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12-08 December 2008

https://ntrs.nasa.gov/search.jsp?R=20080048022 2018-05-26T12:51:05+00:00Z

NASA Tech Briefs, December 2008 1

INTRODUCTIONTech Briefs are short announcements of innovations originating from research and develop-

ment activities of the National Aeronautics and Space Administration. They emphasize information considered likely to be transferable across industrial, regional, or disciplinary linesand are issued to encourage commercial application.

Availability of NASA Tech Briefs and TSPsRequests for individual Tech Briefs or for Technical Support Packages (TSPs) announced herein shouldbe addressed to

National Technology Transfer CenterTelephone No. (800) 678-6882 or via World Wide Web at http://www.nttc.edu/about/contactus.asp

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 also available at the same facility oron the World Wide Web at http://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 CenterLisa L. Lockyer(650) [email protected]

Dryden Flight Research CenterGregory Poteat(661) [email protected]

Glenn Research CenterKathy Needham(216) [email protected]

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

Jet Propulsion LaboratoryKen Wolfenbarger(818) [email protected]

Johnson Space CenterMichele Brekke(281) [email protected]

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

Langley Research CenterMartin Waszak(757) [email protected]

Marshall Space Flight CenterJim Dowdy(256) [email protected]

Stennis Space CenterJohn Bailey(228) 688-1660 [email protected]

Carl Ray, Program ExecutiveSmall Business Innovation Research (SBIR) & Small Business Technology Transfer (STTR) Programs(202) [email protected]

Doug Comstock, DirectorInnovative Partnerships Program Office(202) [email protected]

NASA Field Centers and Program Offices

Technology Focus: Data Acquisition5 Crew Activity Analyzer

6 Distributing Data to Hand-Held Devices in aWireless Network

6 Reducing Surface Clutter in Cloud Profiling Radar Data

7 MODIS Atmospheric Data Handler

7 Multibeam Altimeter Navigation Update UsingFaceted Shape Model

9 Electronics/Computers9 Spaceborne Hybrid-FPGA System for Processing

FTIR Data

9 FPGA Coprocessor for Accelerated Classificationof Images

9 SiC JFET Transistor Circuit Model for ExtremeTemperature Range

10 TDR Using Autocorrelation and Varying-DurationPulses

10 Update on Development of SiC Multi-Chip Power Modules

11 Radio Ranging System for Guidance ofApproaching Spacecraft

11 Electromagnetically Clean Solar Arrays

12 Improved Short-Circuit Protection for Power Cells in Series

12 Electromagnetically Clean Solar Arrays

13 Logic Gates Made of N-Channel JFETs andEpitaxial Resistors

14 Improved Short-Circuit Protection for Power Cells in Series

14 Communication Limits Due to Photon-DetectorJitter

15 Manufacturing & Prototyping15 System for Removing Pollutants From Incinerator

Exhaust

15 Sealing and External Sterilization of a SampleContainer

17 Software17 Converting EOS Data From HDF-EOS to netCDF

17 HDF-EOS 2 and HDF-EOS 5 Compatibility Library

17 HDF-EOS Web Server

17 HDF-EOS 5 Validator

17 XML DTD and Schemas for HDF-EOS

18 Converting From XML to HDF-EOS

18 Simulating Attitudes and Trajectories of MultipleSpacecraft

18 Specialized Color Function for Display of Signed Data

18 Delivering Alert Messages to Members of a Work Force

18 Delivering Images for Mars Rover SciencePlanning

21 Materials21 Oxide Fiber Cathode Materials for Rechargeable

Lithium Cells

21 Electrocatalytic Reduction of Carbon Dioxide to Methane

21 Heterogeneous Superconducting Low-NoiseSensing Coils

22 Progress Toward Making Epoxy/Carbon-NanotubeComposites

22 Predicting Properties of Unidirectional-NanofiberComposites

23 Mechanics/Machinery23 Deployable Crew Quarters

23 Nonventing, Regenerable, Lightweight HeatAbsorber

23 Miniature High-Force, Long-Stroke SMA LinearActuators

24 “Bootstrap” Configuration for Multistage Pulse-Tube Coolers

24 Reducing Liquid Loss During Ullage Venting inMicrogravity

25 Books & Reports25 Ka-Band Transponder for Deep-Space Radio

Science

25 Replication of Space-Shuttle Computers in FPGAs and ASICs

25 Demisable Reaction-Wheel Assembly

25 Spatial and Temporal Low-Dimensional Models for Fluid Flow

27 Information Sciences27 Advanced Land Imager Assessment System

29 Physical Sciences29 Range Imaging Without Moving Parts

12-08 December 2008


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


The crew activity analyzer (CAA) is asystem of electronic hardware and soft-ware for automatically identifying pat-terns of group activity among crewmembers working together in an office,cockpit, workshop, laboratory, or otherenclosed space. The CAA synchronouslyrecords multiple streams of data fromdigital video cameras, wireless micro-phones, and position sensors, then playsback and processes the data to identifyactivity patterns specified by human an-alysts. The processing greatly reducesthe amount of time that the analystsmust spend in examining large amountsof data, enabling the analysts to concen-trate on subsets of data that representactivities of interest. The CAA has po-tential for use in a variety of governmen-tal and commercial applications, includ-ing planning for crews for future longspace flights, designing facilities

wherein humans must work in proxim-ity for long times, improving crew train-ing and measuring crew performance inmilitary settings, human-factors andsafety assessment, development of teamprocedures, and behavioral and ethno-graphic research.

The data-acquisition hardware of theCAA (see figure) includes two video cam-eras: an overhead one aimed upward at aparaboloidal mirror on the ceiling andone mounted on a wall aimed in a down-ward slant toward the crew area. As manyas four wireless microphones can beworn by crew members. The audio sig-nals received from the microphones aredigitized, then compressed in prepara-tion for storage. Approximate locationsof as many as four crew members aremeasured by use of a Cricket indoor loca-tion system. [The Cricket indoor loca-tion system includes ultrasonic/radio

beacon and listener units. A Cricket bea-con (in this case, worn by a crew mem-ber) simultaneously transmits a pulse ofultrasound and a radio signal that con-tains identifying information. EachCricket listener unit measures the differ-ence between the times of reception ofthe ultrasound and radio signals from anidentified beacon. Assuming essentiallyinstantaneous propagation of the radiosignal, the distance between that beaconand the listener unit is estimated fromthis time difference and the speed ofsound in air.] In this system, six Cricketlistener units are mounted in various po-sitions on the ceiling, and as many asfour Cricket beacons are attached tocrew members. The three-dimensionalposition of each Cricket beacon can beestimated from the time-difference read-ings of that beacon from at least threeCricket listener units.

Crew Activity Analyzer Video, audio, and position data are recorded and analyzed. Ames Research Center, Moffett Field, California

Activities of Crew Members Are Monitored by use of video cameras, microphones, and Cricket beacon and listener units. Monitor data are recorded, thenplayed back and analyzed to identify patterns of group activity.

CricketListener Units

VideoCamera Video

Camera

ParaboloidalMirror

Wireless Microphones

Cricket Beacons

FirewireHub

Receivers

Interface

UniversalSerial Bus

Hub

Wireless Microphones

Technology Focus: Data Acquisition

6 NASA Tech Briefs, December 2008

The CAA includes a notebook com-puter that controls the rest of the systemand can be used to process the dataupon playback. The CAA software in-cludes components that separately cap-ture the video, audio, and position datastreams and store them in files on thehard drive of this computer. Alterna-tively or in addition, the data can bestored on one or more external harddrive(s) or on a digital videodisk. Datacan be played back from any of thesestorage media. The CAA can store datafor an observation interval as long astwo weeks.

In addition to the video image data,the video-data-storage software compo-nent records the times of individualframes from each camera, enabling syn-

chronization of the video data with theaudio and position data during play-back and analysis. The position-data-storage software component reads datafrom the six Cricket listener units, cal-culates the three-dimensional positionsof the Cricket beacons according to theprinciple described above, and savesthese positions in a text file. The posi-tion-data-storage software componentalso creates, reads, and writes a Cricketcalibration-data file.

The CAA software further includescomponents for playback and analysis ofthe recorded data. One of these softwarecomponents provides capabilities forsearching and playback using the video,audio, and position data files as well asfiles that describe rectangular areas of

interest (AOIs) on the floor as definedby the user with the help of another soft-ware component. Several other compo-nents perform a variety of analyses ofimage data. Still another software com-ponent reads the position and AOI datafiles and generates reports on activitiesof interest represented in the data (e.g.,it generates histograms of occupation ofAOIs by crew members). The data in thereports can be saved in a format suitablefor export to a spreadsheet program.

This work was done by James Murray andAlexander Kirillov of Foster-Miller, Inc. forAmes Research Center. Inquiries concerningrights for the commercial use of this inventionshould be addressed to Judith Gertler, Divi-sion Manager, Foster-Miller Inc. at (781)684-4270. Refer to ARC-15162-1.

ADROIT is a developmental com-puter program for real-time distribu-tion of complex data streams for displayon Web-enabled, portable terminalsheld by members of an operationalteam of a spacecraft-command-and-con-trol center who may be located awayfrom the center. Examples of such ter-minals include personal data assistants,laptop computers, and cellular tele-phones. ADROIT would make it unnec-essary to equip each terminal with plat-form-specific software for access to thedata streams or with software that im-plements the information-sharing pro-tocol used to deliver telemetry data toclients in the center.

ADROIT is a combination of middle-ware plus software specific to the center.(Middleware enables one applicationprogram to communicate with anotherby performing such functions as conver-sion, translation, consolidation, and/orintegration.) ADROIT translates a datastream (voice, video, or alphanumericaldata) from the center into ExtensibleMarkup Language, effectuates a sub-scription process to determine who getswhat data when, and presents the data toeach user in real time. Thus, ADROIT isexpected to enable distribution of oper-ations and to reduce the cost of opera-tions by reducing the number of personsrequired to be in the center.

This program was written by Mark Hodgesand Layne Simmons of TenXsys, Inc. forJohnson Space Center. For further informa-tion, contact the JSC Innovative PartnershipsOffice at (281) 483-3809.

In accordance with Public Law 96-517,the contractor has elected to retain title tothis invention. Inquiries concerning rightsfor its commercial use should be addressedto:

TenXsys, Inc.408 S. Eagle RoadSuite 201Eagle, ID 83616Refer to MSC-24152-1, volume and num-

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

Distributing Data to Hand-Held Devices in a Wireless NetworkLyndon B. Johnson Space Center, Houston, Texas

An algorithm has been devised to re-duce ground clutter in the data prod-ucts of the CloudSat Cloud ProfilingRadar (CPR), which is a nadir-lookingradar instrument, in orbit around theEarth, that measures power backscat-tered by clouds as a function of distancefrom the instrument. Ground cluttercontaminates the CPR data in the low-est 1 km of the atmospheric profile,heretofore making it impossible to use

CPR data to satisfy the scientific interestin studying clouds and light rainfall atlow altitude.

The algorithm is based partly on thefact that the CloudSat orbit is such thatthe geodetic altitude of the CPR variescontinuously over a range of approxi-mately 25 km. As the geodetic altitudechanges, the radar timing parametersare changed at intervals defined byflight software in order to keep the tro-

posphere inside a data-collection timewindow. However, within each interval,the surface of the Earth continuously“scans through” (that is, it moves across)a few range bins of the data time win-dow. For each radar profile, only fewsamples [one for every range-bin incre-ment (Δr = 240 m)] of the surface-clut-ter signature are available around therange bin in which the peak of surfacereturn is observed, but samples in con-

Reducing Surface Clutter in Cloud Profiling Radar Data Radar data can be processed to study clouds closer to the surface.NASA’s Jet Propulsion Laboratory, Pasadena, California


A method of incorporating informa-tion, acquired by a multibeam laser orradar altimeter system, pertaining to thedistance and direction between the sys-tem and a nearby target body, into an es-timate of the state of a vehicle uponwhich the system is mounted, involvesthe use of a faceted model to representthe shape of the target body. In the orig-inal intended application, the vehiclewould be a spacecraft and the targetbody would be an asteroid, comet, orsimilar body that the spacecraft was re-quired to approach. The method could

also be used in navigating aircraft at lowaltitudes over terrain that is roughand/or occupied by objects of signifi-cant structure.

Fundamentally, what one seeks tomeasure is the distance from the vehicleto the target body. The present methodis the product of a generalization of aprior method of altimetry, in which thetarget body has a simple shape repre-sented by a spherical or ellipsoidalmodel. In principle, the estimate of dis-tance or altitude obtained by use of amultibeam altimeter can be more robust

than that obtained by use of a single-beam altimeter, but if the surface of thetarget body has a complex and/or irreg-ular shape, then it becomes more diffi-cult to define the distance and computethe distance from readings of a multi-beam altimeter.

The faceted shape model of the pres-ent method facilitates the definition andcomputation of distance to a target ob-ject having almost any shape, no matterhow irregular and complex. The use offaceted shape models to represent com-plex three-dimensional objects is com-

Multibeam Altimeter Navigation Update Using Faceted Shape ModelThe model is applicable to a body having almost any complex shape.NASA’s Jet Propulsion Laboratory, Pasadena, California

MODIS Atmospheric Data HandlerStennis Space Center, Mississippi

A number of science data sets are derivedfrom the observations of the ModerateResolution Imaging Spectroradiometer(MODIS) instrument onboard NASA’sTerra and Aqua satellites. These datatypically contain information on re-trieval techniques, quality-control flags,and geo-referencing information.These datasets, distributed in HDF (Hi-erachical Data Format), must be fur-ther processed to extract relevant infor-mation for weather analysis studies andnumerical models input. The MODIS-Atmosphere Data Handler softwareconverts the HDF data to ASCII format,and outputs: (1) atmospheric profiles

of temperature and dew point and (2)total precipitable water. Quality-controldata are also considered in the exportprocedure.

The package currently consists of pro-grams to process the MOD05 andMOD07 data products from MODIS.The software is written using the C pro-gramming language and contains Make-files for easier compilation and installa-tion. The MODIS-ADH software helpsease the overhead involved in data pro-cessing so that the numerical modelersmay concentrate on their science andmodeling tasks rather than manipulat-ing data for their models.

This program was written by ValentineAnantharaj and Patrick Fitzpatrick of theNorthern Gulf Institute at Mississippi StateUniversity for Stennis Space Center.

Inquiries concerning rights for its commer-cial use should be addressed to:

Mississippi State UniversityNorthern Gulf InstituteBLDG 1103, Room 233Stennis Space Center, MS 39529Phone No.: (228) 688-1157Fax: (228) 688-7100E-mail: [email protected] to SSC-00267, volume and number

of this NASA Tech Briefs issue, and thepage number.

secutive radar profiles are offset slightly(by amounts much less than Δr) with re-spect to each other according to the rel-ative change in geodetic altitude. As aconsequence, in a case in which the sur-face area under examination is homoge-nous (e.g., an ocean surface), a se-quence of consecutive radar profiles ofthe surface in that area contains samplesof the surface response with range reso-lution (Δρ) much finer than the range-bin increment (Δρ << Δr).

Once the high-resolution surface re-sponse has thus become available, theprofile of surface clutter can be accu-rately estimated by use of a conventionalmaximum-correlation scheme: A trans-

lated and scaled version of the high-res-olution surface response is fitted to theobserved low-resolution profile. Thetranslation and scaling factors that opti-mize the fit in a maximum-correlationsense represent (1) the true position ofthe surface relative to the sampled sur-face peak and (2) the magnitude of thesurface backscatter.

The performance of this algorithm hasbeen tested on CloudSat data acquiredover an ocean surface. A preliminaryanalysis of the test data showed a surface-clutter-rejection ratio over flat surfaces of>10 dB and a reduction of the contami-nated altitude over ocean from about 1km to about 0.5 km (over the ocean).

The algorithm has been embedded inCloudSat L1B processing as of Release 04(July 2007), and the estimated flat sur-face clutter is removed in L2B-GEOPROFproduct from the observed profile of re-flectivity (see CloudSat product docu-mentation for details and performance athttp://www.cloudsat.cira.colostate.edu/dataSpecs.php?prodid=1).

This work was done by Simone Tanelli,Kyung Pak, Stephen Durden, and Eastwood Imof Caltech for NASA’s Jet Propulsion Laboratory.

The software used in this innovation isavailable for commercial licensing. Pleasecontact Karina Edmonds of the California In-stitute of Technology at (626) 395-2322.Refer to NPO-44873.


mon in the computer-graphics literatureand in the movie and video-game indus-tries. In this method, the distance to bemeasured is defined as the length of thevector (ρ) from the center of mass of themultifaceted shape model to the centerof mass of the vehicle, as depicted in theupper part of the figure.

The state-update information derivedfrom the most recent set of multibeam-

altimeter measurements is listed system-atically in a range-measurement table(RMT), depicted in the lower part of thefigure, in which the planar facets of theshape model are represented in Hesse’snormal form. Each row of the table con-tains the data from one of the altimeterbeams. The first column contains therow index (i), which is the cardinal num-ber of the affected beam. The second

column contains a number, between 0and 1, representing the degree of confi-dence in the measurements. At the pres-ent state of development of the method,the confidence is taken to be either 0(signifying complete rejection) or 1(representing complete acceptance) ofthe data in the row. The third columncontains the scalar range measurement|r| of the ith beam; the fourth columncontains the standard deviation (σ) ofthe range measurement.

The fifth column contains the Carte-sian components [Nx, Ny, Nz] of thetranspose of the unit vector (NT) normalto the model facet containing the inter-section of the ith laser beam with thesurface of the target object. Typically,this intersection point is not known ex-actly and must be estimated, on the basisof the current state estimate, by a previ-ously developed method that lies be-yond the scope of this article. The sixthcolumn contains the facet constant, κ(the perpendicular distance from thecenter of mass of the target body to theaffected facet). The seventh columncontains the Cartesian components [dx,dy, dz] of the unit vector along the ithlaser beam. The seventh column con-tains the Cartesian components [cx, cy, cz]of the position vector from the center ofmass of the vehicle to the origin of theith laser beam.

The entries in the RMT are mappedinto a measurement equation for use bya Kalman filter that incorporates altime-try information into the final estimate ofthe state of a spacecraft or other vehiclemaneuvering in the vicinity of a targetbody. The relative position vector, ρ, ispart of the state vector that is updated byuse of the Kalman filter.

This work was done by David S. Bayard,Paul Brugarolas, and Steve Broschart of Caltech for NASA’s Jet Propulsion Labo-ratory. For more information, contact [email protected]. NPO-44428

The Laser or Radar Altimeter measures the magnitude of the vector (r) from the origin of each beamto the intersection of the beam with a target body represented by a multifaceted shape model. Thereare multiple beams, but only one is shown here for simplicity. The measurement data and associatedmodel data are listed in the range-measurement table.

InertialReference Frame

Target

TargetReference

Frame

VehicleReference

Frame

Facet

Altimeter LaserBeam

r= r d

N

c

# Confidence NT = dT = cT =r[Nx, Ny, Nz] [dx, dy, dz] [cx, cy, cz]

1

2

RANGE-MEASUREMENT TABLE


Electronics/Computers

Spaceborne Hybrid-FPGA System for Processing FTIR Data NASA’s Jet Propulsion Laboratory, Pasadena, California

Progress has been made in a continu-ing effort to develop a spaceborne com-puter system for processing readout datafrom a Fourier-transform infrared(FTIR) spectrometer to reduce the vol-ume of data transmitted to Earth. Theapproach followed in this effort, ori-ented toward reducing design time andreducing the size and weight of the spec-trometer electronics, has been to exploitthe versatility of recently developed hy-brid field-programmable gate arrays(FPGAs) to run diverse software on em-bedded processors while also taking ad-

vantage of the reconfigurable hardwareresources of the FPGAs.

The specific FPGA/embedded-proces-sor combination selected for this effort isthe Xilinx Virtex-4 FX hybrid FPGA withone of its two embedded IBM PowerPC405 processors. The effort has involvedexploration of various architectures andhardware and software optimizations. Byincluding a dedicated floating-point unitand a dot-product coprocessor in thehardware and utilizing optimized single-precision math library functions and amodified PowerPC performance library

in the software, it has been possible to re-duce execution time to an eighth of thatof a non-optimized software-only imple-mentation. A concept for utilizing bothembedded PowerPC processors to fur-ther reduce execution time has also beenconsidered.

This work was done by Dmitriy L. Bekker,Jean-Francois L. Blavier, and Paula J. Pin-gree of Caltech and Marcin Lukowiak andMuhammad Shaaban of Rochester Instituteof Technology for NASA’s Jet Propulsion Lab-oratory. For more information, contact [email protected]. NPO-45957

FPGA Coprocessor for Accelerated Classification of Images NASA’s Jet Propulsion Laboratory, Pasadena, California

An effort related to that described inthe preceding article focuses on develop-ing a spaceborne processing platform forfast and accurate onboard classificationof image data, a critical part of modernsatellite image processing. The approachagain has been to exploit the versatility ofrecently developed hybrid Virtex-4FXfield-programmable gate array (FPGA) torun diverse science applications on em-bedded processors while taking advan-tage of the reconfigurable hardware re-sources of the FPGAs. In this case, theFPGA serves as a coprocessor that imple-ments legacy C-language support-vector-machine (SVM) image-classification algo-rithms to detect and identify natural

phenomena such as flooding, volcaniceruptions, and sea-ice break-up. TheFPGA provides hardware acceleration forincreased onboard processing capabilitythan previously demonstrated in software.

The original C-language program —demonstrated on an imaging instrumentaboard the Earth Observing-1 (EO-1)satellite — implements a linear-kernelSVM algorithm for classifying parts ofthe images as snow, water, ice, land, orcloud or unclassified. Current onboardprocessors, such as on EO-1, have lim-ited computing power, extremely lim-ited active storage capability and are nolonger considered state-of-the-art.Using commercially available software

that translates C-language programs intohardware description language (HDL)files, the legacy C-language program,and two newly formulated programs fora more capable expanded-linear-kerneland a more accurate polynomial-kernelSVM algorithm, have been implementedin the Virtex-4FX FPGA. In tests, theFPGA implementations have exhibitedsignificant speedups over conventionalsoftware implementations running ongeneral-purpose hardware.

This work was done by Paula J. Pingree,Lucas J. Scharenbroich, and Thomas A.Werne of Caltech for NASA’s Jet PropulsionLaboratory. For more information, [email protected]. NPO-45961

SiC JFET Transistor Circuit Model for Extreme Temperature RangeSimple modifications of common silicon model provide reasonable approximation from 25 to 500 °C.John H. Glenn Research Center, Cleveland, Ohio

A technique for simulating extreme-temperature operation of integrated cir-cuits that incorporate silicon carbide(SiC) junction field-effect transistors(JFETs) has been developed. The tech-nique involves modification ofNGSPICE, which is an open-source ver-sion of the popular Simulation Program

with Integrated Circuit Emphasis(SPICE) general-purpose analog-inte-grated-circuit-simulating software.NGSPICE in its unmodified form is usedfor simulating and designing circuitsmade from silicon-based transistors thatoperate at or near room temperature.

Two rapid modifications of NGSPICE

source code enable SiC JFETs to be sim-ulated to 500 °C using the well-known“Level 1” model for silicon metal oxidesemiconductor field-effect transistors(MOSFETs). First, the default value ofthe MOSFET surface potential must bechanged. In the unmodified sourcecode, this parameter has a value of 0.6,


which corresponds to slightly more thanhalf the bandgap of silicon. In NGSPICEmodified to simulate SiC JFETs, this pa-rameter is changed to a value of 1.6, cor-responding to slightly more than halfthe bandgap of SiC. The second modifi-cation consists of changing the tempera-ture dependence of MOSFET transcon-ductance and saturation parameters.The unmodified NGSPICE source codeimplements a T–1.5 temperature depend-ence for these parameters. In order tomimic the temperature behavior of ex-

perimental SiC JFETs, a T–1.3 tempera-ture dependence must be implementedin the NGSPICE source code.

Following these two simple modifica-tions, the “Level 1” MOSFET model ofthe NGSPICE circuit simulation pro-gram reasonably approximates themeasured high-temperature behavior ofexperimental SiC JFETs properly oper-ated with zero or reverse bias applied tothe gate terminal. Modification of addi-tional silicon parameters in theNGSPICE source code was not neces-

sary to model experimental SiC JFETcurrent-voltage performance across theentire temperature range from 25 to500 °C.

This work was done by Philip G. Neudeckof Glenn Research Center. Further informa-tion is contained 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: Steve Fedor, MailStop 4–8, 21000 Brookpark Road, Cleve-land, Ohio 44135. Refer to LEW-18342-1.

TDR Using Autocorrelation and Varying-Duration PulsesSignal-to-noise ratios may be increased.John F. Kennedy Space Center, Florida

In an alternative to a prior techniqueof time-domain-reflectometry (TDR) inwhich very short excitation pulses areused, the pulses have very short rise andfall times and the pulse duration is var-ied continuously between a minimumand a maximum value. In both the pres-ent and prior techniques, the basic ideais to (1) measure the times between thegeneration of excitation pulses and thereception of reflections of the pulses asindications of the locations of one ormore defects along a cable and (2)measure the amplitudes of the reflec-tions as indication of the magnitudes ofthe defects.

In general, an excitation pulse has aduration T. Each leading and trailing

edge of an excitation pulse generates areflection from a defect, so that a uniquepair of reflections is associated with eachdefect. In the present alternative tech-nique, the processing of the measuredreflection signal includes computationof the autocorrelation function

R(τ)≡∫x(t)x(t – τ)dtwhere t is time, x(t) is the measured reflec-tion signal at time t, and τ is the correla-tion interval. The integration is per-formed over a measurement time intervalshort enough to enable identification andlocation of a defect within the correspon-ding spatial interval along the cable. Typi-cally, where there is a defect, R(τ) exhibitsa negative peak having maximum magni-tude for τ in the vicinity of T. This peak

can be used as a means of identifying aleading-edge/trailing-edge reflection pair.

For a given spatial interval, measure-ments are made and R(τ) computed, asdescribed above, for pulse durations Tranging from the minimum to the maxi-mum value. The advantage of doing thisis that the effective signal-to-noise ratiomay be significantly increased over thatattainable by use of a fixed pulse dura-tion T.

This work was done by Angel Lucena, PamMullinex, PoTien Huang, and Josephine Santi-ago of Kennedy Space Center and Pedro Medelius,Carlos Mata, Carlos Zavala, and John Lane ofASRC Aerospace Corp. Further information iscontained in a TSP (see page 1).KSC-12856

Progress has been made in a continuingeffort to develop multi-chip power mod-ules (SiC MCPMs). This effort at an earlierstage was reported in “SiC Multi-ChipPower Modules as Power-System BuildingBlocks” (LEW-18008-1), NASA Tech Briefs,Vol. 31, No. 2 (February 2007), page 28.

The following unavoidably lengthy reca-pitulation of information from the citedprior article is prerequisite to a meaningfulsummary of the progress made since then:• SiC MCPMs are, more specifically, elec-

tronic power-supply modules containingmultiple silicon carbide power integrated-circuit chips and silicon-on-insulator

(SOI) control integrated-circuit chips.SiC MCPMs are being developed as build-ing blocks of advanced expandable, re-configurable, fault-tolerant power-supplysystems. Exploiting the ability of SiC semi-conductor devices to operate at tempera-tures, breakdown voltages, and currentdensities significantly greater than thoseof conventional Si devices, the designs ofSiC MCPMs and of systems comprisingmultiple SiC MCPMs are expected to af-ford a greater degree of miniaturizationthrough stacking of modules with re-duced requirements for heat sinking.

• The stacked SiC MCPMs in a given sys-

tem can be electrically connected in se-ries, parallel, or a series/parallel combi-nation to increase the overall power-handling capability of the system. Inaddition to power connections, themodules have communication connec-tions. The SOI controllers in the mod-ules communicate with each other asnodes of a decentralized control net-work, in which no single controller ex-erts overall command of the system.Control functions effected via the net-work include synchronization of switch-ing of power devices and rapid recon-figuration of power connections to

Update on Development of SiC Multi-Chip Power ModulesModules and a modular power system have been built and tested.John H. Glenn Research Center, Cleveland, Ohio


enable the power system to continue tosupply power to a load in the event offailure of one of the modules.

• In addition to serving as buildingblocks of reliable power-supply systems,SiC MCPMs could be augmented withexternal control circuitry to make themperform additional power-handlingfunctions as needed for specific appli-cations. Because identical SiC MCPMbuilding blocks could be utilized insuch a variety of ways, the cost and dif-ficulty of designing new, highly reliablepower systems would be reduced con-siderably. This concludes the informa-tion from the cited prior article.The main activity since the previously

reported stage of development was thedesign, fabrication, and testing a 120-

VDC-to-28-VDC modular power-con-verter system composed of eight SiCMCPMs in a 4 (parallel)-by-2 (series)matrix configuration, with normally-offcontrollable power switches. The SiCMCPM power modules include closed-loop control subsystems and are capableof operating at high power density orhigh temperature. The system was testedunder various configurations, load con-ditions, load-transient conditions, andfailure-recovery conditions.

Planned future work includes refine-ment of the demonstrated modular sys-tem concept and development of a newconverter hardware topology that wouldenable sharing of currents without theneed for communication among mod-ules. Toward these ends, it is also

planned to develop a new convertercontrol algorithm that would providefor improved sharing of current andpower under all conditions, and to im-plement advanced packaging conceptsthat would enable operation at higherpower density.

This work was done by Alexander Lostetter,Edgar Cilio, Gavin Mitchell, and RobertoSchupbach of Arkansas Power Electronics Inter-national, Inc. for Glenn Research Center. Fur-ther information is contained in a TSP (seepage 1).

Inquiries concerning rights for the commer-cial use of this invention should be addressed toNASA Glenn Research Center, InnovativePartnerships Office, Attn: Steve Fedor, MailStop 4–8, 21000 Brookpark Road, Cleveland,Ohio 44135. Refer to LEW-18341-1.

Radio Ranging System for Guidance of Approaching SpacecraftLyndon B. Johnson Space Center, Houston, Texas

A radio communication and rangingsystem has been proposed for determin-ing the relative position and orienta-tions of two approaching spacecraft toprovide guidance for docking maneu-vers. On Earth, the system could be usedsimilarly for guiding approaching air-craft and for automated positioning oflarge, heavy objects. In principle, the

basic idea is to (1) measure distances be-tween radio transceivers on the twospacecraft and (2) compute the relativeposition and orientations from themeasured distances.

Half-duplex communication linkswould be established between transceiverson the two spacecraft, and pulses havingdurations of the order of a nanosecond

would be exchanged. The distanceswould be determined by the pulse-time-of-flight method. Data signals could betransmitted in addition to ranging pulses.

This work was done by Vikram Manikondaand Eric van Doorn of Intelligent Automation,Inc. for Johnson Space Center. For further infor-mation, contact the JSC Innovation PartnershipsOffice at (281) 483-3809. MSC-23474-1

Electromagnetically Clean Solar ArraysCells are laminated with shielding, narrow-current-loop wiring, and structural supports.John H. Glenn Research Center, Cleveland, Ohio

The term “electromagnetically cleansolar array” (“EMCSA”) refers to a panelthat contains a planar array of solar pho-tovoltaic cells and that, in comparisonwith a functionally equivalent solar-arraypanel of a type heretofore used on space-craft, (1) exhibits less electromagnetic in-terference to and from other nearby elec-trical and electronic equipment and (2)can be manufactured at lower cost. Thereduction of electromagnetic interfer-ence is effected through a combination of(1) electrically conductive, electricallygrounded shielding and (2) reduction ofareas of current loops (in order to reducemagnetic moments). The reduction ofcost is effected by designing the array tobe fabricated as a more nearly unitarystructure, using fewer components andfewer process steps. Although EMSCAs

were conceived primarily for use onspacecraft, they are also potentially advan-tageous for terrestrial applications inwhich there are requirements to limitelectromagnetic interference.

In a conventional solar panel of the typemeant to be supplanted by an EMCSApanel, the wiring is normally located onthe back side, separated from the cells,thereby giving rise to current loops havingsignificant areas and, consequently, signifi-cant magnetic moments. Current-loopgeometries are chosen in an effort to bal-ance opposing magnetic moments to limitfar-field magnetic interactions, but the rel-atively large distances separating currentloops makes full cancellation of magneticfields problematic. The panel is assembledfrom bare photovoltaic cells by means ofmultiple sensitive process steps that con-

tribute significantly to cost, especially ifelectromagnetic cleanliness is desired. Thesteps include applying a cover glass andelectrical-interconnection tabs to each cellto create a cell-interconnect-cell (CIC) sub-assembly, connecting the CIC subassem-blies into strings of series-connected cells,laying down and adhesively bonding thestrings onto a panel structure that has beenmade in a separate multi-step process, andmounting the wiring on the back of thepanel. Each step increases the potential foroccurrence of latent defects, loss of processcontrol, and attrition of components.

An EMCSA panel includes an integralcover made from a transparent siliconematerial. The silicone cover supplants theindividual cover glasses on the cells andserves as an additional unitary structuralsupport that offers the advantage, relative


to glass, of the robust, forgiving nature ofthe silicone material. The cover containspockets that hold the solar cells in placeduring the lamination process. The coveris coated with indium tin oxide to make itssurface electrically conductive, so that itserves as a contiguous, electricallygrounded electromagnetic shield over theentire panel surface.

The cells are mounted in proximity tometallic printed wiring. The printed-wiringlayer comprises metal-film traces on a sheetof Kapton (or equivalent) polyimide. Thetraces include contact pads on one side ofthe sheet for interconnecting the cells. Re-turn leads are on the opposite side of the

sheet, positioned to form the return cur-rents substantially as mirror images of, andin proximity to, the cell sheet currents,thereby minimizing magnetic moments.The printed-wiring arrangement mimicsthe back-wiring arrangement of conven-tional solar arrays, but the current-loopareas and the resulting magnetic momentsare much smaller because the return-cur-rent paths are much closer to the solar-cellsheet currents.

The contact pads are prepared withsolder for electrical and mechanicalbonding to the cells. The pocketedcover/shield, the solar cells, the printed-wiring layer, an electrical-bonding agent,

a mechanical-bonding agent, a compos-ite structural front-side face sheet, analuminum honeycomb core, and a com-posite back-side face sheet are all assem-bled, then contact pads are soldered tothe cells and the agents are cured in asingle lamination process.

This work was done by Theodore G. Stern andAnthony E. Kenniston of DR Technologies, Inc.for Glenn Research Center.

Inquiries concerning rights for the commercialuse of this invention should be addressed toNASA Glenn Research Center, Innovative Part-nerships Office, Attn: Steve Fedor, Mail Stop4–8, 21000 Brookpark Road, Cleveland, Ohio44135. Refer to LEW-18156-1.

Improved Short-Circuit Protection for Power Cells in SeriesLyndon B. Johnson Space Center, Houston, Texas

A scheme for protection against shortcircuits has been devised for seriesstrings of lithium electrochemical cellsthat contain built-in short-circuit protec-tion devices, which go into a high-resist-ance, current-limiting state when heatedby excessive current. If cells are simplyconnected in a long series string to ob-tain a high voltage and a short circuit oc-curs, whichever short-circuit protectiondevice trips first is exposed to nearly thefull string voltage, which, typically, is

large enough to damage the device. De-pending on the specific cell design, thedamage can defeat the protective func-tion, cause a dangerous internal shortcircuit in the affected cell, and/or cas-cade to other cells.

In the present scheme, reversediodes rated at a suitably high currentare connected across short series sub-strings, the lengths of which are chosenso that when a short-circuit protectiondevice is tripped, the voltage across it

does not exceed its rated voltage. Thisscheme preserves the resetting proper-ties of the protective devices. It pro-vides for bypassing of cells that failopen and limits cell reversal, thoughnot as well as does the more-expensivescheme of connecting a diode acrossevery cell.

This work was done by Francis Davies of Her-nandez Engineering Inc. for Johnson Space Cen-ter. Further information is contained in a TSP(see page 1).. MSC-23446-1

Electromagnetically Clean Solar ArraysCells are laminated with shielding, narrow-current-loop wiring, and structural supports.John H. Glenn Research Center, Cleveland, Ohio

The term “electromagnetically cleansolar array” (“EMCSA”) refers to a panelthat contains a planar array of solar pho-tovoltaic cells and that, in comparisonwith a functionally equivalent solar-arraypanel of a type heretofore used on space-craft, (1) exhibits less electromagnetic in-terference to and from other nearby elec-trical and electronic equipment and (2)can be manufactured at lower cost. Thereduction of electromagnetic interfer-ence is effected through a combination of(1) electrically conductive, electricallygrounded shielding and (2) reduction ofareas of current loops (in order to reducemagnetic moments). The reduction ofcost is effected by designing the array tobe fabricated as a more nearly unitarystructure, using fewer components and

fewer process steps. Although EMSCAswere conceived primarily for use onspacecraft, they are also potentially advan-tageous for terrestrial applications inwhich there are requirements to limitelectromagnetic interference.

In a conventional solar panel of the typemeant to be supplanted by an EMCSApanel, the wiring is normally located onthe back side, separated from the cells,thereby giving rise to current loops havingsignificant areas and, consequently, signifi-cant magnetic moments. Current-loopgeometries are chosen in an effort to bal-ance opposing magnetic moments to limitfar-field magnetic interactions, but the rel-atively large distances separating currentloops makes full cancellation of magneticfields problematic. The panel is assembled

from bare photovoltaic cells by means ofmultiple sensitive process steps that con-tribute significantly to cost, especially ifelectromagnetic cleanliness is desired. Thesteps include applying a cover glass andelectrical-interconnection tabs to each cellto create a cell-interconnect-cell (CIC) sub-assembly, connecting the CIC subassem-blies into strings of series-connected cells,laying down and adhesively bonding thestrings onto a panel structure that has beenmade in a separate multi-step process, andmounting the wiring on the back of thepanel. Each step increases the potential foroccurrence of latent defects, loss of processcontrol, and attrition of components.

An EMCSA panel includes an integralcover made from a transparent siliconematerial. The silicone cover supplants the


individual cover glasses on the cells andserves as an additional unitary structuralsupport that offers the advantage, relativeto glass, of the robust, forgiving nature ofthe silicone material. The cover containspockets that hold the solar cells in placeduring the lamination process. The coveris coated with indium tin oxide to make itssurface electrically conductive, so that itserves as a contiguous, electricallygrounded electromagnetic shield over theentire panel surface.

The cells are mounted in proximity tometallic printed wiring. The printed-wiring layer comprises metal-film traceson a sheet of Kapton (or equivalent)polyimide. The traces include contact

pads on one side of the sheet for inter-connecting the cells. Return leads areon the opposite side of the sheet, posi-tioned to form the return currents sub-stantially as mirror images of, and inproximity to, the cell sheet currents,thereby minimizing magnetic moments.The printed-wiring arrangement mimicsthe back-wiring arrangement of conven-tional solar arrays, but the current-loopareas and the resulting magnetic mo-ments are much smaller because the re-turn-current paths are much closer tothe solar-cell sheet currents.

The contact pads are prepared with sol-der for electrical and mechanical bondingto the cells. The pocketed cover/shield,

the solar cells, the printed-wiring layer, anelectrical-bonding agent, a mechanical-bonding agent, a composite structuralfront-side face sheet, an aluminum honey-comb core, and a composite back-side facesheet are all assembled, then contact padsare soldered to the cells and the agents arecured in a single lamination process.

This work was done by Theodore G. Stern andAnthony E. Kenniston of DR Technologies, Inc.for Glenn Research Center.


Logic Gates Made of N-Channel JFETs and Epitaxial ResistorsGates could be implemented in SiC ICs for operation at high temperatures.John H. Glenn Research Center, Cleveland, Ohio

Prototype logic gates made of n-chan-nel junction field-effect transistors(JFETs) and epitaxial resistors have beendemonstrated, with a view toward even-tual implementation of digital logic de-vices and systems in silicon carbide (SiC)integrated circuits (ICs). This develop-ment is intended to exploit the inherentability of SiC electronic devices to func-tion at temperatures from 300 to some-what above 500 °C and withstand largedoses of ionizing radiation. SiC-based

digital logic devices and systems couldenable operation of sensors and robotsin nuclear reactors, in jet engines, nearhydrothermal vents, and in other envi-ronments that are so hot or radioactiveas to cause conventional silicon elec-tronic devices to fail.

At present, current needs for digitalprocessing at high temperatures exceedSiC integrated circuit production capa-bilities, which do not allow for highly in-tegrated circuits. Only single to small

number component production of de-pletion mode n-channel JFETs and epi-taxial resistors on a single substrate ispossible. As a consequence, the finematching of components is impossible,resulting in rather large direct-currentparameter distributions within a groupof transistors typically spanning multi-ples of 5 to 10. Add to this the lack of p-channel devices to complement the n-channel FETs, the lack of precisedropping diodes, and the lack of en-

Vdd Vdd

Vss

R

R

R1

R2

R

OutputInputs

Input Input 2 Input nInput 1Q1 Q1

Q2

Qn

Q2

Vss

R3

Output

Q Follower

Vdd

R1

R2

Q1 Q2 Qn

Vss

R3

Output

Q Follower

INVERTER NAND GATE NOR GATE

This Inverter, NAND Gate, and NOR Gate are examples of logic circuits designed according to the principles described in the text. Other gates having greatercomplexity have also been designed.


Communication Limits Due to Photon-Detector JitterNASA’s Jet Propulsion Laboratory, Pasadena, California

A theoretical and experimental studywas conducted of the limit imposed byphoton-detector jitter on the capacity ofa pulse-position-modulated optical com-munication system in which the receiveroperates in a photon-counting (weak-sig-nal) regime. Photon-detector jitter is arandom delay between impingement ofa photon and generation of an electricalpulse by the detector.

In the study, jitter statistics were com-puted from jitter measurements madeon several photon detectors. The proba-

bility density of jitter was mathematicallymodeled by use of a weighted sum ofGaussian functions. Parameters of themodel were adjusted to fit histogramsrepresenting the measured-jitter statis-tics. Likelihoods of assigning detector-output pulses to correct pulse time slotsin the presence of jitter were derivedand used to compute channel capacitiesand corresponding losses due to jitter.

It was found that the loss, expressedas the ratio between the signal powerneeded to achieve a specified capacity

in the presence of jitter and that neededto obtain the same capacity in the ab-sence of jitter, is well approximated as aquadratic function of the standard devi-ation of the jitter in units of pulse-time-slot duration.

This work was done by Bruce E. Moisionand William H. Farr of Caltech for NASA’s JetPropulsion Laboratory. For more information,contact [email protected]. NPO-45809

hancement mode devices at these ele-vated temperatures and the use of con-ventional direct coupled and buffereddirect coupled logic gate design tech-niques is impossible.

The presented logic gate design is tol-erant of device parameter distributionsand is not hampered by the lack of com-plementary devices or dropping diodes.In addition to n-channel JFETs, thesegates include level-shifting and load re-

sistors (see figure). Instead of relying onprecise matching of parameters amongindividual JFETS, these designs rely onchoosing the values of these resistorsand of supply potentials so as to makethe circuits perform the desired func-tions throughout the ranges over whichthe parameters of the JFETs are distrib-uted. The supply rails Vdd and Vss andthe resistors R are chosen as functionsof the distribution of direct-current op-

erating parameters of the group of tran-sistors used.

This work was done by Michael J. Kra-sowski of Glenn Research Center. Further in-formation is contained 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: Steve Fedor, MailStop 4–8, 21000 Brookpark Road, Cleve-land, Ohio 44135. Refer to LEW-18256-1.

Improved Short-Circuit Protection for Power Cells in SeriesLyndon B. Johnson Space Center, Houston, Texas

A scheme for protection against shortcircuits has been devised for seriesstrings of lithium electrochemical cellsthat contain built-in short-circuit protec-tion devices, which go into a high-resist-ance, current-limiting state when heatedby excessive current. If cells are simplyconnected in a long series string to ob-tain a high voltage and a short circuit oc-curs, whichever short-circuit protectiondevice trips first is exposed to nearly thefull string voltage, which, typically, is

large enough to damage the device. De-pending on the specific cell design, thedamage can defeat the protective func-tion, cause a dangerous internal shortcircuit in the affected cell, and/or cas-cade to other cells.

In the present scheme, reversediodes rated at a suitably high currentare connected across short series sub-strings, the lengths of which are chosenso that when a short-circuit protectiondevice is tripped, the voltage across it

does not exceed its rated voltage. Thisscheme preserves the resetting proper-ties of the protective devices. It pro-vides for bypassing of cells that failopen and limits cell reversal, thoughnot as well as does the more-expensivescheme of connecting a diode acrossevery cell.

This work was done by Francis Davies ofHernandez Engineering Inc. for JohnsonSpace Center. Further information is con-tained in a TSP (see page 1). MSC-23446-1


Manufacturing & Prototyping

Sealing and External Sterilization of a Sample Container This method would enable safe transport of a biologically hazardous sample. NASA’s Jet Propulsion Laboratory, Pasadena, California

A method of (1) sealing a sample ofmaterial acquired in a possibly biologi-cally contaminated (“dirty”) environ-ment into a hermetic container, (2) ster-ilizing the outer surface of the container,then (3) delivering the sealed containerto a clean environment has been pro-posed. This method incorporates themethod reported in “Separation andSealing of a Sample Container UsingBrazing” (NPO-41024), NASA Tech Briefs,Vol. 31, No. 8 (August 2007), page 42.Like the previously reported method,the method now proposed was originallyintended to be used to return samplesfrom Mars to Earth, but could also beused on Earth to transport material sam-ples acquired in environments that con-tain biological hazards and/or, in somecases, chemical hazards.

To recapitulate from the cited prior ar-ticle: the process described therein is de-noted “S3B” (separation, seaming, andsealing using brazing) because sealing ofthe sample into the hermetic container,separating the container from the dirtyenvironment, and bringing the con-tainer with a clean outer surface into theclean environment are all accomplishedsimultaneously with an inductive-heating

brazing operation. At the beginning ofthe process, the sample container is theinner part of a double-wall container,and the inner and outer parts of the dou-ble-wall container are bonded togetherat a flange/braze joint at the top. Byvirtue of this configuration, the inside ofthe sample container is exposed to thedirty environment while the outer sur-face of the sample container is isolatedfrom the dirty environment.

During the S3B process, a lid that ispart of a barrier assembly between thedirty and clean environments becomesbrazed onto the sample container, andthe sample container with the lid at-tached becomes separated from theouter part of the double-wall containerand is pushed into the clean environ-ment. The brazing material is chosen tohave a sufficiently high melting tempera-ture (typically >500 °C) so that the braz-ing process sterilizes the outer surface ofthe lid/wall seam region of the newly cre-ated hermetic container. The outer sur-face of the inner container is coveredwith a layer of thermal-insulation mate-rial to prevent heat damage of the sampleduring brazing. Alternatively, in an appli-cation in which there is no concern about

A Sample Would Be Packaged in a magazine withredundant mechanical and brazed seals. Prior tosealing, the surfaces destined to become the out-side surface of the magazine would be kept isolatedfrom the dirty sample-collection environment. Asan extra precaution, after sealing, the outside sur-face could be sterilized by ignition of pyrotechnicpaint.

Clean OuterSurface

CleanInsulatingFoam in

Sealed Volume

BEFORE:SAMPLE (OR SAMPLE IN COLLECTIONCONTAINER) IN DIRTY ENVIRONMENT

AFTER:SAMPLE (OR SAMPLE IN COLLECTIONCONTAINER) SEALED IN MAGAZINE

System for Removing Pollutants From Incinerator ExhaustLyndon B. Johnson Space Center, Houston, Texas

A system for removing pollutants —primarily sulfur dioxide and mixed ox-ides of nitrogen (NOx) — from inciner-ator exhaust has been demonstrated.The system is also designed secondarilyto remove particles, hydrocarbons, andCO. The system is intended for use in anenclosed environment, for which a priorNOx-and-SO2-removal system designedfor industrial settings would not be suit-able. The incinerator exhaust first en-counters a cyclone separator, a primaryheat exchanger, and a fabric filter that,together, remove particles and reducethe temperature to 500 °C. The exhaustthen passes through a porous bed, main-

tained at ≈ 450 °C, that containsNa2CO3, which absorbs SO2.

Next, a commercial catalyst main-tained at 400 °C accelerates the oxida-tion of the carbon in hydrocarbons toCO and CO2. A heat exchanger thencools the exhaust to ≈ 300 °C beforepassage over a catalyst that causes 95percent of the NO to be oxidized toNO2. The first of two water scrubbersremoves most of the NO2, which is con-verted to KNO3 and KNO2. The secondwater scrubber contains sodium bisul-fite, which, with an aminophenol cata-lyst, converts most of the remainingNO2 to N2.

This work was done by David T. Wickham,James Bahr, Rita Dubovik, Steven C. Geb-hard, and Jeffrey Lind of TDA Research, Inc.for Johnson Space Center. For further informa-tion, contact the JSC Innovative PartnershipsOffice 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:

TDA Research12345 West 52nd Ave.Wheat Ridge, CO 80033Refer to MSC-23440-1, volume and num-



biological contamination, it could be fea-sible to substitute a lower-melting-tem-perature solder for the brazing material.

The method now proposed goes be-yond what was reported previously byproviding for container-design modifica-tions and additional process steps to en-sure cleanliness and delivery of a her-metically enclosed dirty sample to aclean environment. Implementation ofthe proposed method in the original in-tended Mars-to-Earth application wouldentail the use of dedicated machinery ina multistep augmented version of thepreviously reported S3B process thatwould result in sealing of the sample ina magazine and (see figure) and place-ment of the magazine in the nose coneof a spacecraft. Modified versions of themachinery and process, without provi-sion for placement in a nose cone, couldbe devised for terrestrial applications.One feature of the outer-space processthat might be useful in some terrestrialapplications would be coating the outersurface of the magazine with a pyrotech-nic paint, which would be ignited to in-

sure sterilization before releasing themagazine into the clean environment.

The method as now proposed also pro-vides additional options to choose mate-rials and process conditions to suit spe-cific applications. These options includethe following: • The sample container and the lid could

be made of a nonmetallic material, inwhich case a mixture of plastic andmetallic particles could serve as an ap-propriate lower-melting-temperature al-ternative to a brazing material. Themetallic particles would render the mix-ture amenable to inductive heating, sothat the plastic component could bemelted to make or break a seal.

• During brazing or during the cool-down after brazing, expansion or con-traction, respectively, of the gas insidethe sample container could push thebrazing material away from the desiredbraze joint. One way to limit expansionand contraction to a harmlessly lowlevel would be to line the inside of thesample container with a thermally in-sulating material.

• Instead of trying to limit the afore-mentioned expansion and contrac-tion, one could fabricate the samplecontainer with a small breathing holeto accommodate the expansion andcontraction. The hole would besealed in a small, localized brazingoperation after the main S3B brazingoperation. This work was done by Yoseph Bar-Cohen,

Mircea Badescu, Xiaoqi Bao, Stewart Sherrit,and Ayoola Olorunsola of Caltech for NASA’sJet Propulsion Laboratory.


Innovative Technology Assets ManagementJPLMail Stop 202-2334800 Oak Grove DrivePasadena, CA 91109-8099E-mail: [email protected] to NPO-45610, volume and number



Software

Converting EOS Data FromHDF-EOS to netCDF

A C-language computer program ac-cepts, as input, a set of scientific data andmetadata from an Earth Observing Sys-tem (EOS) satellite and converts the setfrom (1) the format in which it was cre-ated and delivered to (2) another formatfor processing and exchange of data onEarth. The first-mentioned format canbe either HDF-EOS 2 or HDF-EOS 5(“HDF” signifies “Hierarchical Data For-mat”). The second-mentioned format isnetCDF (“CDF” signifies “Common DataFormat”), which is an open-standard,machine-independent, self-describingformat for scientific-data files. In the ab-sence of this or a similar program, in-compatibilities among the three file for-mats can cause loss of metadata uponconversion.

This program preserves as many of themetadata as possible upon conversion.The program opens the input HDF-EOS2 or HDF-EOS 5 file, queries the compo-nents of the file by use of the HDF-EOS 2and HDF-EOS 5 Compatibility Library(which is described in the immediatelyfollowing article and provides uniformaccess to HDF-EOS 2 and HDF-EOS 5files), and writes the data and metadatacomponents into a netCDF file followingthe Climate and Forecast (CF) metadataconventions.

This program was written by Richard Ull-man of Goddard Space Flight Center; BobBane of Global Science & Technology, Inc.;and Jingli Yang of Earth Resources Technol-ogy, Inc. Further information is contained in aTSP (see page 1). GSC-15007-1

HDF-EOS 2 and HDF-EOS 5Compatibility Library

The HDF-EOS 2 and HDF-EOS 5Compatibility Library contains C-lan-guage functions that provide uniformaccess to HDF-EOS 2 and HDF-EOS 5files through one set of application pro-gramming interface (API) calls. (“HDF-EOS 2” and “HDF-EOS 5” are defined inthe immediately preceding article.)Without this library, differences betweenthe APIs of HDF-EOS 2 and HDF-EOS 5would necessitate writing of differentprograms to cover HDF-EOS 2 and HDF-EOS 5. The API associated with this li-brary is denoted “he25.”

For nearly every HDF-EOS 5 API call,there is a corresponding he25 API call.If a file in question is in the HDF-EOS 5format, the code reverts to the corre-sponding HDF-EOS 5 call; if the file is inthe HDF-EOS 2 format, the code trans-lates the arguments to HDF-EOS 2equivalents (if necessary), calls the HDF-EOS 2 call, and retranslates the resultsback to HDF-EOS 5 (if necessary).

This program was written by Richard Ull-man of Goddard Space Flight Center; BobBane of Global Science & Technology, Inc.;and Jingli Yang of Earth Resources Technol-ogy, Inc. Further information is contained in aTSP (see page 1). GSC-15008-1

HDF-EOS Web ServerA shell script has been written as a

means of automatically making HDF-EOS-formatted data sets available via theWorld Wide Web. (“HDF-EOS” and vari-ants thereof are defined in the first ofthe two immediately preceding articles.)The shell script chains together somesoftware tools developed by the Data Us-ability Group at Goddard Space FlightCenter to perform the following actions:• Extract metadata in Object Definition

Language (ODL) from an HDF-EOS file,• Convert the metadata from ODL to

Extensible Markup Language (XML),• Reformat the XML metadata into

human-readable Hypertext MarkupLanguage (HTML),

• Publish the HTML metadata and theoriginal HDF-EOS file to a Web serverand an Open-source Project for a Net-work Data Access Protocol (OPeN-DAP) server computer, and

• Reformat the XML metadata and sub-mit the resulting file to the EOS Clear-inghouse, which is a Web-based meta-data clearinghouse that facilitatessearching for, and exchange of, Earth-Science data.This program was written by Richard Ull-

man of Goddard Space Flight Center; BobBane of Global Science & Technology, Inc.;and Jingli Yang of Earth Resources Technol-ogy, Inc. Further information is contained in aTSP (see page 1). GSC-15011-1

HDF-EOS 5 ValidatorA computer program partly automates

the task of determining whether an HDF-EOS 5 file is valid in that it conforms to

specifications for such characteristics asattribute names, dimensionality of dataproducts, and ranges of legal data values.[“HDF-EOS” and variants thereof are de-fined in “Converting EOS Data FromHDF-EOS to netCDF” (GSC-15007-1),which is the first of several preceding arti-cles in this issue of NASA Tech Briefs.] Pre-viously, validity of a file was determined ina tedious and error-prone process inwhich a person examined human-read-able dumps of data-file-format informa-tion.

The present software helps a user toencode the specifications for an HDF-EOS 5 file, and then inspects the file forconformity with the specifications: First,the user writes the specifications in Ex-tensible Markup Language (XML) by useof a document type definition (DTD)that is part of the program. Next, the por-tion of the program (denoted the valida-tor) that performs the inspection is exe-cuted, using, as inputs, the specificationsin XML and the HDF-EOS 5 file to be val-idated. Finally, the user examines the out-put of the validator.

This program was written by Richard Ull-man of Goddard Space Flight Center; Bob Baneof Global Science & Technology, Inc.; andJingli Yang of Earth Resources Technology, Inc.Further information is contained in a TSP (seepage 1). GSC-15015-1

XML DTD and Schemas forHDF-EOS

An Extensible Markup Language (XML)document type definition (DTD) standardfor the structure and contents of HDF-EOSfiles and their contents, and an equivalentstandard in the form of schemas, have beendeveloped. (“HDF-EOS” and variantsthereof are defined in the first two of fourrelated articles immediately preceding thisone.) More specifically, this standard de-scribes the structure and contents of a sin-gle HDF-EOS 5 file based on the HDF-EOSmodel as published in Volumes 1 and 2 ofthe HDF-EOS Library Users Guide. TheDTD and schemas are easy-to-use represen-tations of a complex file format, enablingdisplay of data in multiple ways.

By means of HDF5 XML softwaretools from the National Center for Super-computing Applications, the user cantransform HDF5 files into XML files orvice versa. Inasmuch as HDF-EOS 5 filesare HDF5 files, the same software tools can


be used to (1) transform any HDF-EOS 5file into an XML file or vice versa or (2)convert, into an HDF-EOS 5 file, any XMLfile that conforms to the DTD or schemas.

This program was written by Richard Ull-man of Goddard Space Flight Center; JingliYang of Earth Resources Technology, Inc.; andMuhammad Rabi of Global Science & Tech-nology, Inc. Further information is containedin a TSP (see page 1). GSC-15016-1

Converting From XML toHDF-EOS

A computer program recreates anHDF-EOS file from an ExtensibleMarkup Language (XML) representa-tion of the contents of that file. (“HDF-EOS” and variants thereof are definedin the first of five related articles thatimmediately precede this article.) Thisprogram is one of two programs writtento enable testing of the schemas de-scribed in the immediately precedingarticle to determine whether theschemas capture all details of HDF-EOSfiles. (The other program converts anHDF-EOS file into an XML file.) Thisprogram uses a General Purpose Lan-guage (GPL) parser called “expat” toparse XML and control extraction ofdata from an input XML file.

This program was written by Richard Ull-man of Goddard Space Flight Center; BobBane of Global Science & Technology, Inc.;and Jingli Yang of Earth Resources Technol-ogy, Inc. Further information is contained in aTSP (see page 1).GSC-15017-1

Simulating Attitudes andTrajectories of MultipleSpacecraft

A computer program called “42” simu-lates the attitudes and trajectories of multi-ple spacecraft flying in formation any-where in the Solar System. The rotationaldynamics are represented by high-fidelitymodels of spacecraft, each comprising asmany as three connected rigid bodies andcontaining as many as four flywheel mech-anisms for storing angular momentum forcontrolling attitude. The translational dy-namics are represented partly by Encke’smethod of orbit perturbation, which en-ables the use of a reference trajectoryshared by multiple spacecraft and, in sodoing, enables separation of gigameter-scale trajectory features from nanometer-scale formation adjustments to preservethe numerical accuracy needed for simu-lating precise multi-spacecraft formations.

Other models include planetary

ephemerides and models for solar-radia-tion pressure, effects of the terrestrial mag-netic field, effects of the terrestrial atmos-phere, and non-spherical components ofthe geopotential. The program provides agraphical display that facilitates visualiza-tion of individual behaviors of, and inter-actions among, the spacecraft in a forma-tion. Models of spacecraft sensors, controllaws, and control-actuator dynamics are in-cluded; these models can be customized(this can include linking to real flight soft-ware) to enable high-fidelity simulation.

This program was written by Eric Stonek-ing of Goddard Space Flight Center. Furtherinformation is contained in a TSP (see page1). GSC-14817-1

Specialized Color Functionfor Display of Signed Data

This Mathematica script defines a colorfunction to be used with Mathematica’splotting modules for differentiating data at-taining both positive and negative values.Positive values are shown as shades of blue,and negative values are shown in red. Theintensity of the color reflects the absolutevalue of the data value.

The quantization is the same for bothpositive and negative values, so that com-parable intensities accurately reflectcomparable data magnitudes. Cus-tomization is done through several soft-ware switches. The number of color binsto be used is selected by “nshades.” “Lin-ear” is set to 1 for a linear mapping ofdata magnitudes to color, and set to 0 fornonlinear mapping. The nonlinearchoice uses a cube root data-mapping toencompass a large data range while ac-centuating the smaller data values. Thisinnovation allows nonlinear stretchingof data to enhance visualization at thelow end of the scale while still viewingthe entire data range (the data range setby the user).

This work was done by Virginia Kalb ofGoddard Space Flight Center. For further in-formation, contact the Goddard InnovativePartnerships Office at (301) 286-5810. GSC-15128-1

Delivering Alert Messages toMembers of a Work Force

Global Alert Resolution Network(GARNET) is a software system for deliv-ering emergency alerts as well as less-ur-gent messages to members of the God-dard Space Flight Center work force viaan intranet or the Internet, and can beadapted to similar use in other large or-ganizations. Messages can be presented

in visible and audible forms on such di-verse terminals as desktop computers,portable alphanumeric pagers, tele-phones, fire alarms, and closed-circuittelevision. GARNET includes client com-ponents running on workers’ desktopcomputers, and server components run-ning on redundant computers behindfirewalls.

An authorized user enters a message,selecting its degree of urgency and thegroup of intended recipients. The mes-sage is then disseminated to the recipientsalong with a link to more-detailed infor-mation. GARNET can deliver a messageby server push (in which it interrupts auser’s work to present the message on theuser’s computer or other device) or clientpull (in which a user’s computer polls theserver periodically). GARNET determineswhether a given client receives alerts viaclient pull or server push when the clientlogs onto the server. To reduce networktraffic, GARNET gives preference toserver push.

This program was written by Julia Loftis andStephanie Nickens of Goddard Space Flight Cen-ter and Melissa Pell and Vince Pell of ScienceSystems and Applications, Inc. Further informa-tion is contained in a TSP (see page 1). GSC-14927-1

Delivering Images for MarsRover Science Planning

A methodology has been developedfor delivering, via the Internet, imagestransmitted to Earth from cameras onthe Mars Explorer Rovers, the PhoenixMars Lander, the Mars Science Labora-tory, and the Mars Reconnaissance Or-biter spacecraft. The images in questionare used by geographically dispersed sci-entists and engineers in planning Roverscientific activities and Rover maneuverspertinent thereto.

The methodology, which effects acompromise among levels of image de-tail, fidelity, and delivery speed, com-bines image compression with an adap-tive level-of-detail image-deliverystrategy that scales very well up to largerimages that can include mosaic andhigh-resolution orbital images. In thismethodology, images are tiled at multi-ple levels of detail. An image-browsingapplication program makes requests fortiles instead of entire images, therebygreatly accelerating delivery of images.At one extreme, a tile could contain alow-resolution representation of whatoriginated as a large mosaic or high-res-olution image. At the other extreme, a


tile could contain a high-resolution rep-resentation of a small portion of a largeimage. For either extreme or for an in-termediate case, rather than waste timetransmitting data that are not used, onlytiles that fill users’ screens are delivered.

This work was done by Mark W. Pow-ell, Thomas M. Crockett. Joseph C.Joswig, Jeffrey S. Norris, Khawaja S.Shams, Jason M. Fox, and Recaredo JayTorres of Caltech for NASA’s Jet Propul-sion Laboratory.

The software used in this innova-tion is available for commercial licens-ing. Please contact Karina Edmondsof the California Institute of Technol-ogy at (626) 395-2322. Refer to NPO-45671.


Materials

Oxide Fiber Cathode Materials for Rechargeable Lithium CellsLyndon B. Johnson Space Center, Houston, Texas

LiCoO2 and LiNiO2 fibers have beeninvestigated as alternatives to LiCoO2 andLiNiO2 powders used as lithium-intercala-tion compounds in cathodes of recharge-able lithium-ion electrochemical cells. Inmaking such a cathode, LiCoO2 orLiNiO2 powder is mixed with a binder[e.g., poly(vinylidene fluoride)] and anelectrically conductive additive (usuallycarbon) and the mixture is pressed toform a disk. The binder and conductiveadditive contribute weight and volume,reducing the specific energy and energydensity, respectively.

In contrast, LiCoO2 or LiNiO2 fiberscan be pressed and sintered to form a

cathode, without need for a binder or aconductive additive. The inter-graincontacts of the fibers are stronger andhave fewer defects than do those ofpowder particles. These characteristicstranslate to increased flexibility andgreater resilience on cycling and, con-sequently, to reduced loss of capacityfrom cycle to cycle. Moreover, in com-parison with a powder-based cathode, afiber-based cathode is expected to ex-hibit significantly greater ionic andelectronic conduction along the axesof the fibers. Results of preliminarycharge/discharge-cycling tests suggestthat energy densities of LiCoO2- and

LiNiO2-fiber cathodes are approxi-mately double those of the correspon-ding powder-based cathodes.

This work was done by Catherine E. Riceand Mark F. Welker of TPL, Inc., for JohnsonSpace Center.

In accordance with Public Law 96-517, thecontractor has elected to retain title to this inven-tion. Inquiries concerning rights for its commer-cial use should be addressed to:

TPL, Inc.3921 Academy Parkway North, NEAlbuquerque, NM 87109-4416Refer to MSC-22892-1, volume and num-


Electrocatalytic Reduction of Carbon Dioxide to MethaneLyndon B. Johnson Space Center, Houston, Texas

A room-temperature electrocatalyticprocess that effects the overall chemi-cal reaction CO2 + 2H2O → CH4 + 2O2

has been investigated as a means of re-moving carbon dioxide from air andrestoring oxygen to the air. Theprocess was originally intended for usein a spacecraft life-support system, inwhich the methane would be vented toouter space. The process may also havepotential utility in terrestrial applica-tions in which either or both of the

methane and oxygen produced mightbe utilized or vented to the atmos-phere.

A typical cell used to implement theprocess includes a polymer solid-elec-trolyte membrane, onto which are de-posited cathode and anode films. Thecathode film is catalytic for electrolyticreduction of CO2 at low overpotential.The anode film is typically made of plat-inum. When CO2 is circulated past thecathode, water is circulated past the

anode, and a suitable potential is ap-plied, the anode half-cell reaction is4H2O → 2O2 + 8H+ + 8e–. The H+ ionstravel through the membrane to thecathode, where they participate in thehalf-cell reaction CO2 + 8H+ + 8e– → CH4

+ 2H2O.This work was done by Anthony F. Sam-

mells and Ella F. Spiegel of Eltron Research,Inc. for Johnson Space Center. Further infor-mation is contained in a TSP (see page1).MSC-23097-1

A heterogeneous material construc-tion has been devised for sensing coils ofsuperconducting quantum interferencedevice (SQUID) magnetometers thatare subject to a combination of require-ments peculiar to some advanced appli-cations, notably including low-field mag-netic resonance imaging for medicaldiagnosis. The requirements in questionare the following:

• The sensing coils must be largeenough (in some cases having dimen-sions of as much as tens of centime-ters) to afford adequate sensitivity;

• The sensing coils must be made electri-cally superconductive to eliminate John-son noise (thermally induced noise pro-portional to electrical resistance); and

• Although the sensing coils must becooled to below their superconduct-

ing-transition temperatures with suffi-cient cooling power to overcome mod-erate ambient radiative heat leakage,they must not be immersed in cryo-genic liquid baths.For a given superconducting sensing

coil, this combination of requirementscan be satisfied by providing a suffi-ciently thermally conductive link be-tween the coil and a cold source. How-

Heterogeneous Superconducting Low-Noise Sensing CoilsElectrically superconductive outer layers are supported by highly thermally conductive skeletons.NASA’s Jet Propulsion Laboratory, Pasadena, California


ever, the superconducting coil materialis not suitable as such a link becauseelectrically superconductive materialsare typically poor thermal conductors.

The heterogeneous material construc-tion makes it possible to solve both theelectrical- and thermal-conductivityproblems. The basic idea is to constructthe coil as a skeleton made of a highlythermally conductive material (typically,annealed copper), then coat the skele-ton with an electrically superconductivealloy (typically, a lead-tin solder) [see fig-ure]. In operation, the copper skeletonprovides the required thermally conduc-tive connection to the cold source, whilethe electrically superconductive coatingmaterial shields against Johnson noisethat originates in the copper skeleton.

This work was done by Inseob Hahn, Kon-stantin I. Penanen, and Byeong Ho Eom of

Caltech for NASA’s Jet Propulsion Laboratory.Further information is contained in a TSP(see page 1).


Innovative Technology Assets ManagementJPLMail Stop 202-2334800 Oak Grove DrivePasadena, CA 91109-8099E-mail: [email protected] to NPO-45929, volume and number


Soft solder (Sn-Pb)layer

Copper rod

A Solder-Covered Copper Rod or Wire affordsthe benefit of high thermal conductivity of thecopper and, when sufficiently cold, electrical su-perconductivity of the solder.

Progress Toward Making Epoxy/Carbon-Nanotube CompositesLyndon B. Johnson Space Center, Houston, Texas

A modicum of progress has been madein an effort to exploit single-walled carbonnanotubes as fibers in epoxy-matrix/fibercomposite materials. Two main obstaclesto such use of carbon nanotubes are thefollowing: (1) bare nanotubes are not sol-uble in epoxy resins and so they tend to ag-glomerate instead of becoming dispersedas desired; and (2) because of lack of affin-ity between nanotubes and epoxy matri-ces, there is insufficient transfer of me-chanical loads between the nanotubes andthe matrices.

Part of the effort reported here wasoriented toward (1) functionalization ofsingle-walled carbon nanotubes withmethyl methacrylate (MMA) to increasetheir dispersability in epoxy resins andincrease transfer of mechanical loadsand (2) ultrasonic dispersion of thefunctionalized nanotubes in tetrahydro-furan, which was used as an auxiliary sol-vent to aid in dispersing the functional-ized nanotubes into a epoxy resin. Inanother part of this effort, poly(styrenesulfonic acid) was used as the dispersant

and water as the auxiliary solvent. In oneexperiment, the strength of compositeof epoxy with MMA-functionalized-nan-otubes was found to be 29 percentgreater than that of a similar compositeof epoxy with the same proportion ofuntreated nanotubes.

This work was done by Thomas Tiano,Margaret Roylance, and John Gassner of Fos-ter-Miller, Inc. and William Kyle (consultant)for Johnson Space Center. Further informa-tion is contained in a TSP (see page 1). MSC-23278-1

Predicting Properties of Unidirectional-Nanofiber CompositesJohn H. Glenn Research Center, Cleveland, Ohio

A theory for predicting mechanical,thermal, electrical, and other propertiesof unidirectional-nanofiber/matrixcom p osite materials is based on theprior theory of micromechanics of com-posite materials. In the development ofthe present theory, the prior theory ofmicromechanics was extended, throughprogressive substructuring, to the levelof detail of a nanoscale slice of ananofiber. All the governing equationswere then formulated at this level.

The substructuring and the equationshave been programmed in the

ICAN/JAVA computer code, which wasreported in “ICAN/JAVA: IntegratedComposite Analyzer Recoded in Java”(LEW-17247), NASA Tech Briefs, Vol. 26,No. 12 (December 2002), page 36. In ademonstration, the theory as embodiedin the computer code was applied to agraphite-nanofiber/epoxy laminate andused to predict 25 properties. Most ofthe properties were found to be distrib-uted along the through-the-thickness di-rection. Matrix-dependent propertieswere found to have bimodal through-the-thickness distributions with discon-

tinuous changes from mode to mode.This work was done by Christos C. Chamis,

Louis M. Handler, and Jane Manderscheid ofGlenn Research Center. Further information iscontained in a TSP (see page 1).



The deployable crew quarters (DCQ)have been designed for the InternationalSpace Station (ISS). Each DCQ would bea relatively inexpensive, deployable box-like structure that is designed to fit in arack bay. It is to be occupied by onecrewmember to provide privacy andsleeping functions for the crew. A DCQcomprises mostly hard panels, made of alightweight honeycomb or matrix/fibermaterial, attached to each other by clothhinges. Both faces of each panel are cov-ered with a layer of Nomex cloth andnoise-suppression material to providenoise isolation from ISS.

On Earth, the unit is folded flat and at-tached to a rigid pallet for transport tothe ISS. On the ISS, crewmembers un-

fold the unit and install it in place, at-taching it to ISS structural members byuse of soft cords (which also help to iso-late noise and vibration). A few hardpieces of equipment (principally, a venti-lator and a smoke detector) are shippedseparately and installed in the DCQ unitby use of a system of holes, slots, andquarter-turn fasteners.

Full-scale tests showed that the time re-quired to install a DCQ unit amounts totens of minutes. The basic DCQ designcould be adapted to terrestrial applicationsto satisfy requirements for rapid deploy-able emergency shelters that would belightweight, portable, and quickly erected.The Temporary Early Sleep Station (TeSS)currently on-orbit is a spin-off of the DCQ.

This work was done by William C. Schnei-der, Kriss J. Kennedy, and Nathan R. Mooreof Johnson Space Center and James Mabie ofMuniz Engineering. Further information iscontained in a TSP (see page 1).

In accordance with Public Law 96-517, thecontractor has elected to retain title to this inven-tion. Inquiries concerning rights for its commer-cial use should be addressed to:

MEI Technologies, Corporate Headquarters2525 Bay Area Blvd., Suite 300Houston, Texas 77058Phone No.: (281) 283-6200 / (888) 895-3014Fax No.: (281) 283-6170E-mail: [email protected] to MSC-23132-1, volume and number

of this NASA Tech Briefs issue, and the pagenumber.

Mechanics/Machinery

Deployable Crew QuartersLyndon B. Johnson Space Center, Houston, Texas

Nonventing, Regenerable, Lightweight Heat AbsorberLyndon B. Johnson Space Center, Houston, Texas

A lightweight, regenerable heat ab-sorber (RHA), developed for rejectingmetabolic heat from a space suit, mayalso be useful on Earth for short-termcooling of heavy protective garments.Unlike prior space-suit-cooling systems,a system that includes this RHA does notvent water. The closed system containswater reservoirs, tubes through whichwater is circulated to absorb heat, anevaporator, and an absorber/radiator.The radiator includes a solution of LiClcontained in a porous material in tita-nium tubes.

The evaporator cools water that cir-culates through a liquid-cooled gar-

ment. Water vapor produced in theevaporator enters the radiator tubeswhere it is absorbed into the LiCl solu-tion, releasing heat. Much of the heatof absorption is rejected to the environ-ment via the radiator. After use, theRHA is regenerated by heating it to atemperature of 100 °C for about 2hours to drive the absorbed water backto the evaporator. A system including aprototype of the RHA was found to becapable of maintaining a temperatureof 20 °C while removing heat at a rateof 200 W for 6 hours.

This work was done by Michael G. Izensonand Weibo Chen of Creare Inc. for Johnson

Space Center. Further information is con-tained in a TSP (see page 1).

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:

Creare Inc.P.O. Box 7116 Great Hollow RoadHanover, NH 03755Phone No. (603) 643-3800Fax No.: (603) 643-4657URL: www.creare.comRefer to MSC-23914-1, volume and num-


Improved long-stroke shape-memory-alloy (SMA) linear actuators are being de-veloped to exert significantly higherforces and operate at higher activation

temperatures than do prior SMA actua-tors. In these actuators, long linear strokesare achieved through the principle of dis-placement multiplication, according to

which there are multiple stages, each in-termediate stage being connected bystraight SMA wire segments to the nextstage so that relative motions of stages are

Miniature High-Force, Long-Stroke SMA Linear ActuatorsStroke forces, stroke lengths, cycle speeds, and structural strengths are increased.John H. Glenn Research Center, Cleveland, Ohio


A “bootstrap” configuration has beenproposed for multistage pulse-tube cool-ers that, for instance, provide final-stagecooling to temperatures as low as 20 K.The bootstrap configuration supplantsthe conventional configuration, inwhich customarily the warm heat ex-changers of all stages reject heat at ambi-ent temperature. In the bootstrap con-

figuration, the warm heat exchanger,the inertance tube, and the reservoir ofeach stage would be thermally anchoredto the cold heat exchanger of the nextwarmer stage. The bootstrapped config-uration is superior to the conventionalsetup, in some cases increasing the 20 Kcooler’s coefficient of performance two-fold over that of an otherwise equivalent

conventional layout. The increased effi-ciency could translate into less powerconsumption, less cooler mass, and/orlower cost for a given amount of cooling.

This work was done by Ali Kashani andBen Helvensteijn of Atlas Scientific for John-son Space Center. Further information is con-tained in a TSP (see page 1).MSC-23500-1

“Bootstrap” Configuration for Multistage Pulse-Tube CoolersLyndon B. Johnson Space Center, Houston, Texas

additive toward the final stage, which isthe output stage.

Prior SMA actuators typically includepolymer housings or shells, steel or alu-minum stages, and polymer pads betweensuccessive stages of displacement-multipli-cation assemblies. Typical output forces ofprior SMA actuators range from 10 to 20N, and typical strokes range from 0.5 to1.5 cm. An important disadvantage ofprior SMA wire actuators is relatively lowcycle speed, which is related to actuationtemperature as follows: The SMA wires inprior SMA actuators are typically made ofa durable nickel/titanium alloy that has ashape-memory activation temperature of80 °C. An SMA wire can be heated quicklyfrom below to above its activation temper-ature to obtain a stroke in one direction,but must then be allowed to cool to some-what below its activation temperature(typically, to ≤ 60 °C in the case of an acti-vation temperature of 80 °C) to obtain astroke in the opposite direction (returnstroke). At typical ambient temperatures,cooling times are of the order of severalseconds. Cooling times thus limit cyclespeeds. Wires made of SMA alloys havingsignificantly higher activation tempera-tures [denoted ultra-high-temperature

(UHT) SMA alloys] cool to the requiredlower return-stroke temperatures morerapidly, making it possible to increasecycle speeds.

The present development is motivatedby a need, in some applications (espe-cially aeronautical and space-flight appli-cations) for SMA actuators that exerthigher forces, operate at greater cyclespeeds, and have stronger housings thatcan withstand greater externally appliedforces and impacts. The main novel fea-tures of the improved SMA actuators arethe following:• The ends of the wires are anchored in

compact crimps made from short steeltubes. Each wire end is inserted in atube, the tube is flattened between pla-nar jaws to make the tube grip the wire,the tube is compressed to a slight U-cross-section deformation to strengthenthe grip, then the crimp is welded ontoone of the actuator stages. The pullstrength of a typical crimp is about 125N — comparable to the strength of theSMA wire and greater than the typicalpull strengths of wire-end anchors inprior SMA actuators. Greater pullstrength is one of the keys to achieve-ment of higher actuation force.

• For greater strength and resistance toimpacts, housings are milled from alu-minum instead of being made frompolymers. Each housing is made fromtwo pieces in a clamshell configura-tion. The pieces are anodized to re-duce sliding friction.

• Stages are made stronger (to beargreater compression loads without ex-cessive flexing) by making them fromsteel sheets thicker than those used inprior SMA actuators. The stages con-tain recessed pockets to accommodatethe crimps. Recessing the pocketshelps to keep overall dimensions assmall as possible.

• UHT SMA wires are used to satisfy thehigher-speed/higher-temperature re-quirement.This work was done by Mark A. Cummin,

William Donakowski, and Howard Cohen ofMIGA Motor Co. for Glenn Research Center.Further information is contained in a TSP(see page 1).

Inquiries concerning rights for the commercialuse of this invention should be addressed toNASA Glenn Research Center, Innovative Part-nerships Office, Attn: Steve Fedor, Mail Stop 4–8,21000 Brookpark Road, Cleveland, Ohio44135. Refer to LEW-18267-1.

Reducing Liquid Loss During Ullage Venting in MicrogravityLyndon B. Johnson Space Center, Houston, Texas

A centripetal-force-based liquid/gasseparator has been proposed as a meansof reducing the loss of liquid duringventing of the ullage of a tank in micro-gravity as a new supply of liquid ispumped into the tank. Centripetal-force-based liquid/gas separators areused on Earth, where mechanical drives(e.g., pumps and spinners) are used to

impart flow speeds sufficient to generatecentripetal forces large enough to effectseparation of liquids from gases.

For the proposed application, the sep-arator would be designed so that therewould be no need for such a pump be-cause the tank-pressure-induced outflowspeed during venting of the ullagewould be sufficient for centripetal sepa-

ration. A relatively small pump would beused, not for separation, but for return-ing the liquid recovered by the separatorto the tank.

This work was done by Bich Nguyen andLauren Nguyen of The Boeing Co. for JohnsonSpace Center. For further information, contactthe JSC Innovation Partnerships Office at(281) 483-3809. MSC-23230-1


Books & Reports

Ka-Band Transponder forDeep-Space Radio Science

A one-page document describes a Ka-band transponder being developed foruse in deep-space radio science. Thetransponder receives in the Deep SpaceNetwork (DSN) uplink frequency bandof 34.2 to 34.7 GHz, transmits in the 31.8-to 32.3 GHz DSN downlink band, andperforms regenerative ranging on a DSNstandard 4-MHz ranging tone subcarrierphase-modulated onto the uplink carriersignal. A primary consideration in thisdevelopment is reduction in size, relativeto other such transponders.

The transponder design is all-analog,chosen to minimize not only the size butalso the number of parts and the designtime and, thus, the cost. The receiver fea-tures two stages of frequency down-con-version. The receiver locks onto the up-link carrier signal. The exciter signal forthe transmitter is derived from the samesource as that used to generate the first-stage local-oscillator signal. The ranging-tone subcarrier is down-converted alongwith the carrier to the second intermedi-ate frequency, where the 4-MHz tone isdemodulated from the composite signaland fed into a ranging-tone-tracking loop,which regenerates the tone. The regener-ated tone is linearly phase-modulatedonto the downlink carrier.

This work was done by Matthew S. Dennis,Narayan R. Mysoor, William M. Folkner, Ri-cardo Mendoza, and Jaikrishna Venkatesan ofCaltech for NASA’s Jet Propulsion Laboratory.Further information is contained in a TSP(see page 1).NPO-45598

Replication of Space-ShuttleComputers in FPGAs andASICs

A document discusses the replicationof the functionality of the onboardspace-shuttle general-purpose comput-ers (GPCs) in field-programmable gate

arrays (FPGAs) and application-specificintegrated circuits (ASICs). The pur-pose of the replication effort is to en-able utilization of proven space-shuttleflight software and software-develop-ment facilities to the extent possibleduring development of software forflight computers for a new generationof launch vehicles derived from thespace shuttles. The replication involvesspecifying the instruction set of the cen-tral processing unit and theinput/output processor (IOP) of thespace-shuttle GPC in a hardware de-scription language (HDL).

The HDL is synthesized to form a“core” processor in an FPGA or, lesspreferably, in an ASIC. The coreprocessor can be used to create a flight-control card to be inserted into a newavionics computer. The IOP of the GPCas implemented in the core processorcould be designed to support data-busprotocols other than that of a multi-plexer interface adapter (MIA) used inthe space shuttle. Hence, a computercontaining the core processor could betailored to communicate via the space-shuttle GPC bus and/or one or moreother buses.

This work was done by Roscoe C. Fergusonof United Space Alliance for Johnson SpaceCenter. Further information is contained in aTSP (see page 1).MSC-24141-1

Demisable Reaction-WheelAssembly

A document discusses the concept of ademisable motor-drive-and-flywheel as-sembly [reaction-wheel assembly(RWA)] used in controlling the attitudeof a spacecraft. “Demisable” as used heredoes not have its traditional legal mean-ing; instead, it signifies susceptible tomelting, vaporizing, and/or otherwisedisintegrating during re-entry of thespacecraft into the atmosphere of theEarth so as not to pose a hazard to any-

one or anything on the ground. PriorRWAs include parts made of metals(e.g., iron, steel, and titanium) that meltat high temperatures and include struc-tures of generally closed character thatshield some parts (e.g., magnets) againstre-entry heating.

In a demisable RWA, the flywheelwould be made of aluminum, whichmelts at a lower temperature. The fly-wheel web would not be a solid disk butwould have a more open, nearly-spoke-like structure so that it would disinte-grate more rapidly; hence, the flywheelrim would separate more rapidly so thatparts shielded by the rim would be ex-posed sooner to re-entry heating. In ad-dition, clearances between the flywheeland other components would be madegreater, imparting a more open charac-ter and thus increasing the exposure ofthose components.

This work was done by Russell Roder andEliezer Ahronovich of Goddard Space FlightCenter and Milton C. Davis III of PurdueUniversity. Further information is containedin a TSP (see page 1).GSC-14845-1

Spatial and Temporal Low-Dimensional Modelsfor Fluid Flow

A document discusses work that ob-tains a low-dimensional model thatcaptures both temporal and spatialflow by constructing spatial and tem-poral four-mode models for two classicflow problems. The models are basedon the proper orthogonal decomposi-tion at two reference Reynolds num-bers. Model predictions are made at anintermediate Reynolds number andcompared with direct numerical simu-lation results at the new Reynoldsnumber.

This work was done by Virginia Kalb of God-dard Space Flight Center. Further informationis contained in a TSP (see page 1). GSC-15130-1


Advanced Land Imager Assessment SystemAn integrated system provides radiometric and geometric calibration and validation dataprocessing for a multispectral pushbroom instrument.Goddard Space Flight Center, Greenbelt, Maryland

The Advanced Land Imager Assess-ment System (ALIAS) supports radiomet-ric and geometric image processing forthe Advanced Land Imager (ALI) instru-ment onboard NASA’s Earth Observing-1(EO-1) satellite. ALIAS consists of twoprocessing subsystems for radiometricand geometric processing of the ALI’smultispectral imagery. The radiometricprocessing subsystem characterizes andcorrects, where possible, radiometricqualities including: coherent, impulse;and random noise; signal-to-noise ratios(SNRs); detector operability; gain; bias;saturation levels; striping and banding;and the stability of detector performance.

The geometric processing subsystem andanalysis capabilities support sensor align-ment calibrations, sensor chip assembly(SCA)-to-SCA alignments and band-to-band alignment; and perform geodetic ac-curacy assessments, modulation transferfunction (MTF) characterizations, andimage-to-image characterizations. ALIASalso characterizes and corrects band-to-band registration, and performs systematicprecision and terrain correction of ALI im-ages. This system can geometrically correct,and automatically mosaic, the SCA imagestrips into a seamless, map-projected image.

This system provides a large database,

which enables bulk trending for all ALIimage data and significant instrumenttelemetry. Bulk trending consists of twofunctions: Housekeeping Processing andBulk Radiometric Processing. The House-keeping function pulls telemetry and tem-perature information from the instrumenthousekeeping files and writes this infor-mation to a database for trending. TheBulk Radiometric Processing functionwrites statistical information from the darkdata acquired before and after the Earthimagery and the lamp data to the databasefor trending. This allows for multi-scenestatistical analyses.

An important aspect of this is the par-titioning and indexing of data within thedatabase, which enables efficient storageand retrieval of data as well as extremelyrapid calibration assessments. TheALIAS team processed the entire ALIarchive (over 20,000 scenes) and popu-lated this trending database, approach-ing one terabyte in size. This databasehas opened doors for long-term trend-ing, data analyses, and algorithm devel-opment not previously possible with theLandsat 7 Image Assessment System(IAS). One area where this bulk trend-ing database appears particularly usefulis in the normalization of the detector’s

responses within a band, so called flat-fielding. On the assumption that, over aperiod of several months to a whole mis-sion, all detectors in a band see statisti-cally the same distribution of the Earthradiance, these statistics can be used tomatch the detector’s responses.

ALIAS is built upon previous softwareused in the Landsat 7 IAS, and by the ALIScience Validation Team (SVT). This in-novation takes advantage of open sourcesoftware, in that it references open sourceexternal libraries. This means no softwarelicenses are required. However, no opensource code is integrated directly in theALIAS software.

ALIAS was a joint effort between NASA andthe United States Geological Survey (USGS). Thework was done by Tim Beckmann, GyaneshChander, Mike Choate, Jon Christopherson,Doug Hollaren, Ron Morfitt, Jim Nelson, SharNelson, and James Storey of SAIC@USGS/EarthResources Observation and Science (EROS);Dennis Helder and Tim Ruggles of SouthDakota State University; Ed Kaita, Raviv Levy,and Lawrence Ong of SSAI@NASA/GoddardSpace Flight Center(GSFC); and BrianMarkham and Robert Schweiss of GoddardSpace Flight Center. Further information iscontained in a TSP (see page 1).GSC-15185-1

Information Sciences


Range Imaging Without Moving PartsPotential applications include proximity detection, robotic vision, and terrain mapping.Goddard Space Flight Center, Greenbelt, Maryland

Range-imaging instruments of a typenow under development are intended togenerate the equivalent of three-dimen-sional images from measurements of theround-trip times of flight of laser pulsesalong known directions. These instru-ments could also provide information oncharacteristics of targets, including rough-nesses and reflectivities of surfaces andoptical densities of such semi-solid objectsas trees and clouds. Unlike in prior range-imaging instruments based on times offlight along known directions, therewould be no moving parts; aiming of thelaser beams along the known directionswould not be accomplished by mechani-cal scanning of mirrors, prisms, or otheroptical components. Instead, aimingwould be accomplished by using solid-state devices to switch input and outputbeams along different fiber-optic paths.Because of the lack of moving parts, theseinstruments could be extraordinarily reli-able, rugged, and long-lasting.

An instrument of this type would in-clude an optical transmitter that wouldsend out a laser pulse along a chosen di-rection to a target. An optical receiver co-aligned with the transmitter would meas-ure the temporally varying intensity of

laser light reflected from the target to de-termine the distance and surface charac-teristics of the target.

The transmitter would be a combina-tion of devices for generating precise di-rectional laser illumination. It would in-clude a pulsed laser, the output of whichwould be coupled into a fiber-optic cablewith a fan-out and solid-state opticalswitches that would enable switching ofthe laser beam onto one or more opticalfibers terminated at known locations inan array on a face at the focal plane of atelescope. The array would be imaged bythe telescope onto the target space.

The receiver optical system couldshare the aforementioned telescope withthe transmitter or could include a sepa-rate telescope aimed in the same direc-tion as that of the transmitting telescope.In either case, light reflected from thetarget would be focused by the receiveroptical system onto an array of opticalfibers matching the array in the transmit-ter. These optical fibers would couple thereceived light to one or more photode-tector(s). Optionally, the receiver couldinclude solid-state optical switches forchoosing which optical fiber(s) wouldcouple light to the photodetector(s).

This instrument architecture is flexi-ble and can be optimized for a wide va-riety of applications and levels of per-formance. For example, it is scalable toany number of pixels and pixel resolu-tions and is compatible with a variety ofranging and photodetection method-ologies, including, for example, rangingby use of modulated (including pulsedand encoded) light signals. The use offixed arrays of optical fibers to generatecontrolled illumination patterns wouldeliminate the mechanical complexityand much of the bulk of optomechani-cal scanning assemblies. Furthermore,digital control of the selection of thefiber-optic pathways for the transmittedbeams could afford capabilities not seenin previous three-dimensional range-im-aging systems. Instruments of this typecould be specialized for use as, for ex-ample, proximity detectors, three-di-mensional robotic vision systems, air-borne terrain-mapping systems, andinspection systems.

This work was done by J. Bryan Blair, V.Stanley Scott III, and Luis Ramos-Izquierdo ofGoddard Space Flight Center. Further informa-tion is contained in a TSP (see page 1).GSC-15184-1

Physical Sciences

National Aeronautics andSpace Administration

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