Technology Focus Electronics/Computers - NASA

Technology Focus

Electronics/Computers

Software

Materials

Mechanics/Machinery

Manufacturing

Bio-Medical

Physical Sciences

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Books and Reports

Green Design

02-11 February 2011

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 www.nttc.edu

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://www.nasa.gov/offices/ipp/network/index.html

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 CenterMary Walsh(650) [email protected]

Dryden Flight Research CenterYvonne D. Gibbs(661) [email protected]

Glenn Research CenterJoe Shaw, Acting Chief(216) [email protected]

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

Jet Propulsion LaboratoryIndrani Graczyk(818) [email protected]

Johnson Space Centerinformation(281) [email protected]

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

Langley Research CenterElizabeth B. Plentovich(757) [email protected]

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

Stennis Space CenterRamona Travis(228) 688-3832 [email protected]

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

Doug Comstock, Partnerships Innovation and CommercialSpace Program Office (formerly IPP)(202) [email protected]

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

NASA Tech Briefs, February 2011 1

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

NASA Tech Briefs, Febuary 2011 3

02-11 February 2011

5 Technology Focus: Test & Measurement

5 Multi-Segment Radius Measurement Using anAbsolute Distance Meter Through a Null Assem-bly

5 Fiber-Optic Magnetic-Field-Strength Measure-ment System for Lightning Detection

6 Photocatalytic Active Radiation Measurementsand Use

6 Computer Generated Hologram System forWavefront Measurement System Calibration

7 Non-Contact Thermal Properties MeasurementWith Low-Power Laser and IR Camera System

9 Electronics/Computers9 SpaceCube 2.0: An Advanced Hybrid Onboard

Data Processor

9 CMOS Imager Has Better Cross-Talk and Full-WellPerformance

10 High-Performance Wireless Telemetry

11 Telemetry-Based Ranging

13 Software13 JWST Wavefront Control Toolbox

13 Java Image I/O for VICAR, PDS, and ISIS

13 X-Band Acquisition Aid Software

15 Manufacturing & Prototyping15 Antimicrobial-Coated Granules for

Disinfecting Water

15 Range 7 Scanner Integration With PaR RobotScanning System

15 Methods of Antimicrobial Coating of Diverse Materials

16 High-Operating-Temperature Barrier Infrared Detector With Tailorable Cutoff Wavelength

17 Materials & Coatings17 A Model of Reduced Kinetics for Alkane

Oxidation Using Constituents and Species for N-Heptane

17 Thermally Conductive Tape Based on CarbonNanotube Arrays

18 Two Catalysts for Selective Oxidation of Contaminant Gases

18 Nanoscale Metal Oxide Semiconductors for Gas Sensing

19 Lightweight, Ultra-High-Temperature, CMC-LinedCarbon/Carbon Structures

21 Mechanics/Machinery21 Sample Acquisition and Handling System From

a Remote Platform

22 Improved Rare-Earth Emitter Hollow Cathode

22 High-Temperature Smart Structures for EngineNoise Reduction and Performance Enhancement

23 Cryogenic Scan Mechanism for Fourier Transform Spectrometer

23 Piezoelectric Rotary Tube Motor

25 Green Design25 Thermoelectric Energy Conversion

Technology for High-Altitude Airships

25 Combustor Computations for CO2-Neutral Aviation

27 Physical Sciences27 Use of Dynamic Distortion to Predict and

Alleviate Loss of Control

27 Cycle Time Reduction in Trapped Mercury IonAtomic Frequency Standards

28 A 201Hg+ Comagnetometer for 199Hg+

Trapped Ion Space Atomic Clocks


Technology Focus: Test & Measurement

This system was one of the test meth-ods considered for measuring the radiusof curvature of one or more of the 18segmented mirrors that form the 6.5 mdiameter primary mirror (PM) of theJames Webb Space Telescope (JWST).The assembled telescope will be tested atcryogenic temperatures in a 17-m diame-ter by 27-m high vacuum chamber at theJohnson Space Center. This system uses aLeica Absolute Distance Meter (ADM),at a wavelength of 780 nm, combinedwith beam-steering and beam-shapingoptics to make a differential distancemeasurement between a ring mirror onthe reflective null assembly and individ-ual PM segments. The ADM is located in-side the same Pressure-Tight Enclosure(PTE) that houses the test interferome-ter. The PTE maintains the ADM and in-terferometer at ambient temperatureand pressure so that they are not directlyexposed to the telescope’s harsh cryo-genic and vacuum environment.

This system takes advantage of the ex-isting achromatic objective and reflec-tive null assembly used by the test inter-ferometer to direct four ADM beamlets

to four PM segments through an opticalpath that is coincident with the interfer-ometer beam. A mask, positioned on alinear slide, contains an array of 1.25mm diameter circular subapertures thatmap to each of the 18 PM segments aswell as six positions around the ring mir-ror. A down-collimated 4 mm ADMbeam simultaneously covers 4 adjacentPM segment beamlets and one ring mir-ror beamlet. The radius, or spacing, ofall 18 segments can be measured withthe addition of two orthogonally-ori-ented scanning pentaprisms used tosteer the ADM beam to any one of sixdifferent sub-aperture configurations atthe plane of the ring mirror.

The interferometer beam, at a wave-length of 687 nm, and the ADM beam-lets, at a wavelength of 780 nm, passthrough the objective and null so thatthe rays are normally incident on theparabolic PM surface. After reflectingoff the PM, both the ADM and interfer-ometer beams return to their respectiveinstruments on nearly the same path. Afifth beamlet, acting as a differential ref-erence, reflects off a ring mirror at-

tached to the objective and null and re-turns to the ADM. The spacings betweenthe ring mirror, objective, and null areknown through manufacturing toler-ances as well as through an in situ nullwavefront alignment of the interferome-ter test beam with a reflective hologramlocated near the caustic of the null.Since total path length between the ringmirror and PM segments is highly deter-ministic, any ADM-measured departuresfrom the predicted path length can beattributed to either spacing error or ra-dius error in the PM. It is estimated thatthe path length measurement betweenthe ring mirror and a PM segment is ac-curate to better than 100 μm.

The unique features of this inventioninclude the differential distance measur-ing capability and its integration into anexisting cryogenic and vacuum compati-ble interferometric optical test.

This work was done by Cormic Merle, EricWick, and Joseph Hayden of ITT Corp. forGoddard Space Flight Center. For further in-formation, contact the Goddard InnovativePartnerships Office at (301) 286-5810. GSC-15674-1

Multi-Segment Radius Measurement Using an Absolute DistanceMeter Through a Null AssemblyThis system can be used by fabricators or optics integrators for telescopes or other imaging systems.NASA’s Goddard Space Flight Center, Greenbelt, MD

A fiber-optic sensor system is de-signed to measure magnetic fields asso-ciated with a lightning stroke. Field vec-tor magnitudes are detected andprocessed for multiple locations. Sincephysical limitations prevent the sensorelements from being located in closeproximity to highly conductive materi-als such as aluminum, the copper wiresensor elements (3) are located inside a

4-cubic-in. (≈66-cubic-cm) plastic hous-ing sensor head and connected to afiber-optic conversion module byshielded cabling, which is limited to theshortest length feasible. The signal pathbetween the conversion module andthe avionics unit which processes thesignals are fiber optic, providing en-hanced immunity from electromag-netic radiation incident in the vicinity

of the measurements. The sensors arepassive, lightweight, and much smallerthan commercial B-dot sensors in theconfiguration which measures a three-dimensional magnetic field. The systemis expandable, and provides a standard-format output signal for downstreamprocessing.

Inside of the sensor head, threesmall search coils, each having a few

Fiber-Optic Magnetic-Field-Strength Measurement System forLightning DetectionFiber optics used for signal paths provide enhanced immunity from electromagnetic radiationincident in the vicinity of the measurements.John F. Kennedy Space Center, Florida

6 NASA Tech Briefs, February 2011

turns on a circular form, are mountedorthogonally inside the non-metallichousing. The fiber-optic conversionmodule comprises three interferome-ters, one for each search coil. Each in-terferometer has a high bandwidth op-tical phase modulator that impressesthe signal received from its search coilonto its output. The output of each in-terferometer travels by fiber opticcable to the avionics unit, and thesearch coil signal is recovered by anoptical phase demodulator. The out-put of each demodulator is fed to an

analog-to-digital converter, whose sam-pling rate is determined by the maxi-mum expected rate of rise and peaksignal magnitude. The output of thedigital processor is a faithful reproduc-tion of the coil response to the inci-dent magnetic field. This informationis provided in a standard output for-mat on a 50-ohm port that can be con-nected to any number of data collec-tion and processing instrumentsand/or systems.

The measurement of magnetic fieldsusing fiber-optic signal processing is

novel because it eliminates limitations ofa traditional B-dot system. These limita-tions include the distance from the sen-sor to the measurement device, the po-tential for the signal to degrade or becorrupted by EMI from lightning, andthe size and weight of the sensor and as-sociated plate.

This work was done by Jay Gurecki ofKennedy Space Center; Bob Scully of JohnsonSpace Center; and Allen Davis, Clay Kirk-endall, and Frank Bucholtz of the Naval Re-search Laboratory. Further information is con-tained in a TSP (see page 1). KSC-13221

Photocatalytic materials are beingused to purify air, to kill microbes, andto keep surfaces clean. A wide variety ofmaterials are being developed, many ofwhich have different abilities to absorbvarious wavelengths of light. Materialvariability, combined with both spectralillumination intensity and spectral distri-bution variability, will produce a widerange of performance results. The pro-posed technology estimates photocat-alytic active radiation (PcAR), a unit ofradiation that normalizes the amount oflight based on its spectral distributionand on the ability of the material to ab-sorb that radiation.

Photocatalytic reactions depend uponthe number of electron-hole pairs gen-erated at the photocatalytic surface. Thenumber of electron-hole pairs produceddepends on the number of photons perunit area per second striking the surfacethat can be absorbed and whose energyexceeds the bandgap of the photocat-alytic material. A convenient parameterto describe the number of useful pho-

tons is the number of moles of photonsstriking the surface per unit area persecond. The unit of micro-einsteins (ormicromoles) of photons per m2 per secis commonly used for photochemicaland photoelectric-like phenomena. Thistype of parameter is used in photochem-istry, such as in the conversion of lightenergy for photosynthesis.

Photosynthetic response correlateswith the number of photons rather thanby energy because, in this photochemi-cal process, each molecule is activatedby the absorption of one photon. Inphotosynthesis, the number of photonsabsorbed in the 400–700 nm spectralrange is estimated and is referred to asphotosynthetic active radiation (PAR).PAR is defined in terms of the photosyn-thetic photon flux density measured inmicro-einsteins of photons per m2 persec. PcAR is an equivalent, similarlymodeled parameter that has been de-fined for the photocatalytic processes.

Two methods to measure the PcARlevel are being proposed. In the first

method, a calibrated spectrometerwith a cosine receptor is used to meas-ure the spectral irradiance. This meas-urement, in conjunction with the pho-tocatalytic response as a function ofwavelength, is used to estimate thePcAR. The photocatalytic responsefunction is determined by measuringphotocatalytic reactivity as a functionof wavelength. In the second method,simple shaped photocatalytic responsefunctions can be simulated with abroad-band detector with a cosine re-ceptor appropriately filtered to repre-sent the spectral response of the pho-tocatalytic material. This secondmethod can be less expensive thanusing a calibrated spectrometer.

This work was done by Bruce A. Davis ofStennis Space Center and Robert E. Ryanand Lauren W. Underwood of Science Sys-tems and Applications, Inc. Inquiries con-cerning the technology should be addressed tothe Intellectual Property Manager, StennisSpace Center, (228) 688-1929. Refer to SSC-00328.

Photocatalytic Active Radiation Measurements and UseThis technology can be used to improve the ability to predict the performance of photocatalyticmaterials under different illumination conditions.Stennis Space Center, Mississippi

Computer Generated Holograms(CGHs) have been used for some timeto calibrate interferometers that re-quire nulling optics. A typical scenariois the testing of aspheric surfaces with

an interferometer placed near theparaxial center of curvature. ExistingCGH technology suffers from a re-duced capacity to calibrate middleand high spatial frequencies. The root

cause of this shortcoming is as follows:the CGH is not placed at an imageconjugate of the asphere due to limita-tions imposed by the geometry of thetest and the allowable size of the CGH.

Computer Generated Hologram System for WavefrontMeasurement System Calibration NASA’s Goddard Space Flight Center, Greenbelt, Maryland


As shown by the Phoenix Mars Lan-der’s Thermal and Electrical Conduc-tivity Probe (TECP), contact measure-ments of thermal conductivity anddiffusivity (using a modified flux-plateor line-source heat-pulse method) areconstrained by a number of factors. Ro-botic resources must be used to placethe probe, making them unavailablefor other operations for the duration ofthe measurement. The range of place-ment is also limited by mobility, partic-ularly in the case of a lander. Placementis also subject to irregularities in con-tact quality, resulting in non-repeatableheat transfer to the material under test.Most important from a scientific per-spective, the varieties of materialswhich can be measured are limited tounconsolidated or weakly-cohesive re-golith materials, rocks, and ices beingtoo hard for nominal insertionstrengths.

Accurately measuring thermal prop-erties in the laboratory requires signifi-cant experimental finesse, involvingsample preparation, controlled and re-peatable procedures, and, practically,instrumentation much more volumi-nous than the sample being tested(heater plates, insulation, temperaturesensors). Remote measurements (in-frared images from orbiting space-craft) can reveal composite properties

like thermal inertia, but suffer bothfrom a large footprint (low spatial res-olution) and convolution of the ther-mal properties of a potentially layeredmedium. In situ measurement tech-niques (the Phoenix TECP is the onlyrobotic measurement of thermal prop-erties to date) suffer from problems ofplacement range, placement quality,occupation of robotic resources, andthe ability to only measure materials oflow mechanical strength.

A spacecraft needs the ability to per-form a non-contact thermal propertiesmeasurement in situ. Essential compo-nents include low power consumption,leveraging of existing or highly-devel-oped flight technologies, and mechani-cal simplicity.

This new in situ method, by virtue ofits being non-contact, bypasses all ofthese problems. The use of photons toboth excite and measure the thermal re-sponse of any surface material to a highresolution (estimated footprint ≈ 10cm2) is a generational leap in physicalproperties measurements.

The proposed method consists ofspot-heating the surface of a materialwith a low (<1 W) power laser. This pro-duces a moderate (5-10 K) temperatureincrease in the material. As the heatpropagates in a hemisphere from thepoint of heating, it raises the tempera-

ture of the surrounding surface. Thetemperature of the heating spot itself,and that of the surrounding material, ismonitored remotely with an infraredcamera system. Monitoring is done dur-ing both the heating and cooling (afterthe laser is turned off) phases. Temper-ature evolution as a function of dis-tance from the heating point containsinformation about the material’s ther-mal properties, and can be extractedthrough curve-fitting to analytical mod-els of heat transport.

In situ measurement of thermal prop-erties of planetary surface materials pro-vides ground-truth for remote sensingobservations and high-resolution, site-specific data for any landed spacecraftenvironment. Thermal properties arenecessary parameters for modeling andunderstanding thermal evolution of thesurface and subsurface, climate state andhistory, and predicting the presence ofsubsurface water/ice. The applicationsextend to all solid bodies in the solar sys-tem, but with greatest applicability tobodies with thin or tenuous atmosphereswhere conduction and radiation are thedominant heat-transport properties.

This work was done by Troy L. Hudson andMichael H. Hecht of Caltech for NASA’s JetPropulsion Laboratory. FFurther informationis contained in a TSP (see page 1). NPO-47390

Non-Contact Thermal Properties Measurement With Low-Power Laser and IR Camera System Photons both excite and are used to measure the thermal response of any surface material. NASA’s Jet Propulsion Laboratory, Pasadena, California

This innovation provides a calibra-tion system where the imaging proper-ties in calibration can be made compa-rable to the test configuration. Thus, ifthe test is designed to have good imag-ing properties, then middle and highspatial frequency errors in the test sys-tem can be well calibrated. The im-proved imaging properties are pro-vided by a rudimentary auxiliary opticas part of the calibration system. The

auxiliary optic is simple to characterizeand align to the CGH. Use of the auxil-iary optic also reduces the size of theCGH required for calibration and thedensity of the lines required for theCGH. The resulting CGH is less expen-sive than the existing technology andhas reduced write error and alignmenterror sensitivities.

This CGH system is suitable for anykind of calibration using an interferom-

eter when high spatial resolution is re-quired. It is especially well suited fortests that include segmented opticalcomponents or large apertures.

This work was done by Gene Olczak ofITT Geospatial Systems for GoddardSpace Flight Center. For further informa-tion, contact the Goddard InnovativePartnerships Office at (301) 286-5810.GSC-15676-1


Electronics/Computers

The SpaceCube 2.0 is a compact, high-performance, low-power onboard pro-cessing system that takes advantage of cut-ting-edge hybrid (CPU/FPGA/DSP)processing elements. The SpaceCube 2.0design concept includes two commercialVirtex-5 field-programmable gate array(FPGA) parts protected by “radiationhardened by software” technology, andpossesses exceptional size, weight, andpower characteristics [5×5×7 in., 3.5 lb(≈12.7×12.7×17.8 cm, 1.6 kg) 5–25 W, de-pending on the application’s requiredclock rate]. The two Virtex-5 FPGA partsare implemented in a unique back-to-back configuration to maximize datatransfer and computing performance.

Draft computing power specificationsfor the SpaceCube 2.0 unit include four

PowerPC 440s (1100 DMIPS each), 500+DSP48Es (2×580 GMACS), 100+ LVDShigh-speed serial I/Os (1.25 Gbps each),and 2×190 GFLOPS single-precision (65GFLOPS double-precision) floatingpoint performance. The SpaceCube 2.0includes PROM memory for CPU boot,health and safety, and basic commandand telemetry functionality; RAM mem-ory for program execution; andFLASH/EEPROM memory to store algo-rithms and application code for theCPU, FPGA, and DSP processing ele-ments. Program execution can be recon-figured in real time and algorithms canbe updated, modified, and/or replacedat any point during the mission. GigabitEthernet, Spacewire, SATA and high-speed LVDS serial/parallel I/O chan-

nels are available for instrument/sensordata ingest, and mission-unique instru-ment interfaces can be accommodatedusing a compact PCI (cPCI) expansioncard interface.

The SpaceCube 2.0 can be utilized inNASA Earth Science, Helio/Astro-physics and Exploration missions, andDepartment of Defense satellites for on-board data processing. It can also beused in commercial communication andmapping satellites.

This work was done by Michael Lin,Thomas Flatley, John Godfrey, AlessandroGeist, Daniel Espinosa, and David Petrick ofGoddard Space Flight Center. Further infor-mation is contained in a TSP (see page 1).GSC-15760-1

SpaceCube 2.0: An Advanced Hybrid Onboard Data ProcessorTwo FPGAs maximize data and computing performance while minimizing physical size.Goddard Space Flight Center, Greenbelt, Maryland

CMOS Imager Has Better Cross-Talk and Full-Well Performance Electrically isolated areas containing imaging and readout structures are optimized separately. NASA’s Jet Propulsion Laboratory, Pasadena, California

A complementary metal oxide/semi-conductor (CMOS) image detectornow undergoing development is de-signed to exhibit less cross-talk andgreater full-well capacity than do priorCMOS image detectors of the sametype. Imagers of the type in questionare designed to operate from low-volt-age power supplies and are fabricatedby processes that yield device featureshaving dimensions in the deep submi-cron range.

Because of the use of low supply po-tentials, maximum internal electricfields and depletion widths are corre-spondingly limited. In turn, these limita-tions are responsible for increases incross-talk and decreases in charge-han-dling capacities. Moreover, for small pix-els, lateral depletion cannot be ex-tended. These adverse effects are evenmore accentuated in a back-illuminatedCMOS imager, in which photogeneratedcharge carriers must travel across the en-tire thickness of the device.

The figure shows a partial cross sec-tion of the structure in the device layerof the present developmental CMOS im-ager. (In a practical imager, the devicelayer would sit atop either a heavilydoped silicon substrate or a thin siliconoxide layer on a silicon substrate, notshown here.) The imager chip is dividedinto two areas: area C, which containsreadout circuits and other electronic cir-cuits; and area I, which contains the im-aging (photodetector and photogener-ated-charge-collecting) pixel structures.Areas C and I are electrically isolatedfrom each other by means of a trenchfilled with silicon oxide.

The electrical isolation between areasC and I makes it possible to apply differ-ent supply potentials to these areas,thereby enabling optimization of thesupply potential and associated designfeatures for each area. More specifi-cally, metal oxide semiconductor field-effect transistors (MOSFETs) that aretypically included in CMOS imagers

now reside in area C and can remainunchanged from established designsand operated at supply potentials pre-scribed for those designs, while thedopings and the lower supply potentialsin area I can be tailored to optimize im-ager performance.

In area I, the device layer includes ann+-doped silicon layer on which isgrown an n–-doped silicon layer. A p–-doped silicon layer is grown on top ofthe n–-doped layer. The total imagingdevice thickness is the sum of the thick-ness of the n+, n, and p– layers. A pixelphotodiode is formed between a sur-face n+ implant, a p implant under-neath it, the aforementioned p– layer,and the n and n+ layers. Adjacent tothe diode is a gate for transferring pho-togenerated charges out of the photodi-ode and into a floating diffusionformed by an implanted p+ layer on animplanted n-doped region. Metal con-tact pads are added to the back-side forproviding back-side bias.


The n– and p– doping concentrationsare chosen such that everywhere in area I,a depletion region exists between the n–

and p– layers. This depletion region en-ables electrical isolation between the sev-eral front (top) doped regions and theback (bottom) n and n+ layers. Conse-quently, the bias potentials applied to thetop of the diode and the adjacent transfergate can be different from the bias appliedto the bottom. Thus, while CMOS-compat-ible potentials (e.g., 3 V) are applied at thetop, the bottom of the structure can be bi-ased to greater potential (e.g., 5 V) via theback-side metal contact pads to com-pletely deplete the photodiode. The re-

sulting depletion region is indicated in thefigure as the area enclosed by the dashedoutline. Complete depletion of the photo-diode results in collection of charge carri-ers (holes in this case) under the influ-ence of an electric field, and hence, asignificant reduction of cross-talk. Com-plete depletion also increases the charge-storage volume, and, hence, the charge-handling capacity. Thus, the structuredescribed here provides for large deple-tion width around each photodiode, inde-pendent of the CMOS power-supply volt-age and pixel size.

This work was done by Bedabrata Pain andThomas J. Cunningham of Caltech for NASA’s

Jet Propulsion Laboratory. Further informationis contained in a TSP (see page 1).

In accordance with Public Law 96-517,the contractor has elected to retain title tothis invention. Inquiries concerningrights for its commercial use should be ad-dressed to:

Innovative Technology Assets ManagementJPLMail Stop 202-2334800 Oak Grove DrivePasadena, CA 91109-8099E-mail: [email protected] to NPO-45964, volume and number

of this NASA Tech Briefs issue, and thepage number.

This Simplified Cross Section (not to scale) shows essential features of the developmental device structure. A key feature of the structure is the depletion region (indicated by the dashed outline) along the entire n–/p– junction.

Gate

C C

I

Depletion Region Trench Filled WithSilicon Oxidep n nn+

n–p– n+

p+

Metal Contact Pads

High-Performance Wireless TelemetryThis technology is applicable to any kind of aviation or power-plant turbine testing.John H. Glenn Research Center, Cleveland, Ohio

Prior technology for machinery dataacquisition used slip rings, FM radiocommunication, or non-real-time digitalcommunication. Slip rings are oftennoisy, require much space that may notbe available, and require access to theshaft, which may not be possible. FMradio is not accurate or stable, and is lim-ited in the number of channels, oftenwith channel crosstalk, and intermittentas the shaft rotates. Non-real-time digitalcommunication is very popular, but com-plex, with long development time, andobjections from users who need continu-ous waveforms from many channels.

This innovation extends the amountof information conveyed from a rotatingmachine to a data acquisition system

while keeping the development timeshort and keeping the rotating electron-ics simple, compact, stable, and rugged.The data are all real time. The productof the number of channels, times the bitresolution, times the update rate, gives adata rate higher than available by oldermethods. The telemetry system consistsof a data-receiving rack that suppliesmagnetically coupled power to a rotat-ing instrument amplifier ring in the ma-chine being monitored. The ring digi-tizes the data and magnetically couplesthe data back to the rack, where it ismade available.

The transformer is generally a ringpositioned around the axis of rotationwith one side of the transformer free to

rotate and the other side held stationary.The windings are laid in the ring; thisgives the data immunity to any rotationthat may occur.

A medium-frequency sine-wave powersource in a rack supplies power througha cable to a rotating ring transformerthat passes the power on to a rotating setof electronics. The electronics power aset of up to 40 sensors and provides in-strument amplifiers for the sensors. Theoutputs from the amplifiers are filteredand multiplexed into a serial ADC. Theoutput from the ADC is connected toanother rotating ring transformer thatconveys the serial data from the rotatingsection to the stationary section. Fromthere, a cable conveys the serial data to


the remote rack, where it is recondi-tioned to logic level specifications, de-se-rialized, and converted back to analog.In the rotating electronics are code gen-erators to indicate the beginning of filesfor data synchronization.

An alternative method would be touse two symmetrical coils. Since the twocoils are rotationally symmetrical, rota-tion does not influence the magneticcoupling from the primary to the sec-ondary. Since the secondary coil is elec-trostatically shielded, environmentalnoise pickup is intrinsically low. Sincethe transformer is air-core, the uncom-pressed bandwidth can be high — 50MHz, 200 MHz, or higher.

The rotating coil is the primary com-ponent of the transformer and is in the

shape of a thin ring, containing a fewturns of wire. The plane of the ring isperpendicular to the axis of rotation. Ra-dially, just beyond the rotating primarycoil, is the secondary coil in the shape ofa ring, and lying close to the primary.The secondary coil is a single turn ofcoaxial cable with the center conductorconnected to the shield of the cablewhere it leaves the coil. The binary dataare fed into both ends of the primarycoil through an impedance matching re-sistor, with one end receiving the data in-verted. This double-ended (full-bridge)approach reduces propagation delay dis-tortions and increases signal strength.The secondary coil has an impedancematching resistor at the end of thecable. Use of a coaxial cable reduces ca-

pacitive coupling, but freely allows mag-netic coupling. To enhance the cou-pling, ferrite cloth can be laid into agroove and the primary coil wound ontop of it. Similarly, ferrite cloth can beformed around the secondary coil. Cop-per rings can be placed on either side ofthe coil set to reduce outside influences.

This work was done by Elmer Griebeler,Nuha Nawash, and James Buckley of GlennResearch Center. Further information is con-tained in a TSP (see page 1).

Inquiries concerning rights for the com-mercial use of this invention should be ad-dressed to NASA Glenn Research Center, In-novative Partnerships Office, Attn: StevenFedor, Mail Stop 4–8, 21000 BrookparkRoad, Cleveland, Ohio 44135. Refer toLEW-18575-1/7-1.

A telemetry-based ranging schemewas developed in which the downlinkranging signal is eliminated, and therange is computed directly from thedownlink telemetry signal. This is thefirst Deep Space Network (DSN) rang-ing technology that does not requirethe spacecraft to transmit a separateranging signal. By contrast, the evolu-tionary ranging techniques used overthe years by NASA missions, includingsequential ranging (transmission of asequence of sinusoids) and PN-ranging(transmission of a pseudo-noise se-quence) — whether regenerative(spacecraft acquires, then regeneratesand retransmits a noise-free rangingsignal) or transparent (spacecraft feedsthe noisy demodulated uplink ranging

signal into the downlink phase modula-tor) — relied on spacecraft power andbandwidth to transmit an explicit rang-ing signal.

The state of the art in ranging is de-scribed in an emerging CCSDS (Con-sultative Committee for Space Data Sys-tems) standard, in which apseudo-noise (PN) sequence is trans-mitted from the ground to the space-craft, acquired onboard, and the PN se-quence is coherently retransmittedback to the ground, where a delay meas-urement is made between the uplinkand downlink signals. In this work, thetelemetry signal is aligned with the up-link PN code epoch. The ground sta-tion computes the delay between theuplink signal transmission and the re-

ceived downlink telemetry. Such a com-putation is feasible because symbol syn-chronizability is already an integral partof the telemetry design.

Under existing technology, thetelemetry signal cannot be used forranging because its arrival-time informa-tion is not coherent with any Earth refer-ence signal. By introducing this coher-ence, and performing joint telemetrydetection and arrival-time estimation onthe ground, a high-rate telemetry signalcan provide all the precision necessaryfor spacecraft ranging.

This work was done by Jon Hamkins, Vic-tor A. Vilnrotter, Kenneth S. Andrews, andShervin Shambayati of Caltech for NASA’s JetPropulsion Laboratory. For more information,contact [email protected]. NPO-47170

Telemetry-Based Ranging NASA’s Jet Propulsion Laboratory, Pasadena, California


Software

JWST Wavefront Control Toolbox

A Matlab-based toolbox has been de-veloped for the wavefront control andoptimization of segmented optical sur-faces to correct for possible misalign-ments of James Webb Space Telescope(JWST) using influence functions. Thetoolbox employs both iterative andnon-iterative methods to converge toan optimal solution by minimizing thecost function. The toolbox could beused in either of constrained and un-constrained optimizations. The controlprocess involves 1 to 7 degrees-of-free-dom perturbations per segment of pri-mary mirror in addition to the 5 de-grees of freedom of secondary mirror.

The toolbox consists of a series ofMatlab/Simulink functions and mod-ules, developed based on a “wrapper”approach, that handles the interfaceand data flow between existing commer-cial optical modeling software packagessuch as Zemax and Code V. The limita-tions of the algorithm are dictated bythe constraints of the moving parts inthe mirrors.

This work was done by Shahram Ron Shiriand David L. Aronstein of Goddard SpaceFlight Center. For further information, con-tact the Goddard Innovative Partnerships Of-fice (301) 286-5810. GSC-15567-1

Java Image I/O for VICAR,PDS, and ISIS

This library, written in Java, supportsinput and output of images and meta-data (labels) in the VICAR, PDS image,and ISIS-2 and ISIS-3 file formats. Threelevels of access exist.

The first level comprises the low-level,direct access to the file. This allows anapplication to read and write specificimage tiles, lines, or pixels and to ma-nipulate the label data directly. Thislayer is analogous to the C-language“VICAR Run-Time Library” (RTL),which is the image I/O library for the(C/C++/Fortran) VICAR image pro-cessing system from JPL MIPL (Multi-mission Image Processing Lab). Thislow-level library can also be used to read

and write labeled, uncompressed im-ages stored in formats similar to VICAR,such as ISIS-2 and -3, and a subset ofPDS (image format).

The second level of access involvestwo codecs based on Java Advanced Im-aging (JAI) to provide access to VICARand PDS images in a file-format-inde-pendent manner. JAI is supplied by SunMicrosystems as an extension to desktopJava, and has a number of codecs for for-mats such as GIF, TIFF, JPEG, etc. Al-though Sun has deprecated the codecmechanism (replaced by IIO), it is stillused in many places. The VICAR andPDS codecs allow any program writtenusing the JAI codec spec to use VICARor PDS images automatically, with nospecific knowledge of the VICAR or PDSformats. Support for metadata (labels) isincluded, but is format-dependent. ThePDS codec, when processing PDS im-ages with an embedded VIAR label(“dual-labeled images,” such as used forMER), presents the VICAR label in anew way that is compatible with theVICAR codec.

The third level of access involvesVICAR, PDS, and ISIS Image I/O plug-ins. The Java core includes an “ImageI/O” (IIO) package that is similar inconcept to the JAI codec, but is newerand more capable. Applications writtento the IIO specification can use anyimage format for which a plug-in exists,with no specific knowledge of the for-mat itself.

This work was done by Robert G. Deen andSteven R. Levoe of Caltech for NASA’s JetPropulsion Laboratory. For more informa-tion, contact [email protected].

This software is available for commercial li-censing. Please contact Daniel Broderick ofthe California Institute of Technology [email protected]. Refer to NPO-47184.

X-Band Acquisition Aid Software

The X-band Acquisition Aid (AAP)software is a low-cost acquisition aid forthe Deep Space Network (DSN) anten-nas, and is used while acquiring a space-craft shortly after it has launched. Whenenabled, the acquisition aid provides

corrections to the antenna-predicted tra-jectory of the spacecraft to compensatefor the variations that occur during theactual launch. The AAP software alsoprovides the corrections to the antenna-predicted trajectory to the navigationteam that uses the corrections to refinetheir model of the spacecraft in order toproduce improved antenna-predictedtrajectories for each spacecraft thatpasses over each complex.

The software provides an automatedAcquisition Aid receiver calibration, andprovides graphical displays to the opera-tor and remote viewers via an Ethernetconnection. It has a Web server, and theremote workstations use the Firefoxbrowser to view the displays. At any giventime, only one operator can control anyparticular display in order to avoid con-flicting commands from more than onecontrol point. The configuration andcontrol is accomplished solely via thegraphical displays. The operator does nothave to remember any commands. Only afew configuration parameters need to bechanged, and can be saved to the appro-priate spacecraft-dependent configura-tion file on the AAP’s hard disk.

AAP automates the calibration se-quence by first commanding the an-tenna to the correct position, startingthe receiver calibration sequence, andthen providing the operator with the op-tion of accepting or rejecting the newcalibration parameters. If accepted, thenew parameters are stored in the appro-priate spacecraft-dependent configura-tion file. The calibration can be per-formed on the Sun, greatly expandingthe window of opportunity for calibra-tion. The spacecraft traditionally usedfor calibration is in view typically twiceper day, and only for about ten minuteseach pass.

This work was done by Michael J. Britcliffeand Martha M. Strain of Caltech andMichael Wert of ITT for NASA’s Jet Propul-sion Laboratory. Further information is con-tained in a TSP (see page 1).

The software used in this innovation isavailable for commercial licensing. Pleasecontact Daniel Broderick of the California In-stitute of Technology at [email protected] to NPO-47004.


Manufacturing & Prototyping

An interface bracket and coordinatetransformation matrices were designedto allow the Range 7 scanner to bemounted on the PaR Robot detector armfor scanning the heat shield or other ob-ject placed in the test cell. A process wasdesigned for using Rapid Form XOR tostitch data from multiple scans togetherto provide an accurate 3D model of theobject scanned.

An accurate model was required forthe design and verification of an existingheat shield. The large physical size andcomplex shape of the heat shield doesnot allow for direct measurement of cer-tain features in relation to other features.Any imaging devices capable of imagingthe entire heat shield in its entirety suf-fers a reduced resolution and cannotimage sections that are blocked fromview. Prior methods involved tools suchas commercial measurement arms, tak-

ing images with cameras, then perform-ing manual measurements. These priormethods were tedious and could not pro-vide a 3D model of the object beingscanned, and were typically limited to afew tens of measurement points atprominent locations.

Integration of the scanner with therobot allows for large complex objects tobe scanned at high resolution, and for3D Computer Aided Design (CAD)models to be generated for verificationof items to the original design, and togenerate models of previously undocu-mented items.

The main components are the mount-ing bracket for the scanner to the robotand the coordinate transformation ma-trices used for stitching the scanner datainto a 3D model. The steps involvemounting the interface bracket to therobot’s detector arm, mounting the scan-

ner to the bracket, and then scanningsections of the object and recording thelocation of the tool tip (in this case thecenter of the scanner’s focal point).

A novel feature is the ability to stitchimages together by coordinates insteadof requiring each scan data set to haveoverlapping identifiable features. Thissetup allows models of complex objectsto be developed even if the object islarge and featureless, or has sectionsthat don’t have visibility to other parts ofthe object for use as a reference. In addi-tion, millions of points can be used forcreation of an accurate model [i.e.within 0.03 in. (≈0.8 mm) over a span of250 in. (≈635 mm)].

This work was done by Bradley Burns, Jef-frey Carlson, Mark Minich, and Jason Schuler ofKennedy Space Center. Further information iscontained in a TSP (see page 1). KSC-13489/95

Range 7 Scanner Integration With PaR Robot Scanning System Models of complex objects can be developed even if the objects are large and featureless. John F. Kennedy Space Center, Florida

Methods of preparing antimicrobial-coated granules for disinfecting flowingpotable water have been developed.Like the methods reported in the imme-diately preceding article, these methodsinvolve chemical preparation of sub-strate surfaces (in this case, the surfacesof granules) to enable attachment of an-timicrobial molecules to the surfaces viacovalent bonds. A variety of granularmaterials have been coated with a vari-

ety of antimicrobial agents that includeantibiotics, bacteriocins, enzymes, bac-tericides, and fungicides. When em-ployed in packed beds in flowing water,these antimicrobial-coated granuleshave been proven effective againstgram-positive bacteria, gram-negativebacteria, fungi, and viruses. Compositebeds, consisting of multiple layers con-taining different granular antimicrobialmedia, have proven particularly effec-

tive against a broad spectrum of mi-croorganisms. These media have alsoproven effective in enhancing or poten-tiating the biocidal effects of in-line iod-inated resins and of very low levels ofdissolved elemental iodine.

This work was done by James R. Akse, JohnT. Holtsnider, and Helen Kliestik of UmpquaResearch Co. for Johnson Space Center. Fur-ther information is contained in a TSP (seepage 1). MSC-23468-1

Antimicrobial-Coated Granules for Disinfecting Water Lyndon B. Johnson Space Center, Houston, Texas

Methods of coating diverse substratematerials with antimicrobial agentshave been developed. Originally in -tended to reduce health risks to astro-nauts posed by pathogenic microorgan-

isms that can grow on surfaces in space-craft, these methods could also be usedon Earth — for example, to ensuresterility of surgical inserts and othermedical equipment. The methods in-

volve, generally, chemical preparationof substrate surfaces to enable attach-ment of antimicrobial molecules to thesubstrate surfaces via covalent bonds.Substrate materials that have been

Methods of Antimicrobial Coating of Diverse MaterialsLyndon B. Johnson Space Center, Houston, Texas


treated successfully include aluminum,glass, a corrosion-resistant nickel alloy,stainless steel, titanium, and poly(tetra-fluoroethylene). Antimi crobial agentsthat have been successfully immobi-lized include antibiotics, enzymes, bac-teriocins, bactericides, and fungicides.

A variety of linkage chem istries wereemployed. Activity of antimicrobialcoatings against gram-positive bacteria,gram-negative bacteria, and fungi wasdemonstrated. Results of investigationsindicate that the most suitable combi-nation of antimicrobial agent, sub-

strate, and coating method dependsupon the intended application.

This work was done by James R. Akse, John T.Holtsnider, and Helen Kliestik of Umpqua Re-search Co. for Johnson Space Center. For further in-formation, contact the Johnson Commercial Tech-nology Office at (281) 483-3809. MSC-23467-1

High-Operating-Temperature Barrier Infrared Detector WithTailorable Cutoff Wavelength Novel materials allow the detector to operate at higher temperatures. NASA’s Jet Propulsion Laboratory, Pasadena, California

A mid-wavelength infrared (MWIR)barrier photodetector is capable of op-erating at higher temperature than theprevailing MWIR detectors based onInSb. The standard high-operating-tem-perature barrier infrared detector(HOT-BIRD) is made with an InAsSb in-frared absorber that is lattice-matchedto a GaSb substrate, and has a cutoffwavelength of approximately 4 microns.To increase the versatility and utility ofthe HOT-BIRD, it is implemented withIR absorber materials with customizablecutoff wavelengths.

The HOT-BIRD can be built with thequaternary alloy GaInAsSb as the ab-sorber, GaAlSbAs as the barrier, on a lat-tice-matching GaSb substrate. The cut-off wavelength of the GaInAsSb can betailored by adjusting the alloy composi-tion. To build a HOT-BIRD requires amatching pair of absorber and barriermaterials with the following properties:(1) their valence band edges must beapproximately the same to allow unim-peded hole flow, while their conduction

band edges should have a large differ-ence to form an electron barrier; and(2) the absorber and the barrier mustbe respectively lattice-matched andclosely lattice-matched to the substrateto ensure high material quality and lowdefect density.

To make a HOT-BIRD with cutoffwavelength shorter than 4 microns, aGaInAsSb quaternary alloy was used asthe absorber, and a matching GaAlS-bAs quaternary alloy as the barrier. Bychanging the alloy composition, theband gap of the quaternary alloy ab-sorber can be continuously adjustedwith cutoff wavelength ranging from 4microns down to the short wavelengthinfrared (SWIR). By carefully choosingthe alloy composition of the barrier, aHOT-BIRD structure can be formed.With this method, a HOT-BIRD can bemade with continuously tailorable cut-off wavelengths from 4 microns downto the SWIR.

The HOT-BIRD detector technologyis suitable for making very-large-format

MWIR/SWIR focal plane arrays thatcan be operated by passive coolingfrom low Earth orbit. High-operating-temperature infrared with reducedcooling requirement would benefitspace missions in reduction of size,weight, and power, and an increase inmission lifetime.

This work was done by David Z. Ting, CoryJ. Hill, Alexander Soibel, Sumith V. Bandara,and Sarath D. Gunapala of Caltech forNASA’s Jet Propulsion Laboratory. For moreinformation, contact [email protected].

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

Innovative Technology Assets ManagementJPLMail Stop 202-2334800 Oak Grove DrivePasadena, CA 91109-8099E-mail: [email protected] to NPO-46477, volume and number

of this NASA Tech Briefs issue, and thepage number.


Materials & Coatings

The reduction of elementary or skele-tal oxidation kinetics to a subgroup oftractable reactions for inclusion in tur-bulent combustion codes has been thesubject of numerous studies. The skele-tal mechanism is obtained from the ele-mentary mechanism by removing fromit reactions that are considered negligi-ble for the intent of the specific studyconsidered. As of now, there are manychemical reduction methodologies.

A methodology for deriving a reducedkinetic mechanism for alkane oxidationis described and applied to n-heptane.The model is based on partitioning thespecies of the skeletal kinetic mecha-nism into lights, defined as those havinga carbon number smaller than 3, andheavies, which are the complement ofthe species ensemble. For modeling pur-poses, the heavy species are mathemati-cally decomposed into constituents,which are similar but not identical togroups in the group additivity theory.

From analysis of the LLNL (LawrenceLivermore National Laboratory) skele-tal mechanism in conjunction withCHEMKIN II, it is shown that a similar-ity variable can be formed such that the appropriately non-dimensionalized

global constituent molar density ex-hibits a self-similar behavior over a verywide range of equivalence ratios, initialpressures and initial temperatures thatis of interest for predicting n-heptaneoxidation. Furthermore, the oxygenand water molar densities are shown todisplay a quasi-linear behavior with re-spect to the similarity variable. The lightspecies ensemble is partitioned intoquasi-steady and unsteady species. Thereduced model is based on conceptsconsistent with those of Large EddySimulation (LES) in which functionalforms are used to replace the smallscales eliminated through filtering ofthe governing equations; in LES, thesesmall scales are unimportant as far asthe overwhelming part of dynamic en-ergy is concerned.

Here, the scales thought unimportantfor recovering the thermodynamic en-ergy are removed. The concept is testedby using tabular information from theLLNL skeletal mechanism in conjunc-tion with CHEMKIN II utilized as surro-gate ideal functions replacing the neces-sary functional forms. The test revealsthat the similarity concept is indeed jus-tified and that the combustion tempera-

ture is well predicted, but that the igni-tion time is over-predicted, a fact tracedto neglecting a detailed description ofthe processes leading to the heavieschemical decomposition. To palliate thisdeficiency, functional modeling is incor-porated into this conceptual reductionin addition to the modeling the evolu-tion of the global constituent molar den-sity, the enthalpy evolution of the heav-ies, the contribution to the reaction rateof the unsteady lights from other lightspecies and from the heavies, the molardensity evolution of oxygen and water,and the mole fractions of the quasi-steady light species.

The model is compact in that thereare only nine species-related progressvariables. Results are presented showingthe performance of the model for pre-dicting the temperature and species evo-lution. The model reproduces the igni-tion time over a wide range ofequivalence ratios, initial pressure, andinitial temperature.

This work was done by Kenneth G.Harstad and Josette Bellan of Caltech forNASA’s Jet Propulsion Laboratory. For moreinformation, contact [email protected]

A Model of Reduced Kinetics for Alkane Oxidation UsingConstituents and Species for N-Heptane When certain variables are judiciously combined, a self-similarity appears, allowing for acompact chemistry reduction mechanism that predicts ignition time. NASA’s Jet Propulsion Laboratory, Pasadena, California

To increase contact conductance be-tween two mating surfaces, a conductive“tape” has been developed by growingdense arrays of carbon nanotubes (CNTs,graphite layers folded into cylinders) onboth sides of a thermally conductivemetallic foil. When the two mating sur-faces are brought into contact with theconductive tape in between, the CNT ar-rays will adhere to the mating surface.

The van der Waals force between the con-tacting tubes and the mating surface pro-vides adhesion between the two matingsurfaces. Even though the thermal con-tact conductance of a single tube-to-tubecontact is small, the tremendous amountof CNTs on the surface leads to a verylarge overall contact conductance.

Interface contact thermal resistance risesfrom the microroughness and the macro-

scopic non-planar quality of mating sur-faces. When two surfaces come into contactwith each other, the actual contact area maybe much less than the total area of the sur-faces. The real area of contact depends onthe load, the surface roughness, and theelastic and inelastic properties of the sur-face. This issue is even more important atcryogenic temperatures, where materialsbecome hard and brittle and vacuum is

Thermally Conductive Tape Based on Carbon Nanotube ArraysThis material can be used for thermal management of microelectronic packages and electronic systems.Goddard Space Flight Center, Greenbelt, Maryland


used, which prevents any gas conductionthrough the interstitial region.

A typical approach to increase thermalcontact conductance is to use thermallyconducting epoxies or greases, which arenot always compatible with vacuum condi-tions. In addition, the thermal conductiv-ities of these compounds are often rela-tively low. The CNTs used in thisapproach can be metallic or semiconduct-ing, depending on the folding angle anddiameter. The electrical resistivity of mul-tiwalled carbon nanotubes (MWCNTs)has been reported. MWCNTs can pass a

current density and remain stable at hightemperatures in air. The thermal conduc-tivity of a MWCNT at room temperature ismeasured to be approximately 3,000W/m-K, which is much larger than that ofdiamond. At room temperature, the ther-mal conductance of a 0.3 cm2 array ofCNTs was measured to be as high as 10W/K. The high thermal conductivity andthe nanoscale size make CNTs ideal asthermal interface materials.

The CNT-based thermal tape can beused for the thermal management of mi-croelectronic packages and electronic

systems. It also can be integrated withcurrent device technology and packag-ing. The material would allow for an effi-cient method to manage excess heat gen-eration without requiring any additionalpower. Lastly, the CNT tape can be usedto enhance thermal contact conduc-tance across two mating surfaces onsome NASA missions.

This work was done by Ali Kashani ofAtlas Scientific for Goddard Space Flight Cen-ter. For further information, contact the God-dard Innovative Partnerships Office at (301)286-5810. GSC-15607-1

Two catalysts for the selective oxida-tion of trace amounts of contaminantgases in air have been developed for useaboard the International Space Station.These catalysts might also be useful forreducing concentrations of fumes in ter-restrial industrial facilities — especiallyfacilities that use halocarbons as sol-vents, refrigerant liquids, and foamingagents, as well as facilities that generateor utilize ammonia.

The first catalyst is of the supported-precious-metal type. This catalyst ishighly active for the oxidation of halo-carbons, hydrocarbons, and oxygenatesat low concentrations in air. This cata-lyst is more active for the oxidation ofhydrocarbons and halocarbons thanare competing catalysts developed inrecent years. This catalyst completelyconverts these airborne contaminantgases to carbon dioxide, water, andmineral acids that can be easily re-

moved from the air, and does not makeany chlorine gas in the process. The cat-alyst is thermally stable and is not poi-soned by chlorine or fluorine atomsproduced on its surface during the de-struction of a halocarbon. In addition,the catalyst can selectively oxidize am-monia to nitrogen at a temperature be-tween 200 and 260 °C, without makingnitrogen oxides, which are toxic. Thetemperature of 260 °C is higher thanthe operational temperature of anyother precious-metal catalyst that canselectively oxidize ammonia.

The purpose of the platinum in thiscatalyst is to oxidize hydrocarbons andto ensure that the oxidation of halocar-bons goes to completion. However, theplatinum exhibits little or no activityfor initiating the destruction of halo-carbons. Instead, the attack on thehalocarbons is initiated by the support.The support also provides a high sur-

face area for exposure of the platinum.Moreover, the support resists deactiva-tion or destruction by halogens re-leased during the destruction of halo-carbons.

The second catalyst is of the sup-ported-metal-oxide type. This catalystcan selectively oxidize ammonia to nitro-gen at temperatures up to 400 °C, with-out producing nitrogen oxides. This cat-alyst converts ammonia completely tonitrogen, even when the concentrationof ammonia is very low. No other catalystis known to oxidize ammonia selectivelyat such a high temperature and low con-centration. Both the metal oxide andthe support contribute to the activityand selectivity of this catalyst.

This work was done by John D. Wright ofTDA Research for Johnson Space Center. Forfurther information, contact the JSC Innova-tion Partnerships Office at (281) 483-3809.MSC-23054-1

Two Catalysts for Selective Oxidation of Contaminant GasesOne oxidizes halocarbons and ammonia; the other oxidizes ammonia. Lyndon B. Johnson Space Center, Houston, Texas

A report describes the fabrication andtesting of nanoscale metal oxide semi-conductors (MOSs) for gas and chemi-cal sensing. This document examinesthe relationship between processing ap-proaches and resulting sensor behavior.This is a core question related to arange of applications of nanotechnol-ogy and a number of different synthesismethods are discussed: thermal evapo-

ration-condensation (TEC), controlledoxidation, and electrospinning. Advan-tages and limitations of each techniqueare listed, providing a processingoverview to developers of nanotechnol-ogy-based systems.

The results of a significant amount oftesting and comparison are also de-scribed. A comparison is made betweenSnO2, ZnO, and TiO2 single-crystal

nanowires and SnO2 polycrystallinenanofibers for gas sensing. The TEC-synthesized single-crystal nanowiresoffer uniform crystal surfaces, resistanceto sintering, and their synthesis may bedone apart from the substrate. The TEC-produced nanowire response is very low,even at the operating temperature of200 °C. In contrast, the electrospunpolycrystalline nanofiber response is

Nanoscale Metal Oxide Semiconductors for Gas SensingJohn H. Glenn Research Center, Cleveland, Ohio


Lightweight, Ultra-High-Temperature, CMC-LinedCarbon/Carbon StructuresThis refractory composite material is applicable to defense vehicles, combustion chambers,rocket nozzles, hot gas generators, and valves using both liquid and solid propellants.John H. Glenn Research Center, Cleveland, Ohio

Carbon/carbon (C/C) is an estab-lished engineering material used exten-sively in aerospace. The beneficial proper-ties of C/C include high strength, lowdensity, and toughness. Its shortcoming isits limited usability at temperatureshigher than the oxidation temperature ofcarbon — approximately 400 °C. Ceramicmatrix composites (CMCs) are used in-stead, but carry a weight penalty. Combin-ing a thin laminate of CMC to a bulkstructure of C/C retains all of the benefitsof C/C with the high temperature oxidiz-ing environment usability of CMCs.

Ultramet demonstrated the feasibilityof combining the light weight of C/Ccomposites with the oxidation resistanceof zirconium carbide (ZrC) and zirco-nium-silicon carbide (Zr-Si-C) CMCs in aunique system composed of a C/C pri-mary structure with an integral CMCliner with temperature capability up to4,200 °F (≈2,315 °C). The system effec-tively bridged the gap in weight and per-formance between coated C/C and bulkCMCs. Fabrication was demonstratedthrough an innovative variant of Ultra-

met’s rapid, pressureless melt infiltrationprocessing technology. The fully devel-oped material system has strength that iscomparable with that of C/C, lower den-sity than Cf/SiC, and ultra-high-tempera-ture oxidation stability. Application ofthe reinforced ceramic casing to a pre-dominantly C/C structure creates ahighly innovative material with the po-tential to achieve the long-sought goal oflong-term, cyclic high-temperature useof C/C in an oxidizing environment.The C/C substructure provided most ofthe mechanical integrity, and the CMCstrengths achieved appeared to be suffi-cient to allow the CMC to perform its pri-mary function of protecting the C/C.

Nozzle extension components werefabricated and successfully hot-fire tested.Test results showed good thermochemi-cal and thermomechanical stability of theCMC, as well as excellent interfacialbonding between the CMC liner and theunderlying C/C structure. In particular,hafnium-containing CMCs on C/C wereshown to perform well at temperaturesexceeding 3,500 °F (≈1,925 °C).

The melt-infiltrated CMC-lined C/Ccomposites offered a lower density thanCf/SiC. The melt-infiltrated compositesoffer greater use temperature thanCf/SiC because of the more refractoryceramic matrices and the C/C substruc-ture provides greater high-temperaturestrength.

The progress made in this work willallow multiple high-temperature compo-nents used in oxidizing environments totake advantage of the low density andhigh strength of C/C combined with thehigh-temperature oxidation resistanceof melt-infiltrated CMCs.

This work was done by Matthew J. Wright,Gautham Ramachandran, and Brian E.Williams of Ultramet for Glenn Research Cen-ter. Further information is contained in aTSP (see page 1).

Inquiries concerning rights for the com-mercial use of this invention should be ad-dressed to NASA Glenn Research Center, In-novative Partnerships Office, Attn: StevenFedor, Mail Stop 4–8, 21000 BrookparkRoad, Cleveland, Ohio 44135. Refer toLEW-18618-1.

high, suggesting that junction potentialsare superior to a continuous surface de-pletion layer as a transduction mecha-nism for chemisorption. Using a catalystdeposited upon the surface in the formof nanoparticles yields dramatic gains insensitivity for both nanostructured, one-dimensional forms.

For the nanowire materials, the re-sponse magnitude and response rate uni-formly increase with increasing operat-ing temperature. Such changes areinterpreted in terms of accelerated sur-face diffusional processes, yielding

greater access to chemisorbed oxygenspecies and faster dissociative chemisorp-tion, respectively. Regardless of operat-ing temperature, sensitivity of thenanofibers is a factor of 10 to 100 greaterthan that of nanowires with the same cat-alyst for the same test condition. In sum-mary, nanostructure appears critical togoverning the reactivity, as measured byelectrical resistance of these SnO2 nano-materials towards reducing gases. Withregard to the sensitivity of the differentnascent nanostructures, the electrospunnanofibers appear preferable.

This work was done by Gary W. Hunter,Laura Evans, and Jennifer C. Xu of Glenn Re-search Center; Randy L. Vander Wal of PennState University; and Gordon M. Berger andMichael J. Kulis of the National Center forSpace Exploration Research. Further informa-tion is contained in a TSP (see page 1).

Inquiries concerning rights for the com-mercial use of this invention should be ad-dressed to NASA Glenn Research Center, In-novative Partnerships Office, Attn: StevenFedor, Mail Stop 4–8, 21000 BrookparkRoad, Cleveland, Ohio 44135. Refer toLEW-18492-1.


Mechanics/Machinery

A system has been developed to ac-quire and handle samples from a sus-pended remote platform. The system in-cludes a penetrator, a penetratordeployment mechanism, and a samplehandler. A gravity-driven harpoon sam-pler was used for the system, but othersolutions can be used to supply the pen-etration energy, such as pyrotechnic,pressurized gas, or springs. The deploy-ment mechanism includes a line that isattached to the penetrator, a spool forreeling in the line, and a line engage-ment control mechanism.

The penetrator has removable tipsthat can collect liquid, ice, or solid sam-ples. The handling mechanism consistsof a carousel that can store a series ofidentical or different tips, assist in pene-trator reconfiguration for multiple sam-ple acquisition, and deliver the sampleto a series of instruments for analysis.The carousel sample handling systemwas combined with a brassboard reelingmechanism and a penetrator with re-movable tips. It can attach the remov-able tip to the penetrator, release and re-trieve the penetrator, remove the tip,and present it to multiple instrumentstations. The penetrator can be remotelydeployed from an aerobot, penetrateand collect the sample, and be retrievedwith the sample to the aerobot.

The penetrator with removable tips in-cludes sample interrogation windows anda sample retainment spring for unconsol-idated samples. The line engagementmotor can be used to control the penetra-tor release and reeling engagement, andto evenly distribute the line on the spoolby rocking between left and right ends ofthe spool. When the arm with the guidingring is aligned with the spool axis, the lineis free to unwind from the spool withoutrotating the spool. When the arm is per-pendicular to the spool axis, the line canmove only if the spool rotates.

This work was done by Mircea Badescu,Stewart Sherrit, and Jack A. Jones of Caltechfor NASA’s Jet Propulsion Laboratory. Fur-ther information is contained in a TSP (seepage 1). NPO-46585

Sample Acquisition and Handling System From a Remote Platform This technology can be used for surface sampling of large areas such as deserts, or for agricultural sampling. NASA’s Jet Propulsion Laboratory, Pasadena, California

The main functional components of the Penetrator Deployment Mechanism (top), and (bottom) theBrassboard with a simplified sample acquisition component and the carousel sample handler.

Reel Mechanism

Harpoon Body WithQuick Coupling

Penetrator Removable Tip

SamplePyrolysis Cup

Rotation Mechanism

Carousel

Linear Mechanism

Line engagement control motor assembly(motor, gearhead, arm with guiding ring)

Reel control motor assembly (brake, motor,

gearhead, spool with line)

Penerator assembly(Penetrator body, tip)


An improvement has been made tothe design of the hollow cathode geom-etry that was created for the rare-earthelectron emitter described in “CompactRare Earth Emitter Hollow Cathode”(NPO-44923), NASA Tech Briefs, Vol. 34,No. 3 (March 2010), p. 52. The originalinterior assembly was made entirely ofgraphite in order to be compatible withthe LaB6 material, which cannot betouched by metals during operation dueto boron diffusion causing embrittle-ment issues in high-temperature refrac-tory materials. Also, the graphite tubewas difficult to machine and was subjectto vibration-induced fracturing.

This innovation replaces the graphitetube with one made out of refractorymetal that is relatively easy to manufac-ture. The cathode support tube is made

of molybdenum or molybdenum-rhe-nium. This material is easily gun-boredto near the tolerances required, and fin-ish machined with steps at each end thatcapture the orifice plate and the mount-ing flange. This provides the manufac-turability and robustness needed forflight applications, and eliminates theneed for expensive e-beam welding usedin prior cathodes. The LaB6 insert isprotected from direct contact with therefractory metal tube by thin, graphitesleeves in a cup-arrangement aroundthe ends of the insert. The sleeves, in-sert, and orifice plate are held in placeby a ceramic spacer and tungsten springinserted inside the tube.

To heat the cathode, an insulatingtube is slipped around the refractorymetal hollow tube, which can be made

of high-temperature materials likeboron nitride or aluminum nitride. Ascrew-shaped slot, or series of slots, ismachined in the outside of the ceramictube to constrain a refractory metal wirewound inside the slot that is used as theheater. The screw slot can hold a singleheater wire that is then connected tothe front of the cathode tube by tack-welding to complete the electrical cir-cuit, or it can be a double slot that takesa bifilar wound heater with both leadscoming out the back. This configura-tion replaces the previous sheathedheater design that limited the cycling-life of the cathode.

This work was done by Dan M. Goebel ofCaltech for NASA’s Jet Propulsion Laboratory.Further information is contained in a TSP(see page 1). NPO-46782

Improved Rare-Earth Emitter Hollow Cathode These cathodes have applications in electric thrusters and in industry for plasma processing ofoptical coatings. NASA’s Jet Propulsion Laboratory, Pasadena, California

One of key NASA goals is to developand integrate noise reduction technol-ogy to enable unrestricted air trans-portation service to all communities.One of the technical priorities of this ac-tivity has been to account for and reducenoise via propulsion/airframe interac-tions, identifying advanced concepts tobe integrated with the airframe to miti-gate these noise-producing mechanisms.

An adaptive geometry chevron usingembedded smart structures technologyoffers the possibility of maximizing en-gine performance while retaining andpossibly enhancing the favorable noisecharacteristics of current designs. Newhigh-temperature shape memory alloy(HTSMA) materials technology enablesthe devices to operate in both low-tem-perature (fan) and high-temperature(core) exhaust flows. Chevron-equippedengines have demonstrated reducednoise in testing and operational use. It isdesirable to have the noise benefits ofchevrons in takeoff/landing conditions,but have them deployed into a mini-

mum drag position for cruise flight.The central feature of the innovation

was building on rapidly maturingHTSMA technology to implement anext-generation aircraft noise mitiga-tion system centered on adaptivechevron flow control surfaces. In gen-eral, SMA-actuated devices have the po-tential to enhance the demonstratednoise reduction effectiveness of chevronsystems while eliminating the associatedperformance penalty. The use of struc-turally integrated smart devices willminimize the mechanical and subsys-tem complexity of this implementation.

The central innovations of the effortentail the modification of prior chevrondesigns to include a small cut that re-laxes structural stiffness without com-promising the desired flow characteris-tics over the surface; the reorientationof SMA actuation devices to apply forcesto deflect the chevron tip, exploitingthis relaxed stiffness; and the use ofhigh-temperature SMA (HTSMA) mate-rials to enable operation in the de-

manding core chevron environment.The overall conclusion of these de-

sign studies was that the cut chevronconcept is a critical enabling step inbringing the variable geometry corechevron within reach. The presence ofthe cut may be aerodynamically undesir-able in some respects, but it is presentonly when the chevron is not immersedin the core jet exhaust. When deployed,the gap closes as the chevron tip entersthe high-speed, high-temperature corestream. Aeroacoustic testing and flow vi-sualization support the contention thatthis cut is inconsequential to chevronperformance.

This work was done by Todd R. Quacken-bush and Robert M. McKillip, Jr., of Contin-uum Dynamics, Inc. for Glenn Research Cen-ter.

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-18416-1

High-Temperature Smart Structures for Engine NoiseReduction and Performance EnhancementThe most direct beneficiary of this hardware would be next-generation subsonic transports.John H. Glenn Research Center, Cleveland, Ohio


A compact and lightweight mecha-nism has been developed to accuratelymove a Fourier transform spectrometer(FTS) scan mirror (a cube corner) in anear-linear fashion with near constantspeed at cryogenic temperatures. Thisinnovation includes a slide mechanismto restrict motion to one dimension, anactuator to drive the motion, and a lin-ear velocity transducer (LVT) to meas-ure the speed. The cube corner mirror isdouble-passed in one arm of the FTS;double-passing is required to compen-sate for optical beam shear resultingfrom tilting of the moving cube corner.

The slide, actuator, and LVT are off-the-shelf components that are capable

of cryogenic vacuum operation. Theactuator drives the slide for the re-quired travel of 2.5 cm. The LVTmeasures translation speed. A propor-tional feedback loop compares theLVT voltage with the set voltage(speed) to derive an error signal todrive the actuator and achieve nearconstant speed. When the end of thescan is reached, a personal computerreverses the set voltage.

The actuator and LVT have no mov-ing parts in contact, and have magneticproperties consistent with cryogenic op-eration. The unlubricated slide restrictsmotion to linear travel, using crossedroller bearings consistent with 100-mil-

lion-stroke operation. The mechanismtilts several arc seconds during trans-port of the FTS mirror, which wouldcompromise optical fringe efficiencywhen using a flat mirror. Consequently,a cube corner mirror is used, which con-verts a tilt into a shear. The shearedbeam strikes (at normal incidence) aflat mirror at the end of the FTS armwith the moving mechanism, thereby re-turning upon itself and compensatingfor the shear.

This work was done by John C. Brasunasand John J. Francis of Goddard Space FlightCenter. For further information, contact theGoddard Innovative Partnerships Office at(301) 286-5810. GSC-15556-1

Cryogenic Scan Mechanism for Fourier Transform SpectrometerThis mechanism would be applicable to FTS use in forensic, scientific, medical, and defense industries.Goddard Space Flight Center, Greenbelt, Maryland

A custom rotary SQUIGGLE® motorhas been developed that sets new bench-marks for small motor size, high posi-tion resolution, and high torque withoutgear reduction. Its capabilities cannot beachieved with conventional electromag-netic motors. It consists of piezoelectricplates mounted on a square flexibletube. The plates are actuated via voltagewaveforms 90° out of phase at the reso-

nant frequency of the device to createrotary motion.

The motors were incorporated into atwo-axis postioner that was designed forfiber-fed spectroscopy for ground-basedand space-based projects. The positionerenables large-scale celestial object surveysto take place in a practical amount of time.

This work was done by Charles D. Fisher,Mircea Badescu, and David F. Braun of Cal-

tech and Rob Culhane of New Scale Technolo-gies for NASA’s Jet Propulsion Laboratory.For more information about the motor and thepositioner, visit the following sites:http://www.newscaletech.com/custom_overview.html#rotaryhttp://www.newscaletech.com/app_notes/7Cobra-JPL-article.html

NPO-46992

Piezoelectric Rotary Tube Motor NASA’s Jet Propulsion Laboratory, Pasadena, California


Green Design

The High Altitude Air-ship (HAA) has various ap-plication potential and mis-sion scenarios that requireonboard energy harvestingand power distribution sys-tems. The power technol-ogy for HAA maneuverabil-ity and mission-orientedapplications must comefrom its surroundings, e.g.solar power. The energyharvesting system consid-ered for HAA is based onthe advanced thermoelec-tric (ATE) materials beingdeveloped at NASA LangleyResearch Center. The mate-rials selected for ATE are sil-icon germanium (SiGe)and bismuth telluride(Bi2Te3), in multiple layers.The layered structure of theadvanced TE materials is specifically engi-neered to provide maximum efficiencyfor the corresponding range of opera-tional temperatures. For three layers ofthe advanced TE materials that operate athigh, medium, and low temperatures,correspondingly in a tandem mode, thecascaded efficiency is estimated to begreater than 60 percent.

The first layer is built from the arrayof SiGe, while the second and third lay-ers are respectively built from PbTe and

Bi2Te3 as regenerative cycles. Such anarrangement allows effective energy har-vesting from a heat source. First, solarflux is concentrated and heats up thefirst layer, which is built with high-tem-perature SiGe. The unused thermal en-ergy from the first layer is subsequentlyused by the second layer, which is builtwith mid-temperature PbTe. The thirdlayer of Bi2Te3 uses the unused energyfrom the second layer to maximize theconversion of the energy that is other-

wise dumped away. In thisfashion, the ATE devicesbecome more effectivethan solar cells because theperformance of solar cellsis monolithically tied toband-gap energy structure,so that they only couplewith certain spectral lines.

For nighttime, thepower required must beaugmented from the on-board fuel cells, battery,and a rectenna array that isattached at the bottom sur-face of HAA. These systemscombined provide at least amegawatt level of power forthe intermittent operation.

Commercial applicationsinclude monitoring andcontrolling the ever-increas-ing complexities of aerial

and maritime transportation and telecom-munication networks. Military applicationsinclude close and persistent surveillance ofadversarial elements, possibly controllingenemy infiltrations through open air andsea and shooting down enemy missiles dur-ing their boosting phase.

This work was done by Sang H. Choi, JamesR. Elliott, Glen C. King, Yeonjoon Park, Jae-WooKim, and Sang-Hyon Chu of Langley ResearchCenter. Further information is contained in aTSP (see page 1). LAR-17213-1

Thermoelectric Energy Conversion Technology for High-Altitude AirshipsApplications include surveillance for homeland security, and Earth observation for weather monitoring.Langley Research Center, Hampton, Virginia

The ATE Energy Conversion Device consists of triple layers of p-n-junction arrays ina tandem mode. The first layer is built from the array of SiGe, while the second andthird layers are built from PbTe and Bi2Te3, respectively, as regenerative cycles. Suchan arrangement allows effective energy harvesting from a heat source.

Bi2Te3 Layer

PbTe Layer

SiGe Layer

Concentrated Solar Energy

RemovedHeat

OutputPower

Knowing the pure component Cp0 or

mixture Cp0 as computed by a flexible code

such as NIST-STRAPP or McBride-Gor-don, one can, within reasonable accuracy,determine the thermophysical properties

necessary to predict the combustion char-acteristics when there are no tabulated orcomputed data for those fluid mixtures3or limited results for lower temperatures.(Note: Cp

0 is molar heat capacity at con-

stant pressure.) The method can be usedin the determination of synthetic and bio-logical fuels and blends using the NISTcode to compute the Cp

0 of the mixture.In this work, the values of the heat ca-

Combustor Computations for CO2-Neutral AviationThis method can be used to determine synthetic and biological fuels and blends.John H. Glenn Research Center, Cleveland, Ohio


pacity were set at “zero” pressure, whichprovided the basis for integration to de-termine the required combustor prop-erties from the injector to the combus-tor exit plane. The McBride-Gordoncode was used to determine the heat ca-pacity at zero pressure over a widerange of temperatures (room to 6,000K). The selected fluids were Jet-A,224TMP (octane), and C12. It wasfound that each heat capacity loci wereform-similar. It was then determinedthat the results [near 400 to 3,000 K]could be represented to within accept-able engineering accuracy with the sim-plified equation Cp

0 = A/T + B, where Aand B are fluid-dependent constantsand T is temperature (K).

With this information, a model for JP8was established using NIST Code STRAPPwith a 12-component mixture. Selectedpure components such as C12 and224TMP have representations in both the

McBride-Gordon and NIST codes, andwere calculated and compared. A 12-com-ponent mixture was defined for JP8 and Cp

0

computed using the NIST code to 1,000 K.The simplified representation of the Cp

0 forJP8 was form-similar to Jet-A, C12, and224TMP over the range of 400 to 3,000 K.This defined the ability to predict the Cp

0

for a variety of hydrocarbon mixtures usingthe NIST code to 1,000 K, and representingthese data by the simplified Cp

0, which canthen be extrapolated to 3,000 K within rea-sonable engineering accuracy. KnowingCp

0(T) results for enthalpy, entropy, andfree energy can be determined and inputinto the combustion code.

The simplified form of the gas phasecaloric equations generated using theNIST STRAPP code, the NASA McBridecode, and a systematic curve-fittingmethodology, work well within an estab-lished computational fluid dynamics(CFD) flow solver. Computed flow struc-

ture for the four fuels, using a trappedvortex combustor experimental rig as atest case, show strong similarities. This istrue for the temperature as well as theCO and CO2 mass fraction contours. In-spection of the mass-averaged combustorexit quantities, however, indicates thattemperature differences may be suffi-cient to require reconsideration of tur-bine fueling schemes.

This work was done by Robert C. Hen-dricks of Glenn Research Center; AndrejaBrankovic and Robert C. Ryder of FlowParametrics; and Marcia Huber of the Na-tional Institute of Standards and Technol-ogy. Further information is contained in aTSP (see page 1).

Inquiries concerning rights for the commer-cial use of this invention should be addressedto NASA Glenn Research Center, InnovativePartnerships Office, Attn: Steve Fedor, MailStop 4–8, 21000 Brookpark Road, Cleve-land, Ohio 44135. Refer to LEW-18453-1.


Physical Sciences

The use of the mercury ion isotope201Hg+ was examined for an atomicclock. Taking advantage of the fasteroptical pumping time in 201Hg+ reducesboth the state preparation and the statereadout times, thereby decreasing theoverall cycle time of the clock and re-ducing the impact of medium-term LOnoise on the performance of the fre-quency standard. The spectral overlapbetween the plasma discharge lampused for 201Hg+ state preparation andreadout is much larger than that of thelamp used for the more conventional199Hg+. There has been little study of201Hg+ for clock applications (in fact,

all trapped ion clock work in mercuryhas been with 199Hg+); however, re-cently the optical pumping time in201Hg+ has been measured and foundto be 0.45 second, or about three timesfaster than in 199Hg+ due largely to thebetter spectral overlap. This can beused to reduce the overall clock cycletime by over 2 seconds, or up to a factorof 2 improvement.

The use of the 201Hg+ for an atomicclock is totally new. Most attempts to re-duce the impact of LO noise have fo-cused on reducing the interrogationtime. In the trapped ion frequency stan-dards built so far at JPL, the optical

pumping time is already at its minimumso that no enhancement can be had byshortening it. However, by using 201Hg+,this is no longer the case. Furthermore,integrity monitoring, the mechanismthat determines whether the clock isfunctioning normally, cannot happenfaster than the clock cycle time. There-fore, a shorter cycle time will enablequicker detection of failure modes andrecovery from them.

This work was done by Eric A. Burt, RobertL. Tjoelker, and Shervin Taghavi of Caltechfor NASA’s Jet Propulsion Laboratory. For moreinformation, contact [email protected]

Cycle Time Reduction in Trapped Mercury Ion AtomicFrequency Standards NASA’s Jet Propulsion Laboratory, Pasadena, California

This research has developed and eval-uated the specific concepts, termed“Smart-Cue” and “Smart-Gain,” to allevi-ate aircraft loss of control that resultsfrom unfavorable pilot/vehicle systeminteractions, including pilot-induced os-cillations (PIOs). Unfavorable pilot/vehicle-system interactions have longbeen an aviation safety problem. Whilethe effective aircraft dynamic propertiesinvolved in these events have been exten-sively studied and understood, similarscrutiny has not been paid to the manyaspects of the primary manual controlsystem that converts the pilot control in-puts to motions of the control surfaces.The purpose of the Smart-Cue andSmart-Gain developments is to redressthis neglect, and to develop and validateremedial manual control systems.

The program began with a review ofthe historical precedent for providingcueing to the pilot via the cockpit con-trols along with the many control sur-face rate-limiting alleviation schemesand PIO suppression filter concepts thathave been proposed and evaluated overthe years. A McFadden hydraulic control

loader capable of generating proposedSmart-Cue forces was integrated with theSTI PC-based flight simulator. Candidatemechanizations of the Smart-Cue con-cept were created, implemented, as-sessed, and refined through a series ofevaluations using guest test pilots. TheSmart-Gain concept was developed in re-sponse to the Smart-Cue performanceduring the precision offset landings con-ducted during the checkout flights.Rapid prototyping of the Smart-Gainmechanization was made via the pilotedsimulation, and the concept was in-cluded as part of the formal flight testevaluations. Five test pilots participatedin the Smart-Cue/Smart-Gain evalua-tions with the Learjet in-flight simulator.

In this work, the “distortion” of inter-est results from control surface rate-lim-iting, and is quantified by the surface Po-sition Error, while the “distortionmetric” is the Position Lag. A force feed-back cue, the constraining function,and/or a command path gain reduc-tion, are created when the PositionError exceeds the Position Lag, or thealerting function. The overall imple-

mentation does, however, require hard-ware in the form of a back-driven force-feel system included as part of the cock-pit manipulator. The feasibility of theSmart-Cue/Smart-Gain approach usinga back-driven manipulator implementedin a variable stability aircraft was success-fully demonstrated in flight.

The hypothesis stated that the Smart-Cue will change pilot behavior to de-crease the chance of adverse pilot/vehi-cle system interactions. Thus, if thisassumption about the pilot-vehicle sys-tem was found to be true, then a de-graded flight-control system in the pres-ence of dynamic distortions will haveimproved stability and performance.This hypothesis was found to be true inflight-testing evaluations that replicatedhigh-gain, continuous closed-loop tasksfor both cruise and terminal flight oper-ations, especially for those cases that in-cluded the addition of the Smart-Gain.

This work was done by David Klyde, Chi-Ying Liang, and Daniel Alvarez of SystemsTechnology, Inc. for Dryden Flight ResearchCenter. Further information is contained in aTSP (see page 1). DRC-007-083

Use of Dynamic Distortion to Predict and Alleviate Loss of ControlThis work alleviates aircraft loss due to unfavorable pilot/vehicle interactions.Dryden Flight Research Center, Edwards, California


A method has been developed for un-ambiguously measuring the exact mag-netic field experienced by trapped mer-cury ions contained within an atomicclock intended for space applications. Ingeneral, atomic clocks are insensitive toexternal perturbations that wouldchange the frequency at which theclocks operate. On a space platform,these perturbative effects can be muchlarger than they would be on theground, especially in dealing with themagnetic field environment. The solu-tion is to use a different isotope of mer-cury held within the same trap as theclock isotope. The magnetic field can bevery accurately measured with a mag-netic-field-sensitive atomic transition in

the added isotope. Further, this meas-urement can be made simultaneouslywith normal clock operation, therebynot degrading clock performance.

Instead of using a conventional mag-netometer to measure ambient fields,which would necessarily be placed somedistance away from the clock atoms, first-order field-sensitive atomic transitionfrequency changes in the atoms them-selves determine the variations in themagnetic field. As a result, all ambiguityover the exact field value experienced bythe atoms is removed. Atoms used inatomic clocks always have an atomictransition (often referred to as the“clock transition”) that is sensitive tomagnetic fields only in second order,

and usually have one or more transitionsthat are first-order field sensitive. For op-erating parameters used in the 199Hg+

clock, the latter can be five orders ofmagnitude or more sensitive to fieldfluctuations than the clock transition,thereby providing an unambiguousprobe of the magnetic field strength.

This work was done by Eric A. Burt, ShervinTaghavi, and Robert L. Tjoelker of Caltech forNASA’s Jet Propulsion Laboratory. For more in-formation, contact [email protected].

This invention is owned by NASA, and apatent application has been filed. Inquiriesconcerning nonexclusive or exclusive licensefor its commercial development should be ad-dressed to the Patent Counsel, NASA Man-agement Office–JPL. Refer to NPO-46938.

A201Hg+ Comagnetometer for 199Hg+ Trapped Ion SpaceAtomic ClocksNASA’s Jet Propulsion Laboratory, Pasadena, California

National Aeronautics andSpace Administration

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