technology focus electronics/computers · elements used to define the polarization sensitivity of...

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Electronics/Computers

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Materials

Mechanics/Machinery

Manufacturing

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Physical Sciences

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Books and Reports

12-13 December 2013

https://ntrs.nasa.gov/search.jsp?R=20130014512 2020-03-13T21:30:49+00:00Z

NASA Tech Briefs, December 2013 1

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

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

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

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

Ames Research CenterDavid Morse(650) [email protected]

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

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

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

Jet Propulsion LaboratoryDan Broderick(818) [email protected]

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

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

Langley Research CenterMichelle Ferebee(757) [email protected]

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

Stennis Space CenterRamona Travis(228) [email protected]

NASA Headquarters

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

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

NASA Field Centers and Program Offices

5 Technology Focus: Electronic Components

5 Microwave Kinetic Inductance Detector WithSelective Polarization Coupling

5 Flexible Microstrip Circuits for Superconducting Electronics

7 Software7 CFD Extraction Tool for TecPlot From DPLR Solutions7 RECOVIR Software for Identifying Viruses7 Enhanced Contact Graph Routing (ECGR)

MACHETE Simulation Model7 Orbital Debris Engineering Model (ORDEM) v.38 Scatter-Reducing Sounding Filtration Using a Genetic

Algorithm and Mean Monthly Standard Deviation

9 Manufacturing & Prototyping9 Thermo-Mechanical Methodology for Stabilizing

Shape Memory Alloy Response9 Hermetic Seal Designs for Sample Return

Sample Tubes10 Silicon Alignment Pins: An Easy Way To Realize

a Wafer-to-Wafer Alignment

13 Mechanics/Machinery13 Positive-Buoyancy Rover for Under Ice Mobility13 Electric Machine With Boosted Inductance to Stabilize

Current Control14 International Space Station-Based Electromagnetic

Launcher for Space Science Payloads

15 Books & Reports15 Advanced Hybrid Spacesuit Concept Featuring

Integrated Open Loop and Closed Loop Ventilation Systems

15 Data Quality Screening Service


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.

12-13 December 2013


Technology Focus: Electronic Components

Flexible Microstrip Circuits for Superconducting Electronics Improved wiring geometry should further reduce the size of the wiring while also reducing thecrosstalk among wire pairs. Goddard Space Flight Center, Greenbelt, Maryland

Flexible circuits with superconductingwiring atop polyimide thin films arebeing studied to connect large numbersof wires between stages in cryogenic ap-paratus with low heat load. The feasibil-ity of a full microstrip process, consistingof two layers of superconducting mate-rial separated by a thin dielectric layer on5 mil (≈0.13 mm) Kapton sheets, wheremanageable residual stress remains inthe polyimide film after processing, hasbeen demonstrated. The goal is a 2-mil(≈0.051-mm) process using spin-on poly-imide to take advantage of the smootherpolyimide surface for achieving high-quality metal films. Integration of mi-crostrip wiring with this polyimide film

may require high-temperature bakes torelax the stress in the polyimide film be-tween metallization steps. Focal planes of cryogenic detectors

typically have detectors at the lowesttemperature stage with bias and readoutlocated at higher temperature stages toreduce the cooling power requirementon the refrigerator stage that achievesthe base temperature for the detectors.Large numbers of wires between cryo-genic stages are often necessary andneed to be designed to maintain a man-ageable heat load to each stage. A mi-crostripline wiring configuration is alsodesired to suppress thermal crosstalkinto the detectors due to amplifier

switching and bias changes. With thesize of focal planes increasing into therange of thousands of biased elements,and a further need for compactness ofthe focal plane architecture, a technol-ogy is needed that can accommodatethousands of superconducting wires be-tween cryogenic components. Flexible niobium wiring has been

demonstrated on Kapton pieces wherethe impedance of the line was set by thedistance between the Nb wires and thedielectric properties of the Kapton. Thiswork proposes to fabricate microstripNb wiring consisting of a narrow Nbtrace atop a wider trace separated by athin dielectric layer. This wiring geome-

A conventional low-noise detector re-quires a technique to both absorb inci-dent power and convert it to an electricalsignal at cryogenic temperatures. This in-novation combines low-noise detectorand readout functionality into one de-vice while maintaining high absorption,controlled polarization sensitivity, andbroadband detection capability. The re-sulting far-infrared detectors can be readout with a simple approach, which iscompact and minimizes thermal loading.The proposed microwave kinetic in-

ductance detector (MKID) consists ofthree basic elements. The first is the ab-sorptive section in which the incidentpower is coupled to a superconductingresonator at far-infrared frequencyabove its superconducting critical fre-quency (where superconductor be-comes normal conductor). This ab-sorber’s shape effectively absorbs signalsin the desired polarization state and isresonant at the radio frequency (RF)

used for readout of the device. Controlover the metal film used in the absorberallows realization of structures with ei-ther a 50% broadband or 100% reso-nance absorptance over a 30% frac-tional bandwidth. The second element is a microwave

resonator — which is realized from thethin metal films used to make the ab-sorber as transmission lines — whose res-onance frequency changes due to a vari-ation in its kinetic inductance. Theresonator’s kinetic inductance is a func-tion of the power absorbed by the device.A low-loss dielectric (mono-crystalline sil-icon) is used in a parallel-plate transmis-sion line structure to realize the desiredsuperconducting resonators. There isnegligible coupling among the adjacentelements used to define the polarizationsensitivity of each detector. The finalcomponent of the device is a microwavetransmission line, which is coupled to theresonator, and allows detection of

changes in resonance frequency for eachdetector in the focal plane array.The spiral shape of the detector’s ab-

sorber allows incident power with twopolarizations to couple to the detectorequally. A stepped impedance resonatorwas used that allows the incident powerabsorbed in the detecting membranearea to be uniformly distributed in thedetector’s transmission line at the RFreadout frequency. This maximizes thesensitivity of the detector. The signal isread out via a frequency multiplexingtechnique that requires a minimumnumber of interface transmission linesfor readout. This reduces the packagingcomplexity and coupling to the device’sthermal environment. This work was done by Edward Wollack,

Kongpop U-yen, Thomas Stevenson, Ari Brown,Samuel Moseley, and Wen-Ting Hsieh of God-dard Space Flight Center. Further informationis contained in a TSP (see page 1). GSC-16342-1

Microwave Kinetic Inductance Detector With SelectivePolarization CouplingLow-noise detector and readout functionality are combined into one device.Goddard Space Flight Center, Greenbelt, Maryland

6 NASA Tech Briefs, December 2013

try, in comparison to the coplanar de-signs, should further reduce the size ofthe wiring while also reducing thecrosstalk among wire pairs. Further, theuse of a thin polyimide layer will enablelower heat loads between stages for asimilar length of flexible wiring. It was shown that 5-mil (≈0.13-mm)

sheets could be readily mountedsmoothly onto the substrate. The sub-strates were taken through all processsteps, including Nb deposition and etch,

oxide deposition, and aluminum deposi-tion and etch. In all cases, the heat-re-lease tape held the Kapton onto the sub-strate, indicating that the processescould be run serially to complete a fullmicrostrip process. A Kapton film with apatterned Nb layer on it was released,and showed that the film was supercon-ducting at a temperature close to the ex-pected critical temperature of Nb. Poly-imide layers that were free of roughnessand pitting were generated through a

spin-on process that used successivespins and bakes, with gradual heat lipand cooldown cycles, to build up thefilm to a full thickness of 2 mils (»0.051mm). The full thickness film is baked atelevated temperatures to relieve residualstress in the film. This work was done by James Chervenak of

Goddard Space Flight Center, and JennetteMateo of SB Microsystems. Further informa-tion is contained in a TSP (see page 1).GSC-16718-1


CFD Extraction Tool for TecPlot From DPLR Solutions

This invention is a TecPlot macro of acomputer program in the TecPlot pro-gramming language that processes datafrom DPLR solutions in TecPlot format.DPLR (Data-Parallel Line Relaxation) isa NASA computational fluid dynamics(CFD) code, and TecPlot is a commer-cial CFD post-processing tool. The Tec-Plot data is in SI units (same as DPLRoutput). The invention converts the SIunits into British units. The macro mod-ifies the TecPlot data with unit conver-sions, and adds some extra calculations.After unit conversions, the macro cuts aslice, and adds vectors on the currentplot for output format. The macro canalso process surface solutions.Existing solutions use manual conver-

sion and superposition. The conversionis complicated because it must be ap-plied to a range of inter-related scalarsand vectors to describe a 2D or 3D flowfield. It processes the CFD solution tocreate superposition/comparison ofscalars and vectors.The existing manual solution is cum-

bersome, open to errors, slow, and can-not be inserted into an automatedprocess. This invention is quick and easyto use, and can be inserted into an auto-mated data-processing algorithm.This work was done by David Norman, Jr.

of The Boeing Company for Johnson SpaceCenter. For further information, contact theJSC Innovation Partnerships Office at (281)483-3809. MSC-24982-1

RECOVIR Software forIdentifying Viruses

Most single-stranded RNA (ssRNA)viruses mutate rapidly to generate a largenumber of strains with highly divergentcapsid sequences. Determining the capsidresidues or nucleotides that uniquelycharacterize these strains is critical in un-derstanding the strain diversity of theseviruses. RECOVIR (an acronym for “rec-ognize viruses”) software predicts thestrains of some ssRNA viruses from theirlimited sequence data. Novel phyloge-netic-tree-based databases of protein ornucleic acid residues that uniquely char-acterize these virus strains are created.Strains of input virus sequences (partial or

complete) are predicted through residue-wise comparisons with the databases.RECOVIR uses unique characterizing

residues to identify automatically strainsof partial or complete capsid sequencesof picorna and caliciviruses, two of themost highly diverse ssRNA virus families.Partition-wise comparisons of the data-base residues with the correspondingresidues of more than 300 complete andpartial sequences of these viruses re-sulted in correct strain identification forall of these sequences.This study shows the feasibility of cre-

ating databases of hitherto unknownresidues uniquely characterizing thecapsid sequences of two of the mosthighly divergent ssRNA virus families.These databases enable automatedstrain identification from partial or com-plete capsid sequences of these humanand animal pathogens.This work was done by Sugoto Chakravarty,

George E. Fox, and Dianhui Zhu of the Uni-versity of Houston for Johnson Space Center.For further information, contact the JSC Inno-vation Partnerships Office at (281) 483-3809. MSC-24358-1

Enhanced Contact Graph Routing (ECGR) MACHETE SimulationModel

Contact Graph Routing (CGR) forDelay/Disruption Tolerant Networking(DTN) space-based networks makes useof the predictable nature of node con-tacts to make real-time routing decisionsgiven unpredictable traffic patterns. Thecontact graph will have been dissemi-nated to all nodes before the start ofroute computation. CGR was designedfor space-based networking environ-ments where future contact plans areknown or are independently com-putable (e.g., using known orbital dy-namics). For each data item (known as abundle in DTN), a node independentlyperforms route selection by examiningpossible paths to the destination. Routecomputation could conceivably runthousands of times a second, so compu-tational load is important.This work refers to the simulation soft-

ware model of Enhanced Contact GraphRouting (ECGR) for DTN Bundle Proto-col in JPL’s MACHETE simulation tool.The simulation model was used for per-

formance analysis of CGR and led to sev-eral performance enhancements. Thesimulation model was used to demon-strate the improvements of ECGR overCGR as well as other routing methods inspace network scenarios. ECGR movedto using earliest arrival time because it isa global monotonically increasing metricthat guarantees the safety propertiesneeded for the solution’s correctnesssince route re-computation occurs ateach node to accommodate unpredictedchanges (e.g., traffic pattern, link qual-ity). Furthermore, using earliest arrivaltime enabled the use of the standardDijkstra algorithm for path selection.The Dijkstra algorithm for path selectionhas a well-known inexpensive computa-tional cost. These enhancements havebeen integrated into the open sourceCGR implementation. The ECGR modelis also useful for route metric experimen-tation and comparisons with other DTNrouting protocols particularly when com-bined with MACHETE’s space network-ing models and Delay Tolerant LinkState Routing (DTLSR) model.This work was done by John S. Segui, Es-

ther H. Jennings, and Loren P. Clare of Cal-tech for NASA’s Jet Propulsion Laboratory.Further information is contained in a TSP(see page 1).The software used in this innovation is avail-

able for commercial licensing. Please contact DanBroderick at [email protected] to NPO-47650.

Orbital Debris EngineeringModel (ORDEM) v.3

A model of the manmade orbital de-bris environment is required by space-craft designers, mission planners, andothers in order to understand and miti-gate the effects of the environment ontheir spacecraft or systems. A manmadeenvironment is dynamic, and can be al-tered significantly by intent (e.g., theChinese anti-satellite weapon test of Jan-uary 2007) or accident (e.g., the colli-sion of Iridium 33 and Cosmos 2251spacecraft in February 2009).Engineering models are used to por-

tray the manmade debris environment inEarth orbit. The availability of new sen-sor and in situ data, the re-analysis ofolder data, and the development of newanalytical and statistical techniques hasenabled the construction of this more

Software


comprehensive and sophisticated model.The primary output of this model is theflux [#debris/area/time] as a functionof debris size and year. ORDEM may beoperated in spacecraft mode or tele-scope mode. In the former case, an ana-lyst defines an orbit for a spacecraft and“flies” the spacecraft through the orbitaldebris environment. In the latter case, ananalyst defines a ground-based sensor(telescope or radar) in terms of latitude,azimuth, and elevation, and the modelprovides the number of orbital debristraversing the sensor’s field of view.An upgraded graphical user interface

(GUI) is integrated with the software.This upgraded GUI uses project-orientedorganization and provides the user withgraphical representations of numerousoutput data products. These range fromthe conventional flux as a function of de-bris size for chosen analysis orbits (orviews), for example, to the more com-plex color-contoured two-dimensional(2D) directional flux diagrams in localspacecraft elevation and azimuth.This work was done by Mark Matney of

Johnson Space Center; Paula Krisko and Yu-

Lin Xu of Jacobs Technology; and MatthewHorstman of ERC. Further information iscontained in a TSP (see page 1). MSC-25457-1

Scatter-Reducing SoundingFiltration Using a GeneticAlgorithm and MeanMonthly Standard Deviation

Retrieval algorithms like that used bythe Orbiting Carbon Observatory(OCO)-2 mission generate massivequantities of data of varying quality andreliability. A computationally efficient,simple method of labeling problematicdatapoints or predicting soundings thatwill fail is required for basic operation,given that only �6% of the retrieved datamay be operationally processed. Thismethod automatically obtains a filter de-signed to reduce scatter based on a smallnumber of input features.Most machine-learning filter construc-

tion algorithms attempt to predict error inthe CO2 value. By using a surrogate goal ofMean Monthly STDEV, the goal is to re-duce the retrieved CO2 scatter rather than

solving the harder problem of reducingCO2 error. This lends itself to improved in-terpretability and performance.This software reduces the scatter of re-

trieved CO2 values globally based on aminimum number of input features. Itcan be used as a prefilter to reduce thenumber of soundings requested, or as apost-filter to label data quality. The useof the MMS (Mean Monthly Standarddeviation) provides a much cleaner,clearer filter than the standardABS(CO2-truth) metrics previously em-ployed by competitor methods.The software’s main strength lies in a

clearer (i.e., fewer features required) fil-ter that more efficiently reduces scatterin retrieved CO2 rather than focusing onthe more complex (and easily removed)bias issues.This work was done by Lukas Mandrake of

Caltech for NASA’s Jet Propulsion Laboratory.Further information is contained in a TSP(see page 1).This software is available for commercial li-

censing. Please contact Dan Broderick [email protected]. Refer toNPO-48255.


Manufacturing & Prototyping

Hermetic Seal Designs for Sample Return Sample TubesPrototype sample tube seals prevent material loss and maintain sample integrity. NASA’s Jet Propulsion Laboratory, Pasadena, California

Prototypes have been developed ofpotential hermetic sample sealing tech-niques for encapsulating samples in a≈1-cm-diameter thin-walled sampletube that are compatible with IMSAH(Integrated Mars Sample Acquisitionand Handling) architecture. Techniquesinclude a heat-activated, finned, shapememory alloy plug; a contracting shape

memory alloy activated cap; an expand-ing shape memory alloy plug; and an ex-panding torque plug.Initial helium leak testing of the shape

memory alloy cap and finned shapememory alloy plug seals showed her-metic-seal capability compared againstan industry standard of <1×10–8 atm-cc/sHe. These tests were run on both clean

tubes and dirty tubes dipped in MMS(Mojave Mars Simulant). The leak testswere also performed after thermal cy-cling between –135 and +55 ºC to ensureseal integrity after Martian diurnal cy-cles. Developmental testing is currentlybeing done on the expanding torqueplug, and expanding shape memoryalloy plug seal designs.

This innovation is capable of signifi-cantly reducing the amount of time re-quired to stabilize the strain-tempera-ture response of a shape memory alloy(SMA). Unlike traditional stabilizationprocesses that take days to weeks toachieve stabilized response, this innova-tion accomplishes stabilization in a mat-ter of minutes, thus making it highly use-ful for the successful and practicalimplementation of SMA-based technolo-gies in real-world applications. The in-novation can also be applied to complexgeometry components, not just simplegeometries like wires or rods.SMAs are being developed for use as

actuators, switches, and other devices inaerospace, automotive, and many otherindustries. An important aspect of devel-oping a useful SMA technology is theability to achieve a stabilized material re-sponse. Most SMAs exhibit dimensionalinstability when thermally cycled in thepresence of applied stress. In order tomitigate the need for the design to dealwith such issues, “training” or stabiliza-tion of the materials response must beachieved prior to utilizing the materialunder service conditions.The process of stabilizing an SMA for

actuator response is generally thoughtof as a stabilization of the strain duringthermal cycling under conditions of

fixed stress (the so-called isobaric re-sponse). Although this formulation isentirely appropriate, the underlying rea-son for the strain stabilization is gov-erned by the internal states that thecombination of stress and temperatureproduce (in this case, one of the driversbeing transient and one being fixed).Hence, any combination of stress andtemperature that would produce thesame strain state could also stabilize thematerial for the intended service condi-tion. In general, thermal cycling underfixed stress is commonly used to achievestabilized behavior, but this process isnot only time-consuming but costly.The current innovation replaces this

process with an alternate method utiliz-ing mechanical cycles under conditionsof fixed temperature (the so-calledisothermal response), since mechanicalcycling takes far less time than thermal cy-cling. The current innovation describes aprocess for determining this link, fol-lowed by achieving stabilization by arapid and efficient mechanical cyclingtreatment. To begin, the stabilizationpoint for the material (the absolute strainlevels achieved after stabilization) is es-tablished by performing an isobaric ex-periment under conditions identical tothose that will be used during service.Once known, a set of isothermal mechan-

ical cycling experiments is performedusing different levels of applied stress.Each of these mechanical cycling experi-ments is left to run until the strain re-sponse has stabilized. Once the stress lev-els required to achieve stabilizationunder isothermal conditions are known,they can be utilized to train the materialin a fraction of the time that would be re-quired to train the material isobarically.Once the strain state is achieved isother-mally, the material can be switched backunder isobaric conditions, and will re-main stabilized for the service conditions.The advantage of approaching the

problem via this technique is that it isnow possible to reduce the amount oftime required to achieve a stabilized ma-terial response from days to weeks, downto a matter of minutes. The significantreduction in time translates into a morecost-effective solution for SMA-basedtechnologies that in turn improves theviability of SMA device utilization.This work was done by Santo Padula of

Glenn Research Center. Further informationis contained in a TSP (see page 1).Inquiries concerning rights for the commer-

cial use of this invention should be addressed toNASA Glenn Research Center, InnovativePartnerships Office, Attn: Steven Fedor, MailStop 4–8, 21000 Brookpark Road, Cleveland,Ohio 44135. Refer to LEW-18594-1.

Thermo-Mechanical Methodology for Stabilizing ShapeMemory Alloy ResponseThis innovation is directly applicable to actuator applications employing shape memory alloys.John H. Glenn Research Center, Cleveland, Ohio


The finned shape memory alloy(SMA) plug currently shows hermeticsealing capability based on preliminarytests. The finned SMA plug sealingtechnique requires a heater to actuatethe plug. Materials have been selectedto comply with current sample compat-ibility, contamination control, andplanetary protection concerns. VariousNitinol SMA chemistries are currentlybeing investigated that allow the sealto start activating at temperatures aslow as 45 �ºC (if low-temperature seal-ing is required for sample integrity),and as high as 135 �ºC (if planetaryprotection dry heat microbial reduc-tion is required).The contracting shape memory alloy

cap requires a heater to actuate an SMAring that swages the toothed cap ontothe outside of the tube. The expandingSMA plug also requires a heater to actu-ate a ring that swages the toothed capinto the inside of the tube.The benefit to the expanding torque

plug is that no heat is required to createa seal. All that is needed is a rotating ac-tuator to actuate the plug.This work was done by Paulo J. Younse of

Caltech for NASA’s Jet Propulsion Laboratory.Further information is contained in a TSP(see page 1). NPO-48927

Contracting Shape Memory Alloy Cap

304 Stainless Steel Tube

Expanding Torque Plug


Torque

Expanding Shape Memory Alloy Plug


Finned Shape Memory Alloy Plug

Titanium Ti-5AI-2.5Sn Tube

Potential hermetic Sample Sealing Techniques include a contracting shape memory alloy cap, expand-ing torque plug, expanding shape memory alloy plug, and a finned shape memory alloy plug.

Silicon Alignment Pins: An Easy Way To Realize a Wafer-to-Wafer AlignmentEtched pockets and silicon pins are used to align two wafers together.NASA’s Jet Propulsion Laboratory, Pasadena, California

Submillimeter heterodyne instru-ments play a critical role in addressingfundamental questions regarding theevolution of galaxies as well as being acrucial tool in planetary science. Tomake these instruments compatible withsmall platforms, especially for the studyof the outer planets, or to enable the de-velopment of multi-pixel arrays, it is es-sential to reduce the mass, power, andvolume of the existing single-pixel het-erodyne receivers.Silicon micromachining technology

is naturally suited for making thesesubmillimeter and terahertz compo-nents, where precision and accuracyare essential. Waveguide and channelcavities are etched in a silicon bulk ma-terial using deep reactive ion etching(DRIE) techniques. Power amplifiers,multiplier and mixer chips are then in-

tegrated and the silicon pieces arestacked together to form a supercom-pact receiver front end. By using sili-con micromachined packages for thesecomponents, instrument mass can bereduced and higher levels of integra-tion can be achieved.A method is needed to assemble accu-

rately these silicon pieces together, and atechnique was developed here usingetched pockets and silicon pins to aligntwo wafers together. Each silicon piece ispatterned with the pockets on both sidesof the wafer, front and back, which arethen etched down to ≈130 �µm.Meanwhile, the silicon pins are

etched in a 200-µm thick wafer. By etch-ing a C-shaped pin, the pin can be com-pressed to fit into the alignment pocketby an appropriate choice of the pin wallthickness. When released, the pin ex-

pands to fill the pocket. A tight fit is en-sured by choosing the relaxed pin diam-eter to be greater than the pocket diam-eter. This approach reduces themisalignment tolerance to the posi-tional variation between the photolitho-graphically defined pockets, which istypically under 3 µm.During assembly, the silicon com-

pression pins are placed on the etchedpockets of the first wafer, and the waferto be aligned will find the right loca-tion using its own “back” etched pock-ets. The two wafers are thereforequickly and easily aligned. If morewafers need to be stacked, one canplace additional layers, each time usingthe pins and the etched pockets asalignment features.Using this method, one can align

several wafers, if needed, by only han-


dling and aligning two wafers at a time.Also, for accurate and tight align-ments, the tolerances can be chosendown to only 1 µm by using more accu-rate lithography.This work was done by Cecile Jung-Kubiak,

Theodore J. Reck, Robert H. Lin, AlejandroPeralta, John J. Gill, Choonsup Lee, JoseSiles, Risaku Toda, Goutam Chattopadhyay,

Ken B. Cooper, and Imran Mehdi of Caltech;and Bertrand Thomas of RPG RadiometerPhysics GmbH for NASA’s Jet Propulsion Lab-oratory. For more information, contact [email protected] 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 321-1234800 Oak Grove DrivePasadena, CA 91109-8099E-mail: [email protected] to NPO-48079/608, volume and

number of this NASA Tech Briefs issue, andthe page number.

A buoyant rover has been developedto traverse the underside of ice-coveredlakes and seas. The rover operates at theice/water interface and permits directobservation and measurement ofprocesses affecting freeze- over and thawevents in lake and marine environments.Operating along the 2- D ice-water inter-face simplifies many aspects of underwa-ter exploration, especially when com-pared to submersibles, which havedifficulty in station-keeping and preci-sion mobility. The buoyant rover consists of an all

aluminum body with two aluminum saw-tooth wheels. The two independent

body segments are sandwiched betweenfour actuators that permit isolation ofwheel movement from movement ofthe central tether spool. For normal op-erations, the wheels move while thetether spool feeds out line and the cam-eras on each segment maintain a user-controlled fixed position. Typically onecamera targets the ice/water interfaceand one camera looks down to the lakefloor to identify seep sources. Eachwheel can be operated independentlyfor precision turning and adjustments.The rover is controlled by a touch- �tabletinterface and wireless goggles enablereal- time viewing of video streamed

from the rover cameras. The buoyant rover was successfully de-

ployed and tested during an October2012 field campaign to investigatemethane trapped in ice in lakes alongthe North Slope of Alaska. This work was done by John M. Leichty, An-

drew T. Klesh, Daniel F. Berisford, Jaret B.Matthews, and Kevin P. Hand of Caltech forNASA’s Jet Propulsion Laboratory. Further in-formation is contained in a TSP (see page 1).NPO-48863


Mechanics/Machinery

Electric Machine With Boosted Inductance to Stabilize Current ControlLyndon B. Johnson Space Center, Houston, Texas

High-powered motors typically havevery low resistance and inductance (Rand L) in their windings. This makesthe pulse-width modulated (PWM)control of the current very difficult, es-pecially when the bus voltage (V) ishigh. These R and L values are dictatedby the motor size, torque (Kt), andback-emf (Kb) constants. These con-stants are in turn set by the voltage andthe actuation torque-speed require-ments. This problem is often addressedby placing inductive chokes within thecontroller. This approach is undesir-

able in that space is taken and heat isadded to the controller.By keeping the same motor frame, re-

ducing the wire size, and placing a cor-respondingly larger number of turns ineach slot, the resistance, inductance,torque constant, and back-emf constantare all increased. The increased induc-tance aids the current control but ruinsthe Kt and Kb selections. If, however, afraction of the turns is moved fromtheir “correct slot” to an “incorrectslot,” the increased R and L values areretained, but the Kt and Kb values are

restored to the desired values. This ap-proach assumes that increased resist-ance is acceptable to a degree. In effect,the heat allocated to the added induc-tance has been moved from the con-troller to the motor body, which insome cases is preferred.The slew-rate of the current is calcu-

lated as V/L and can easily be 250,000A/s. With a pulse width resolution of 10µs, for example, the current could slew2.5 A, which in some cases may exceedthe resolution needed for the currentcontrol loop. If L is increased, the prob-

Figure 1. The JPL Buoyant Under- Ice Rover shown on the ice (left) and crawling on the underside ofthe ice (right) during a 2012 field campaign in Alaska. For scale, the rover is 0.54 m wide.

Positive-Buoyancy Rover for Under Ice MobilityThis floating rover operates at the ice/water interface in lakes and seas. NASA’s Jet Propulsion Laboratory, Pasadena, California

Figure 2. Computer aided design (CAD) model ofthe JPL Buoyant Under Ice Rover showing thetwo independent chassis regions each withwheel, camera, and instrument capability. Thecentral tether spool can also operate independ-ent of the side chassis.


lem is proportionately improved. Con-sider a certain motor size and gear trainselection where the back-emf constanthas been selected to meet a requiredoutput speed. The correspond ing Ktand L, however, produce an uncontrol-lable current regulator. If the wire size isdecreased by three gauges, for example,and the slots arc filled with twice as manyturns (the slots will be full in this exam-

ple), then the R and L will increase by afactor of four, while the Kt and Kb will in-crease by a factor of two. If the slots areonly filled 67 percent in the correct fash-ion and the other 33 percent of thewindings are placed in incorrect slots,then the Kt and Kb are reduced to theiroriginal levels. The fourfold benefit of the induc-

tance increase assists the current con-

trol. The resistance increase will causemore heating since the current level isunchanged in this example. If this is aproblem, the motor thermal mass can beincreased as a solution.This work was done by Steve Abel of Hon-

eywell Aerospace for Johnson Space Center. Forfurther information, contact the JSC Innova-tion Partnerships Office at (281) 483-3809.MSC-24906-1

International Space Station-Based Electromagnetic Launcher forSpace Science PayloadsNASA’s Jet Propulsion Laboratory, Pasadena, California

A method was developed of loweringthe cost of planetary exploration mis-sions by using an electromagneticpropulsion/launcher, rather than achemical-fueled rocket for propulsion.An electromagnetic launcher (EML)based at the International Space Station(ISS) would be used to launch small sci-ence payloads to the Moon and nearEarth asteroids (NEAs) for the science

and exploration missions. An ISS-basedelectromagnetic launcher could also in-ject science payloads into orbits aroundthe Earth and perhaps to Mars.The EML would replace rocket tech-

nology for certain missions. The EML isa high-energy system that uses electricityrather than propellant to accelerate pay-loads to high velocities. The most com-mon type of EML is the rail gun. Other

types are possible, e.g., a coil gun, alsoknown as a Gauss gun or mass driver.The EML could also “drop” science pay-loads into the Earth’s upper atmospherefor science investigations.This work was done by Ross M. Jones of Cal-

tech for NASA’s Jet Propulsion Laboratory. Formore information, contact [email protected]


Books & Reports

Advanced Hybrid Spacesuit Concept Featuring Integrated Open Loop and ClosedLoop Ventilation Systems

A document discusses the design andprototype of an advanced spacesuit con-cept that integrates the capability to func-tion seamlessly with multiple ventilationsystem approaches. Traditionally, space-suits are designed to operate both depend-ently and independently of a host vehicleenvironment control and life support sys-tem (ECLSS). Spacesuits that operate in-dependent of vehicle-provided ECLSSservices must do so with equipment self-contained within or on the spacesuit. Suitsthat are dependent on vehicle-providedconsumables must remain physically con-nected to and integrated with the vehicleto operate properly. This innovation is the design and proto-

type of a hybrid spacesuit approach thatconfigures the spacesuit to seamlessly in-terface and integrate with either type ofvehicular systems, while still maintainingthe ability to function completely inde-pendent of the vehicle. An existing Ad-vanced Crew Escape Suit (ACES) was uti-lized as the platform from which todevelop the innovation. The ACES wasretrofitted with selected components and

one-off items to achieve the objective.The ventilation system concept was de-

veloped and prototyped/retrofitted to anexisting ACES. Components were selectedto provide suit connectors, hoses/umbili-cals, internal breathing system ducting/conduits, etc. The concept utilizes a low-pressure-drop, high-flow ventilation systemthat serves as a conduit from the vehiclesupply into the suit, up through a neckseal, into the breathing helmet cavity, backdown through the neck seal, out of thesuit, and returned to the vehicle. The con-cept also utilizes a modified demand-basedbreathing system configured to functionseamlessly with the low-pressure-dropclosed-loop ventilation system.This work was done by Brian A. Daniel,

Garret R. Fitzpatrick, Dustin M. Gohmert,Rick M. Ybarra, and Mark O. Dub of JohnsonSpace Center. Further information is con-tained in a TSP (see page 1). MSC-24804-1

Data Quality ScreeningService

A report describes the Data QualityScreening Service (DQSS), which is de-signed to help automate the filtering ofremote sensing data on behalf of scienceusers. Whereas this process often involvesmuch research through quality docu-ments followed by laborious coding, the

DQSS is a Web Service that provides datausers with data pre-filtered to their partic-ular criteria, while at the same time guid-ing the user with filtering recommenda-tions of the cognizant data experts. The DQSS design is based on a formal

semantic Web ontology that describes datafields and the quality fields for applyingquality control within a data product. Theaccompanying code base handles severalremote sensing datasets and quality con-trol schemes for data products stored inHierarchical Data Format (HDF), a com-mon format for NASA remote sensingdata. Together, the ontology and code sup-port a variety of quality control schemesthrough the implementation of theBoolean expression with simple, reusableconditional expressions as operands. Additional datasets are added to the

DQSS simply by registering instances inthe ontology if they follow a qualityscheme that is already modeled in theontology. New quality schemes areadded by extending the ontology andadding code for each new scheme.This work was done by Richard Strub,

Christopher Lynnes, Thomas Hearty, andYoung-In Won of Goddard Space Flight Cen-ter; and Peter Fox and Stephan Zednik ofRensselaer Polytechnic Institute. Further in-formation is contained in a TSP (see page 1).GSC-16227-1

National Aeronautics andSpace Administration

technology focus electronics/computers · elements used to define the polarization sensitivity of...

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