfilled with an inert gas pressurizedto roughly 100 psi (≈690 kPa)above the high, balanced pressureproduct oxygen and hydrogen gasstreams. The inert gas acts to re-duce the clamping load on elec-trolyzer stack tie bolts since thedome pressure acting axially in-ward helps offset the outward axialforces from the stack gas pressure.Likewise, radial and circumferen-tial stresses on electrolyzer framesare minimized. Because the domeis operated at a higher pressurethan the electrolyzer product gas,any external electrolyzer leak pre-vents oxygen or hydrogen from

The Pressure Dome consists of two machined segments. An O-ring is placed in a groove in the flange of thebottom segment and is trapped by the flange on the top dome segment when these components are boltedtogether with high-strength bolts.

withstand both the impact of the initialdrop, as well as the impact of the differ-ent obstacles it would encounter whiletraversing the surface of Mars. Thispolymer should not deteriorate with the100 K daily temperature swings on Mars.The inner layer should consist of a verylight gas such as nitrogen or helium. Interms of maneuvering, six very lightweights placed at strategic locationswould give moballs the ability to turn, oreven hop, over hazardous (e.g., sharp)obstacles, or even initiate a movement(before getting more help from thewind to be carried around) when stuck.Maneuvering would be necessary inorder to get closer to objects of interest.If the weights would be allowed to movefreely, they could also be used to gener-ate energy.

To deploy the moballs, NASA Stan-dard Initiators (NSIs) would carry a lightgas in the middle, and a few NSIs in theouter layer would carry the liquid formof a selected polymer. As soon as themoballs would get released by the de-ployer, the inner capsule would be ex-ploded and the gas would fill out theinner layer of the moball, making itround. The NSI capsules containing thespecial polymer would then be broken,releasing the polymer that fills out theouter layer. In this manner, hundreds or

even thousands of deflated moballscould be compacted inside the deployerand inflated just after the deploymentand before their initial drop.

For the inner sphere of the moball,three principal (XYZ) axes with movableweights inside them would be con-structed. The movable weights could beused to balance the motion of themoball. In this manner, the trajectory ofthe sphere could be corrected with amotorized controller that sits in the cen-ter of the sphere and that would controlthe distance of each weight from thecenter. This system of weights could beused to deflect the trajectory of themoball. If the weights would be magnet,they could generate power while tum-bling around too.

The design described here (in termsof the inner and outer layer, and thethree principal axes with controllableweights) would be novel. No pumpwould be required to deflate or inflatethe moballs, saving power, and also re-ducing the risk of failure. However, it isemphasized that the novelty in this de-sign would make the “hopping” move-ment of the moball much easier thanearlier methods. Previous techniques formaking a spherically-shaped robot hopover an object on Mars have assumedthat the initial condition of the robot

was stationary, i.e., the robot would hopfrom a position of complete stillness.This would be difficult to do on Mars,since the gravity is around 1/3 of thegravity of Earth, making the reactionforce much less than what one would ex-pect. However, since the moballs pro-posed here would be in a wind-driven(or downward rolling) movement al-ready, they would have an “initial veloc-ity,” which would make hopping all themore easy. This is believed to be themost possible way of hopping over a haz-ardous object on Mars.

This work was done by Faranak Davoodi ofCaltech and Farhooman Davoudi, TechnicalConsultant, for NASA’s Jet PropulsionLaboratory.. For more information, [email protected].

In accordance with Public Law 96-517,the contractor has elected to retain title to thisinvention. Inquiries concerning rights for itscommercial use should be addressed to:

Innovative Technology Assets ManagementJPLMail Stop 202-2334800 Oak Grove DrivePasadena, CA 91109-8099E-mail: [email protected] to NPO-48643, volume and number

of this NASA Tech Briefs issue, and thepage number.


Cascading Tesla Oscillating Flow Diode for Stirling Engine Gas BearingsJohn H. Glenn Research Center, Cleveland, Ohio

Replacing the mechanical check-valvein a Stirling engine with a microma-chined, non-moving-part flow diodeeliminates moving parts and reduces therisk of microparticle clogging.

At very small scales, helium gas hassufficient mass momentum that it canact as a flow controller in a similar wayas a transistor can redirect electrical sig-nals with a smaller bias signal. The inno-vation here forces helium gas to flow inpredominantly one direction by offer-ing a clear, straight-path microchannel

in one direction of flow, but thenthrough a sophisticated geometry, thereversed flow is forced through a tortu-ous path. This redirection is achieved byusing microfluid channel flow to forcethe much larger main flow into this tor-tuous path.

While microdiodes have been devel-oped in the past, this innovation cas-cades Tesla diodes to create a muchhigher pressure in the gas bearing sup-ply plenum. In addition, the specialshape of the leaves captures loose parti-

cles that would otherwise clog the mi-crochannel of the gas bearing pads.

This work was done by Rodger Dyson forGlenn Research Center. Further information iscontained in a TSP (see page 1).

Inquiries concerning rights for the com-mercial use of this invention should be ad-dressed to NASA Glenn Research Center, In-novative Partnerships Office, Attn: StevenFedor, Mail Stop 4–8, 21000 BrookparkRoad, Cleveland, Ohio 44135. Refer toLEW-18862-1.

leaking into the dome. Instead the af-fected stack gas stream pressure rises de-tectably, thereby enabling a system shut-down. All electrical and fluidconnections to the stack are made in-side the pressure dome and require spe-cial plumbing and electrical dome inter-faces for this to be accomplished.Further benefits of the dome are that itcan act as a containment shield in theunlikely event of a catastrophic failure.

Studies indicate that, for a given activearea (and hence, cell ID), frame outsidediameter must become ever larger to sup-port stresses at higher operating pres-sures. This can lead to a large footprintand increased costs associated withthicker and/or larger diameter end-plates, tie-rods, and the frames them-selves. One solution is to employ ringsthat fit snugly around the frame. Thiscomplicates stack assembly and is some-times difficult to achieve in practice, as itssuccess is strongly dependent on frame

and ring tolerances, gas pressure, and op-erating temperature. A pressure domepermits an otherwise low-pressure stackto operate at higher pressures withoutgrowing the electrolyzer hardware.

The pressure dome consists of twomachined segments. An O-ring isplaced in an O-ring groove in theflange of the bottom segment and istrapped by the flange on the top domesegment when these components arebolted together with high-strengthbolts. The pressure dome has severalunique features. It is made (to ASMEPressure Vessel guidelines) in a high-strength aluminum alloy with thestrength of stainless steel and theweight benefits of aluminum. Theflange of the upper dome portion con-tains specially machined flats formounting the dome, and other flatsdedicated to the special feedthroughsfor electrical connections. A pressuredome can be increased in length to

house larger stacks (more cells) of thesame diameter with the simple additionof a cylindrical segment.

To aid in dome assembly, two stainlesssteel rings are employed. One is used be-neath the heads of the high-strengthbolts in lieu of individual hardened wash-ers, and another is used instead of indi-vidual nuts. Like electrolyzers could beoperated at low or high pressures simplyby operating the electrolyzer outside orinside a pressurized dome.

This work was done by Timothy Normanand Edwin Schmitt of Giner ElectrochemicalSystems, LLC for Glenn Research Center.Further information is contained in a TSP(see page 1).

Inquiries concerning rights for the com-mercial use of this invention should be ad-dressed to NASA Glenn Research Center, In-novative Partnerships Office, Attn: StevenFedor, Mail Stop 4–8, 21000 BrookparkRoad, Cleveland, Ohio 44135. Refer toLEW-18772-1.

Actuators are critical to all the roboticand manipulation mechanisms that areused in current and future NASA mis-sions, and are also needed for manyother industrial, aeronautical, and spaceactivities. There are many types of actua-tors that were designed to operate as lin-ear or rotary motors, but there is still aneed for low-force, low-noise linear actu-

ators for specialized applications, and thedisclosed mechanism addresses thisneed.

A simpler implementation of a rotaryactuator was developed where the end ef-fector controls the motion of a brush forcleaning a thermal sensor. The mecha-nism uses a SMA (shape-memory alloy)wire for low force, and low noise. The lin-

ear implementation of the actuator incor-porates a set of springs and mechanicalhard-stops for resetting and fault toler-ance to mechanical resistance. The actu-ator can be designed to work in a pull orpush mode, or both. Depending on thevolume envelope criteria, the actuatorcan be configured for scaling its volumedown to 4×2×1 cm3. The actuator design

Compact, Low-Force, Low-Noise Linear Actuator This actuator has potential uses in military and automotive applications. NASA’s Jet Propulsion Laboratory, Pasadena, California


has an inherent fault tolerance to me-chanical resistance. The actuator has theflexibility of being designed for both lin-ear and rotary motion. A specific configu-ration was designed and analyzed wherefault-tolerant features have been imple-mented. In this configuration, an exter-nally applied force larger than the designforce does not damage the active compo-nents of the actuator. The actuator hous-ing can be configured and produced

using cost-effective methods such as injec-tion molding, or alternatively, its compo-nents can be mounted directly on a smallcircuit board.

The actuator is driven by a SMA -NiTias a primary active element, and it re-quires energy on the order of 20 Ws(J)per cycle. Electrical connections topoints A and B are used to apply electri-cal power in the resistive NiTi wire, caus-ing a phase change that contracts the

wire on the order of 5%. The actuationperiod is of the order of a second forgenerating the stroke, and 4 to 10 sec-onds for resetting. Thus, this design al-lows the actuator to work at a frequencyof up to 0.1 Hz.

The actuator does not make use of thewhole range of motion of the SMA mate-rial, allowing for large margins on themechanical parameters of the design.The efficiency of the actuator is of theorder of 10%, including the margins.The average dissipated power while driv-ing at full speed is of the order of 1 W,and can be scaled down linearly if therate of cycling is reduced. This designproduces an extremely quiet actuator; itcan generate a force greater than 2 Nand a stroke greater than 1 cm. The op-erational duration of SMA materials is ofthe order of millions of cycles with somereduced stroke over a wide temperaturerange up to 150 ºC.

This work was done by Mircea Badescu,Stewart Sherrit, and Yoseph Bar-Cohen of Cal-tech for NASA’s Jet Propulsion Laboratory.Further information is contained in a TSP(see page 1). NPO-47991

The Actuator is driven by shape memory alloy as a primary active element. Electrical connections topoints A and B are used to apply electrical power in the resistive NiTi wire, causing a phase changethat contracts the wire on the order of 5%.

Active SMA element

Actuator shaftFault tolerant and resetting actuator elements

This invention is an electronicallycommutated brushless motor controllerthat incorporates Hall-array sensing in asmall, 42-gram package that provides4096 absolute counts per motor revolu-tion position sensing. The unit is thesize of a miniature hockey puck, and is a44-pin male connector that providesmany I/O channels, including CANbus,RS-232 communications, general-pur-pose analog and digital I/O (GPIO),analog and digital Hall inputs, DCpower input (18–90 VDC, 0–l0 A),three-phase motor outputs, and a straingauge amplifier.

This controller replaces air coolingwith conduction cooling via a high-ther-mal-conductivity epoxy casting. A sec-ondary advantage of the relatively goodheat conductivity that comes with ultra-small size is that temperature differenceswithin the controller become smaller, sothat it is easier to measure the hottesttemperature in the controller with fewertemperature sensors, or even one tem-perature sensor.

Another size-sensitive design featureis in the approach to electrical noiseimmunity. At a very small size, whereconduction paths are much shorterthan in conventional designs, theground becomes essentially isopoten-tial, and so certain (space-consuming)electrical noise control componentsbecome unnecessary, which helpsmake small size possible. One winding-current sensor, applied to all of thewindings in fast sequence, is smallerand wastes less power than the two ormore sensors conventionally used tosense and control winding currents. Anunexpected benefit of using only onecurrent sensor is that it actually im-proves the precision of current controlby using the “same” sensors to readeach of the three phases. Folding theencoder directly into the controllerelectronics eliminates a great deal ofredundant electronics, packaging, con-nectors, and hook-up wiring. The re-duction of wires and connectors sub-tracts substantial bulk and eliminates

their role in behaving as EMI (electro-magnetic interference) antennas.

A shared knowledge by each motorcontroller of the state of all the motorsin the system at 500 Hz also allows paral-lel processing of higher-level kinematicmatrix calculations.

This work was done by William T.Townsend, Adam Crowell, and TravelerHauptman of Barrett Technology, Inc.; andGill Andrews Pratt of Olin College for John-son Space Center. For further information,contact the JSC Innovation Partnerships Of-fice at (281) 483-3809.

In accordance with Public Law 96-517,the contractor has elected to retain title to thisinvention. Inquiries concerning rights for itscommercial use should be addressed to:

Barrett Technology, Inc.625 Mount Auburn StreetCambridge, MA 02138-4555Phone No.: (617) 252-9000Web site: www.barrett.comRefer to MSC-23930-1, volume and num-

ber of this NASA Tech Briefs issue, and thepage number.

Ultra-Compact Motor ControllerApplications include industrial robotic arms, industrial machinery, and automobiles.Lyndon B. Johnson Space Center, Houston, Texas


Bio-Medical

There is a growing concern that des-iccation and extreme radiation-resist-ant, non-spore-forming microorgan-isms associated with spacecraftsurfaces can withstand space environ-mental conditions and subsequentproliferation on another solar body.Such forward contamination wouldjeopardize future life detection or sam-ple return technologies. The primefocus of NASA’s planetary protectionefforts is the development of strategiesfor inactivating resistance-bearing mi-croorganisms. Erad ication techniquescan be designed to target resistance-conferring microbial populations byfirst identifying and understandingtheir physiologic and biochemical ca-pabilities that confers its elevated tol-erance (as is being studied in Deinococ-cus phoenicis, as a result of thisdescription). Fur thermore, hospitals,food, and government agencies fre-quently use biological indicators to en-sure the efficacy of a wide range of ra-diation-based sterilization processes.Due to their resistance to a variety ofperturbations, the non-spore formingD. phoenicis may be a more appropriatebiological indicator than those cur-rently in use.

The high flux of cosmic rays duringspace travel and onto the unshieldedsurface of Mars poses a significant haz-ard to the survival of microbial life.

Thus, radiation-resistant microorgan-isms are of particular concern that cansurvive extreme radiation, desiccation,and low temperatures experienced dur-ing space travel. Spore-forming bacteria,a common inhabitant of spacecraft as-sembly facilities, are known to toleratethese extreme conditions. Since theViking era, spores have been utilized toassess the degree and level of microbio-logical contamination on spacecraft andtheir associated spacecraft assembly fa-cilities. Members of the non-spore-form-ing bacterial community such asDeinococcus radiodurans can survive acuteexposures to ionizing radiation (5 kGy),ultraviolet light (1 kJ/m2), and desicca-tion (years). These resistive phenotypesof Deinococcus enhance the potential fortransfer, and subsequent proliferation,on another solar body such as Mars andEuropa. These organisms are morelikely to escape planetary protection as-says, which only take into account pres-ence of spores. Hence, presences of ex-treme radiation-resistant Deinococcus inthe cleanroom facility where spacecraftare assembled pose a serious risk for in-tegrity of life-detection missions.

The microorganism describedherein was isolated from the surfacesof the cleanroom facility in which thePhoenix Lander was assembled. Theisolated bacterial strain was subjectedto a comprehensive polyphasic analysis

to characterize its taxonomic position.This bacterium exhibits very low16SrRNA similarity with any other envi-ronmental isolate reported to date.Both phenotypic and phylogeneticanalyses clearly indicate that this iso-late belongs to the genus Deinococcusand represents a novel species. Thename Deinococcus phoenicis was pro-posed after the Phoenix spacecraft,which was undergoing assembly, test-ing, and launch operations in thespacecraft assembly facility at the timeof isolation. D. phoenicis cells exhibitedhigher resistance to ionizing radiation(cobalt-60; 14 kGy) than the cells of theD. radiodurans (5 kGy). Thus, it is in thebest interest of NASA to thoroughlycharacterize this organism, which willfurther assess in determining the po-tential for forward contamination.Upon the completion of genetic andphysiological characteristics of D.phoenicis, it will be added to a planetaryprotection database to be able to fur-ther model and predict the probabilityof forward contamination.

This work was done by Parag A.Vaishampayan and Kasthuri J.Venkateswaran of Caltech, and PetraSchwendner of Institute of Aerospace Medi-cine, German Aerospace Center (DLR), Ger-many for NASA’s Jet Propulsion Laboratory.For more information, contact [email protected]. NPO-48008

Extreme Ionizing-Radiation-Resistant Bacterium Deinococcus phoenicis sp. nov. can be used as an indicator for sterilization processes in food,aerospace, medical, and pharmaceutical applications. NASA’s Jet Propulsion Laboratory, Pasadena, California

The microgravity conditions of spacetravel result in unique physiological de-mands on the human body. In particu-lar, the absence of the continual me-chanical stresses on the skeletal systemthat are present on Earth cause thebones to decalcify. Trabecular structure

decreases in thickness and increases inspacing, resulting in decreased bonestrength and increased risk of injury.Thus, monitoring bone health is a highpriority for long-term space travel. Asingle probe covering all frequencybands of interest would be ideal for

such measurements, and this wouldalso minimize storage space and elimi-nate the complexity of integrating mul-tiple probes.

This invention is an ultrasound trans-ducer for the structural characterizationof bone. Such characterization meas-

Wideband Single-Crystal Transducer for Bone CharacterizationThese transducers have uses in medical ultrasound imaging and room-temperature ultrasonic flow meters. John H. Glenn Research Center, Cleveland, Ohio


This innovation is a coupled fluores-cence-activated cell sorting (FACS) andfluorescent staining technology for puri-fying (removing cells from sampling ma-trices), separating (based on size, den-sity, morphology, and live versus dead),and concentrating cells (spores,prokaryotic, eukaryotic) from an envi-ronmental sample.

Currently, the state of the art is lim-ited to the sorting of larger eukaryoticcells (e.g., yeast, mammalian). Over thepast decade, cell sorting technologieshave evolved significantly and sensitivitylevels have increased remarkably, ren-dering bacterial cell sorting a feasibleconcept. In parallel, optimized proto-cols for broad-spectrum fluorescencestaining of bacterial cells and sporeshave been established, most of which arebased on nucleic acid-intercalating dyes.

Smaller DNA-intercalating dyes, suchas SYTO-9, permeate the intact mem-brane of living, viable cells and sporesand upon excitation with white light,emit a detectable signal such as the

green spectra emitted by DNA-boundSYTO-9. A larger DNA-intercalating dyesuch as 7- amino actinomycin (7-AAD),which is unable to permeate the mem-branes of healthy, viable cells and sporesand thus only able to access the DNA ofdead or dying cells and spores throughcompromised membranes, is also ap-plied to the sample. This larger dye isengineered to fluoresce red spectraupon excitation. Ergo, the membranesof healthy, viable bacterial cells andspores preclude the infiltration of thelarger red dyes (which have a greateraffinity for DNA than the smaller greendyes) and as a result, their DNA fluo-resces green. The DNA of dead or dyingcells and spores fluoresces red as a resultof the high-affinity binding and of thelarger red dyes. This motif makes possi-ble the ability to sort and segregate livefrom dead bacterial cells and spores viafluorescence staining.

This technology directly contributesto NASA missions as it focuses on theseparation, purification, and concen-

tration of cells or spores from a givenspacecraft or associated facility sample.Coupling live/dead fluorescence dyesand flow cytometry enhances the resolv-ing power of any attempt at predictingthe microbial genetic that actuallyposes a forward contamination threat.The capability to provide an account ofthe living organisms present on space-craft surfaces, to the exclusion of theexpired population, will facilitate muchmore accurate predictive risk assess-ments of forward contamination onmissions with challenging planetaryprotection issues. A specific account ofonly the living microbial populationwill also allow for immediate feedbackto a project as to the success of clean-ing, microbial reduction, and generalhousekeeping processes.

This work was done by James N. Benar-dini, Myron T. La Duc, Rochelle Diamond,and Josh Verceles of Caltech for NASA’s JetPropulsion Laboratory. Further informationis contained in a TSP (see page 1). NPO-48176

Fluorescence-Activated Cell Sorting of Live Versus DeadBacterial Cells and Spores Commercial applications include hospital operating room cleanliness validation assays,pharmaceutical development, and semiconductor development. NASA’s Jet Propulsion Laboratory, Pasadena, California

ures features of reflected and transmit-ted ultrasound signals, and correlatesthese signals with bone structure met-rics such as bone mineral density, tra-becular spacing, and thickness, etc. Thetechniques used to determine these var-ious metrics require measurements overa broad range of ultrasound frequen-cies, and therefore, complete character-ization requires the use of several nar-rowband transducers.

This is a single transducer capable ofmaking these measurements in all therequired frequency bands. The deviceachieves this capability through aunique combination of a broadbandpiezoelectric material; a design incorpo-rating multiple resonator sizes with dis-tinct, overlapping frequency spectra;and a micromachining process for pro-ducing the multiple-resonator patternwith common electrode surfaces be-tween the resonators.

This device consists of a pattern of res-onator bars with common electrodesthat is wrapped around a central man-

drel such that the radiating faces of theresonators are coplanar and can be si-multaneously applied to the sample tobe measured. The device operates asboth a source and receiver of acousticenergy. It is operated by connection toan electronic system capable of bothproviding an excitation signal to thetransducer and amplifying the signal re-ceived from the transducer. The excita-tion signal may be either a wide-band-width signal to excite the transduceracross its entire operational spectrum,or a narrow-bandwidth signal optimizedfor a particular measurement technique.The transducer face is applied to theskin covering the bone to be character-ized, and may be operated in through-transmission mode using two transduc-ers, or in pulse-echo mode.

The transducer is a unique combina-tion of material, design, and fabricationtechnique. It is based on single-crystallead magnesium niobate lead titanate(PMN-PT) piezoelectric material. Ascompared to the commonly used piezo-

ceramics, this piezocrystal has superiorpiezoelectric and elastic properties,which results in devices with superiorbandwidth, source level, and power re-quirements. This design necessitates asingle resonant frequency. However, byoperating in a transverse length-exten-sional mode, with the electric field ap-plied orthogonally to the extensional di-rection, resonators of different sizes canshare common electrodes, resulting in amultiply-resonant structure. With care-fully sized resonators, and the superiorbandwidth of piezocrystal, the reso-nances can be made to overlap to form asmooth, wide-bandwidth characteristic.

This work was done by Yu Liang and KevinSnook of TRS Technologies, Inc. for Glenn Re-search Center. Further information is con-tained in a TSP (see page 1).

Inquiries concerning rights for the commer-cial use of this invention should be addressedto NASA Glenn Research Center, InnovativePartnerships Office, Attn: Steven Fedor, MailStop 4–8, 21000 Brookpark Road, Cleveland,Ohio 44135. Refer to LEW-18842-1.


A method combines solid phase acidi-fication with two non-toxic biocides toprevent ammonia volatilization and mi-crobial proliferation. The safe, non-oxi-dizing biocide combination consists of aquaternary amine and a food preserva-tive. This combination has exhibited ex-cellent stabilization of both acidifiedand unacidified urine.

During pretreatment tests, compositeurine collected from donors was chal-lenged with a microorganism known toproliferate in urine, and then wasprocessed using the nonhazardousurine pre-treatment method. The challenge microorganisms included Es-cherichia coli, a common gram-negativebacteria; Enterococcus faecalis, a ureolyticgram-positive bacteria; Candida albicans,a yeast commonly found in urine; andAspergillus niger, a problematic moldthat resists urine pre-treatment.

Urine processed in this manner re-mained microbially stable for over 57days. Such effective urine stabilization

was achieved using non-toxic, non-oxi-dizing biocides at higher pH (3.6 to 5.8)than previous methods in use or pro-jected for use aboard the InternationalSpace Station (ISS). ISS urine pretreat-ment methods employ strong oxidantsincluding ozone and hexavalentchromium (Cr(VI)), a carcinogenic ma-terial, under very acidic conditions (pH= 1.8 to 2.4).

The method described here offers amuch more benign chemical environ-ment than previous pretreatmentmethods, and will lower equivalent sys-tem mass (ESM) by reducing contain-ment volume and mass, system com-plexity, and crew time needed tohandle pre-treatment chemicals. Thebiocides, being non-oxidizing, mini-mize the potential for chemical reac-tions with urine constituents to pro-duce volatile, airborne contaminantssuch as cyanogen chloride. Addition-ally, the biocides are active under sig-nificantly less acidic conditions than

those used in the current system,thereby reducing the degree of re-quired acidification.

A simple flow-through solid phaseacidification (SPA) bed is employed toovercome the natural buffering capacityof urine, and to lower the pH to levelsthat fix ammoniacal nitrogen in thenon-volatile and highly water solubleNH4

+ form. Citric acid, a highly soluble,solid tricarboxylic acid essential to cellu-lar metabolism, and typically used as afood preservative, has also been shownto efficiently acidify urine in conjunc-tion with non-oxidizing biocides to pro-vide effective stabilization with respectto both microbial growth and ammoniavolatilization.

This work was done by James R. Akse andJohn T. Holtsnider of Umpqua Research Com-pany for Johnson Space Center. For further in-formation, contact the JSC Innovation Part-nerships Office at (281) 483-3809. MSC-24520-1

Nonhazardous Urine Pretreatment Method This method can be used as a means for safe urine storage on ships, planes, and recreational vehicles, or in conjunction with portable restrooms.Lyndon B. Johnson Space Center, Houston, Texas


Physical Sciences

In this innovation, the three-way com-biner consists internally of two branch-line hybrids that are connected in seriesby a short length of waveguide. Eachbranch-line hybrid is designed to com-bine input signals that are in phase withan amplitude ratio of two. The com-biner is constructed in an E-plane split-block arrangement and is precision ma-chined from blocks of aluminum withstandard WR-28 waveguide ports. Theport impedances of the combiner arematched to that of a standard WR-28waveguide. The component parts in-clude the power combiner and theMMIC (monolithic microwave inte-grated circuit) power amplifiers (PAs).The three-way series power combiner isa six-port device. For basic operation,power that enters ports 3, 5, and 6 iscombined in phase and appears at port1. Ports 2 and 4 are isolated ports. Theapplication of the three-way combinerfor combining three PAs with unequaloutput powers was demonstrated.

NASA requires narrow-band solid-state power amplifiers (SSPAs) at Ka-

band frequencies with output power inthe range of 3 to 5 W for radio or gravityscience experiments. In addition, NASAalso requires wideband, high-efficiencySSPAs at Ka-band frequencies with out-put power in the range of 5 to 15 W forhigh-data-rate communications fromdeep space to Earth. The three-way

power combiner is designed to operateover the frequency band of 31.8 to 32.3GHz, which is NASA’s deep-space fre-quency band.

For the proof-of-concept demonstra-tion of this innovation, three availablePAs were selected with output powers of0.1, 0.2, and 0.6 W to meet the ampli-

Ka-Band Waveguide Three-Way Serial Combiner for MMIC AmplifiersThis device is a power combiner that can be used for a solid-state power amplifier.John H. Glenn Research Center, Cleveland, Ohio

This photo of the fabricated Serial Combiner shows the split-block construction arrangement.

An active laser was developed rangingin real-time with two terminals, emulat-ing interplanetary distances, and withsubmillimeter accuracy. In order toovercome the limitations to ranging ac-curacy from jitters and delay driftswithin the transponders, architecturewas proposed based on asynchronouspaired one-way ranging with local refer-ences. A portion of the transmitted lightis directed, via a reference path, to thelocal detector. This allows for compen-sation of any jitter in the timing of theemitted laser pulse. The same detectoris used to measure the time of the re-

ceived pulses emitted from the remoteterminal. This approach removes anychange in the delay caused by the detec-tor or its electronics.

Two separate terminals using com-mercial off-the-shelf hardware were builtto emulate active laser ranging over in-terplanetary distances. The communica-tion link for the command to startrecording pulse arrival times and datatransfer from one terminal to the otherwas achieved using a standard wirelesslink, emulating free space laser commu-nication. The deviation is well below thegoal of 1-mm precision. This leaves

enough margin to achieve 1-mm preci-sion when including the fluctuationsdue to atmospheric turbulence whileranging to Mars through the Earth’s at-mosphere. The two terminals aremounted on translation stages, whichcan be moved freely on rails to yield awide range of distances with fine adjust-ment. The two terminals were separatedby approximately 16 meters.

This work was done by Hamid Hemmati,Yijiang Chen, and Kevin Birnbaum of Cal-tech for NASA’s Jet Propulsion Laboratory.For more information, contact [email protected]. NPO-48125

Laser-Ranging Transponders for Science Investigations of theMoon and Mars NASA’s Jet Propulsion Laboratory, Pasadena, California


tude ratio of two. The 0.1- and 0.2-WPAs, which are in the 1:2 power ratio, areinitially combined in a branch-line hy-brid that has a coupling value of 4.77dB. Likewise, the combined output ofthe first branch-line hybrid is combinedwith the output from the third PA in asecond branch-line hybrid, also with acoupling value of 4.77 dB. The meas-ured combining efficiency at the center

frequency of 32.05 GHz is greater than90% for a wide range of power ratiosboth below and above two. The meas-ured return loss at the output port 1 andthe isolation among the input ports 3, 5,and 6 of the three-way combiner aregreater than 16 and 22 dB, respectively.

This work was done by Rainee N. Simons,Edwin G. Wintucky, and Jon C. Freeman ofGlenn Research Center; and Christine T.

Chevalier of QinetiQ North America Corp.Further information is contained in a TSP(see page 1).

Inquiries concerning rights for the com-mercial use of this invention should be ad-dressed to NASA Glenn Research Center, In-novative Partnerships Office, Attn: StevenFedor, Mail Stop 4–8, 21000 BrookparkRoad, Cleveland, Ohio 44135. Refer toLEW-18688-1

Structural health monitoring (SHM)is one of the most important tools avail-able for the maintenance, safety, and in-tegrity of aerospace structural systems.Lightweight, electromagnetic-interfer-ence-immune, fiber-optic sensor-basedSHM will play an increasing role in moresecure air transportation systems. Manu-facturers and maintenance personnelhave pressing needs for significantly im-proving safety and reliability while pro-viding for lower inspection and mainte-nance costs. Undetected or untreateddamage may grow and lead to cata-strophic structural failure.

Damage can originate from thestrain/stress history of the material, im-perfections of domain boundaries inmetals, delamination in multi-layer ma-terials, or the impact of machine tools inthe manufacturing process. Damage canlikewise develop during service life fromwear and tear, or under extraordinarycircumstances such as with unusualforces, temperature cycling, or impact offlying objects. Monitoring and early de-tection are key to preventing a cata-strophic failure of structures, especiallywhen these are expected to performnear their limit conditions.

The ultimate goal of SHM technologyis to develop autonomous (preventive)maintenance systems for continuousmonitoring, inspection, and damage de-tection of structures with minimumlabor involvement in real time, and inorder to prevent catastrophic structuralfailure with timely service/maintenance.The ultimate solution will include bothadvanced hardware and advanced math-ematical algorithms.

On the hardware side, a high-speed,high-channel-count fiber-optic sensorinterrogation system was developed.On the SHM algorithmic side, algorith-mic methods were developed for char-acterizing the damage from sensorydata collected over several strategicallyplaced sensors.

A dynamic response-based damage de-tection technique is relatively easy to im-plement and offers a wealth of differen-tial diagnostic capabilities. The basicassumptions of this technique are thatthe dynamic parameters such as naturalfrequencies, mode shapes, transfer func-tions, or response functions depend onthe physical properties across the struc-tures. Therefore, the changes in thesedynamic characteristics can be used tolocate and assess problem areas. Smartoptical fiber Bragg grating (FBG) sen-sors have been increasingly used inSHM, and they could be either surface-bonded or embedded within the struc-tures, and form an array of sensors fordynamic response measurement. For asmall-scale demonstration, Lamb wavesare excited by a single piezoelectric actu-ator and captured by three FBG sensorswhose response is in turn captured by aparallel processing FBG interrogator ca-

Structural Health Monitoring With Fiber Bragg Grating andPiezo ArraysA nondestructive damage identification and assessment capability can be used in monitoringsystems for maintenance and disaster avoidance.Dryden Flight Research Center, Edwards, California

The Fiber Bragg Grating/Piezo Array sensor-actuator system as a concept demonstration for structuralhealth monitoring.

Composite Panel With FBG/Piezo Array Sensor-

Actuator Systems

Damage(Delamination)

Ultra Lamb Wave

Data ManagementDiagnosis/Prognosis

IFOS Ultra-FastFBG Interrogator

Function Generator +Driver for Piezoelectric

PiezoelectricActuator

PiezoelectricActuator

FBG1

FBG2FBG3


The Juno mission to Jupiter requiresan antenna with a torus-shaped an-tenna pattern with approximately 6dBic gain and circular polarization overthe Deep Space Network (DSN) 7-GHztransmit frequency and the 8-GHz re-ceive frequency. Given the large dis-tances that accumulate en-route toJupiter and the limited power affordedby the solar-powered vehicle, thistoroidal low-gain antenna requires asmuch gain as possible while maintain-ing a beam width that could facilitate a±10° edge of coverage.

The natural antenna that produces atoroidal antenna pattern is the dipole,but the limited ≈2.2 dB peak gain wouldbe insufficient. Here a shaped variationof the standard bicone antenna is pro-posed that could achieve the requiredgains and bandwidths while maintain-ing a size that was not excessive. Thefinal geometry that was settled on con-sisted of a corrugated, shaped bicone,which is fed by a WR112 waveguide-to-coaxial-waveguide transition. Thistoroidal low-gain antenna (TLGA)

geometry produced the requisite gain,moderate sidelobes, and the torus-shaped antenna pattern while maintain-ing a very good match over the entirerequired frequency range. Its “horn”geometry is also low-loss and capable ofhandling higher powers with large mar-gins against multipactor breakdown.The final requirement for the antennawas to link with the DSN with circularpolarization. A four-layer meander-linearray polarizer was implemented; an ap-proach that was fairly well suited to theTLGA geometry.

The principal development of thiswork was to adapt the standard linearbicone such that its aperture could beincreased in order to increase the avail-able gain of the antenna. As one in-creases the aperture of a standard bi-cone, the phase variation across theaperture begins to increase, so thelarger the aperture becomes, thegreater the phase variation. In order tomaximize the gain from any apertureantenna, the phase should be kept asuniform as possible. Thus, as the stan-

dard bicone’s aperture increases, thegain increase becomes less until onereaches a point of diminishing returns.

In order to overcome this problem, ashaped aperture is used. Rather than thestandard linear bicone, a parabolic bi-cone was found to reduce the amount ofphase variation as the aperture increases.In fact, the phase variation is half of thestandard linear bicone, which leads tohigher gain with smaller aperture sizes.The antenna pattern radiated from thisparabolic-shaped bicone antenna hasfairly high side lobes. The Juno projectrequested that these sidelobes be mini-mized. This was accomplished by addingcorrugations to the parabolic shape. Thiscorrugated-shaped bicone antenna hadreasonably low sidelobes, and the appro-priate gain and beamwidth to meet proj-ect requirements.

This work was done by Luis R. Amaro,Ronald C. Kruid, and Joseph D. Vacchione of Caltech, and Aluizio Prata of University of Southern California for NASA’s Jet Propul-sion Laboratory. For more information, con-tact [email protected]. NPO-48320

Low-Gain Circularly Polarized Antenna With Torus-Shaped Pattern A shaped aperture is used, and rather than the standard linear bicone, a parabolic bicone wasfound to reduce the amount of phase variation as the aperture increases.NASA’s Jet Propulsion Laboratory, Pasadena, California

pable of sampling each sensor simulta-neously at hundreds of kilohertz. Thenumber of sensors required for damagedetection is fewer than low-frequencytechniques that can also use FBGs, such

as those based on the mode shapes ofthe structure.

This work was done by Richard J. Black,Ferey Faridian, Behzad Moslehi, andVahid Sotoudeh of Intelligent Fiber Optic

Systems Corporation (IFOS) for DrydenFlight Research Center. Further informa-tion is contained in a TSP (see page 1).DRC-010-015


Software

Stereo and IMU- Assisted Visual Odometry for Small Robots

This software performs two functions:(1) taking stereo image pairs as input, itcomputes stereo disparity maps fromthem by cross-correlation to achieve 3D(three-dimensional) perception; (2) tak-ing a sequence of stereo image pairs asinput, it tracks features in the image se-quence to estimate the motion of thecameras between successive image pairs.A real-time stereo vision system with IMU(inertial measurement unit)-assisted vi-sual odometry was implemented on a sin-gle 750 MHz/520 MHz OMAP3530 SoC(system on chip) from TI (Texas Instru -ments). Frame rates of 46 fps (frames persecond) were achieved at QVGA (QuarterVideo Graphics Array i.e. 320×240), or 8fps at VGA (Video Graphics Array640×480) resolutions, while simultane-ously tracking up to 200 features, takingfull advantage of the OMAP3530’s integerDSP (digital signal processor) and float-ing point ARM processors. This is a sub-stantial advancement over previous workas the stereo implementation produces146 Mde/s (millions of disparities evalu-ated per second) in 2.5W, yielding astereo energy efficiency of 58.8 Mde/J,which is 3.75× better than prior DSPstereo while providing more functionality.

The focus is on stereo vision and IMU-aided visual odometry for small un -manned ground vehicle applications. It isexpected that elements of this implemen-tation will carry over to small unmannedair vehicles in future work. Because theobjective is to advance the state of the artin compact, low-power implementationfor small robots, highly efficient algo-rithms that have already been field testedhave been chosen. This system combinesthe sum of absolute differences (SAD)-based, local optimization stereo with two-frame visual odometry using FAST fea-tures (Features from Accelerated Seg ment Test). By exploiting the densedepth map to provide stereo correspon-dence for the FAST features, it achievesvery respectable position errors of 0.35%of distance traveled on datasets covering400 m of travel. The algorithms used bythis system were heavily tested in previousprojects, which gives a solid basis for theirimplementation on the OMAP3530. Inthe future, cost/performance trade-offs

of algorithm variants may be explored. The novelty of this system is the parallel

computation of stereo vision and visualodometry on both cores of the OMAPSoC. All stereo-related computation ishandled on the C64x+ side of the OMAP,while feature detection, matching/track-ing, and egomotion estimation is handledon the ARM side. This is a convenient di-vision of processing, as stereo computa-tion is entirely an integer process, wellsuited to the integer only C64x+, whileseveral parts of visual odometry involvefloating point operations. The TI codecengine’s IUniversal wrapper was used tointegrate the ARM and DSP processes.

This work was done by Larry H. Matthies ofCaltech and Steven B. Goldberg of Indelible Sys-tems Inc. for NASA’s Jet Propulsion Labora-tory. For more information, download theTechnical Support Package (free whitepaper) at www.techbriefs.com/tsp under theSoftware category.

The software used in this innovation isavailable for commercial licensing. Please con-tact Daniel Broderick of the California Insti-tute of Technology at [email protected] to NPO-48103.

Global Swath and GriddedData Tiling

This software generates cylindricallyprojected tiles of swath-based or griddedsatellite data for the purpose of dynami-cally generating high-resolution globalimages covering various time periods,scaling ranges, and colors called “tiles.”It reconstructs a global image given a setof tiles covering a particular time range,scaling values, and a color table. Theprogram is configurable in terms of tilesize, spatial resolution, format of inputdata, location of input data (local or dis-tributed), number of processes run inparallel, and data conditioning.

This software can dynamically generateglobal images of various temporal andspatial resolutions without having to goback to the original data files, reading andconditioning, and re-projecting thesource values. It can be utilized to effi-ciently generate global imagery of varioustemporal and spatial resolutions basedupon cylindrically projected tiles thathave been created from swath and grid-ded data sets.

The package supports JPL’s PhysicalOceanography Distributed Active Archive

Center’s (PO.DAAC) State of the OceanWeb page (http://podaac.jpl.nasa.gov/soto), a Google Earth-based Web interac-tive visualization tool.

This work was done by Charles K. Thomp-son of Caltech for NASA’s Jet PropulsionLaboratory. For more information, contact [email protected].

This software is available for commercial li-censing. Please contact Daniel Broderick of the California Institute of Technology [email protected]. Refer to NPO-48113.

GOES-R: Satellite Insight GOES-R: Satellite Insight seeks to bring

awareness of the GOES-R (GeostationaryOperational Environmental Satellite — RSeries) satellite currently in developmentto an audience of all ages on the emerg-ing medium of mobile games. TheiPhone app (Satellite Insight) was createdfor the GOES-R Program. The app de-scribes in simple terms the types of dataproducts that can be produced fromGOES-R measurements. The game is easyto learn, yet challenging for all audiences.It includes educational content and apath to further information about GOES-R, its technology, and the benefits of thedata it collects.

The game features action-puzzle gameplay in which the player must prevent anoverflow of data by matching fallingblocks that represent different types ofGOES-R data. The game adds more differ-ent types of data blocks over time, as longas the player can prevent a data overflowcondition. Points are awarded formatches, and players can compete withthemselves to beat their highest score.

This work was done by Austin J. Fitzpatrick,Nancy J. Leon, Alexander Novati, Laura K.Lincoln, and Diane K. Fisher of Caltech, andDaniel Karlson of NOAA for NASA’s JetPropulsion Laboratory. For more information,contact [email protected].


Aquarius iPhone Application

The Office of the CIO at JPL has de-veloped an iPhone application for theAquarius/SAC-D mission. The applica-tion includes specific information about


the science and purpose of the Aquariussatellite and also features daily missionnews updates pulled from sources atGoddard Space Flight Center as well asTwitter. The application includes amedia and data tab section. The mediasection displays images from the obser-vatory, viewing construction up to thelaunch and also includes various videosand recorded diaries from the AquariusProject Manager. The data tab highlightsmany of the factors that affect theEarth’s ocean and the water cycle. The

application leverages the iPhone’s ac-celerometer to move the Aquarius Satel-lite over the Earth, revealing these fac-tors. Lastly, this application features acountdown timer to the satellite’slaunch, which is currently counting thedays since launch. This application washighly successful in promoting theAquarius Mission and educating thepublic about how ocean salinity is para-mount to understanding the Earth.

This is a public application available atthe time of this reporting in The Apple

App Store: http://itunes.apple.com/us/app/ aquarius/id437313730?mt=8

This work was done by Joseph C. Estes Jr, Je-remy M. Arca, Michael A. Ko, and Boris Oksof Caltech for NASA’s Jet Propulsion Labora-tory. For more information, [email protected].



Information Technology

Shewhart control charts have been es-tablished as an expedient method foranalyzing dynamic, trending data inorder to identify anomalous subsystemperformance as soon as such perform-ance would exceed a statistically estab-lished baseline. Additionally, this lead-ing indicator tool integrates a selectionmethodology that reduces false positiveindications, optimizes true leading indi-cator events, minimizes computerprocessor unit duty cycles, and ad-dresses human factor concerns (i.e., thepotential for flight-controller data over-load). This innovation leverages statisti-cal process control, and provides a rela-tively simple way to allow flightcontrollers to focus their attention on

subtle system changes that could lead todramatic off-nominal system perform-ance. Finally, this capability improves re-sponse time to potential hardware dam-age and/or crew injury, therebyimproving space flight safety.

Shewhart control charts require nor-malized data. However, the telemetryfrom the ISS Early External ThermalControl System (EETCS) was not nor-mally distributed. A method for normal-izing the data was implemented, as was ameans of selecting data windows, thenumber of standard deviations (SigmaLevel), the number of consecutivepoints out of limits (Sequence), and di-rection (increasing or decreasing trenddata). By varying these options, and

treating them like dial settings, the num-ber of nuisance alerts and leading indi-cators were optimized. The goal was tocapture all leading indicators while min-imizing the number of nuisances. LeanSix Sigma (L6S) design of experimentmethodologies were employed. To opti-mize the results, Perl programming lan-guage was used to automate the massiveamounts of telemetry data, control chartplots, and the data analysis.

This work was done by Jeffery T. Fitch, AlanL. Simon, John A. Gouveia, Andrew M.Hillin, and Steve A. Hernandez of UnitedSpace Alliance for Johnson Space Center. Fur-ther information is contained in a TSP (seepage 1). MSC-24530-1

Monitoring of International Space Station Telemetry Using Shewhart Control ChartsThis technique can be applied to monitoring critical systems such as electrical power generation and manufacturing equipment.Lyndon B. Johnson Space Center, Houston, Texas

Planar arrays of waveguide-fed slotshave been employed in many radar andremote sensing applications. Such ar-rays are designed in the standing waveconfiguration because of high effi-ciency. Traveling wave arrays can pro-duce greater bandwidth at the expenseof efficiency due to power loss in theload or loads. Traveling wave planarslot arrays may be designed with a longfeed waveguide consisting of centered-inclined coupling slots. The feed wave-guide is terminated in a matched load,and the element spacing in the feedwaveguide is chosen to produce a beamsquinted from the broadside.

The traveling wave planar slot arrayconsists of a long feed waveguide con-taining resonant-centered inclinedcoupling slots in the broad wall, cou-

pling power into an array of stacked ra-diating waveguides orthogonal to it.The radiating waveguides consist oflongitudinal offset radiating slots in astanding wave configuration. For thetraveling wave feed of a planar slotarray, one has to design the tilt angleand length of each coupling slot suchthat the amplitude and phase of excita-tion of each radiating waveguide areclose to the desired values. The cou-pling slot spacing is chosen for an ap-propriate beam squint. Scattering ma-trix parameters of resonant couplingslots are used in the design process toproduce appropriate excitations of ra-diating waveguides with constraintsplaced only on amplitudes.

Since the radiating slots in each radi-ating waveguide are designed to pro-

duce a certain total admittance, the scat-tering (S) matrix of each coupling slot isreduced to a 2×2 matrix. Elements ofeach 2×2 S-matrix and the amount ofcoupling into the corresponding radiat-ing waveguide are expressed in terms ofthe element S11. S matrices are con-verted into transmission (T) matrices,and the T matrices are multiplied to cas-cade the coupling slots and waveguide sections, starting from the load end andproceeding towards the source.

While the use of non-resonant cou-pling slots may provide an additionaldegree of freedom in the design, reso-nant coupling slots simplify the designprocess. The amplitude of the wavegoing to the load is set at unity. The S11parameter, r’ of the coupling slot clos-est to the load, is assigned an arbitrary

Theory of a Traveling Wave Feed for a Planar Slot Array AntennaA design procedure was developed for the coupling slots between the feed waveguide and theradiating waveguides.NASA’s Jet Propulsion Laboratory, Pasadena, California


Data analysis is a process of inspect-ing, cleaning, transforming, and mod-eling data to highlight useful informa-tion and suggest conclusions. Accuratetimestamps and a timeline of vehicleevents are needed to analyze flightdata. When data is gathered onboard arocket, precise time stamping is evenmore important due to the rocket’shigh speeds and the requirement to in-tegrate data over time for inertial navi-gation calculations.

Accurately time-tagging data cur-rently requires an additional accuratetimecode generator board. This solu-tion is costly but is usually adequate forground-based systems. However, this so-lution is not adequate for flight proces-sors on rockets. Rocket systems requiremore costly ruggedized equipmentwhere weight, size, and power con-straints are an issue. Redundancy is alsorequired, adding even more to the sys-

tem’s weight, size, and power consump-tion.

By moving the timekeeping to theflight processor, there is no longer aneed for a redundant time source. Ifeach flight processor is initially syn-chronized to GPS, they can freewheeland maintain a fairly accurate timethroughout the flight with no addi-tional GPS time messages received.How ever, additional GPS time messageswill ensure an even greater accuracy.

Some modern microprocessorsmaintain a 64-bit internal time-baseregister that is incremented by a crystaloscillator, usually with a 20- to 100-MHzfrequency. This time-base register canbe read in an interrupt service routine(ISR) generated by the 1 pps signalfrom the GPS receiver. Next, a GPStime message is received. The time-base count is associated with the GPStime message time.

When a timestamp is required, a get-time function is called that immedi-ately reads the time-base register. Adelta count is calculated from the lastGPS sync. The current time is calcu-lated by adding this delta time to thelast sync time. This process calculates atimestamp with an accuracy measuredin microseconds, depending on theprocessor clock speed and the accuracyof the processor clock. If a 1 pps GPSISR is not available, the time base regis-ter can be synchronized with the re-ceipt of the GPS time message. If themicroprocessor does not have a 64-bitinternal time-base register, a count-down timer can be used.

This work was done by Roger Zoerner ofASRC Aerospace Corporation for KennedySpace Center. For more information, contactthe Kennedy Space Center Innovative Part-nerships Office at 321-867-5033. KSC-13406

Time Manager Software for a Flight Processor John F. Kennedy Space Center, Florida

value. A larger value of r’ will reducethe power dissipated in the load whileincreasing the reflection coefficient atthe input port. It is now possible to ob-tain the excitation of the radiatingwaveguide closest to the load and thecoefficients of the wave incident and re-flected at the input port of this cou-pling slot. The next coupling slot pa-rameter, r’, is chosen to realize theexcitation of that radiating waveguide.One continues this process moving to-wards the source, until all the couplingslot parameters r’ and hence the S11parameter of the 4-port coupler, r, areknown for each coupling slot. The goal

is to produce the desired array aperturedistribution in the feed direction. Froman interpolation of the computed mo-ment method data for the slot parame-ters, all the coupling slot tilt angles andlengths are obtained. From the excita-tions of the radiating waveguides com-puted from the coupling values, radiat-ing slot parameters may be obtained soas to attain the desired total normal-ized slot admittances. This processyields the radiating slot parameters,offsets, and lengths. The design is re-peated by choosing different values ofr’ for the last coupling slot until thepercentage of power dissipated in the

load and the input reflection coeffi-cient values are satisfactory.

Numerical results computed for theradiation pattern, the tilt angles andlengths of coupling slots, and excitationphases of the radiating waveguides, arepresented for an array with uniform am-plitude excitation. The design processhas been validated using computer sim-ulations. This design procedure is validfor non-uniform amplitude excitationsas well.

This work was done by Sembiam Ren-garajan of Caltech for NASA’s Jet Propul-sion Laboratory. For more information, con-tact [email protected]. NPO-48221

The simulation of high-pressure tur-bulent flows, where the pressure, p, islarger than the critical value, pc, for thespecies under consideration, is relevantto a wide array of propulsion systems,e.g. gas turbine, diesel, and liquid rocket

engines. Most turbulence models, how-ever, have been developed for atmos-pheric-p turbulent flows. The differencebetween atmospheric-p and supercriti-cal-p turbulence is that, in the former sit-uation, the coupling between dynamics

and thermodynamics is moderate tonegligible, but for the latter it is very sig-nificant, and can dominate the flowcharacteristics. The reason for this stemsfrom the mathematical form of theequation of state (EOS), which is the

Simulation of Oxygen Disintegration and Mixing WithHydrogen or Helium at Supercritical PressureThese models can be used in simulations of gas turbine engines.NASA’s Jet Propulsion Laboratory, Pasadena, California


perfect-gas EOS in the former case, andthe real-gas EOS in the latter case.

For flows at supercritical pressure, p,the large eddy simulation (LES) equa-tions consist of the differential conserva-tion equations coupled with a real-gasEOS. The equations use transport prop-erties that depend on the thermody-namic variables. Compared to previousLES models, the differential equationscontain not only the subgrid scale (SGS)fluxes, but also new SGS terms, each de-noted as a “correction.” These addi-tional terms, typically assumed null foratmospheric pressure flows, stem fromfiltering the differential governing equa-tions, and represent differences betweena filtered term and the same term com-puted as a function of the filtered flowfield. In particular, the energy equation

contains a heat-flux correction (q-cor-rection) that is the difference betweenthe filtered divergence of the heat fluxand the divergence of the heat flux com-puted as a function of the filtered flowfield. In a previous study, there was onlypartial success in modeling the q-correc-tion term, but in this innovation, successhas been achieved by using a differentmodeling approach.

This analysis, based on a temporalmixing layer Direct Numerical Simula-tion database, shows that the focus inmodeling the q-correction should be onreconstructing the primitive variablegradients rather than their coefficients,and proposes the approximate deconvo-lution model (ADM) as an effectivemeans of flow field reconstruction forLES heat flux calculation. Further, re-

sults for a study conducted for temporalmixing layers initially containing oxygenin the lower stream, and hydrogen orhelium in the upper stream, show that,for any LES, including SGS-flux models(constant-coefficient Gradient or Scale-Similarity models, dynamic-coefficientSmagorinsky/Yoshizawa or mixedSmagorinsky/Yoshizawa/Gradient mod-els), the inclusion of the q-correction inthe LES leads to the theoretical maxi-mum reduction of the SGS heat-flux dif-ference. The remaining error in model-ing this new subgrid term is thusirreducible.

This work was done by Josette Bellan andEzgi Taskinoglu of Caltech for NASA’s JetPropulsion Laboratory. For more informa-tion, contact [email protected]. NPO-47645


Books & Reports

A Superfluid Pulse Tube Re-frigerator Without Moving Parts for Sub-Kelvin Cooling

A report describes a pulse tube refrig-erator that uses a mixture of 3He and su-perfluid 4He to cool to temperaturesbelow 300 mK, while rejecting heat attemperatures up to 1.7 K. The refrigera-tor is driven by a novel thermodynami-cally reversible pump that is capable ofpumping the 3He–4He mixture withoutthe need for moving parts.

The refrigerator consists of a reversiblethermal magnetic pump module, twowarm heat exchangers, a recuperativeheat exchanger, two cold heat exchang-ers, two pulse tubes, and an orifice. It istwo superfluid pulse tubes that run 180°out of phase. All components of this ma-chine except the reversible thermalpump have been demonstrated at least asproof-of-concept physical models in pre-vious superfluid Stirling cycle machines.The pump consists of two canisterspacked with pieces of gadolinium galliumgarnet (GGG). The canisters are con-nected by a superleak (a porous piece ofVYCOR® glass). A superconducting mag-netic coil surrounds each of the canisters.

This work was done by Franklin K. Miller offor Goddard Space Flight Center. Further infor-mation is contained in a TSP (see page 1).GSC-15580-1

Sapphire Viewports for aVenus Probe

A document discusses the creation of aviewport suitable for use on the surfaceof Venus. These viewports are rated for500 °C and 100 atm pressure with appro-priate safety factors and reliability re-quired for incorporation into a VenusLander. Sapphire windows should easilywithstand the chemical, pressure, andtemperatures of the Venus surface.Novel fixture designs and seals appropri-ate to the environment are incorporated,as are materials compatible with explo-ration vessels. A test cell was fabricated,tested, and leak rate measured. The win-dow features polish specification of thesides and corners, soft metal padding ofthe sapphire, and a metal C-ring seal.The system safety factor is greater than 2,and standard mechanical design theorywas used to size the window, flange, and

attachment bolts using available materialproperty data. Maintenance involves sim-ple cleaning of the window aperture sur-faces. The only weakness of the system isits moderate rather than low leak rate forvacuum applications.

This work was done by Stephen Bates ofThoughtventions Unlimited for GoddardSpace Flight Center. Further information iscontained in a TSP (see page 1). GSC-16095-1

The Mobile Chamber A document discusses a simulation

chamber that represents a shift from thethermal-vacuum chamber stereotype.This innovation, currently in develop-ment, combines the capabilities of spacesimulation chambers, the user-friendli-ness of modern-day electronics, and themodularity of plug-and-play computing.The Mobile Chamber is a customizedtest chamber that can be deployed withgreat ease, and is capable of bringingpayloads at temperatures down to 20 K,in high vacuum, and with the desiredmetrology instruments integrated to thesystems control. Flexure plans to leaseMobile Chambers, making them afford-able for smaller budgets and available toa larger customer base.

A key feature of this design will be anApple iPad-like user interface that allowssomeone with minimal training to con-trol the environment inside the chamber,and to simulate the required extreme en-vironments. The feedback of thermal,pressure, and other measurements is de-livered in a 3D CAD model of the cham-ber’s payload and support hardware. ThisGUI will provide the user with a betterunderstanding of the payload than anyexisting thermal-vacuum system.

This work was done by Gregory Scharfsteinand Russell Cox of Flexure LLC for GoddardSpace Flight Center. Further information is con-tained in a TSP (see page 1). GSC-16469-1

Electric Propulsion Induced Secondary MassSpectroscopy

A document highlights a means tocomplement remote spectroscopywhile also providing in situ surface sam-ples without a landed system. Histori-cally, most compositional analysis ofsmall body surfaces has been done re-

motely by analyzing reflection or nu-clear spectra. However, neither pro-vides direct measurement that can un-ambiguously constrain the globalsurface composition and most impor-tantly, the nature of trace compositionand second-phase impurities.

Recently, missions such as Deep Space1 and Dawn have utilized electricpropulsion (EP) accelerated, high-en-ergy collimated beam of Xe+ ions to pro-pel deep space missions to their targetbodies. The energies of the Xe+ are suf-ficient to cause sputtering interactions,which eject material from the top mi-crons of a targeted surface. Using a massspectrometer, the sputtered material canbe determined. The sputtering proper-ties of EP exhaust can be used to deter-mine detailed surface composition of at-mosphereless bodies by electricpropulsion induced secondary massspectroscopy (EPI-SMS).

EPI-SMS operation has three high-level requirements: EP system, massspectrometer, and altitude of about 10km. Approximately 1 keV Xe+ has beenstudied and proven to generate highsputtering yields in metallic substrates.Using these yields, first-order calcula-tions predict that EPI-SMS will yieldhigh signal-to-noise at altitudes greaterthan 10 km with both electrostatic andHall thrusters.

This work was done by Rashied Amini ofCaltech and Geoffrey Landis of Glenn Re-search Center for NASA’s Jet Propulsion Lab-oratory. Further information is contained ina TSP (see page 1). NPO-47798

Radiation-Tolerant DC-DC Converters

A document discusses power con-verters suitable for space use that meetthe DSCC MIL-PRF-38534 Appendix Gradiation hardness level P classifica-tion. A method for qualifying commer-cially produced electronic parts forDC-DC converters per the DefenseSupply Center Columbus (DSCC) radi-ation hardened assurance require-ments was developed.

Development and compliance testingof standard hybrid converters suitablefor space use were completed for mis-sions with total dose radiation require-ments of up to 30 kRad. This innova-tion provides the same overall


performance as standard hybrid con-verters, but includes assurance of radia-tion-tolerant design through compo-nents and design compliance testing.This availability of design-certified radi-

ation-tolerant converters can signifi-cantly reduce total cost and deliverytime for power converters for space ap-plications that fit the appropriate DSCCclassification (30 kRad).

This work was done by Glenn Skutt, DanSable, Leonard Leslie, and Shawn Graham ofVPT, Inc. for Johnson Space Center. Furtherinformation is contained in a TSP (see page1). MSC-24497-1

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