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Technology Focus

Electronics/Computers

Software

Materials

Mechanics

Machinery/Automation

Manufacturing

Bio-Medical

Physical Sciences

Information Sciences

Books and Reports

06-04 June 2004

https://ntrs.nasa.gov/search.jsp?R=20110016826 2020-07-25T15:10:49+00:00Z

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

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

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

National Technology Transfer CenterTelephone No. (800) 678-6882 or via World Wide Web at www2.nttc.edu/leads/

Please reference the control numbers appearing at the end of each Tech Brief. Information on NASA’s Commercial Technology Team, its documents, and services is also available at the same facility or on the World Wide Web at www.nctn.hq.nasa.gov.

Commercial Technology Offices and Patent Counsels are located at NASA field centers to providetechnology-transfer access to industrial users. Inquiries can be made by contacting NASA field centersand program offices listed below.

Ames Research CenterCarolina Blake(650) [email protected]

Dryden Flight Research CenterJenny Baer-Riedhart(661) [email protected]

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

Jet Propulsion LaboratoryArt Murphy, Jr.(818) [email protected]

Johnson Space CenterCharlene E. Gilbert(281) [email protected]

Kennedy Space CenterJim Aliberti(321) [email protected]

Langley Research CenterJesse Midgett(757) [email protected]

John H. Glenn Research Center atLewis FieldLarry Viterna(216) [email protected]

Marshall Space Flight CenterVernotto McMillan(256) [email protected]

Stennis Space CenterRobert Bruce(228) [email protected]

Carl RaySmall Business InnovationResearch Program (SBIR) &Small Business TechnologyTransfer Program (STTR)(202) 358-4652 [email protected]

Benjamin NeumannInnovativeTechnology TransferPartnerships (Code RP)(202) [email protected]

John MankinsOffice of Space Flight (Code MP)(202) 358-4659 [email protected]

Terry HertzOffice of Aero-SpaceTechnology (Code RS)(202) 358-4636 [email protected]

Glen MucklowOffice of Space Sciences(Code SM)(202) 358-2235 [email protected]

Roger CrouchOffice of Microgravity ScienceApplications (Code U)(202) 358-0689 [email protected]

Granville PaulesOffice of Mission to Planet Earth(Code Y) (202) 358-0706 [email protected]

NASA Field Centers and Program Offices

NASA Program Offices

At NASA Headquarters there are seven major program offices that develop and oversee technology projects of potential interest to industry:

NASA Tech Briefs, June 2004 1

5 Technology Focus: Test & Measurement

5 COTS MEMS Flow-Measurement Probes

5 Measurement of an Evaporating Drop on aReflective Substrate

7 Airplane Ice Detector Based on a MicrowaveTransmission Line

7 Microwave/Sonic Apparatus Measures Flow andDensity in Pipe

8 Reducing Errors by Use of Redundancy in Gravity

11 Electronics/Computers

11 Membrane-Based Water Evaporator for a Space Suit

11 Compact Microscope Imaging System WithIntelligent Controls

12 Chirped-Superlattice, Blocked-Intersubband QWIP

13 Charge-Dissipative Electrical Cables

13 Deep-Sea Video Cameras Without PressureHousings

14 RFID and Memory Devices Fabricated Integrallyon Substrates

15 Software

15 Analyzing Dynamics of Cooperating Spacecraft

15 Spacecraft Attitude Maneuver Planning UsingGenetic Algorithms

15 Forensic Analysis of Compromised Computers

15 Document Concurrence System

16 Managing an Archive of Images

16 MPT Prediction of Aircraft-Engine Fan Noise

16 Improving Control of Two Motor Controllers

17 Materials

17 Electrodeionization Using Microseparated BipolarMembranes

18 Safer Electrolytes for Lithium-Ion Cells

19 Mechanics

19 Rotating Reverse-Osmosis for Water Purification

20 Making Precise Resonators for MesoscaleVibratory Gyroscopes

20 Robotic End Effectors for Hard-Rock Climbing

21 Improved Nutation Damper for a Spin-StabilizedSpacecraft

23 Machinery

23 Exhaust Nozzle for a Multitube DetonativeCombustion Engine

24 Arc-Second Pointer for Balloon-BorneAstronomical Instrument

25 Compact, Automated Centrifugal Slide-StainingSystem

26 Two-Armed, Mobile, Sensate Research Robot

27 Physical Sciences

27 Compensating for Effects of Humidity onElectronic Noses

27 Brush/Fin Thermal Interfaces

28 Multispectral Scanner for Monitoring Plants

29 Information Sciences

29 Coding for Communication Channels With Dead-Time Constraints

29 System for Better Spacing of Airplanes En Route

30 Algorithm for Training a Recurrent MultilayerPerceptron

31 Books & Reports

31 Orbiter Interface Unit and Early CommunicationSystem

31 White-Light Nulling Interferometers for DetectingPlanets

31 Development of Methodology for ProgrammingAutonomous Agents

06-04 June 2004

This document was prepared under the sponsorship of the National Aeronautics and Space Administration. Neither the United States Governmentnor any person acting on behalf of the United States Government assumes any liability resulting from the use of the information contained in thisdocument, or warrants that such use will be free from privately owned rights.



COTS MEMS Flow-Measurement ProbesThese relatively inexpensive probes are compact and have short response times.John H. Glenn Research Center, Cleveland, Ohio

As an alternative to conventional tub-ing instrumentation for measuring air-flow, designers and technicians at GlennResearch Center have been fabricatingpackaging components and assemblinga set of unique probes that contain com-mercial off-the-shelf (COTS) micro-electromechanical systems (MEMS) sen-sor chips. MEMS sensor chips offersome compelling advantages over stan-dard macroscopic measurement de-vices. MEMS sensor technology has ma-tured through mass production and usein the automotive and aircraft indus-tries. At present, MEMS are the devicesof choice for sensors in such applica-tions as tire-pressure monitors, altime-ters, pneumatic controls, cable leak de-tectors, and consumer appliances.Compactness, minimality of power de-mand, rugged construction, and moder-ate cost all contribute to making MEMSsensors attractive for instrumentationfor future research.

Conventional macroscopic flow-mea-surement instrumentation includestubes buried beneath the aerodynamicsurfaces of wind-tunnel models or inwind-tunnel walls. Pressure is introducedat the opening of each such tube. Thepressure must then travel along the tubebefore reaching a transducer that gener-ates an electronic signal. The lengths ofsuch tubes typically range from 20 ft (≈ 6m) to hundreds of feet (of the order of100 m). The propagation of pressure sig-nals in the tubes damps the signals con-

siderably and makes it necessary to delaymeasurements until after test rigs havereached steady-state operation. In con-trast, a MEMS pressure sensor that gen-erates electronic output can take read-ings continuously under dynamicconditions in nearly real time.

In order to use stainless-steel tubingfor pressure measurements, it is neces-sary to clean many tubes, cut them tolength, carefully install them, delicatelydeburr them, and splice them. A clusterof a few hundred 1/16-in.- (≈1.6-mm-)diameter tubes (such clusters are com-mon in research testing facilities) can beseveral inches (of the order of 10 cm) indiameter and could weigh enough thattwo technicians are needed to handle it.Replacing hard tubing with electronic

chips can eliminate much of the bulk.Each sensor would fit on the tip of a1/16-in. tube with room to spare.

The Lucas NovaSensor P592 piezore-sistive silicon pressure sensor was cho-sen for this project because of its cost,availability, and tolerance to extremeambient conditions. The sensor chip is1 mm square by 0.6 mm thick (about0.039 by 0.039 by 0.024 in.) and in-cludes 0.12-mm (≈0.005-in.) wire con-nection tabs.

The figure shows a flow-angularityprobe that was built by use of three suchMEMS chips. It is planned to demon-strate this MEMS probe as an alternativeto a standard tube-type “Cobra” probenow used routinely in wind tunnels andaeronautical hardware. This MEMSprobe could be translated across a flowfield by use of a suitable actuator, so thatits accuracy and the shortness of its re-sponse time could be exploited to ob-tain precise dynamic measurements of asort that cannot be made by use of con-ventional tubing-based instrumentation.

This work was done by Chip Redding, FloydA. Smith, and Greg Blank of Glenn ResearchCenter and Charles Cruzan of NASA’s JetPropulsion Laboratory. Further information iscontained in a TSP (see page 1).

Inquiries concerning rights for the commer-cial use of this invention should be addressedto NASA Glenn Research Center, CommercialTechnology Office, Attn: Steve Fedor, MailStop 4–8, 21000 Brookpark Road, Cleve-land, Ohio 44135. Refer to LEW-17243.

This Probe Containing Three COTS MEMS Sen-sor Chips is designed to measure flow angularityin a plane. A planned similar probe will containfive MEMS sensors for measuring flow angular-ity in three dimensions.

Measurement of an Evaporating Drop on a Reflective SubstrateThis system complements a prior one for measuring on a transparent substrate.John H. Glenn Research Center, Cleveland, Ohio

The figure depicts an apparatus thatsimultaneously records magnified ordi-nary top-view video images and laser-shadowgraph video images of a sessiledrop on a flat, horizontal substrate thatcan be opaque or translucent and is atleast partially specularly reflective. A sim-ilar apparatus for recording such images

of a drop on a transparent substrate wasdescribed in “Measuring Contact Anglesof a Sessile Drop and Imaging Convec-tion Within It” (LEW-17075), NASA TechBriefs, Vol. 25, No. 3 (March 2001), page50. As in the case of the previously re-ported apparatus, the diameter, contactangle, and rate of evaporation of the

drop as functions of time can be calcu-lated from the apparent diameters ofthe drop in sequences of the images ac-quired at known time intervals, and theshadowgrams that contain flow patternsindicative of thermocapillary convection(if any) within the drop. These time-de-pendent parameters and flow patterns

Technology Focus: Test & Measurement

6 NASA Tech Briefs, June 2004

are important for understanding thephysical processes involved in thespreading and evaporation of drops.

The apparatus includes a source ofwhite light and a laser (both omitted fromthe figure), which are used to form the or-dinary image and the shadowgram, re-spectively. Charge-coupled-device (CCD)camera 1 (with zoom) acquires the ordi-nary video images, while CCD camera 2acquires the shadowgrams. With respectto the portion of laser light specularly re-flected from the substrate, the drop actsas a plano-convex lens, focusing the laserbeam to a shadowgram on the projectionscreen in front of CCD camera 2.

The equations for calculating the di-ameter, contact angle, and rate of evap-oration of the drop are readily derivedon the basis of Snell’s law of refractionand the geometry of the optics. Theequations differ from those for the ap-paratus of the cited prior article. Omit-ting intermediate steps of the derivationfor the sake of brevity, the results are thefollowing:

The two related unknown quantities arethe contact angle (θ) and, for light thathas been reflected from the substrate, theangle of refraction (θ2) of that light from

the surface of the drop at a point nearedge. These quantities are found by solv-ing the simultaneous equations

where n is the index of refraction ofthe liquid in the drop, s = the totallength of paths AB and BC, d is the ap-parent diameter of the drop as mea-sured in the ordinary image acquired byCCD camera 1, and D is the diameter ofthe shadowgraphic image acquired byCCD camera 2.

On the basis of a spherical-cap approxi-mation of the shape of the drop, the thick-ness of the drop (h) at its apex is given by

and the volume (Ω) of the drop is given by

The time-average rate of evaporation ofthe drop, Wav, is considered to be animportant parameter for quantifyingevaporation strength and can be deter-mined by

where Ω0 is the initial volume of the dropand tf is the lifetime of the drop. The in-stantaneous rate of evaporation can becalculated by

where ∆Ω is the difference between thevolumes of the drop at two measurementtimes separated by the interval ∆t.

This work was done by David F. Chao ofGlenn Research Center and Nengli Zhangof Ohio Aerospace Institute. Further informa-tion is contained in a TSP (see page 1).

Inquiries concerning rights for the commer-cial use of this invention should be addressedto NASA Glenn Research Center, CommercialTechnology Office, Attn: Steve Fedor, Mail Stop4–8, 21000 Brookpark Road, Cleveland, Ohio44135. Refer to LEW-17301.

Wt

= ∆Ω∆

,

Wt f

av =Ω0 ,

Ω = −

πθ

hd h2

2 3sin.

hd= −( cos )

sin12

θθ

21

2

2

2

2

22 1 2

sd D

nn

( )cot tan

cot tan

sin sinsin

cos sin ,

+=

+−

= − −

θ θθ θ

θ θθ

θ θ

and

The Time-Dependent Diameters d and D measured in images acquired by cameras 1 and 2 can be used to calculate the contact angle, volume, and otherparameters of the drop on the substrate at point A.

Video Printer

Video Recorder 1

Video Recorder 2 Monitor 2

Monitor 1

White Light

LaserBeam

Beam Splitter 1

BeamSplitter 2

Beam Splitter 3

Liquid Drop

Substrate:Aluminized Glass Plate

Screen

Collimator

CCD Camera 1

CCDCamera 2

DCB

A

d

θr

θ2

θ1 θ

θ

Refracted Ray ThatForms Outer Fringe of the

Shadowgraphic ImageParallelBeams

Sessile-Drop Edge

Details of Ray Paths at theSessile-Drop Edge (Area P)

P


Airplane Ice Detector Based on a Microwave Transmission LineElectrical measurements are affected by thawing, freezing, and the presence or absence of water.Lyndon B. Johnson Space Center, Houston, Texas

An electronic instrument that could de-tect the potentially dangerous buildup ofice on an airplane wing is undergoing de-velopment. The instrument is based on amicrowave transmission line configuredas a capacitance probe: at selected spots,the transmission-line conductors arepartly exposed to allow any ice and/or liq-uid water present at those spots to act aspredominantly capacitive electrical loadson the transmission line. These loadschange the input impedance of the trans-mission line, as measured at a suitable ex-citation frequency. Thus, it should be pos-sible to infer the presence of ice and/orliquid water from measurements of theinput impedance and/or electrical para-meters related to the input impedance.

The sensory transmission line is of themicrostrip type and thus thin enough tobe placed on an airplane wing without un-duly disturbing airflow in flight. The sen-sory spots are small areas from which theupper layer of the microstrip has been re-moved to allow any liquid water or ice onthe surface to reach the transmission line.The sensory spots are spaced at nominalopen-circuit points, which are at intervalsof a half wavelength (in the transmissionline, not in air) at the excitation fre-quency. The excitation frequency used inthe experiments has been 1 GHz, forwhich a half wavelength in the transmis-sion line is ≈4 in. (≈10 cm).

The figure depicts a laboratory proto-type of the instrument. The impedance-related quantities chosen for use in thisversion of the instrument are the magni-tude and phase of the scattering parame-ter S11 as manifested in the in-phase (I )and quadrature (Q) outputs of the phasedetector. By careful layout of the trans-mission line (including the half-wave-length sensor spacing), one can ensurethat the amplitude and phase of theinput to the phase detector keep shifting

in the same direction as ice forms on oneor more of the sensor areas. Althoughonly one transmission-line sensor strip isused in the laboratory version, in a prac-tical application, it could be desirable toinstall multiple strips on different areasto detect localized icing. In that case, amultiplexer should be used to connectthe various strips to the phase detectorfor sequential measurements.

Experiments have been performedwith freezing and thawing of water and ofwater/glycol mixtures. The experimentshave shown that, whether or not glycol ispresent, it is possible to distinguish be-tween liquid water and ice via the I and Qoutputs; in particular, the equipment can

be adjusted so that when water freezes, Idecreases and Q increases. With respectto the operation of this instrument, themain effect of glycol is to increase thefreezing or thawing time.

This work was done by G. Dickey Arndtand Phong Ngo of Johnson Space Centerand James R. Carl of Lockheed Martin. Forfurther information, contact G. Dickey Arndtat [email protected].

This invention is owned by NASA, and apatent application has been filed. Inquiriesconcerning nonexclusive or exclusive licensefor its commercial development should beaddressed to the Patent Counsel, JohnsonSpace Center, (281) 483-0837. Refer toMSC-23118.

The I and Q Outputs of the Phase Shifter are affected by the presence or absence of liquid water orice on the sensory spots on the microwave transmission line.

PhaseDetector

AdjustablePhase Shifter

Data-Acquisition Board(Including Analog-to-Digital

Converters)

PortableComputer

Plots and OtherResults of Analysis

I Q

Signal Source(1 GHz)

Low-Loss Coaxial Cable

Microwave TransmissionLine (Stripline)

HalfWavelength

HalfWavelength

Sensory Spot

Microwave/Sonic Apparatus Measures Flow and Density in PipeThe entire flow, rather than a small diverted sample flow, is probed.Lyndon B. Johnson Space Center, Houston, Texas

An apparatus for measuring the rate offlow and the mass density of a liquid orslurry includes a special section of pipeinstrumented with microwave and sonic

sensors, and a computer that processesdigitized readings taken by the sensors.The apparatus was conceived specificallyfor monitoring a flow of oil-well-drilling

mud, but the basic principles of its designand operation are also applicable to mon-itoring flows of other liquids and slurries.

In one configuration, a special section

of pipe is located immediately upstreamof the point of discharge of the flow tobe monitored. The special section ofpipe must be large enough that the pipecan accommodate the entire flow of in-terest (in contradistinction to a small di-verted sample flow), that the flow re-mains laminar at all times, and that thepipe is never entirely full, even at themaximum flow rate.

In another configuration, the appara-tus does not measure the rate of flow orthe density directly: Instead, it (a) mea-sures the height of the fluid in the spe-cial section of pipe and computes theflow rate as a predetermined function ofthe height and (b) measures the speedof sound in the fluid and computes thedensity of the fluid as a predeterminedfunction of the speed of sound in thefluid. To enable the apparatus to per-

form these computations, one must cali-brate the apparatus, prior to operation,by measuring the flow rate as a functionof height and the mass density as a func-tion of the speed of sound for thedrilling mud or other fluid of interest.

In the second configuration, the veloc-ity of the fluid can be measured subsur-face using a set of one transmitter and tworeceivers to measure differential phaseshifts. This second configuration can beused within a filled or unfilled closed pipeto measure volume flow. The microwaveportion of the apparatus (see figure)includes a broadband swept-frequency(more precisely, stepped-frequency)transmitter/receiver pair connected, viaa directional coupler, to an antennaaimed downward at the liquid. Transmit-ted- and received-signal data are processedby an algorithm that uses a modified

Fourier transform to compute the round-trip propagation time of the signal re-flected from top of the fluid. The heightof the fluid is then computed from theround-trip travel time and the knownheight of the antenna. A sonic sensor thatoperates alongside the microwave sensorgives an approximate height reading thatmakes it possible to resolve the integer-multiple-of-2π phase ambiguity of the mi-crowave sensor, while the microwave sen-sor makes it possible to refine the heightmeasurement to within 0.1 in. (≈2.5 mm).

Ultrasonic sensors on the walls nearthe bottom of the special section of pipeare used to measure the speed of soundneeded to compute the density of thefluid. More specifically, what is measuredis the difference between the phase of asignal of known frequency at a transmit-ting transducer and the phase of thesame signal at a receiving transducer aknown distance away. It may also be nec-essary to resolve an integer-multiple-of-2π phase ambiguity. This can be done byusing two sonic frequencies chosen ac-cording to a well-established technique.Alternatively, one could use a singlesonic frequency low enough not to besubject to the phase ambiguity, albeitwith some loss of density resolution. Sim-ulations indicate that a density accuracymeasurement of 0.25 percent (0.0025)can be attained with a single-tone system.

This work was done by G. D. Arndt andPhong Ngo of Johnson Space Centerand J. R. Carl and Kent A. Byerly, indepen-dent consultants.

This invention is owned by NASA, anda patent application has been filed. In-quiries concerning nonexclusive or exclu-sive license for its commercial developmentshould be addressed to the Patent Counsel,Johnson Space Center, (281) 483-0837. Referto MSC-23311.


The Height of the Fluid relative to the antenna is determined from differences between the phases ofstepped-frequency microwave signals transmitted to, and reflected from, the top surface of the fluid.

Microwave Sensor

Stepped-FrequencyTransmitter

Stepped-FrequencyReceiver

DirectionalCoupler

Computer andSoftware

Fluid in Pipe

Broad-Band Antenna

Phase-Stable Coaxial Cable

Data

A methodology for improving gravity-gradient measurement data exploits theconstraints imposed upon the compo-nents of the gravity-gradient tensor bythe conditions of integrability neededfor reconstruction of the gravitationalpotential. These constraints are derived

from the basic equation for the gravita-tional potential and from mathematicalidentities that apply to the gravitationalpotential and its partial derivatives withrespect to spatial coordinates.

Consider the gravitational potential φin a Cartesian coordinate system x1,x2,x3.

The ith component of gravitational ac-celeration is given by

(where i = 1, 2, or 3) and the (α,β) com-

gxi

i= − ∂

∂φ

Reducing Errors by Use of Redundancy in GravityMeasurementsMathematical identities are exploited to suppress noise or reduce numbers of measurements.NASA’s Jet Propulsion Laboratory, Pasadena, California


ponent of the gravity-gradient tensor is given by

where α = 1, 2, or 3 and β = 1, 2, or 3. Theaforementioned constraints are such thatthe components of the gravity-gradienttensor are not independent of each other.In particular, it is easily shown that thegravity-gradient tensor is symmetrical andhas a zero trace; that is,

Γαβ = Γβα and Γ11+ Γ22 +Γ33 = 0.Hence, if one measures all the compo-nents of the gravity-gradient tensor at allpoints of interest within a region of spacein which one seeks to characterize thegravitational field, one obtains redun-dant information. One could utilize the

constraints to select a minimum (that is,nonredundant) set of measurementsfrom which the gravitational potentialcould be reconstructed. Alternatively,one could exploit the redundancy to re-duce errors from noisy measurements.

A convenient example is that of theselection of a minimum set of measure-ments to characterize the gravitationalfield at n3 points (where n is an integer)in a cube. Without the benefit of such aselection, it would be necessary to make9n3 measurements because the gravity-gradient tensor has 9 components ateach point. It has been shown that whenthe constraints are applied to the mea-surement points in an appropriatelychosen sequence, the number of mea-surements needed to compute all 9n3

components is only n3+n2+3n.

The problem of utilizing the redun-dancy to reduce errors in noisy measure-ments is an optimization problem: Given aset of noisy values of the components ofthe gravity-gradient tensor at the measure-ment points, one seeks a set of correctedvalues — a set that is optimum in that itminimizes some measure of error (e.g.,the sum of squares of the differences be-tween the corrected and noisy measure-ment values) while taking account of thefact that the constraints must apply to theexact values. The problem as thus posedleads to a vector equation that can besolved to obtain the corrected values.

This work was done by Igor Kulikov andMichail Zak of Caltech for NASA’s JetPropulsion Laboratory. Further informa-tion is contained in a TSP (see page 1).NPO-30536

Γαβα

β β α

φ≡−∂∂

= ∂∂ ∂

gx x x

2


Electronics/Computers

Membrane-Based Water Evaporator for a Space SuitThis design incorporates recent advances in hydrophobic micropore membranes.Lyndon B. Johnson Space Center, Houston, Texas

A membrane-based water evaporatorhas been developed that is intended toserve as a heat-rejection device for aspace suit. This evaporator would replacethe current sublimator that is sensitive tocontamination of its feedwater. The de-sign of the membrane-based evaporatortakes advantage of recent advances in hy-drophobic micropore membranes toprovide robust heat rejection with muchless sensitivity to contamination. The lowcontamination sensitivity allows use ofthe heat transport loop as feedwater,eliminating the need for the separatefeedwater system used for the sublimator.

A cross section of the evaporator isshown in the accompanying figure. Thespace-suit cooling loop water flows into adistribution plenum, through a narrowannulus lined on both sides with a hy-drophobic membrane, into an exitplenum, and returns to the space suit.Two perforated metal tubes encase themembranes and provide structuralstrength. Evaporation at the membraneinner surface dissipates the waste heatfrom the space suit. The water vaporpasses through the membrane, into asteam duct and is vented to the vacuumenvironment through a back-pressure

valve. The back-pressure setting can be ad-justed to regulate the heat-rejection rateand the water outlet temperature.

This work was done by Eugene K. Ungarand Charles J. McCann of Johnson Space

Center and Mary K. O’Connell and Scott An-drea of Lockheed Martin Corp. For further in-formation, contact the Johnson CommercialTechnology Office at (281) 483-3809.MSC-23317

Cooling LoopWater Inlet

Cooling LoopWater Outlet

Steam Flow

Steam Flow

To Back-Pressure-Regulating Valve

HydrophobicMembranes

Water Flow

Hydrophobic Membranes provide the basis for a simple, robust device for space-suit heat rejection.

The figure presents selected views of acompact microscope imaging system(CMIS) that includes a miniature videomicroscope, a Cartesian robot (a com-puter-controlled three-dimensional trans-lation stage), and machine-vision andcontrol subsystems. The CMIS was builtfrom commercial off-the-shelf instrumen-tation, computer hardware and software,and custom machine-vision software. Themachine-vision and control subsystemsinclude adaptive neural networks that af-ford a measure of artificial intelligence.

The CMIS can perform several auto-mated tasks with accuracy and repeata-

bility tasks that, heretofore, have re-quired the full attention of human tech-nicians using relatively bulky conven-tional microscopes. In addition, theautomation and control capabilities ofthe system inherently include a capabil-ity for remote control. Unlike humantechnicians, the CMIS is not at risk of be-coming fatigued or distracted: theoreti-cally, it can perform continuously at thelevel of the best human technicians. Inits capabilities for remote control andfor relieving human technicians of te-dious routine tasks, the CMIS is ex-pected to be especially useful in bio-

medical research, materials science, in-spection of parts on industrial produc-tion lines, and space science.

The CMIS can automatically focus onand scan a microscope sample, findareas of interest, record the resulting im-ages, and analyze images from multiplesamples simultaneously. Automatic fo-cusing is an iterative process: The trans-lation stage is used to move the micro-scope along its optical axis in asuccession of coarse, medium, and finesteps. A fast Fourier transform (FFT) ofthe image is computed at each step, andthe FFT is analyzed for its spatial-fre-

Compact Microscope Imaging System With Intelligent ControlsThis system automates tasks that, heretofore, required the full attention of human technicians.John H. Glenn Research Center, Cleveland, Ohio


quency content. The microscope posi-tion that results in the greatest dispersalof FFT content toward high spatial fre-quencies (indicating that the imageshows the greatest amount of detail) isdeemed to be the focal position.

In addition to automatic focusing, themachine-vision system is capable of per-

forming the following other functions:• Adaptive Thresholding: This function en-

ables the choice of the best contrastneeded for other image processing.

• Auto-Imaging Scanning: The microscopecan scan along any or all of three Carte-sian coordinate axes within a sample inorder to find an object of interest.

• Identification and Classification of Objects:The system can find, classify, and labelobjects [e.g., living cells of one or moretype(s) of interest] within a predeter-mined area of interest.

• Motion Detection: Movements of objectsin a predetermined area of interestcan be observed and quantified.

• Transition Mapping: In a sample con-taining small particles (e.g., colloids orliving cells), small transitions betweengroups of particles can be detected. Ex-amples of transitions include those be-tween order and disorder, large andsmall objects, light and dark regions,and movement and non-movement.For example, in the case of a colloidalsuspension containing a liquid and anadjacent solid phase, this function canbe helpful in locating the zone of tran-sition between the two phases.This work was done by Mark McDowell of

Glenn Research Center. Further informa-tion is contained in a TSP (see page 1).

Inquiries concerning rights for the commer-cial use of this invention should be addressedto NASA Glenn Research Center, CommercialTechnology Office, Attn: Steve Fedor, MailStop 4-8, 21000 Brookpark Road, Cleveland,Ohio 44135. Refer to LEW-17484.

Microscope andCCD Camera Head Connect to Camera Body

CCD Camera Body Feeds Data to Image-Acquisition Board in PC

Fiber-OpticLight Source

Cartesian RobotIs Controlled ViaPC Board

The CMIS Takes Less Room than does a conventional microscope. Unlike a conventional microscope,the CMIS offers capabilities for remote control and for automation of routine tasks.

Chirped-Superlattice, Blocked-Intersubband QWIPCollection efficiency and, hence, quantum efficiency are expected to increase.NASA’s Jet Propulsion Laboratory, Pasadena, California

An Alx Ga1–x As/GaAs quantum-wellinfrared photodetector (QWIP) of theblocked-intersubband-detector (BID)type, now undergoing development, fea-tures a chirped (that is, aperiodic) su-perlattice. The purpose of the chirpedsuperlattice is to increase the quantumefficiency of the device.

A somewhat lengthy background dis-cussion is necessary to give meaning to abrief description of the present develop-mental QWIP. A BID QWIP was de-scribed in “MQW Based Block Intersub-band Detector for Low-BackgroundOperation” (NPO-21073), NASA TechBriefs Vol. 25, No. 7 (July 2001), page 46.To recapitulate: The BID design was con-ceived in response to the deleterious ef-fects of operation of a QWIP at low tem-perature under low backgroundradiation. These effects can be summa-rized as a buildup of space charge and anassociated high impedance and diminu-tion of responsivity with increasing mod-ulation frequency.

The BID design, which reduces thesedeleterious effects, calls for a heavily dopedmultiple-quantum-well (MQW) emittersection with barriers that are thinner thanin prior MQW devices. The thinning of thebarriers results in a large overlap of sub-level wave functions, thereby creating aminiband. Because of sequential resonantquantum-mechanical tunneling of elec-trons from the negative ohmic contact toand between wells, any space charge isquickly neutralized. At the same time, whatwould otherwise be a large component ofdark current attributable to tunneling cur-rent through the whole device is sup-pressed by placing a relatively thick, un-doped, impurity-free Alx Ga1–x As blockingbarrier layer between the MQW emittersection and the positive ohmic contact.[This layer is similar to the thick, undopedAlx Ga1–x As layers used in photodetectorsof the blocked-impurity-band (BIB) type.]

Notwithstanding the aforementionedadvantage afforded by the BID design,the responsivity of a BID QWIP is very

low because of low collection efficiency,which, in turn, is a result of low electro-static-potential drop across the superlat-tice emitter. Because the emitter must beelectrically conductive to prevent thebuildup of space charge in depletedquantum wells, most of the externally ap-plied bias voltage drop occurs across theblocking-barrier layer. This completesthe background discussion.

In the developmental QWIP, the peri-odic superlattice of the prior BID designis to be replaced with the chirped super-lattice, which is expected to provide abuilt-in electric field. As a result, the ef-ficiency of collection of photoexcitedcharge carriers (and, hence, the netquantum efficiency and thus responsiv-ity) should increase significantly.

This work was done by Sarath Gunapala,David Ting, and Sumith Bandara of Caltechfor NASA’s Jet Propulsion Laboratory.Further information is contained in a TSP(see page 1).NPO-30510


Charge-Dissipative Electrical CablesLossy dielectric layers and grounding conductors drain spurious charges to ground.Goddard Space Flight Center, Greenbelt, Maryland

Electrical cables that dissipate spuri-ous static electric charges, in addition toperforming their main functions of con-ducting signals, have been developed.These cables are intended for use intrapped-ion or ionizing-radiation envi-ronments, in which electric charges tendto accumulate within, and on the sur-faces of, dielectric layers of cables. If thecharging rate exceeds the dissipationrate, charges can accumulate in exces-sive amounts, giving rise to high-currentdischarges that can damage electroniccircuitry and/or systems connected to it.

The basic idea of design and operationof charge-dissipative electrical cables is todrain spurious charges to ground by useof lossy (slightly electrically conductive)dielectric layers, possibly in conjunctionwith drain wires and/or drain shields(see figure). In typical cases, the drainwires and/or drain shields could be elec-trically grounded via the connector as-semblies at the ends of the cables, in anyof the conventional techniques forgrounding signal conductors and signalshields. In some cases, signal shieldscould double as drain shields.

To be suitable for use in a charge-dissi-pating cable, a dielectric material must beinherently lossy throughout its bulk, andnot, say, an insulating polymer with aconductive surface film or containingembedded conductive particles. Conduc-tive surface films can be rendered inef-

fective by flaking off or cracking, espe-cially when cables are bent. Embeddedparticles can act as defect sites that initi-ate arcing within dielectric layers.

The concept of lossiness can be quan-tified: Dielectric materials can be broadlycategorized, as either “excellent” or “lossy”according to their volume electrical re-sistivity (ρ) values. Excellent insulatorsmay be roughly categorized as having ρof the order of 1016Ω⋅m, while lossy ordissipative insulators may be categorizedas having ρ of the order of 109 Ω⋅m.

In designing for a specific application,one must choose the lossy dielectric mate-rial and the configuration of groundingconductors to be capable of dissipating asufficient proportion of static chargewithin an acceptably short time. For a typ-ical cable that handles signals of suffi-ciently low frequencies (having wave-lengths much greater than the length ofthe cable), the effective charge-dissipatingadmittance or conductance must be muchless than the nominal signal admittance orsignal conductance of the circuits con-nected with the cable, so as not to ad-versely affect the transmission of signals.For a typical cable that handles signals ofsufficiently high frequencies (having wave-lengths comparable to or less than thelength of the cable), the effective charge-dissipating admittance or conductancemust be taken into account as part of theoverall signal-propagation cable imped-

ance, and the signal attenuation caused byloss in the dielectric must be acceptablylow. These requirements could be difficultto satisfy if a cable is too long and, hence,imposes either a limit on the allowablelength of the cable or else a requirementto pay closer attention to interactions be-tween the charge-dissipation and signal-propagation aspects of the cable design.

This work was done by John R. Kolasinskiand Edward J. Wollack of Goddard SpaceFlight Center. Further information is con-tained in a TSP (see page 1).GSC-14648-1

DrainWires Drain

Shields

LossyDielectric

SignalConductors

This Cross Section illustrates one of many possi-ble charge-dissipating designs for a cable con-taining 11 signal conductors.

Underwater video cameras of a pro-posed type (and, optionally, their lightsources) would not be housed in pres-sure vessels. Conventional underwatercameras and their light sources arehoused in pods that keep the contentsdry and maintain interior pressures ofabout 1 atmosphere (≈0.1 MPa). Podsstrong enough to withstand the pres-sures at great ocean depths are bulky,heavy, and expensive. Elimination of thepods would make it possible to buildcamera/light-source units that would besignificantly smaller, lighter, and less ex-

pensive. The depth ratings of the pro-posed camera/light source units wouldbe essentially unlimited because thestrengths of their housings would nolonger be an issue.

A camera according to the proposalwould contain an active-pixel image sen-sor and readout circuits, all in the formof a single silicon-based complementarymetal oxide/semiconductor (CMOS) in-tegrated-circuit chip. As long as none ofthe circuitry and none of the electricalleads were exposed to seawater, which iselectrically conductive, silicon inte-

grated-circuit chips could withstand thehydrostatic pressure of even the deepestocean. The pressure would change thesemiconductor band gap by only a slightamount — not enough to degrade imag-ing performance significantly.

Electrical contact with seawater wouldbe prevented by potting the integrated-circuit chip in a transparent plastic case.The electrical leads for supplying powerto the chip and extracting the video sig-nal would also be potted, though notnecessarily in the same transparent plas-tic. The hydrostatic pressure would tend

Deep-Sea Video Cameras Without Pressure HousingsCamera units could be made smaller, lighter, and less expensive.NASA’s Jet Propulsion Laboratory, Pasadena, California


to compress the plastic case and the chipequally on all sides; there would be noneed for great strength because therewould be no need to hold back highpressure on one side against low pressureon the other side. A light source suitablefor use with the camera could consist oflight-emitting diodes (LEDs). Like inte-grated-circuit chips, LEDs can withstandvery large hydrostatic pressures.

If power-supply regulators or filter ca-pacitors were needed, these could be at-

tached in chip form directly onto theback of, and potted with, the imagerchip. Because CMOS imagers dissipatelittle power, the potting would not resultin overheating. To minimize the cost ofthe camera, a fixed lens could be fabri-cated as part of the plastic case. For im-proved optical performance at greatercost, an adjustable glass achromatic lenswould be mounted in a reservoir thatwould be filled with transparent oil andsubject to the full hydrostatic pressure,

and the reservoir would be mounted onthe case to position the lens in front ofthe image sensor. The lens would by ad-justed for focus by use of a motor insidethe reservoir (oil-filled motors alreadyexist).

This work was done by Thomas Cunning-ham of Caltech for NASA’s Jet PropulsionLaboratory. Further information is con-tained in a TSP (see page 1). NPO-30774

Electronic identification devices con-taining radio-frequency identification(RFID) circuits and antennas would befabricated integrally with the objects to beidentified, according to a proposal. Thatis to say, the objects to be identified wouldserve as substrates for the deposition andpatterning of the materials of the devicesused to identify them, and each identifi-cation device would be bonded to theidentified object at the molecular level.Vacuum arc vapor deposition (VAVD) isthe NASA–derived process for depositinglayers of material on the substrate.

This proposal stands in contrast to thecurrent practice of fabricating RFIDand/or memory devices as wafer-based,self-contained integrated-circuit chipsthat are subsequently embedded in or at-tached to plastic cards to make “smart”account-information cards and identifica-tion badges. If one relies on such a chipto store data on the history of an object tobe tracked and the chip falls off or out ofthe object, then one loses both the his-

torical data and the means to track theobject and verify its identity electroni-cally. Also, in contrast is the manufactur-ing philosophy in use today to makemany memory devices. Today’s methodsinvolve many subtractive processes suchas etching. This proposal only uses addi-tive methods, building RFID and memorydevices from the substrate up in thin lay-ers. VAVD is capable of spraying silicon,copper, and other materials commonlyused in electronic devices. The VAVDprocess sprays most metals and some ce-ramics. The material being sprayed has avery strong bond with the substrate,whether that substrate is metal, ceramic,or even wood, rock, glass, PVC, or paper.

An object to be tagged with an identi-fication device according to the pro-posal must be compatible with a vacuumdeposition process. Temperature is sel-dom an issue as the substrate rarelyreaches 150° F (66° C) during the depo-sition process. A portion of the surfaceof the object would be designated as a

substrate for the deposition of the de-vice. By use of a vacuum arc vapor depo-sition apparatus, a thin electrically insu-lating film would first be deposited onthe substrate. Subsequent layers of mate-rials would then be deposited and pat-terned by use of known integrated-cir-cuit fabrication techniques. The totalthickness of the deposited layers couldbe much less than the 100-µm thicknessof the thinnest state-of-the-art self-con-tained microchips. Such a thin depositcould be readily concealed by simplypainting over it. Both large vacuumchambers for production runs andportable hand-held devices for in situ ap-plications are available.

This work was done by Harry F. Schrammof Marshall Space Flight Center.

This invention is owned by NASA, and apatent application has been filed. For furtherinformation, contact Sammy Nabors, MSFCCommercialization Assistance Lead, at (256)544-5226 or [email protected] to MFS-31549.

RFID and Memory Devices Fabricated Integrally on SubstratesThese molecularly bonded devices would be much thinner than microchips.Marshall Space Flight Center, Alabama


Software

Analyzing Dynamics of Cooperating Spacecraft

A software library has been developedto enable high-fidelity computationalsimulation of the dynamics of multiplespacecraft distributed over a region ofouter space and acting with a commonpurpose. All of the modeling capabilitiesafforded by this software are available in-dependently in other, separate softwaresystems, but have not previously beenbrought together in a single system. Auser can choose among several dynami-cal models, many high-fidelity environ-ment models, and several numerical-in-tegration schemes. The user can selectwhether to use models that assume weakcoupling between spacecraft, or strongcoupling in the case of feedback controlor tethering of spacecraft to each other.For weak coupling, spacecraft orbits arepropagated independently, and are syn-chronized in time by controlling thestep size of the integration. For strongcoupling, the orbits are integrated si-multaneously. Among the integrationschemes that the user can choose areRunge-Kutta Verner, Prince-Dormand,Adams-Bashforth-Moulton, and Bulirsh-Stoer. Comparisons of performance areincluded for both the weak- and strong-coupling dynamical models for all of thenumerical integrators. The library wasdesigned for ease of integration withhigh-fidelity environment models al-ready in use in the Flight DynamicsAnalysis Branch, which is one of seveninstitutional support branches withinthe Mission Engineering and SystemsAnalysis Division at Goddard SpaceFlight Center.

This program was written by Stephen P.Hughes and David C. Folta of GoddardSpace Flight Center and Darrel J. Conwayof Thinking Systems, Inc. Further informa-tion is contained in a TSP (see page 1).GSC-14735-1

Spacecraft AttitudeManeuver Planning UsingGenetic Algorithms

A key enabling technology that leadsto greater spacecraft autonomy is the ca-pability to autonomously and optimallyslew the spacecraft from and to differentattitudes while operating under a num-ber of celestial and dynamic constraints.

The task of finding an attitude trajectorythat meets all the constraints is a formi-dable one, in particular for orbiting orfly-by spacecraft where the constraintsand initial and final conditions are oftime-varying nature. This approach forattitude path planning makes full use ofa priori constraint knowledge and is com-putationally tractable enough to be exe-cuted onboard a spacecraft. The ap-proach is based on incorporating theconstraints into a cost function andusing a Genetic Algorithm to iterativelysearch for and optimize the solution.This results in a directed random searchthat explores a large part of the solutionspace while maintaining the knowledgeof good solutions from iteration to itera-tion. A solution obtained this way maybe used ‘as is’ or as an initial solution toinitialize additional deterministic opti-mization algorithms. A number of rep-resentative case examples for time-fixedand time-varying conditions yieldedsearch times that are typically on theorder of minutes, thus demonstratingthe viability of this method. This ap-proach is applicable to all deep spaceand planet Earth missions requiringgreater spacecraft autonomy, andgreatly facilitates navigation and scienceobservation planning.

This work was done by Richard P. Korn-feld of Caltech for NASA’s Jet PropulsionLaboratory. Further information is con-tained in a TSP (see page 1).

This software is available for commerciallicensing. Please contact Don Hart of the Cal-ifornia Institute of Technology at (818) 393-3425. Refer to NPO-40107.

Forensic Analysis of Compromised Computers

Directory Tree Analysis File Generatoris a Practical Extraction and ReportingLanguage (PERL) script that simplifiesand automates the collection of informa-tion for forensic analysis of compromisedcomputer systems. During such an analy-sis, it is sometimes necessary to collectand analyze information about files on aspecific directory tree. Directory TreeAnalysis File Generator collects informa-tion of this type (except informationabout directories) and writes it to a textfile. In particular, the script asks the userfor the root of the directory tree to beprocessed, the name of the output file,

and the number of subtree levels toprocess. The script then processes the di-rectory tree and puts out the aforemen-tioned text file. The format of the text fileis designed to enable the submission ofthe file as input to a spreadsheet pro-gram, wherein the forensic analysis is per-formed. The analysis usually consists ofsorting files and examination of suchcharacteristics of files as ownership, timeof creation, and time of most recent ac-cess, all of which characteristics areamong the data included in the text file.

This program was written by ThomasWolfe of Caltech for NASA’s Jet PropulsionLaboratory. Further information is con-tained in a TSP (see page 1).


Document ConcurrenceSystem

The Document Concurrence Systemis a combination of software modulesfor routing users expressions of con-currence with documents. This systemenables determination of the currentstatus of concurrences and eliminatesthe need for the prior practice of man-ually delivering paper documents to allpersons whose approvals were re-quired. This system runs on a server,and participants gain access via per-sonal computers equipped with Web-browser and electronic-mail software. Auser can begin a concurrence routingprocess by logging onto an administra-tion module, naming the approversand stating the sequence for routingamong them, and attaching docu-ments. The server then sends a mes-sage to the first person on the list.Upon concurrence by the first person,the system sends a message to the sec-ond person, and so forth. A person onthe list indicates approval, places thedocuments on hold, or indicates disap-proval, via a Web-based module. Whenthe last person on the list has con-curred, a message is sent to the initia-tor, who can then finalize the processthrough the administration module. Abackground process running on theserver identifies concurrence processesthat are overdue and sends remindersto the appropriate persons.


This program was written by MansourMuhsin and Ian Walters of Lockheed MartinCorp. for Stennis Space Center.

Inquiries concerning rights for the commercialuse of this invention should be addressed to theIntellectual Property Manager, Stennis SpaceCenter, (228) 688-1929. Refer to SSC-00179.

Managing an Archive ofImages

The SSC Multimedia Archive is an au-tomated electronic system to manage im-ages, acquired both by film and digitalcameras, for the Public Affairs Office(PAO) at Stennis Space Center (SSC).Previously, the image archive was basedon film photography and utilized a man-ual system that, by today’s standards, hadbecome inefficient and expensive. Now,the SSC Multimedia Archive, based on aserver at SSC, contains both catalogs andimages for pictures taken both digitallyand with a traditional, film-based camera,along with metadata about each image.After a “shoot,” a photographer down-loads the images into the database. Mem-bers of the PAO can use a Web-based ap-plication to search, view and retrieveimages, approve images for publication,and view and edit metadata associatedwith the images. Approved images arearchived and cross-referenced with ap-propriate descriptions and information.Security is provided by allowing adminis-trators to explicitly grant access privilegesto personnel to only access componentsof the system that they need to (i.e., allowonly photographers to upload images,only PAO designated employees may ap-prove images).

This work was done by Vince Andres andDavid Walter of Stennis Space Center andCharles Hallal, Helene Jones, and Chris Callacof Lockheed Martin Corp.

Inquiries concerning rights for the commercialuse of this invention should be addressed to theIntellectual Property Manager, Stennis SpaceCenter, (228) 688-1929. Refer to SSC-00185.

MPT Prediction of Aircraft-Engine Fan Noise

A collection of computer programshas been developed that implements aprocedure for predicting multiple-

pure-tone (MPT) noise generated byfan blades of an aircraft engine (e.g., aturbofan engine). MPT noise ariseswhen the fan is operating with super-sonic relative tip Mach No. Under thisflow condition, there is a strong up-stream running shock. The strengthand position of this shock are very sen-sitive to blade geometry variations. Fora fan where all the blades are identical,the primary tone observed upstream ofthe fan will be the blade passing fre-quency. If there are small variations ingeometry between blades, then tonesbelow the blade passing frequencyarise — MPTs. Stagger angle differ-ences as small as 0.1° can give rise tosignificant MPT. It is also noted thatMPT noise is more pronounced whenthe fan is operating in an “unstarted”mode. Computational results using athree-dimensional flow solver to com-pute the complete annulus flow withnon-uniform fans indicate that MPTnoise can be estimated in a relativelysimple way. Hence, once the effect of atypical geometry variation of one bladein an otherwise uniform blade row isknown, the effect of all the bladesbeing different can be quickly com-puted via superposition. Two computerprograms that were developed as partof this work are used in conjunctionwith a user’s computational fluid dy-namics (CFD) code to predict MPTspectra for a fan with a specified set ofgeometric variations:• The first program ROTBLD reads the

users CFD solution files for a singleblade passage via an API (ApplicationProgram Interface). There are optionsto replicate and perturb the geometrywith typical variations stagger, camber,thickness, and pitch. The multi-passageCFD solution files are then written inthe user’s file format using the API.

• The second program SUPERPOSE re-quires two input files: the first is the cir-cumferential upstream pressure distrib-ution extracted from the CFD solutionon the multi-passage mesh, the secondfile defines the geometry variations ofeach blade in a complete fan. Superpo-sition is used to predict the spectra re-sulting from the geometric variations.The user would typically generate a

multi-passage mesh (ROTBLD) with thegeometry of one blade perturbed — typ-

ically, four or five passages are required.A CFD solution would then be gener-ated for this mesh. Using this solutionand specified geometry variations for acomplete fan, the MPT spectra can beestimated using SUPERPOSE.

These programs were written by Stuart D.Connell of General Electric Corp. for GlennResearch Center. Further information iscontained in a TSP (see page 1).

Inquiries concerning rights for the commer-cial use of this invention should be addressedto NASA Glenn Research Center, CommercialTechnology Office, Attn: Steve Fedor, Mail Stop4-8, 21000 Brookpark Road, Cleveland,OH44135. Refer to LEW-17386.

Improving Control of TwoMotor Controllers

A computer program controls motorsthat drive translation stages in a metrologysystem that consists of a pair of two-axiscathetometers. This program is specific toCompumotor Gemini (or equivalent) mo-tors and the Compumotor 6K-series (orequivalent) motor controller. Relative tothe software supplied with the controller,this program affords more capabilities andis easier to use. Written as a Virtual Instru-ment in the LabVIEW software system, theprogram presents an imitation controlpanel that the user can manipulate by useof a keyboard and mouse. There are threemodes of operation: command, move-ment, and joystick. In command mode,single commands are sent to the con-troller for troubleshooting. In movementmode, distance, speed, and/or accelera-tion commands are sent to the controller.Position readouts from the motors andfrom position encoders on the translationstages are displayed in marked fields. Atany time, the position readouts can berecorded in a file named by the user. Injoystick mode, the program yields controlof the motors to a joystick. The programsends commands to, and receives datafrom, the controller via a serial cable con-nection, using the serial-communicationportion of the software supplied with thecontroller.

This program was written by Ronald W.Toland of Goddard Space Flight Cen-ter. Further information is contained in aTSP (see page 1).GSC-14744-1


Materials

Electrodeionization Using Microseparated Bipolar MembranesLow concentrations of ions do not inhibit further removal of ions.Lyndon B. Johnson Space Center, Houston, Texas

An electrochemical technique fordeionizing water, now under develop-ment, is intended to overcome a majorlimitation of prior electrically–basedwater-purification techniques. The lim-itation in question is caused by the de-sired decrease in the concentration ofions during purification: As the con-centration of ions decreases, the elec-trical resistivity of the water increases,posing an electrical barrier to the re-moval of the remaining ions. In thepresent technique, this limitation isovercome by use of electrodes, a flow-field structure, and solid electrolytesconfigured to provide conductive pathsfor the removal of ions from the waterto be deionized, even when the waterhas already been purified to a high de-gree.

The technique involves the use of abipolar membrane unit (BMU), whichincludes a cation-exchange membraneand an anion-exchange membrane sep-arated by a nonconductive mesh thathas been coated by an ionically con-ductive material (see figure). Themesh ensures the desired microsepara-tion between the ion-exchange mem-branes: The interstices bounded by theinner surfaces of the membranes andthe outer surfaces of the coated meshconstitute a flow-field structure that al-lows the water that one seeks to deion-ize (hereafter called “process water”for short) to flow through the BMUwith a low pressure drop. The flow-fieldstructure is such that the distance be-tween any point in the flow field and anionically conductive material is small;thus, the flow-field structure facilitatesthe diffusion of molecules and ions toand from the ion-exchange mem-branes.

The BMU is placed between an anodeand a cathode, but not in direct contactwith these electrodes. Instead, the spacebetween the anionexchange membraneand the anode is denoted the anodecompartment and is filled with an ionicsolution. Similarly, the space betweenthe cation-exchange membrane and thecathode is denoted the cathode com-partment and is filled with a different

ionic solution. The electrodes are madeof titanium coated with platinum.

The process water is introduced intothe BMU, and a dc potential is appliedbetween the electrodes. The ion-ex-change membranes contain networks ofmolecular-size pores with electriccharges fixed to their matrices. An ion-exchange membrane is nominally elec-tronically nonconductive but is conduc-tive to counterions; that is, to ions ofcharge opposite that of the ions immo-bilized in it. Because of the semiperme-ability of the membranes and the direc-tion of the electric field between theelectrodes, negatively charged ions mi-grate from the process water towards theanode and positively charged ions mi-grate from the process water towards thecathode. The ions thus removed fromthe process water become concentratedin the water in the anode and cathodecompartments.

The removal of ions from the processwater includes salt-splitting reactions(e.g., the separation of Na+ and Cl–

ions). In addition, some water moleculesdissociate into H+ and OH– ions. The

combination of this water splitting reac-tion and the highly efficient transfer ofthe H+ and OH– ions by the respectivemembranes ensures high transmem-brane ionic conductivity, even when theconcentrations of other ions in theprocess water are low. The ion-conduct-ing circuit of the electrochemical cell iscompleted by the anode and cathodecompartments.

This work was done by Donald Lyons,George Jackson, Craig C. Andrews, CharlesL. K. Tennakoon, Waheguru Singh, G.Duncan Hitchens, Harry Jabs, James F.Chepin, Shivaun Archer, Anukia Gonzalez-Martinez, and Alan J. Cisar of Lynntech,Inc., for Johnson Space Center.

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:

Lynntech, Inc.Attn: Oliver J. Murphy, President7610 Eastmark Drive, Suite 105College Station, TX 77840Refer to MSC-23042, volume and number

of this NASA Tech Briefs issue, and thepage number.

AnodeIonically-ConductiveCoating

Cathode

Anode Compartment

Anion-ExchangeMembrane

Cathode Compartment

OH–

H2OH2OH2O

NaClProcessWater in

Flow Field

OH– Cl–

H+ H+ Na+

+

–

Cation-ExchangeMembrane

A Bipolar Membrane Unit contains a flow-field structure and solid electrolytes configured to provideconductive paths for the removal of ions from process water.


Safer Electrolytes for Lithium-Ion Cells John H. Glenn Research Center, Cleveland, Ohio

A number of nonvolatile, low-flamma-bility liquid oligomers and polymers basedon aliphatic organic carbonate molecularstructures have been found to be suitableto be blended with ethylene carbonate tomake electrolytes for lithium-ion electro-chemical cells. Heretofore, such elec-trolytes have often been made by blendingethylene carbonate with volatile, flamma-ble organic carbonates. The present non-volatile electrolytes have been found tohave adequate conductivity (about 2mS/cm) for lithium ions and to remain liq-

uid at temperatures down to –5 °C. At nor-mal charge and discharge rates, lithium-ion cells containing these nonvolatile elec-trolytes but otherwise of standard designhave been found to operate at current andenergy densities comparable to those ofcells now in common use. They do not per-form well at high charge and dischargerates — an effect probably attributable toelectrolyte viscosity. Cells containing thenonvolatile electrolytes have also beenfound to be, variously, nonflammable or atleast self-extinguishing. Hence, there ap-

pears to be a basis for the development ofsafer high-performance lithium-ion cells.

This work was done by Joe Kejha, NovisSmith, and Joel McCloskey of LithChem forGlenn Research Center.Further informa-tion is contained in a TSP (see page 1).

Inquiries concerning rights for the commer-cial use of this invention should be addressedto NASA Glenn Research Center, CommercialTechnology Office, Attn: Steve Fedor, MailStop 4-8, 21000 Brookpark Road, Cleveland,Ohio 44135. Refer to LEW-17398.


A new design for a water-filtering de-vice combines rotating filtration with re-verse osmosis to create a rotating re-verse-osmosis system. Rotating filtrationhas been used for separating plasmafrom whole blood, while reverse osmosishas been used in purification of waterand in some chemical processes. Re-verse-osmosis membranes are vulnerableto concentration polarization — a typeof fouling in which the chemicals meantnot to pass through the reverse-osmosismembranes accumulate very near thesurfaces of the membranes. The combi-nation of rotating filtration and reverseosmosis is intended to prevent concen-tration polarization and thereby in-crease the desired flux of filtered waterwhile decreasing the likelihood of pas-sage of undesired chemical speciesthrough the filter. Devices based on thisconcept could be useful in a variety ofcommercial applications, including pu-rification and desalination of drinkingwater, purification of pharmaceuticalprocess water, treatment of householdand industrial wastewater, and treatmentof industrial process water.

A rotating filter consists of a cylindri-cal porous microfilter rotating within astationary concentric cylindrical outershell (see figure). The aqueous suspen-sion enters one end of the annulus be-tween the inner and outer cylinders. Fil-trate passes through the rotatingcylindrical microfilter and is removedvia a hollow shaft. The concentrated sus-pension is removed at the end of the an-nulus opposite the end where the sus-pension entered.

The effectiveness of a rotating filter inpreventing fouling comes from highfluid shear caused by the rotation andfrom the appearance of a vortical flowstructure known as Taylor vortices: theresultant flow field tends to wash parti-cles off the rotating filter.

In reverse osmosis, water is forced athigh pressure through a membranemade of a material through which cont-aminants in aqueous solution passmuch more slowly than does water.Hence, the concentration of undesireddissolved compounds is decreased by

forcing the water through the mem-brane, creating purified water. In con-ventional practice, concentration polar-ization of reverse-osmosis membranes isoften reduced by using cross-flows (flowsparallel to the membrane surfaces) towash away the concentrated chemicals,but this is not always effective withoutcleaning or back washing.

The rotating reverse-osmosis deviceresembles a conventional rotating filter,except that the cylindrical porous mi-crofilter is replaced with a cylindrical re-verse-osmosis membrane. The shear andthe Taylor vortices generated by the ro-tation of the cylindrical reverse-osmosismembrane wash away the concentration-polarization layer. The latest prototypeof a rotating reverse-osmosis module in-corporates special rotating seals to solveone of the most difficult problems in thesystem, enabling the device to withstandthe differential pressures needed for

operation period: Whereas microfiltra-tion systems operate at differential pres-sures of the order of 1 atmosphere (≈0.1MPa), reverse-osmosis systems operate atdifferential pressures as high as 30 to 50atmospheres (≈3 to 5 MPa).

This work was done by Richard M. Luep-tow of Northwestern University for JohnsonSpace Center.


Richard M. Lueptow, ScD, PEProfessor Mechanical EngineeringNorthwestern University2145 Sheridan RoadEvanston, IL 60208-3111Telephone No.: (847) 491-4265;e-mail: [email protected] to MSC-23294, volume and number


Mechanics

Rotating Reverse-Osmosis for Water PurificationThis device would resist fouling.Lyndon B. Johnson Space Center, Houston, Texas

The Flow Through a Rotating Osmosis Device is shown. Shear and vortices that arise in the liquid flow-ing between the rotating filter and the stationary outer shell wash away material that would other-wise accumulate on or near the filter surface and thereby cause fouling.

Rotation (Typical Speed100 rpm)

Stationary Shell

Rotating Porous Filter

Filtrate Channel

ConcentratedWaste Out

ContaminatedWater In

Purified Water Out

Hollow Shaft


An alternative approach to the designand fabrication of vibratory gyroscopesis founded on the use of fabricationtechniques that yield best results in themesoscopic size range, which is charac-terized by overall device dimensions ofthe order of a centimeter. This ap-proach stands in contradistinction toprior approaches in (1) the macro-scopic size range (the size range of con-ventional design and fabrication, char-acterized by overall device dimensionsof many centimeters) and (2) the mi-croscopic size range [the size rangeof microelectromechanical systems(MEMS), characterized by overall de-vice dimensions of the order of a mil-limeter or less]. The mesoscale ap-proach offers some of the advantage ofthe MEMS approach (sizes and powerdemands smaller than those of themacroscale approach) and some of theadvantage of the macroscale approach(the possibility of achieving relative di-mensional precision greater than that ofthe MEMS approach).

Relative dimensional precision is amajor issue in the operation of a vibra-tory gyroscope. The heart of a vibratorygyroscope is a mechanical resonator thatis required to have a specified symmetry

in a plane orthogonal to the axis aboutwhich rotation is to be measured. If theresonator could be perfectly symmetri-cal, then in the absence of rotation, afree vibration of the resonator could re-main fixed along any orientation relativeto its housing; that is, the gyroscopecould exhibit zero drift. In practice,manufacturing imprecision gives rise tosome asymmetry in mass, flexural stiff-ness or dissipation, resulting in a slightdrift or beating motion of an initial vi-bration pattern that cannot be distin-guished from rotation.

In the mesoscale approach, one ex-ploits the following concepts: For agiven amount of dimensional errorgenerated in manufacturing, the asym-metry and hence the rate-of-rotationdrift of the gyroscope can be reducedby increasing the scale. The decrease inasymmetry also reduces coupling of vi-brations to the external environment.Mechanical thermal noise and elec-tronic measurement noise and driftcan also be reduced by increasing thesize of the resonator and its associatedsensors.

In the mesoscale approach, a res-onator is fabricated from a silicon wafer.Central to the mesoscale approach is a

combination of (1) precise polishing ofboth faces of the wafer to form parallelplanar upper and lower resonator sur-faces and (2) dry reactive-ion etching(DRIE) to remove material from thesides of the resonator perpendicular tothe upper and lower surfaces.

An experimental resonator was de-signed and fabricated following themesoscale approach. Its frequency split(the difference between the natural fre-quencies of its two nominal orthogonalvibration modes — a measure of itsasymmetry) was so small as to be unde-tectable at a resonance quality factor (Q)of 105, as observed in operation in anominal vacuum with residual pressureof 10–5 torr (≈1.3 × 10–3 Pa). Through-out intensive experimentation, it was ob-served that keeping the thickness of thewafer as nearly uniform as possible wasthe main requirement for keeping thefrequency split small, whereas the fre-quency split was not much affected bythe side-wall roughness resulting fromDRIE.

This work was done by Eui-Hyeok Yang ofCaltech for NASA’s Jet Propulsion Labo-ratory. Further information is contained ina TSP (see page 1).NPO-30431

Making Precise Resonators for Mesoscale Vibratory GyroscopesIt is essential to polish wafers to precise flatness and uniform thickness.NASA’s Jet Propulsion Laboratory, Pasadena, California

Robotic End Effectors for Hard-Rock ClimbingEnd effectors emulate equipment used by human climbers.NASA’s Jet Propulsion Laboratory, Pasadena, California

Special-purpose robot hands (end ef-fectors) now under development are in-tended to enable robots to traverse cliffsmuch as human climbers do. Potentialapplications for robots having this capa-bility include scientific exploration (bothon Earth and other rocky bodies inspace), military reconnaissance, and out-door search and rescue operations.

Until now, enabling robots to traversecliffs has been considered too difficult atask because of the perceived need ofprohibitively sophisticated planning al-gorithms as well as end effectors as dex-terous as human hands. The presentend effectors are being designed to en-able robots to attach themselves to typi-cal rock-face features with less planning

and simpler end effectors. This advanceis based on the emulation of the equip-ment used by human climbers ratherthan the emulation of the human hand.Climbing-aid equipment, specificallycams, aid hooks, and cam hooks, areused by sport climbers when a quick as-cent of a cliff is desired (see Figure 1).

Currently two different end-effectordesigns have been created. The first, de-noted the simple hook emulator, consistsof three “fingers” arranged around a cen-tral “palm.” Each finger emulates thefunction of a particular type of climbinghook (aid hook, wide cam hook, and anarrow cam hook). These fingers areconnected to the palm via a mechanicallinkage actuated with a leadscrew/nut.

This mechanism allows the fingers to beextended or retracted. The second de-sign, denoted the advanced hook emula-tor (see Figure 2), shares these features,but it incorporates an aid hook and a camhook into each finger. The spring-load-ing of the aid hook allows the passive se-lection of the type of hook used.

The end effectors can be used in sev-eral different modes. In the aid-hookmode, the aid hook on one of the fin-gers locks onto a horizontal ledge whilethe other two fingers act to stabilize theend effector against the cliff face. In thecam-hook mode, the broad, flat tip ofthe cam hook is inserted into a non-hor-izontal crack in the cliff face. A subse-quent transfer of weight onto the end ef-

fector causes the tip to rotate within thecrack, creating a passive, self-locking ac-tion of the hook relative to the crack. Inthe advanced hook emulator, the aid

hook is pushed into its retracted posi-tion by contact with the cliff face as thecam hook tip is inserted into the crack.When a cliff face contains relatively large

pockets or cracks, another type of pas-sive self-locking can be used. Emulatingthe function of the piece of climbingequipment called a “cam” (note: not thesame as a “cam hook”; see Figure 1), thefingers can be fully retracted and the en-tire end effector inserted into the fea-ture. The fingers are then extended asfar as the feature allows. Any weight thentransferred to the end effector will tendto extend the fingers further due to fric-tional force, passively increasing the gripon the feature. In addition to the climb-ing modes, these end effectors can beused to walk on (either on the palm orthe fingertips) and to grasp objects byfully extending the fingers.

This work was done by Brett Kennedy andPatrick Leger of Caltech for NASA’s JetPropulsion Laboratory. Further informa-tion is contained in a TSP (see page 1).NPO-40224


A document proposes an improved liq-uid-ring nutation damper for a spin-stabi-lized spacecraft. The improvement ad-dresses the problem of accommodatingthermal expansion of the damping liq-uid. Heretofore, the problem has beensolved by either (1) filling the ring com-pletely with liquid and accommodatingexpansion by attaching a bellows or (2)partially filling the ring and accepting theformation of bubbles. The disadvantage

of (1) is that a bellows is expensive andmay not be reliable; the disadvantage of(2) is that bubbles can cause fluid lockupand consequent loss of damping. In theimproved damper, the ring would benearly completely filled with liquid, andexpansion would be accommodated, butnot by a bellows. Instead, an escape tubewould be attached to the ring. The es-cape tube would be positioned and ori-ented so that the artificial gravitation and

the associated buoyant force generatedby the spin of the spacecraft would causethe bubbles to migrate toward the tip ofthe tube. In addition, when the space-craft was on the launch pad, the escapetube would be at the top of the ring, sothat bubbles would rise into the tube.

This work was done by Mark A. Woodard ofGoddard Space Flight Center. Further infor-mation is contained in a TSP (see page 1).GSC-14733-1

Improved Nutation Damper for a Spin-Stabilized SpacecraftGoddard Space Flight Center,Greenbelt, Maryland

BASIC HOOK CAM HOOK CAM

Hooks Onto Flats or Over Lips Self Locking Cam Between Walls of a Crack

Self Locking Mechanism for Wide Cracks or Pockets

AID HOOK IN ACTION CAM HOOK IN ACTION

Figure 1. Equipment Now Used by Human Rock Climbers includes specially designed hooks, cams, and hook-and-cam assemblies. Elements of these itemsare being incorporated into robotic end effectors for rock climbing.

Figure 2. The Advanced Hook Emulator can function in a variety of modes. The aid-hook and cam-hook modes shown here correspond to the modes of operation of the conventional basic hook andcam hook, respectively, depicted in Figure 1.


Machinery

Exhaust Nozzle for a Multitube Detonative Combustion EnginePressures at outlets of combustor tubes are approximately constant.Marshall Space Flight Center, Alabama

An improved type of exhaust nozzlehas been invented to help optimize theperformances of multitube detonativecombustion engines. The invention isapplicable to both air-breathing androcket engines used to propel some air-craft and spacecraft, respectively.

In a detonative combustion engine,thrust is generated through the expul-sion of combustion products from a det-onation process in which combustiontakes place in a reaction zone coupled toa shock wave. The combustion releasesenergy to sustain the shock wave, whilethe shock wave enhances the combus-

tion in the reaction zone. The coupledshockwave/reaction zone, commonly re-ferred to as a detonation, propagatesthrough the reactants at very high speed typically of the order of several thou-sands of feet per second (of the order of1 km/s). The very high speed of the det-onation forces combustion to occur veryrapidly, thereby contributing to highthermodynamic efficiency.

A detonative combustion engine of thetype to which the present invention ap-plies includes multiple parallel cylindri-cal combustion tubes, each closed at thefront end and open at the rear end. Each

tube is filled with a fuel/oxidizer mix-ture, and then a detonation wave is initi-ated at the closed end. The wave propa-gates rapidly through the fuel/oxidizermixture, producing very high pressuredue to the rapid combustion. The highpressure acting on the closed end of thetube contributes to forward thrust. Whenthe detonation wave reaches the openend of the tube, it produces a blast wave,behind which the high-pressure combus-tion products are expelled from the tube.

The process of filling each combustiontube with a detonable fuel/oxidizer mix-ture and then producing a detonation is

Rear(Downstream)

Front(Upstream)

Expansion Sector

ThroatCommonPlenum

Exhaust FromFiring Combustor Tube

Exhaust FromFilling Combustor Tube

InterfaceSection

Combustion Tubes

FLOW CROSS SECTION 4-4

FLOW CROSS SECTION 3-3FLOW CROSS SECTION 2-2 FLOW CROSS SECTION 1-1

CoolantManifolds

4

4

3

3

2

21

1

Sequentially Pulsed Exhaust Streams from multiple combustion tubes are channeled in such a manner as to maintain a nearly steady back pressure neededfor refilling the combustion tubes with fuel/oxidizer mixture.


repeated rapidly to obtain repeatedpulses of thrust. Moreover, the multiplecombustion tubes are filled and fired in arepeating sequence. Hence, the pressureat the outlet of each combustion tubevaries cyclically. A nozzle of the present in-vention channels the expansion of thepulsed combustion gases from the multi-ple combustion tubes into a common ex-haust stream, in such a manner as to en-hance performance in two ways:

(1) It reduces the cyclic variations ofpressure at the outlets of the combus-tion tubes so as to keep the pressure ap-proximately constant near the optimumlevel needed for filling the tubes, re-gardless of atmospheric pressure at thealtitude of operation; and

(2) It maximizes the transfer of mo-mentum from the exhaust gas to the en-gine, thereby maximizing thrust.

The figure depicts a typical engineequipped with a nozzle according to the in-vention. The nozzle includes an interfacesection comprising multiple intake ports

that couple the outlets of the combustiontubes to a common plenum. Proceedingfrom its upstream to its downstream end,the interface section tapers to a largercross-sectional area for flow. This taper fos-ters expansion of the exhaust gases flowingfrom the outlets of the combustion tubesand contributes to the desired equalizationof exhaust combustion pressure.

The cross-sectional area for flow in thecommon plenum is greater than, or at leastequal to, the combined cross-sectional flowareas of the combustor tubes. In the com-mon plenum, the exhaust streams fromthe individual combustion tubes mix toform a single compound subsonic exhauststream. Downstream of the commonplenum is the throat that tapers to asmaller flow cross section. In this throat,the exhaust gases become compressed toform a compound sonic gas stream.

Downstream of the throat is an expan-sion section, which typically has a bell or aconical shape. (The expansion section canbe truncated or even eliminated in the

case of an air-breathing engine.) After en-tering the expansion section, the exhaustgases expand rapidly from compoundsonic to compound supersonic speeds andare then vented to the environment.

The basic invention admits of numerousvariations. For example, the combustiontubes can be arranged around the centralaxis in a symmetrical or asymmetrical pat-tern other than the one shown in the fig-ure. For another example, the flow cross-sectional area(s) of one or more of theintake ports in the interface section, of thecommon plenum, the throat, and/or theexpansion section can be varied, eithersymmetrically or asymmetrically, to adjustdynamics of the exhaust stream or to directthe thrust vector away from the central axis.

This work was done by Thomas E.Bratkovich, Kevin E. Williams, Thomas R. A.Bussing, Gary L. Lidstone, and John B.Hinkey of Adroit Systems, Inc., for MarshallSpace Flight Center. Further information iscontained in a TSP (see page 1).MFS-32032

Arc-Second Pointer for Balloon-Borne Astronomical InstrumentA notable innovation would eliminate effects of static friction in bearings.Goddard Space Flight Center, Greenbelt, Maryland

A control system has been designed tokeep a balloon-borne scientific instru-ment pointed toward a celestial objectwithin an angular error of the order of anarc second. The design is intended to beadaptable to a large range of instrumentpayloads. The initial payload to which thedesign nominally applies is considered tobe a telescope, modeled as a simple thin-walled cylinder 24 ft (≈7.3 m) long, 3 ft(≈0.91 m) in diameter, weighing 1,500 lb(having a mass of ≈680 kg).

The instrument would be mountedon a set of motor-driven gimbals inpitch-yaw configuration. The motors onthe gimbals would apply the controltorques needed for fine adjustments ofthe instrument in pitch and yaw. Thepitch-yaw mount would, in turn, be sus-pended from a motor mount at thelower end of a pair of cables hangingdown from the balloon (see figure).The motor in this mount would be usedto effect coarse azimuth control of thepitch-yaw mount.

A notable innovation incorporated inthe design is a provision for keeping thegimbal bearings in constant motion. Thisinnovation would eliminate the deleteri-ous effects of static friction — something

that must be done in order to achievethe desired arc-second precision.

Another notable innovation is theuse of linear accelerometers to providefeedback that would facilitate the early

detection and counteraction of distur-bance torques before they could inte-grate into significant angular-velocityand angular-position errors. The con-trol software processing the sensor data

To Balloon

Instrument (e.g., Telescope)

Coarse Azimuth Adjustment

Gimbals

An Instrument Would Be Suspended below a balloon on motor-driven gimbals at the lower end of aset of cables. The motors would apply torques to correct pointing errors.


would be capable of distinguishing be-tween translational and rotational ac-celerations. The output of the ac-celerometers is combined with that ofangular position and angular-velocitysensors into a proportional + integral +derivative + acceleration control law

for the pitch and yaw torque motors.Preliminary calculations have shownthat with appropriate gains, the powerdemand of the control system would below enough to be satisfiable by meansof storage batteries charged by solarbatteries during the day.

This work was done by Philip R. Ward andKeith DeWeese of Wallops Flight Facility for God-dard Space Flight Center. Further informa-tion is contained in a TSP (see page 1).GSC-14715-1

The Directional Acceleration Vector-Driven Displacement of Fluids (DAVD-DOF) system, under development at thetime of reporting the information for thisarticle, would be a relatively compact, au-tomated, centrifugally actuated system forstaining blood smears and other microbi-ological samples on glass microscopeslides in either a microgravitational or anormal Earth gravitational environment.The DAVD-DOF concept is a successor tothe centrifuge-operated slide stainer(COSS) concept, which was reported in“Slide-Staining System for Microgravity orGravity” (MSC-22949), NASA Tech Briefs,Vol. 25, No. 1 (January, 2001), page 64.The COSS includes reservoirs and a stain-ing chamber that contains a microscopeslide to which a biological sample is af-fixed. The staining chamber is sequen-tially filled with and drained of stainingand related liquids from the reservoirs byuse of a weighted plunger to force liquidfrom one reservoir to another at a con-stant level of hypergravity maintained ina standard swing-bucket centrifuge.

In the DAVD-DOF system, a stainingchamber containing a sample would alsobe sequentially filled and emptied, butwith important differences. Instead of asimple microscope slide, one would use aspecial microscope slide on which wouldbe fabricated a network of very smallreservoirs and narrow channels con-nected to a staining chamber (see fig-ure). Unlike in the COSS, displacementof liquid would be effected by use of theweight of the liquid itself, rather than theweight of a plunger.

The channel from each reservoir tothe staining chamber would be made sonarrow that the combination of surfacetension of the liquid and friction be-tween the liquid and the channel sur-face would suffice to prevent the flow ofliquid from the reservoir to the stainingchamber in the absence of hypergravi-tational centrifugal acceleration below

a specified level. Downstream of thestaining chamber, there would be chan-nel for draining each fluid from thestaining chamber into a waste reservoirafter use; this channel would be widerthan the other channels so that drain-ing could be accomplished at a cen-trifuge speed much lower than thatneeded for filling the staining chamberfrom a reservoir. Flow in this channel

would be restricted by an electrically ac-tuated microvalve controlled by a mi-croprocessor on the spindle of the cen-trifuge.

By suitable choice of width of eachchannel, taking account of propertiesand amount of each liquid, the thresholdcentrifugal accelerations for moving theliquids from the reservoirs to the stainingchamber would be set at successively

Centrifugal Acceleration


MODIFIED MICROSCOPE SLIDE


Modified MicroscopeSlide on Centrifuge

CentrifugalAcceleration

Motion ofDish

Microvalve

Air-Vent Channels

Electrical Contacts for Microvalve

StainingChamber

Channels

WasteReservoir

Centrifuge Dish

Microprocessor Power Supply

CentrifugalAcceleration

ReservoirFill Ports

Air-VentChannels

Reservoir

Reservoir

Reservoir

Reservoir

Liquids Would Be Contained in Small Reservoirs on a modified microscope slide. Different liquidswould be transferred into the staining chamber at different centrifuge speeds.

Compact, Automated Centrifugal Slide-Staining SystemSmall quantities of different liquids would be displaced at different centrifuge speeds.Lyndon B. Johnson Space Center, Houston, Texas


greater values in the sequence in whichthe liquids were required to be used.Then sequential filling of the stainingchamber with the various liquids wouldbe achieved by momentarily increasingthe speed of the centrifuge to exceed thecorresponding threshold accelerations atthe required times. Once the sample hadbeen exposed to each liquid for the re-quired time, the valve would be openedto drain the liquid from the stainingchamber into the waste reservoir.

The reservoirs, channels, and stainingchamber could be created, either on aglass slide or on a uniformly thick coatingmaterial on the slide, by one or more of avariety of techniques that could involve

photolithography, laser writing, and/oretching. Once a slide had been thus pre-pared, a sample would be placed on thestaining-chamber area of a thin glass cover,then cover would be adhesively or electro-statically bonded to the slide or to the coat-ing material. The liquids would then bedispensed into their assigned reservoirs viaaccess ports and the air displaced from thereservoirs would leave through vent ports.The slide would then be placed on a cen-trifuge in the form of a spinning disk, andthe centrifuge would be operated as de-scribed above to expose the sample se-quentially to the various liquids.

This work was done by Daniel L. Feebackof Johnson Space Center and Mark S. F.

Clarke of University Space Research Associa-tion. For further information, contact theJohnson Commercial Technology Office at(281) 483-3809.

In accordance with Public Law 96-517, thecontractor has elected to retain title to this in-vention. Inquiries concerning rights for itscommercial use should be addressed to

University Space Research Association10227 Wincopin Circle, Suite 212Columbia, MD 21044-3459Telephone No.: (410) 730-2656Fax No.: (410) 730-3496Internet: [email protected] to MSC-23179, volume and number


The Anthropomorphic Robotic Test-bed (ART) is an experimental prototypeof a partly anthropomorphic, hu-manoid-size, mobile robot. The basicART design concept provides for a com-bination of two-armed coordination,tactility, stereoscopic vision, mobilitywith navigation and avoidance of obsta-cles, and natural-language communica-tion, so that the ART could emulate hu-mans in many activities. The ART couldbe developed into a variety of highly ca-pable robotic assistants for general orspecific applications. There is especiallygreat potential for the development ofART-based robots as substitutes for live-in health-care aides for home-boundpersons who are aged, infirm, or physi-cally handicapped; these robots couldgreatly reduce the cost of home healthcare and extend the term of indepen-dent living.

The ART is a fully autonomous anduntethered system. It includes a mobilebase on which is mounted an extensibletorso topped by a head, shoulders, andtwo arms. All subsystems of the ART arepowered by a rechargeable, removablebattery pack. The mobile base is a differ-entially-driven, nonholonomic vehiclecapable of a speed >1 m/s and can han-dle a payload >100 kg. The base can becontrolled manually, in forward/back-ward and/or simultaneous rotationalmotion, by use of a joystick. Alterna-tively, the motion of the base can be con-trolled autonomously by an onboardnavigational computer.

By retraction or extension of thetorso, the head height of the ART canbe adjusted from 5 ft (1.5 m) to 6 1/2 ft (2 m), so that the arms can reach eitherthe floor or high shelves, or some ceil-ings. The arms are symmetrical. Eacharm (including the wrist) has a total ofsix rotary axes like those of the humanshoulder, elbow, and wrist joints. Thearms are actuated by electric motors incombination with brakes and gas-springassists on the shoulder and elbow joints.The arms are operated under closed-loop digital control. A receptacle for anend effector is mounted on the tip ofthe wrist and contains a force-and-torque sensor that provides feedbackfor force (compliance) control of thearm. The end effector could be a tool ora robot hand, depending on the appli-cation.

The ART includes several built-in,ready-to-use sensory subsystems and hasroom for addition of other sensors. Oneof the built-in sensory subsystems is abumper/shield subsystem that includesmechanical tape switches and photode-tectors to detect actual or incipient colli-sions with objects on the floor, plus ul-trasonic sensors to detect nearbyoverhanging objects or walls. Otherbuilt-in sensory subsystems include laser-based distance measuring equipment,dual cameras for vision (includingstereoscopic vision), the aforemen-tioned force-and-torque sensors, andshaft-angle encoders and switches thatprovide position feedback for control of

the arms. The two cameras can bepanned and tilted independently ofeach other; they can be aimed in differ-ent directions or the same direction.

Each of the various sensory and mo-tion-control subsystems operates in con-junction with a computer subsystem thatprocesses the incoming sensory data andcontrols the affected component of themotion. The navigational computercommunicates with the sensory andbase-motion-control computers. An-other computer processes the digitizedoutputs of the cameras and controls theaiming, focus, and zoom of the cameras.Still another computer processes thedigitized outputs of the force-and-torquesensors and executes software for con-trol of the motions of, and forces ex-erted by, the arms.

Overall control is exerted by a host com-puter, which is of a Pentium-based laptopclass. This computer runs speech-recogni-tion and speech-synthesis software forcommunication with a human user. Forpurposes of experimentation and devel-opment, the host computer is also capableof radio communication with an externalcomputer or network of computers.

This work was done by J. F. Engelberger, W.Nelson Roberts, David J. Ryan, and AndrewSilverthorne of HelpMate Robotics, Inc., forJohnson Space Center. For further infor-mation, contact:

HelpMate Robotics, Inc.22 Shelter Rock LaneDanbury, CT 06810

Refer to MSC-22985.

Two-Armed, Mobile, Sensate Research RobotThis could be a prototype of robotic home health-care aides.Lyndon B. Johnson Space Center, Houston, Texas


Physical Sciences

Compensating for Effects of Humidity on Electronic NosesCorrections are derived from outputs of separate humidity and temperature sensors.NASA’s Jet Propulsion Laboratory, Pasadena, California

A method of compensating for the ef-fects of humidity on the readouts of elec-tronic noses has been devised andtested. The method is especially appro-priate for use in environments in whichhumidity is not or cannot be controlled— for example, in the vicinity of a chem-ical spill, which can be accompanied bylarge local changes in humidity.

Heretofore, it has been common prac-tice to treat water vapor as merely anotheranalyte, the concentration of which is de-termined, along with that of the other an-alytes, in a computational process basedon deconvolution. This practice workswell, but leaves room for improvement:changes in humidity can give rise to largechanges in electronic-nose responses. Ifcorrections for humidity are not made,the large humidity-induced responsesmay swamp smaller responses associatedwith low concentrations of analytes.

The present method offers an im-provement. The underlying concept issimple: One augments an electronicnose with a separate humidity and aseparate temperature sensor. The out-puts of the humidity and temperaturesensors are used to generate values thatare subtracted from the readings of theother sensors in an electronic nose tocorrect for the temperature-dependentcontributions of humidity to thosereadings. Hence, in principle, what re-mains after corrections are the contri-butions of the analytes only. Laboratoryexperiments on a first-generation elec-tronic nose have shown that thismethod is effective and improves thesuccess rate of identification of ana-lyte/water mixtures. Work on a second-generation device was in progress at thetime of reporting the information forthis article.

This work was done by Margie Homer,Margaret A. Ryan, Kenneth Manatt, Hany-ing Zhou, and Allison Manfreda of Caltechfor NASA’s Jet Propulsion Laboratory.Further information is contained in a TSP(see page 1).


Innovative Technology Assets ManagementJPLMail Stop 202-2334800 Oak Grove DrivePasadena, CA 91109-8099(818) 354-2240E-mail: [email protected] to NPO-30615, volume and number


Brush/Fin Thermal InterfacesHigh thermal conductance sliding interfaces can be achieved.Lyndon B. Johnson Space Center, Houston, Texas

Brush/fin thermal interfaces are beingdeveloped to increase heat-transfer effi-ciency and thereby enhance the thermalmanagement of orbital replaceable units(ORUs) of electronic and other equip-ment aboard the International Space Station.Brush/fin thermal interfaces could also beused to increase heat-transfer efficiency interrestrial electronic and power systems.

In a typical application according toconventional practice, a replaceable heat-generating unit includes a mounting sur-face with black-anodized metal fins thatmesh with the matching fins of a heat sinkor radiator on which the unit is mounted.The fins do not contact each other, buttransfer heat via radiation exchange. Abrush/fin interface also includes inter-meshing fins, the difference being thatthe gaps between the fins are filled withbrushes made of carbon or other fibers.The fibers span the gap between inter-meshed fins, allowing heat transfer by

conduction through the fibers. The fibersare attached to the metal surfaces as vel-vetlike coats in the manner of the carbon-fiber brush heat exchangers described inthe preceding article. The fiber brushesprovide both mechanical compliance andthermal contact, thereby ensuring lowcontact thermal resistance.

A certain amount of force is required tointermesh the fins due to sliding frictionof the brush’s fiber tips against the fins.This force increases linearly with penetra-tion distance, reaching ~1 psi (~6.9 kPa)for full 2-in. (5.1 cm) penetration for theconventional radiant fin interface. Re-moval forces can be greater due to fiberbuckling upon reversing the sliding direc-tion. This buckling force can be greatly re-duced by biasing the fibers at an angleperpendicularly to the sliding direction.Means of containing potentially harmfulcarbon fiber debris, which is electricallyconductive, have been developed.

Small prototype brush/fin thermal in-terfaces have been tested and found toexhibit temperature drops about one-sixth of that of conventional meshing-finthermal interface, when fabricated as aretrofit. In this case, conductionthrough the long, thin metal fins them-selves becomes a thermal bottleneck.Further improvement could be made byprescribing aluminum fins to be shorterand thicker than those of the conven-tional meshing-fin thermal interfaces;the choice of height and thicknesswould be optimized to obtain greateroverall thermal conductance, lowerweight, and lower cost.

This work was done by Timothy R.Knowles, Christopher L. Seaman, and BrettM. Ellman of Energy Science Laboratories,Inc., for Johnson Space Center. For furtherinformation, contact the Johnson CommercialTechnology Office at (281) 483-3809.MSC-23050


Multispectral Scanner for Monitoring PlantsJohn F. Kennedy Space Center, Florida

A multispectral scanner has beenadapted to capture spectral images ofliving plants under various types of illu-mination for purposes of monitoringthe health of, or monitoring the trans-fer of genes into, the plants. In a health-monitoring application, the plants areilluminated with full-spectrum visibleand near infrared light and the scanneris used to acquire a reflected-light spec-tral signature known to be indicative of

the health of the plants. In a gene-trans-fer-monitoring application, the plantsare illuminated with blue or ultravioletlight and the scanner is used to capturefluorescence images from a green fluo-rescent protein (GFP) that is expressedas result of the gene transfer. Thechoice of wavelength of the illumina-tion and the wavelength of the fluores-cence to be monitored depends on thespecific GFP.

This work was done by Nahum Gat of Opto-Knowledge Systems, Inc., for Kennedy SpaceCenter. For further information, contact

Nahum GatOpto-Knowledge Systems, Inc.4030 Spencer Street, Suite 108,Torrance, CA 90503Telephone No.: (310) 371-4445 Ext. 237E-mail: [email protected]

Refer to KSC-12519.


Information Sciences

Coding for Communication Channels With Dead-TimeConstraintsNovel coding schemes may offer significant advantages in some applications.NASA’s Jet Propulsion Laboratory, Pasadena, California

Coding schemes have been designedand investigated specifically for opticaland electronic data-communication chan-nels in which information is conveyed viapulse-position modulation (PPM) subjectto dead-time constraints. These schemesinvolve the use of error-correcting codesconcatenated with codes denoted con-strained codes. These codes are decodedusing an interactive method.

In pulse-position modulation, time ispartitioned into frames of M slots of equalduration. Each frame contains one pulsedslot (all others are non-pulsed). For agiven channel, the dead-time constraintsare defined as a maximum and a mini-mum on the allowable time betweenpulses. For example, if a Q-switched laseris used to transmit the pulses, then theminimum allowable dead time is the timeneeded to recharge the laser for the nextpulse. In the case of bits recorded on amagnetic medium, the minimum allow-able time between pulses depends on therecording/playback speed and the mini-mum distance between pulses needed toprevent interference between adjacentbits during readout. The maximum allow-able dead time for a given channel is themaximum time for which it is possible tosatisfy the requirement to synchronizeslots. In mathematical shorthand, thedead-time constraints for a given channelare represented by the pair of integers(d,k), where d is the minimum allowablenumber of zeroes between ones and k isthe maximum allowable number of ze-roes between ones.

A system of the type to which the pre-sent schemes apply is represented by a bi-

nary-input, real-valued-output channelmodel illustrated in the figure. At thetransmitting end, information bits are firstencoded by use of an error-correctingcode, then further encoded by use of aconstrained code. Several constrainedcodes for channels subject to constraintsof (d,∞) have been investigated theoreti-cally and computationally. The baselinecodes chosen for purposes of comparisonwere simple PPM codes characterized byM-slot PPM frames separated by d-slotdead times.

Another category of codes investigatedwas that of synchronous truncated pulse-position modulation (STPPM), which isgenerated by implementing synchronousvariable-length PPM codes in a new way.In a synchronous variable-length PPMcode, mp bits are mapped to mq bits,where m, p, and q are positive integers, pand q are fixed, and m is allowed to vary.Such a code is characterized by, amongother things, a rate (average number ofbits per slot) of p/q. In generating aSTPPM code, a procedure based partly ona binary tree is followed in mapping un-

constrained binary sequences into the ap-plicable constraint. In addition to thedead-time constraint, the code words in-volved in the mapping are subject to somemathematical constraints, a description ofwhich would greatly exceed the spaceavailable for this article.

The advantages and disadvantages ofthe schemes investigated are not subject toany single, simple characterization. In gen-eral, it was found that for constrained PPMcodes concatenated with error-correctingcodes at the transmitting end and iterativedecoding at the receiving end, there areadvantages over baseline schemes with re-spect to error rate at a given signal-to-noiseratio, throughput at a given error rate, andcomplexity relative to prior schemes thatinclude iterative decoding.

This work was done by Bruce Moision andJon Hamkins of Caltech for NASA’s JetPropulsion Laboratory. Further informa-tion is contained in a TSP (see page 1).


Error-CorrectingCode Encoder

Constrained-Code

Encoder

LaserModulator

Error-CorrectingCode Decoder

Constrained-Code

Decoder

LaserModulator

Coded BitsInformation

Bits

InformationBits

ConstrainedCoded Bits

LikelihoodsReal-Valued

Statistics

Additive WhiteGaussian Noise

Error-Correcting and Constrained PPM Codes are concatenated at the transmitting end of a commu-nication channel.

System for Better Spacing of Airplanes En RouteDeviations from preferred trajectories can be reduced.Ames Research Center, Moffett Field, California

An improved method of computingthe spacing of airplanes en route, andsoftware to implement the method,have been invented. The purpose of the

invention is to help air-traffic con-trollers minimize those deviations of theairplanes from the trajectories pre-ferred by their pilots that are needed to

make the airplanes comply with miles-in-trail spacing requirements (definedbelow). The software is meant to be amodular component of the Center-


TRACON Automation System (CTAS)(TRACON signifies “terminal radar ap-proach control”). The invention re-duces controllers’ workloads and re-duces fuel consumption by reducing thenumber of corrective clearances neededto achieve conformance with specifiedflow rates, without causing conflicts,while providing for more efficient distri-bution of spacing workload upstreamand across air-traffic-control sectors.

Prerequisite to a meaningful sum-mary of the invention are definitions ofthe terms “miles in trail” and “conflictprobe”:• “Miles in trail” signifies a specified dis-

tance, in nautical miles, required to bemaintained between airplanes.

• A conflict probe is a computer pro-gram that assists air-traffic controllersin maintaining safe distances betweenaircraft by predicting conflicts (essen-tially, close approaches with potentialfor collision) as long as 20 minutes inadvance. The predictions are made byuse of a combination of (1) informa-tion on the present state of the aircraft(horizontal positions, altitudes, and ve-locities) obtained by tracking; (2) in-formation on the anticipated states ofthe aircraft obtained from flight plans;(3) information on atmospheric condi-tions; and (4) information on the aero-dynamics and engine performancecharacterization of the airplanes.

In broad terms, the inventive methodinvolves establishment of a spacing ref-erence geometry (described below);prediction of locations of all aircraft ofinterest at the predicted time of inter-section of the path of whichever of theaircraft is expected to first intersect thespacing reference geometry; and deter-mination of the distances between air-craft on the basis of their predicted lo-cations at that time. The design spacingreference geometry includes a collec-tion of fixed waypoints (including loca-tions of navaids, airway intersections,and predetermined latitude/longitudepositions); airspace sector boundaries;arcs defined in reference to airports orother geographical locations; arbitrarylines in space; and combinations of linesegments.

The software generates a display thatincludes the predicted locations andspacings of the aircraft of interest. Thespacings can be indicated in any of a va-riety of formats — for example, al-phanumerically on a list adjacent to aradar display showing flightpaths andspacing-reference-geometry features ofa region of interest. When an alterationin flight characteristics (course, speed,and/or altitude) of one or more of theaircraft is proposed, the predicted loca-tions and spacings are recalculated,thereby providing feedback as to con-formance of the proposed alteration

with the spacing requirement. In addi-tion, a conflict probe is preferably usedto determine whether the proposed al-teration could cause a conflict.

By selection of spacing-calculation pa-rameters, an air-traffic controller canspecify whether the determination ofspacing is one of rolling spacing, fixedspacing, absolute spacing distance, orrelative spacing distance. It is possible toimpose a “meet spacing” requirement,in response to which the software pro-poses, to the controller, changes ofcourse, speed, and altitude of one ormore of aircraft that would satisfy thespacing requirement. Aircraft may beselected by matching aircraft to inputstream characteristics, as well as by di-rectly identifying flights by controllerinput, and the selection process can berepeated at intervals. Spacing advisorydata are preferably reported to othercontrollers responsible for monitoringeach aircraft.

This work was done by Steven Green andHeinz Erzberger of Ames Research Cen-ter. Further information is contained in aTSP (see page 1).

This invention has been patented byNASA (U.S. Patent No. 6,393,358). Inqui-ries concerning nonexclusive or exclusive li-cense for its commercial development shouldbe addressed to the Patent Counsel, AmesResearch Center, (650) 604-5104. Refer toARC-14418.

Algorithm for Training a Recurrent Multilayer PerceptronLyndon B. Johnson Space Center, Houston, Texas

An improved algorithm has been de-vised for training a recurrent multi-layer perceptron (RMLP) for optimalperformance in predicting the behav-ior of a complex, dynamic, and noisysystem multiple time steps into the fu-ture. [An RMLP is a computationalneural network with self-feedback andcross-talk (both delayed by one timestep) among neurons in hidden lay-ers]. Like other neural-network-train-ing algorithms, this algorithm adjustsnetwork biases and synaptic-connec-tion weights according to a gradient-

descent rule. The distinguishing fea-ture of this algorithm is a combinationof global feedback (the use of predic-tions as well as the current output valuein computing the gradient at each timestep) and recursiveness. The recursiveaspect of the algorithm lies in the in-clusion of the gradient of predictionsat each time step with respect to thepredictions at the preceding time step;this recursion enables the RMLP tolearn the dynamics. It has been conjec-tured that carrying the recursion toeven earlier time steps would enable

the RMLP to represent a noisier, more-complex system.

This work was done by Alexander G. Par-los, Omar T. Rais, and Sunil K. Menon ofTexas A&M University and Amir F. Atiyaof Caltech for Johnson Space Center. Forfurther information, contact:

Dr. Alexander G. ParlosDept. of Nuclear EngineeringTexas A&M UniversityCollege Station, TX 77843Telephone No.: (409) 845-7092, Fax No.: (409) 845-6443

Refer to MSC-22893.


Books & Reports

Orbiter Interface Unit andEarly Communication System

A report describes the Orbiter Inter-face Unit (OIU) and the Early Commu-nication System (ECOMM), which aresystems of electronic hardware and soft-ware that serve as the primary communi-cation links for the International SpaceStation (ISS). When a space shuttle is ator near the ISS during assembly and re-supply missions, the OIU sends ground-or crew-initiated commands from thespace shuttle to the ISS and relaystelemetry from the ISS to the space shut-tle’s payload data systems. The shuttlethen forwards the telemetry to theground. In the absence of a space shut-tle, the ECOMM handles communica-tions between the ISS and Johnson SpaceCenter via the Tracking and Data RelaySatellite System (TDRSS). Innovative fea-tures described in the report include (1)a “smart” data-buffering algorithm thathelps to preserve synchronization (andthereby minimize loss) of telemetric databetween the OIU and the space-shuttlepayload data interleaver; (2) an ECOMMantenna-autotracking algorithm that se-lects whichever of two phased-array an-tennas gives the best TDRSS signal andelectronically steers that antenna to trackthe TDRSS source; and (3) an ECOMMradiation-latchup controller, which de-tects an abrupt increase in current in-dicative of radiation-induced latchupand temporarily turns off power to clearthe latchup, restoring power after thecharge dissipates.

This work was done by Ronald M. Cobbs,Michael P. Cooke, Gary L. Cox, Richard El-lenberger, Patrick W. Fink, Dena S. Haynes,Buddy Hyams, Robert Y. Ling, Helen M.Neighbors, Chau T. Phan, Kelly M. Prender-

gast, James D. Siekierski, Randall S. Wade,George A. Weisskopf, Hester J. Yim, Antha A.Adkins, James R. Carl, Y. C. Loh, CharlesRoberts, Douglas J. Steel, Buveneka Kan-ishka DeSilva, Harold B. Killenb, andRobert M. Williams of Johnson Space Cen-ter. For further information, contact theJohnson Commercial Technology Office at(281) 483-3809. MSC-23225

White-Light Nulling Inter-ferometers for DetectingPlanets

A report proposes the development ofa white-light nulling interferometer tobe used in conjunction with a single-aperture astronomical telescope thatwould be operated in outer space. Whensuch a telescope is aimed at a given star,the interferometer would suppress thelight of that star while passing enoughlight from planets (if any) orbiting thestar, to enable imaging or spectroscopicexamination of the planets. In a nullinginterferometer, according to the pro-posal, scattered light would be sup-pressed by spatial filtering in an array ofsingle-mode optical fibers rather than byrequiring optical surfaces to be accuratewithin 1/4,000 wavelength as in a coron-agraph or an apodized telescope. As aresult, angstrom-level precision wouldbe needed in only the small nulling com-biner, and not in large, meter-sized op-tics. The nulling interferometer couldwork as an independent instrument inspace or in conjunction with a corona-graphic system to detect planets outsideour solar system.

This work was done by Bertrand Mennes-son, Eugene Serabyn, Michael Shao, and

Bruce Levine of Caltech for NASA’s JetPropulsion Laboratory. Further informa-tion is contained in a TSP (see page 1). NPO-30547

Development of Methodol-ogy for Programming Autonomous Agents

A brief report discusses the rationalefor, and the development of, a method-ology for generating computer code forautonomous-agent-based systems. Themethodology is characterized as en-abling an increase in the reusability ofthe generated code among and withinsuch systems, thereby making it possibleto reduce the time and cost of develop-ment of the systems. The methodology isalso characterized as enabling reductionof the incidence of those software errorsthat are attributable to the human fail-ure to anticipate distributed behaviorscaused by the software. A major concep-tual problem said to be addressed in thedevelopment of the methodology wasthat of how to efficiently describe the in-terfaces between several layers of agentcomposition by use of a language that isboth familiar to engineers and descrip-tive enough to describe such interfacesunambivalently.

This work was done by Kutluhan Erol, Re-nato Levy, and Jun Lang of Intelligent Au-tomation, Inc., for Johnson Space Center.For further information, contact:

Intelligent Automation, Inc.7519 Standish Place, (S. 200)Rockville, MD 20855Phone: (301) 294-5200Fax: (301) 294-5201E-mail: [email protected]

Refer to MSC-23385.

National Aeronautics andSpace Administration

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