Technology Focus

Computers/Electronics

Software

Materials

Mechanics

Machinery/Automation

Manufacturing

Bio-Medical

Physical Sciences

Information Sciences

Books and Reports

01-06 January 2006
NASA Tech Briefs, January 2006 1

INTRODUCTION

Tech Briefs are short announcements of innovations originating from research and development activities of the National Aeronautics and Space Administration. They emphasize

information considered likely to be transferable across industrial, regional, or disciplinary lines

and are issued to encourage commercial application.

Availability of NASA Tech Briefs and TSPs

Requests for individual Tech Briefs or for Technical Support Packages (TSPs) announced herein should

be addressed to

National Technology Transfer Center

Telephone 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 

Innovative Partnerships Program (IPP), its documents, and services is also available at the same facility or

on the World Wide Web at http://ipp.nasa.gov. 

Innovative Partnerships Offices are located at NASA field centers to provide technology-transfer access to

industrial users. Inquiries can be made by contacting NASA field centers and Mission Directorates listed below.

Ames Research Center

Lisa L. Lockyer

(650) 604-1754

lisa.l.lockyer@nasa.gov

Dryden Flight Research Center

Gregory Poteat

(661) 276-3872

greg.poteat@dfrc.nasa.gov

Goddard Space Flight Center

Nona Cheeks

(301) 286-5810

Nona.K.Cheeks.1@nasa.gov

Jet Propulsion Laboratory

Ken Wolfenbarger

(818) 354-3821

james.k.wolfenbarger@jpl.nasa.gov

Johnson Space Center

Helen Lane

(713) 483-7165

helen.w.lane@nasa.gov

Kennedy Space Center

Jim Aliberti

(321) 867-6224

Jim.Aliberti-1@nasa.gov

Langley Research Center

Ray P. Turcotte

(757) 864-8881

r.p.turcotte@larc.nasa.gov

John H. Glenn Research Center at

Lewis Field

Robert Lawrence

(216) 433-2921

robert.f.lawrence@nasa.gov

Marshall Space Flight Center

Vernotto McMillan

(256) 544-2615

vernotto.mcmillan@msfc.nasa.gov

Stennis Space Center

John Bailey

(228) 688-1660 

john.w.bailey@nasa.gov

Carl Ray

Small Business Innovation 

Research Program (SBIR) &

Small Business Technology

Transfer Program (STTR)

(202) 358-4652

carl.g.ray@nasa.gov

Frank Schowengerdt

Innovative Partnerships Program

(Code TD)

(202) 358-2560

fschowen@hq.nasa.gov

John Mankins

Exploration Systems Research

and Technology Division

(202) 358-4659

john.c.mankins@nasa.gov

Terry Hertz

Aeronautics and Space Mission

Directorate

(202) 358-4636

thertz@mail.hq.nasa.gov

Glen Mucklow

Mission and Systems 

Management Division (SMD)

(202) 358-2235

gmucklow@

mail.hq.nasa.gov

Granville Paules

Mission and Systems 

Management Division (SMD)

(202) 358-0706

gpaules@mtpe.hq.nasa.gov

Gene Trinh

Human Systems Research and

Technology Division (ESMD)

(202) 358-1490

eugene.h.trinh@nasa.gov

John Rush

Space Communications Office

(SOMD)

(202) 358-4819

john.j.rush@nasa.gov

NASA Field Centers and Program Offices

NASA Mission Directorates

At NASA Headquarters there are four Mission Directorates under

which there are seven major program offices that develop and

oversee technology projects of potential interest to industry:
5 Technology Focus: Sensors

5 Semiautonomous Avionics-and-Sensors 

System for a UAV

6 Biomimetic/Optical Sensors for Detecting

Bacterial Species

7 System Would Detect Foreign-Object Damage in

Turbofan Engine

8 Detection of Water Hazards for Autonomous

Robotic Vehicles

9 Electronics/Computers

9 Fuel Cells Utilizing Oxygen From Air at Low

Pressures 

9 Hybrid Ion-Detector/Data-Acquisition System for

a TOF-MS

9 Spontaneous-Desorption Ionizer for a TOF-MS

10 Equipment for On-Wafer Testing From 220 to

325 GHz

11 Software

11 Computing Isentropic Flow Properties of Air/R134a Mixtures

11 Java Mission Evaluation Workstation System

11 Using a Quadtree Algorithm To Assess Line of

Sight

11 Software for Automated Generation of Cartesian

Meshes

12 Optics Program Modified for Multithreaded

Parallel Computing

12 Programs for Testing Processor-in-Memory

Computing Systems

12 PVM Enhancement for Beowulf MultipleProcessor Nodes

13 Materials

13 Ion-Exclusion Chromatography for Analyzing

Organics in Water

13 Selective Plasma Deposition of Fluorocarbon Films

on SAMs

14 Water-Based Pressure-Sensitive Paints

17 Mechanics

17 System Finds Horizontal Location of Center of

Gravity

17 Predicting Tail Buffet Loads of a Fighter Airplane

18 Water Containment Systems for Testing HighSpeed Flywheels 

19 Machinery/Automation

19 Vapor-Compression Heat Pumps for Operation

Aboard Spacecraft

19 Multistage Electrophoretic Separators

20 Recovering Residual Xenon Propellant for an Ion

Propulsion System

21 Manufacturing

21 Automated Solvent Seaming of Large Polyimide

Membranes

21 Manufacturing Precise, Lightweight Paraboloidal

Mirrors

23 Bio-Medical

23 Analysis of Membrane Lipids of Airborne MicroOrganisms

23 Noninvasive Diagnosis of Coronary Artery Disease

Using 12-Lead High-Frequency Electrocardiograms

25 Physical Sciences

25 Dual-Laser-Pulse Ignition

25 Enhanced-Contrast Viewing of White-Hot Objects

in Furnaces

26 Electrically Tunable Terahertz Quantum-Cascade

Lasers

27 Few-Mode Whispering-Gallery-Mode Resonators

29 Information Sciences

29 Conflict-Aware Scheduling Algorithm

29 Real-Time Diagnosis of Faults Using a Bank of

Kalman Filters 

01-06 January 2006

NASA Tech Briefs, January 2006 3

This document was prepared under the sponsorship of the National Aeronautics and Space Administration. Neither the United States Government nor any person acting on behalf of the United States Government assumes any liability resulting from the use of the information contained

in this document, or warrants that such use will be free from privately owned rights.
NASA Tech Briefs, January 2006 5

Semiautonomous Avionics-and-Sensors System for a UAV

Sensors and associated circuitry are packaged compactly on a circuit board.

Langley Research Center, Hampton, Virginia

Unmanned Aerial Vehicles (UAVs) —

autonomous or remotely controlled pilotless aircraft — have been recently

thrust into the spotlight for military applications, for homeland security, and as

test beds for research. In addition to

these functions, there are many space

applications in which lightweight, inexpensive, small UAVS can be used — e.g.,

to determine the chemical composition

and other qualities of the atmospheres

of remote planets. Moreover, on Earth,

such UAVs can be used to obtain information about weather in various regions; in particular, they can be used to

analyze wide-band acoustic signals to aid

in determining the complex dynamics of

movement of hurricanes.

The Advanced Sensors and Electronics

group at Langley Research Center has

developed an inexpensive, small, integrated avionics-and-sensors system to be

installed in a UAV that serves two purposes. The first purpose is to provide

flight data to an AI (Artificial Intelligence) controller as part of an autonomous flight-control system. The second purpose is to store data from a

subsystem of distributed MEMS (microelectromechanical systems) sensors.

Examples of these MEMS sensors include humidity, temperature, and

acoustic sensors, plus chemical sensors

for detecting various vapors and other

gases in the environment. The critical

sensors used for flight control are a differential-pressure sensor that is part of

an apparatus for determining airspeed,

an absolute-pressure sensor for determining altitude, three orthogonal accelerometers for determining tilt and acceleration, and three orthogonal

angular-rate detectors (gyroscopes). By

using these eight sensors, it is possible to

determine the orientation, height,

speed, and rates of roll, pitch, and yaw of

the UAV. This avionics-and-sensors system is shown in the figure.

During the last few years, there has

been rapid growth and advancement in

the technological disciplines of MEMS, of

onboard artificial-intelligence systems,

and of smaller, faster, and smarter wireless

telemetry systems. The major attraction of

MEMS lies in orders-of-magnitude reductions of power requirements relative to

traditional electronic components that

perform equivalent functions. In addition, the compactness of MEMS, relative

to functionally equivalent traditional electronics systems, makes MEMS attractive

for UAV applications. Recent advances in

MEMS have made it possible to produce

pressure, acceleration, humidity, and temperature sensors having masses in subgram range and possessing sensitivities

and accuracies comparable to those of

larger devices.

Some flight-control sensors, including

pressure sensors, incorporate supporting

circuitry that enables adjustment of their

ranges (to values different from those set

at the factory) in order to satisfy mission

needs. Hence, the pressure sensors can be

set to measure pressures in certain ranges

(in effect, an absolute-pressure sensor can

be set to be sensitive to a specific altitude

and/or a differential-pressure sensor can

be set to be sensitive to specific airspeed).

If the altitude and airspeed requirements

of the UAV are changed, the sensor

ranges can be adjusted accordingly. The

accelerometers incorporate circuitry that

adjusts their offset output voltages so that

an onboard analog-to-digital converter

(16-bit ADC) can center on their stable

voltages. The data from the various sensors are multiplexed via the ADC, and the

data are then gathered by an onboard microcontroller. The microcontroller determines the sample rate for each sensor and

processes the digitized sensor data into a

serial stream at a user-programmable rate.

An interface between this avionics-andsensors system and an external system can

be established at any of several points in

the circuitry — which point depending

on the type and level of control needed by

the external system. For example, the serial data stream is sent to an onboard

UART (Universal Asynchronous Receiver/Transmitter), the 0-to-5-volt output

of which can be utilized directly by an external controller or processor. In addition, the data stream is also sent to an onboard RS-232 level converter chip,

enabling a direct serial-port connection to

an external computer when this avionicsand-sensors system is operated in a laboratory. The onboard microcontroller can be

utilized in two ways: enabling an external

microcontroller or computer to simply reThis Photograph of the Avionics-and-Sensors System shows the critical sensors used for flight control.

LAR-16736-1 Fig1 ABPI

03-30-05 LE

Analog Sensor 

Output Terminal

Sensor-Data 

Terminal

Microcontroller

UART GPS-Data 

Terminal

RS232 GPS-Data

Terminal

RS232 Sensor

Data Terminal

Altitude 

Sensor

Accelerometers 

2 and 3

Airspeed Sensor

Gyroscope 3

Power Terminal

Power Switch

Gyroscope 2

Gyroscope 1

Accelerometer 1

Technology Focus: Sensors
6 NASA Tech Briefs, January 2006

ceive and respond to the sensor data, or

controlling the flow of the sensor data.

The UAV control system provides (1)

external connections to flight sensors,

(2) the computational resources necessary to make flight decisions, and (3) a

simple interface through which control

can be exerted over the servomotors

that actuate the flight-control mechanisms of the UAV.

This work was done by Qamar Shams of

Langley Research Center. For further information, contact the Langley Innovative

Partnerships Office at (757) 864-8881.

LAR-16736-1

Biomimetic/Optical Sensors for Detecting Bacterial Species

Bacteria in liquid samples could be detected in real time.

NASA’s Jet Propulsion Laboratory, Pasadena, California

Biomimetic/optical sensors have been

proposed as means of real-time detection

of bacteria in liquid samples through

real-time detection of compounds secreted by the bacteria. Bacterial species

of interest would be identified through

detection of signaling compounds

unique to those species. The best-characterized examples of quorum-signaling

compounds are acyl-homoserine lactones and peptides. Each compound, secreted by each bacterium of an affected

species, serves as a signal to other bacteria of the same species to engage in a collective behavior when the population

density of that species reaches a threshold level analogous to a quorum.

A sensor according to the proposal

would include a specially formulated

biomimetic film, made of a molecularly

imprinted polymer (MIP), that would

respond optically to the signaling compound of interest. The MIP film would

be integrated directly onto an opticalwaveguide-based ring resonator for optical readout. Optically, the sensor

would resemble the one described in

“Chemical Sensors Based on Optical

Ring Resonators” (NPO-40601), NASA

Tech Briefs, Vol. 29, No. 10 (October

2005), page 32.

MIPs have been used before as molecular-recognition compounds,

though not in the manner of the present proposal. Molecular imprinting is

an approach to making molecularly selective cavities in a polymer matrix.

These cavities function much as enzyme receptor sites: the chemical functionality and shape of a cavity in the

polymer matrix cause the cavity to bind

to specific molecules. An MIP matrix is

made by polymerizing monomers in

the presence of the compound of interest (template molecule). The polymer

forms around the template. After the

polymer solidifies, the template molecules are removed from the polymer

matrix by decomplexing them from

their binding sites and then dissolving

them, leaving cavities that are matched

to the template molecules in size,

shape, and chemical functionality. The

cavities thus become molecular-recognition sites that bind only to molecules

matched to the sites; other molecules

are excluded.

In a sensor according to the proposal, the MIP would feature molecular

recognition sites that would bind the

specific signaling molecules selectively

according to their size, shape, and

chemical functionality (see figure). As

the film took up the signaling molecules in the molecular recognition

sites, the index of refraction and thickness of the film would change, causing

a wavelength shift of the peak of the

resonance spectrum. It has been estimated that by measuring this wavelength shift, it should be possible to detect as little as 10 picomoles of a

peptide signaling compound.

This work was done by Margie Homer,

Alexander Ksendzov, Shiao-Pin Yen, and

Margaret Ryan of Caltech and Beth

Lazazzera of the University of California,

Los Angeles, for NASA’s Jet Propulsion

Laboratory. Further information is contained in a TSP (see page 1).

In accordance with Public Law 96-517,

the contractor has elected to retain title to this

invention. Inquiries concerning rights for its

commercial use should be addressed to:

Innovative Technology Assets Management

JPL

Mail Stop 202-233

4800 Oak Grove Drive

Pasadena, CA 91109-8099

(818) 354-2240

E-mail: iaoffice@jpl.nasa.gov

Refer to NPO-40950, volume and number of this NASA Tech Briefs issue, and

the page number.

Capture of Target Molecules at molecular recognition sites in an MIP film would cause a change in the

wavelength of an optical resonance. The change would be proportional to the concentration of bacteria that secreted the target molecules.

C C

C

O

O

O

OH HO

HO

H2N NH2

O

C C

C

O

O

O

OH HO

HO

NH2 H2N

O

+

Molecular Recognition

Site In MIP

Captured Target

Molecule

Target

Molecule

Transmittance

Wavelength
NASA Tech Briefs, January 2006 7

System Would Detect Foreign-Object Damage in 

Turbofan Engine

Vibration-sensor and gas-path-analysis data would be fused.

John H. Glenn Research Center, Cleveland, Ohio

A proposed data-fusion system, to be

implemented mostly in software, would

further process the digitized and preprocessed outputs of sensors in a turbofan engine to detect foreign-object damage (FOD) [more precisely, damage

caused by impingement of such foreign

objects as birds, pieces of ice, and runway debris]. The proposed system could

help a flight crew to decide what, if any,

response is necessary to complete a

flight safely, and could aid mechanics in

deciding what post-flight maintenance

action might be needed.

The sensory information to be utilized

by the proposed system would consist of

(1) the output of an accelerometer in an

engine-vibration-monitoring subsystem

and (2) features extracted from a gas

path analysis. [“Gas path analysis” (GPA)

is a term of art that denotes comprehensive analysis of engine performance derived from readings of fuel-flow meters,

shaft-speed sensors, temperature sensors, and the like.]

• The acceleration signal would first be

processed by a wavelet-transform-based

algorithm, using a wavelet created for

the specific purpose of finding abrupt

FOD-induced changes in noisy accelerometer signals. Two additional

features extracted would be the amplitude of vibration (determined via a single-frequency Fourier transform calculated at the rotational speed of the

engine), and the rate of change in amplitude due to an FOD-induced rotor

imbalance. 

• This system would utilize two GPA features: the fan efficiency and the rate of

change of fan efficiency with time.

The selected GPA and vibrational

features would be assessed by two

fuzzy-logic inference engines, denoted

the “Gas Path Expert” and the “Vibration Expert,” respectively (see Figure

1). Each of these inference engines

would generate a “possibility” distribution for occurrence of an FOD

event: Each inference engine

would assign, to

its input information, degrees of

membership, which would subsequently be transformed into basic

probability assignments for the gaspath and vibration components. The

outputs of the inference engines

would be fused by use of Dempster’s

combination algorithm (more precisely, an algorithm, based on the

Dempster-Shafer-Yager theory of evidence, for fusing uncertain or imprecise information) to provide a reduced body of information to a

human or computer decision maker.

Figure 2 depicts some outputs generated in response to simulated accelerometer and GPA signals.

This work was done by James A. Torso of

QSS Group, Inc. and Jonathan S. Litt of the

U. S. Army Research Laboratory for Glenn

Research Center. Further information is

contained in a TSP (see page 1).

Inquiries concerning rights for the commercial use of this invention should be addressed to NASA Glenn Research Center, Innovative Partnerships Office, Attn: Steve

Fedor, Mail Stop 4–8, 21000 Brookpark

Road, Cleveland, Ohio 44135. Refer to

LEW-17843-1

Figure 1. Outputs of Two “Experts” (fuzzy-logic inference engines) would be

fused at the feature level by means of Dempster’s combination algorithm.

Fan Efficiency Estimated From Sensor

Data by Use of Kalman Filter Fan-Bearing Accelerometer Signal

Extraction of Relevant Features:

Magnitude of Fan Efficiency

Rate of Change in Magnitude

Extraction of Relevant Features:

Wavelet Feature

Vibration Amplitude

Rate of Change in Amplitude

Categorization of Estimated Features

via Fuzzy Interface Techniques

Categorization of Vibration-Data

Features via Fuzzy Interface

Techniques

Basic Probability Assignment for

Occurrence of FOD, Given

GPA Information

Basic Probability Assignments for

Occurrence of FOD, Given

Vibration Information

Reduction of Noise by Use of Moving

Average

Wavelet Decomposition and

Reconstruction of Relevant Vibration

Information

“Gas Path Expert” “Vibration Expert”

Fusion By Use of

Dempster’s Combination Algorithm

Range of Probability of Occurrence of FOD

LEW-17843-1 Fig 1 ABPI 4-6-05 bs

Figure 2. These Example Outputs of the proposed system were generated

in response to simulated vibrational and GPA inputs characteristic of marginal and conflicting evidence, respectively, of occurrence of an FOD event

near the 2-second time mark.

0 0

0.2

0.4

0.6

0.8

1.0

0.5 1.0 1.5 2.0 2.5

Time, Seconds

3.0 3.5 4.0 4.5 5.0

0 0

0.2

0.4

0.6

0.8

1.0

0.5 1.0 1.5 2.0 2.5

Time, Seconds

3.0 3.5 4.0 4.5

Plausibility Function

Belief Function

Plausibility Function

Belief Function

5.0

MARGINAL EVIDENCE

CONFLICTING EVIDENCE

LEW-17843-1 Fig 2 ABPI 4-6-05 bs
Four methods of detection of bodies

of water are under development as

means to enable autonomous robotic

ground vehicles to avoid water hazards

when traversing off-road terrain. The

methods involve processing of digitized

outputs of optoelectronic sensors

aboard the vehicles. It is planned to implement these methods in hardware and

software that would operate in conjunction with the hardware and software for

navigation and for avoidance of solid

terrain obstacles and hazards.

The first method, intended for use

during the day, is based on the observation that, under most off-road conditions, reflections of sky from water are

easily discriminated from the adjacent

terrain by their color and brightness,

regardless of the weather and of the

state of surface waves on the water. Accordingly, this method involves collection of color imagery by a video camera

and processing of the image data by an

algorithm that classifies each pixel as

soil, water, or vegetation according to

its color and brightness values (see figure). Among the issues that arise is the

fact that in the presence of reflections

of objects on the opposite shore, it is

difficult to distinguish water by color

and brightness alone. Another issue is

that once a body of water has been

identified by means of color and

brightness, its boundary must be

mapped for use in navigation. Techniques for addressing these issues are

under investigation.

The second method, which is not limited by time of day, is based on the observation that ladar returns from bodies of

water are usually too weak to be detected. In this method, ladar scans of the

terrain are analyzed for returns and the

absence thereof. In appropriate regions,

the presence of water can be inferred

from the absence of returns. Under

some conditions in which reflections

from the bottom are detectable, ladar

returns could, in principle, be used to

determine depth.

The third method involves the recognition of bodies of water as dark areas

in short-wavelength infrared (SWIR)

images. This method is based on the

fact, well known among experts in remote sensing, that water bodies of any

appreciable depth appear very dark in

near-infrared, overhead imagery. Even

under a thick layer of marine fog, SWIR

illumination is present. Hence, this

method may work even in the presence

of clouds, though it is unlikely to work

at night. Snow and ice also exhibit very

strong absorption at wavelengths

greater than about 1.4 μm. Hence, the

wavelength range of about 1.5 to 1.6

μm might be useable in this method for

recognizing water, snow, and ice. One

notable drawback of this method is that

useful look-ahead distance could be

limited by surface reflections. 

The fourth method, intended for use

at night, involves the contrast between

water and terrain in thermal-infrared

(medium-wavelength infrared) imagery.

This method is based on the fact that at

night, water is usually warmer than the

adjacent terrain. Look-ahead distance

could be limited in this method because,

for reasons not yet fully understood,

water appears to darken in the thermal

infrared with increasing distance. 

This work was done by Larry Matthies,

Paolo Belluta, and Michael McHenry of Caltech for NASA’s Jet Propulsion Laboratory. Further information is contained in a

TSP (see page 1).

The software used in this innovation is

available for commercial licensing. Please

contact Karina Edmonds of the California Institute of Technology at (818) 393-2827.

Refer to NPO-40369.

8 NASA Tech Briefs, January 2006

Images of the Chatfield Reservoir in Denver were acquired under rippled and still surface conditions,

then pixels were classified by color. In the synthetic color classification images, white represents water,

brown represents soil, green signifies vegetation, and blue signifies anything else. In the rippled case,

all of the water is correctly labeled. In the still case, water reflecting the sky is correctly classified, but

water reflecting trees is erroneously classified as vegetation.

STILL

NPO-40369 

ABPI

06-01-04 

RIPPLED

Original Image Color Classification Image

Original Image Color Classification Image

Detection of Water Hazards for Autonomous Robotic Vehicles

Four methods of optoelectronic detection complement each other.

NASA’s Jet Propulsion Laboratory, Pasadena, California
NASA Tech Briefs, January 2006 9

A fuel cell stack has been developed to

supply power for a high-altitude aircraft

with a minimum of air handling. The

fuel cell is capable of utilizing oxygen

from ambient air at low pressure with no

need for compression. For such an application, it is advantageous to take oxygen from the air (in contradistinction to

carrying a supply of oxygen onboard),

but it is a challenging problem to design

a fuel-cell stack of reasonable weight

that can generate sufficient power while

operating at reduced pressures. 

The present fuel-cell design is a response to this challenge. The design features a novel bipolar plate structure in

combination with a gas-diffusion structure based on a conductive metal core

and a carbon gas-diffusion matrix. This

combination makes it possible for the

flow fields in the stack to have a large

open fraction (ratio between open volume and total volume) to permit large

volumes of air to flow through with exceptionally low backpressure. Operations at reduced pressure require a corresponding increase in the volume of

air that must be handled to deliver the

same number of moles of oxygen to the

anodes. Moreover, the increase in the

open fraction, relative to that of a comparable prior fuel-cell design, reduces

the mass of the stack. 

The fuel cell has been demonstrated

to operate at a power density as high as

105 W/cm2 at an air pressure as low as 2

psia (absolute pressure ≈14 kPa), which

is the atmospheric pressure at an altitude

of about 50,000 ft (≈15.2 km). The improvements in the design of this fuel cell

could be incorporated into designs of

other fuel cells to make them lighter in

weight and effective at altitudes higher

than those of prior designs. Potential

commercial applications for these improvements include most applications

now under consideration for fuel cells. 

This work was done by Alan Cisar, Chris

Boyer, and Charles Greenwald of Lynntech,

Inc., for Glenn Research Center. 

Inquiries concerning rights for the commercial use of this invention should be addressed to NASA Glenn Research Center,

Commercial Technology Office, Attn: Steve

Fedor, Mail Stop 4-8, 21000 Brookpark

Road, Cleveland, Ohio 44135. Refer to

LEW-17284-1.

Fuel Cells Utilizing Oxygen From Air at Low Pressures 

Power-to-weight ratios would be higher than in prior fuel cells. 

John H. Glenn Research Center, Cleveland, Ohio

Electronics/Computers

A modified ion-detector/data-acquisition system has been devised to increase

the dynamic range of a time-of-flight mass

spectrometer (TOF-MS) that, previously,

included a microchannel-plate detector

and a data-acquisition system based on

counting pulses and time-tagging them by

use of a time-to-digital converter (TDC).

The dynamic range of the TOF-MS was

limited by saturation of the microchannelplate detector, which can handle no more

than a few million counts per second. The

modified system includes (1) a combined

microchannel plate/discrete ion multiplier and (2) a hybrid data-acquisition system that simultaneously performs analog

current or voltage measurements and

multianode single-ion-pulse-counting

time-of-flight measurements to extend the

dynamic range of a TDC into the regime

in which a mass peak comprises multiple

ions arriving simultaneously at the detector. The multianode data are used to determine, in real time, whether the detector is saturated. When saturation is

detected, the data-acquisition system selectively enables circuitry that simultaneously

determines the ion-peak intensity by measuring the time profile of the analog current or voltage detector-output signal.

This work was done by William D. Burton,

Jr.; J. Albert Schultz; Valentine Vaughn; Michael

McCully; Steven Ulrich; and Thomas F. Egan of

Ionwerks, Inc., for Kennedy Space Center. 

In accordance with Public Law 96-517,

the contractor has elected to retain title to this

invention. Inquiries concerning rights for its

commercial use should be addressed to:

William D. Burton, Jr.

Ionwerks, Inc.

2472 Bolsover, Suite 255

Houston, TX 77005

Phone: (713) 522-9880

E-mail: wmburton@ionwerks.com

Refer to KSC-12619, volume and number

of this NASA Tech Briefs issue, and the

page number.

Hybrid Ion-Detector/Data-Acquisition System for a TOF-MS

John F. Kennedy Space Center, Florida

Spontaneous-Desorption Ionizer for a TOF-MS

John F. Kennedy Space Center, Florida

A time-of-flight mass spectrometer

(TOF-MS) like the one mentioned in

the immediately preceding article has

been retrofitted with an ionizer based

on a surface spontaneous-desorption

process. This ionizer includes an electron multiplier in the form of a microchannel plate (MCP). Relative to

an ionizer based on a hot-filament

electron source, this ionizer offers advantages of less power consumption

and greater mechanical ruggedness.

The current density and stability characteristics of the electron emission of

this ionizer are similar to those of a
10 NASA Tech Briefs, January 2006

filament-based ionizer. In tests of various versions of this ionizer in the

TOF-MS, electron currents up to 100

nA were registered. Currents of microamperes or more — great enough

to satisfy requirements in most TOFMS applications — could be obtained

by use of MCPs different from those

used in the tests, albeit at the cost of

greater bulk. One drawback of this

ionizer is that the gain of the MCP decreases as a function of the charge extracted thus far; the total charge that

can be extracted over the operational

lifetime is about 1 coulomb. An MCP

in the ion-detector portion of the

TOF-MS is subject to the same limitation.

This work was done by J. Albert Schultz of

Ionwerks Inc. for Kennedy Space Center.

In accordance with Public Law 96-517,

the contractor has elected to retain title to this

invention. Inquiries concerning rights for its

commercial use should be addressed to:

Ionwerks Inc.

J. Albert Schultz 

2472 Bolsover, Suite 255

Houston, TX 77005

Phone No.: (713) 522-9880

E-mail: AL@ionwerks.com

Refer to KSC-12607, volume and number

of this NASA Tech Briefs issue, and the

page number.

A system of electronic instrumentation,

constituting the equivalent of a two-port vector network analyzer, has been developed

for use in on-wafer measurement of key

electrical characteristics of semiconductor

devices at frequencies from 220 to 325 GHz.

A prior system designed according to similar principles was reported in “Equipment

for On-Wafer Testing at Frequencies Up to

220 GHz” (NPO-20760), NASA Tech Briefs,

Vol. 25, No. 11 (November 2001), page 42.

As one would expect, a major source of difficulty in progressing to the present higherfrequency-range system was the need for

greater mechanical precision as wavelengths shorten into the millimeter range,

approaching the scale of mechanical tolerances of prior systems.

The system (see figure) includes both

commercial off-the-shelf and custom

equipment. As in the system of the cited

prior article, the equipment includes test

sets that are extended versions of commercial network analyzers that function in a

lower frequency range. The extension to

the higher frequency range is accomplished by use of custom frequency-extension modules that contain frequency multipliers and harmonic mixers. On-wafer

measurement is made possible by waveguide wafer probes that were custom designed and built for this wavelength range,

plus an on-wafer calibration substrate designed for use with these probes. In this

case, the calibration substrate was specially

fabricated by laser milling. The system was

used to make the first on-wafer measurements of a semiconductor device in the

frequency range from 220 to 320 GHz.

Some of the measurement results showed

that the device had gain.

This work was done by Lorene Samoska, Alejandro Peralta, Douglas Dawson, and Karen

Lee of Caltech; Greg Boll of GGB Industries;

and Chuck Oleson of Oleson Microwave Labs

for NASA’s Jet Propulsion Laboratory.

Further information is contained in a TSP (see

page 1).

NPO-40955

Equipment for On-Wafer Testing From 220 to 325 GHz

On-wafer vector network analysis of semiconductors is extended to higher frequencies.

NASA’s Jet Propulsion Laboratory, Pasadena, California

NPO-40955 

ABPI

072505 LE

A Probe Station and Test Sets assembled from commercial-off-the-shelf and custom components enable on-wafer measurement of electrical characteristics of devices in the previously inaccessible frequency range of 220 to 325 GHz.
NASA Tech Briefs, January 2006 11

Software

Computing Isentropic 

Flow Properties of Air/

R-134a Mixtures

MACHRK is a computer program

that calculates isentropic flow properties of mixtures of air and refrigerant

R-134a (tetrafluoroethane), which are

used in transonic aerodynamic testing

in a wind tunnel at Langley Research

Center. Given the total temperature,

total pressure, static pressure, and

mole fraction of R-134a in a mixture,

MACHRK calculates the Mach number

and the following associated flow properties: dynamic pressure, velocity, density, static temperature, speed of sound,

viscosity, ratio of specific heats,

Reynolds number, and Prandtl number. Real-gas effects are taken into account by treating the gases comprising

the mixture as both thermally and

calorically imperfect. The RedlichKwong equation of state for mixtures

and the constant-pressure ideal heatcapacity equation for the mixture are

used in combination with the departure-function approach of thermodynamics to obtain the equations for

computing the flow properties. In addition to the aforementioned calculations for air/R-134a mixtures, a research version of MACHRK can

perform the corresponding calculations for mixtures of air and R-12

(dichlorodifluoromethane) and for

air/SF6 mixtures. [R-12 was replaced by

R-134a because of environmental concerns. SF6 has been considered for use

in increasing the Reynolds-number

range.]

This program was written by Ray Kvaternik

of Langley Research Center. Further information is contained in a TSP (see page 1).

LAR-17095-1

Java Mission Evaluation

Workstation System

The Java Mission Evaluation Workstation System (JMEWS) is a collection of

applications designed to retrieve, display, and analyze both real-time and

recorded telemetry data. This software

is currently being used by both the

Space Shuttle Program (SSP) and the

International Space Station (ISS) program. JMEWS was written in the Java

programming language to satisfy the requirement of platform independence.

An object-oriented design was used to

satisfy additional requirements and to

make the software easily extendable. By

virtue of its platform independence,

JMEWS can be used on the UNIX workstations in the Mission Control Center

(MCC) and on office computers.

JMEWS includes an interactive editor

that allows users to easily develop displays that meet their specific needs. The

displays can be developed and modified

while viewing data. By simply selecting a

data source, the user can view real-time,

recorded, or test data. 

This program was written by Ross Pettinger, Tim Watlington, Richard Ryley, and

Jeff Harbour of Lockheed Martin Corp. for

Johnson Space Center. For further information, contact the Johnson Innovative Partnerships Office at (281) 483-3809. 

MSC-23665

Using a Quadtree Algorithm

To Assess Line of Sight

A matched pair of computer algorithms determines whether line of sight

(LOS) is obstructed by terrain. These

algorithms were originally designed for

use in conjunction with combat-simulation software in military training exercises, but could also be used for such

commercial purposes as evaluating

lines of sight for antennas or determining what can be seen from a “room with

a view.” The quadtree preparation algorithm operates on an array of digital elevation data and only needs to be run

once for a terrain region, which can be

quite large. Relatively little computation time is needed, as each elevation

value is considered only one and onethird times. The LOS assessment algorithm uses that quadtree to answer LOS

queries. To determine whether LOS is

obstructed, a piecewise-planar (or

higher-order) terrain skin is computationally draped over the digital elevation data. Adjustments are made to

compensate for curvature of the Earth

and for refraction of the LOS by the atmosphere. Average computing time appears to be proportional to the number

of queries times the logarithm of the

number of elevation data points. Accuracy is as high as is possible for the available elevation data, and symmetric results are assured. In the simulation, the

LOS query program runs as a separate

process, thereby making more randomaccess memory available for other computations.

These programs were written by Joseph

Gonzalez, Robert Chamberlain, Eric Tailor,

and Gary Gutt of Caltech for NASA’s Jet

Propulsion Laboratory. Further information is contained in a TSP (see page 1).

This software is available for commercial

licensing. Please contact Karina Edmonds of

the California Institute of Technology at

(818) 393-2827. Refer to NPO-40596.

Software for Automated

Generation of Cartesian

Meshes

Cart3D is a collection of computer

programs for generating Cartesian

meshes [for computational fluid dynamics (CFD) and other applications]

in volumes bounded by solid objects.

Aspects of Cart3D at earlier stages of

development were reported in “Robust

and Efficient Generation of Cartesian

Meshes for CFD” (ARC-14275), NASA

Tech Briefs, Vol. 23, No. 8 (August

1999), page 30. The geometric input to

Cart3D comprises surface triangulations like those commonly generated

by computer-aided-design programs.

Complexly shaped objects can be represented as assemblies of simpler ones.

Cart3D deletes all portions of such an

assembled object that are not on the

exterior surface. Intersections between

components are preserved in the resulting triangulation. A tie-breaking

routine unambiguously resolves geometric degeneracies. Then taking the

intersected surface triangulation as

input, the volume mesh is generated

through division of cells of an initially

coarse hexahedral grid. Cells are subdivided to refine the grid in regions of increased surface curvature and/or increased flow gradients. Cells that

become split into multiple unconnected regions by thin pieces of surface are identified.

These programs were written by Michael J.

Aftosmis and John E. Melton of Ames Research Center and Marsha J. Berger of the

Courant Institute of Mathematics at New

York University. Further information is contained in a TSP (see page 1).

Inquiries concerning rights for the commercial use of this invention should be addressed

to the Technology Partnerships Division,

Ames Research Center, (650) 604-2954.

Refer to ARC-14275-1.
12 NASA Tech Briefs, January 2006

Optics Program Modified

for Multithreaded Parallel

Computing

A powerful high-performance computer program for simulating and analyzing adaptive and controlled optical

systems has been developed by modifying the serial version of the Modeling

and Analysis for Controlled Optical

Systems (MACOS) program to impart

capabilities for multithreaded parallel

processing on computing systems

ranging from supercomputers down to

Symmetric Multiprocessing (SMP) personal computers. The modifications

included the incorporation of

OpenMP, a portable and widely supported application interface software,

that can be used to explicitly add multithreaded parallelism to an application program under a shared-memory

programming model. OpenMP was applied to parallelize ray-tracing calculations, one of the major computing

components in MACOS. Multithreading is also used in the diffraction propagation of light in MACOS based on pthreads [POSIX Thread, (where

“POSIX” signifies a portable operating

system for UNIX)]. In tests of the parallelized version of MACOS, the

speedup in ray-tracing calculations was

found to be linear, or proportional to

the number of processors, while the

speedup in diffraction calculations

ranged from 50 to 60 percent, depending on the type and number of processors. The parallelized version of

MACOS is portable, and, to the user,

its interface is basically the same as

that of the original serial version of

MACOS.

This program was written by John Lou,

Dave Bedding, and Scott Basinger of Caltech

for NASA’s Jet Propulsion Laboratory.

Further information is contained in a TSP

(see page 1).

This software is available for commercial

licensing. Please contact Karina Edmonds of

the California Institute of Technology at

(818) 393-2827. Refer to NPO-40572.

Programs for Testing

Processor-in-Memory 

Computing Systems

The Multithreaded Microbenchmarks

for Processor-InMemory (PIM) Compilers, Simulators, and Hardware are

computer programs arranged in a series

for use in testing the performances of

PIM computing systems, including compilers, simulators, and hardware. The

programs at the beginning of the series

test basic functionality; the programs at

subsequent positions in the series test increasingly complex functionality. The

programs are intended to be used while

designing a PIM system, and can be used

to verify that compilers, simulators, and

hardware work correctly. The programs

can also be used to enable designers of

these system components to examine

tradeoffs in implementation. Finally,

these programs can be run on non-PIM

hardware (either single-threaded or

multithreaded) using the POSIX

pthreads standard to verify that the

benchmarks themselves operate correctly. [POSIX (Portable Operating System Interface for UNIX) is a set of standards that define how programs and

operating systems interact with each

other. pthreads is a library of pre-emptive thread routines that comply with

one of the POSIX standards.]

These programs were written by Daniel S.

Katz of Caltech for NASA’s Jet Propulsion

Laboratory. Further information is contained in a TSP (see page 1).

This software is available for commercial

licensing. Please contact Karina Edmonds of

the California Institute of Technology at

(818) 393-2827. Refer to NPO-41206.

PVM Enhancement for 

Beowulf Multiple-Processor

Nodes

A recent version of the Parallel Virtual Machine (PVM) computer program

has been enhanced to enable use of

multiple processors in a single node of a

Beowulf system (a cluster of personal

computers that runs the Linux operating system). A previous version of PVM

had been enhanced by addition of a

software port, denoted BEOLIN, that

enables the incorporation of a Beowulf

system into a larger parallel processing

system administered by PVM, as though

the Beowulf system were a single computer in the larger system. BEOLIN

spawns tasks on (that is, automatically

assigns tasks to) individual nodes within

the cluster. However, BEOLIN does not

enable the use of multiple processors in

a single node. The present enhancement adds support for a parameter in

the PVM command line that enables the

user to specify which Internet Protocol

host address the code should use in

communicating with other Beowulf

nodes. This enhancement also provides

for the case in which each node in a Beowulf system contains multiple processors. In this case, by making multiple

references to a single node, the user can

cause the software to spawn multiple

tasks on the multiple processors in that

node.

This work was done by Paul Springer of

Caltech for NASA’s Jet Propulsion Laboratory. Further information is contained in

a TSP (see page 1).

The software used in this innovation is

available for commercial licensing. Please

contact Karina Edmonds of the California

Institute of Technology at (818) 393-2827.

Refer to NPO-41706.
NASA Tech Briefs, January 2006 13

Materials

Ion-Exclusion Chromatography for Analyzing Organics in Water

Resolution of nonvolatile organic compounds is increased significantly.

Lyndon B. Johnson Space Center, Houston, Texas

A liquid-chromatography technique

has been developed for use in the quantitative analysis of urea (and of other

nonvolatile organic compounds typically

found with urea) dissolved in water. The

technique involves the use of a column

that contains an ion-exclusion resin;

heretofore, this column has been sold

for use in analyzing monosaccharides

and food softeners, but not for analyzing

water supplies.

The prior technique commonly used

to analyze water for urea content has

been one of high-performance liquid

chromatography (HPLC), with reliance

on hydrophobic interactions between analytes in a water sample and long-chain

alkyl groups bonded to an HPLC column. The prior technique has proven inadequate because of a strong tendency

toward co-elution of urea with other compounds. Co-elution often causes the urea

and other compounds to be crowded into

a narrow region of the chromatogram

(see left part of figure), thereby giving

rise to low chromatographic resolution

and misidentification of compounds. It is

possible to quantitate urea or another analyte via ultraviolet- and visible-light absorbance measurements, but in order to

perform such measurements, it is necessary to dilute the sample, causing a significant loss of sensitivity.

The ion-exclusion resin used in the

improved technique is sulfonated polystyrene in the calcium form. Whereas

the alkyl-chain column used in the prior

technique separates compounds on the

basis of polarity only, the ion-exclusionresin column used in the improved technique separates compounds on the basis

of both molecular size and electric

charge. As a result, the degree of separation is increased: instead of being

crowded together into a single chromatographic peak only about 1 to 2 minutes wide as in the prior technique, the

chromatographic peaks of different

compounds are now separated from

each other and spread out over a range

about 33 minutes wide (see right part of

figure), and the urea peak can readily be

distinguished from the other peaks.

Although the analysis takes more time

in the improved technique, this disadvantage is offset by two important advantages:

• Sensitivity is increased. The minimum

concentration of urea that can be

measured is reduced (to between 1/5

and 1/3 of that of the prior technique)

because it is not necessary to dilute the

sample.

• The separation of peaks facilitates the

identification and quantitation of the

various compounds. The resolution of

the compounds other than urea makes

it possible to identify those compounds by use of mass spectrometry.

This work was done by Richard Sauer of

Johnson Space Center and Jeffrey A.

Rutz and John R. Schultz of Wyle Laboratories. For further information, contact the

Johnson Commercial Technology Office at

(281) 483-3809. 

MSC-23000

These Chromatograms were made from samples of space-shuttle humidity condensate, which contained dissolved urea and other impurities.

?

?

?

? ?

? = Unknown Impurity

0.5 mL/minute Water,

25-L Sample,

196-nm Detection

1.5 mL/minute Water,

25-L Sample,

210-nm Detection

PRIOR TECHNIQUE PRESENT (IMPROVED) TECHNIQUE

?

?

Urea, 4 Parts

per Million

Urea, 15 Parts per Million

Unknown Impurities

?

?

0 1 2 3 4 5 0 5

0 –0.2

0.0

0.2

0.4

0.6

0.8

1.0

1.2

2.5

5.0

7.5

10.0

12.5

15.0

17.5

20.0

10 15 20

Time, Minutes Time, Minutes

Chromatographic Intensity, mAU

Chromatographic Intensity, mAU

25 30 35 40

MSC23000

6-23-00 bs

Selective Plasma Deposition of Fluorocarbon Films on SAMs

The fluorocarbon films are useful as etch masks and perhaps as dielectric layers.

Goddard Space Flight Center, Greenbelt, Maryland

A dry plasma process has been

demonstrated to be useful for the selective modification of self-assembled

monolayers (SAMs) of alkanethiolates.

These SAMs are used, during the fabrication of semiconductor electronic devices, as etch masks on gold layers that

are destined to be patterned and incorporated into the devices. The selective

modification involves the formation of

fluorocarbon films that render the SAMs

more effective in protecting the masked
14 NASA Tech Briefs, January 2006

areas of the gold against etching by a

potassium iodide (KI) solution. This

modification can be utilized, not only in

the fabrication of single electronic devices but also in the fabrication of integrated circuits, microelectromechanical

systems, and circuit boards.

In the steps that precede the dry

plasma process, a silicon mold in the desired pattern is fabricated by standard

photolithographic techniques. A stamp

is then made by casting polydimethylsiloxane (commonly known as silicone

rubber) in the mold. The stamp is

coated with an alkanethiol solution,

then the stamp is pressed on the gold

layer of a device to be fabricated in

order to deposit the alkanethiol to form

an alkanethiolate SAM in the desired

pattern (see figure). Next, the workpiece is exposed to a radio-frequency

plasma generated from a mixture of CF4

and H2 gases. After this plasma treatment, the SAM is found to be modified,

while the exposed areas of gold remain

unchanged.

This dry plasma process offers the potential for forming masks superior to

those formed in a prior wet etching

process. Among the advantages over the

wet etching process are greater selectivity, fewer pin holes in the masks, and less

nonuniformity of the masks. The fluorocarbon films formed in this way may also

be useful as intermediate layers for subsequent fabrication steps and as dielectric layers to be incorporated into finished products.

This work was done by Mark M. Crain III,

Kevin M. Walsh, and Robert W. Cohn of the

University of Louisville for Goddard Space

Flight Center. Further information is contained in a TSP (see page 1).

GSC-14440

Water-Based Pressure-Sensitive Paints

Toxicity, and thus costs of ventilation and cleanup, is substantially reduced.

Langley Research Center, Hampton, Virginia

Water-based pressure-sensitive paints

(PSPs) have been invented as alternatives to conventional organic-solventbased pressure-sensitive paints, which

are used primarily for indicating distributions of air pressure on wind-tunnel

models. Typically, PSPs are sprayed onto

aerodynamic models after they have

been mounted in wind tunnels. When

conventional organic-solvent-based PSPs

are used, this practice creates a problem

of removing toxic fumes from inside the

wind tunnels. The use of water-based

PSPs eliminates this problem. The waterbased PSPs offer high performance as

pressure indicators, plus all the advantages of common water-based paints

(low toxicity, low concentrations of

volatile organic compounds, and easy

cleanup by use of water).

A typical PSP (whether conventional

or of the present innovative type) contains the following:

• A luminescent compound, the luminescence of which is quenched by oxygen;

• An oxygen-permeable polymeric

binder;

• Pigment materials to hide the painted

surface and to increase reflectance of

the light emitted from the luminescent

compound; and

• Solvents.

The paint is applied to a surface of interest on a model and allowed to dry.

During a subsequent wind-tunnel test,

under the appropriate illumination, the

intensity of luminescence emitted by the

PSP is inversely proportional to the concentration of oxygen, hence, to the air

pressure at the painted surface.

A water-based PSP contains all the

basic ingredients of a conventional PSP

(see table), except that the organic-solvent content (if any) is much smaller

and the basic ingredients are incorpoA Typical Water-Based PSP Formulation is shown here.

 Proportion in 

Ingredient Weight Percent

water emulsion of 

poly-trifluoroethylmethacrylate-co-isobutylmethacrylate (1:1) 42 to 68.4

propylene glycol 2.28

a glycol ether 10.26

TiO2 (pigment) 11.35

N-methyl pyrrolidinone 6.00

Byk 346 

(or equivalent solution of polyether-modified dimethylpolysiloxane) 0.68

Lubrizol 2062 (or equivalent) aliphatic/aromatic phosphate ester 

for solvent-borne and water-borne coatings 1.03

platinum tetra(pentafluorphenyl)porphyrin (a luminophore) 0.1

A Gold Layer Was Patterned by stamping it with a hexadecanethiol solution. The alkanethiolate SAM

pattern thus formed was modified in a CF4/H2 plasma, forming an etch mask. Then gold was etched

away from the areas not masked.

SAM Mask After Modification Gold Remaining in Masked Areas 

After Etching in KI Solution

GSC-14440 

ABPI

05-25-04 LE
NASA Tech Briefs, January 2006 15

rated in a water matrix. The oxygen-permeable polymer is prepared as a

water-borne emulsion. This is blended

with the necessary coalescing agents,

coupling solvents, luminophore, and

pigments. The resulting water-based PSP

can be applied by spraying to obtain a

single coat, which cures to touch in less

than one hour and cures for use in 12

hours at room temperature. The cured

paint is smooth and has good adhesion

to most metal and plastic substrates.

This work was done by Jeffrey D. Jordan

and A. Neal Watkins of Langley Research Center and Donald M. Oglesby

and JoAnne L. Ingram of Swales Aerospace. Further information is contained in

a TSP (see page 1).

In accordance with Public Law 96-517,

the contractor has elected to retain title to this

invention. Inquiries concerning rights for its

commercial use should be addressed to:

Swales Aerospace

LaRC On-Site Offices

1224T11 N. Wright Street, MS186A

Hampton, VA 23681-9668

Phone: (757) 864-9857

Refer to LAR-16603-1, volume and number of this NASA Tech Briefs issue, and the

page number.
NASA Tech Briefs, January 2006 17

Predicting Tail Buffet Loads of a Fighter Airplane

Airframes can be designed to be more robust.

Langley Research Center, Hampton, Virginia

Buffet loads on aft aerodynamic surfaces pose a recurring problem on most

twin-tailed fighter airplanes: During maneuvers at high angles of attack, vortices

emanating from various surfaces on the

forward parts of such an airplane (engine

inlets, wings, or other fuselage appendages) often burst, immersing the tails

in their wakes. Although these vortices increase lift, the frequency contents of the

burst vortices become so low as to cause

the aft surfaces to vibrate destructively.

Mechanics

An instrumentation system rapidly

and repeatedly determines the horizontal location of the center of gravity of a

laboratory vehicle that slides horizontally on three air bearings (see Figure

1). Typically, knowledge of the horizontal center-of-mass location of such a vehicle is needed in order to balance the

vehicle properly for an experiment

and/or to assess the dynamic behavior

of the vehicle.

The system includes a load cell above

each air bearing, electronic circuits

that generate digital readings of the

weight on each load cell, and a computer equipped with software that

processes the readings. The total

weight and, hence, the mass of the vehicle are computed from the sum of

the load-cell weight readings. Then the

horizontal position of the center of

gravity is calculated straightforwardly

as the weighted sum of the known position vectors of the air bearings, the

contribution of each bearing being

proportional to the weight on that

bearing. In the initial application for

which this system was devised, the center-of-mass calculation is particularly

simple because the air bearings are located at corners of an equilateral triangle. However, the system is not restricted to this simple geometry.

The system acquires and processes

weight readings at a rate of 800 Hz for

each load cell. The total weight and the

horizontal location of the center of gravity

are updated at a rate of 800/3 ≈ 267 Hz.

In a typical application, a technician

would use the center-of-mass output of

this instrumentation system as a guide to

the manual placement of small weights

on the vehicle to shift the center of gravity to a desired horizontal position. Usually, the desired horizontal position is

that of the geometric center. Alternatively, this instrumentation system could

be used to provide position feedback for

a control system that would cause

weights to be shifted automatically (see

Figure 2) in an effort to keep the center

of gravity at the geometric center.

This work was done by Albert S. Johnston, Richard T. Howard, and Linda L.

Brewster of Marshall Space Flight Center. Further information is contained in a

TSP (see page 1).

MFS-31999-1

System Finds Horizontal Location of Center of Gravity

Mass and center-of-mass data are updated at a rate of ≈267 Hz.

Marshall Space Flight Center, Alabama

Figure 1. Three Load Cells measure the weights

applied to three air bearings at the corners of a

triangle.

Figure 2. Motor-Driven Lead Screws would reposition weights, in response to load-cell readings, to

counteract any deviation of the center of gravity from the geometric center.

MFS-31999 Fig 1 ABPI 9-21-03 es

Load

Cell 2

Load

Cell 1

Load

Cell 3

MFS-31999 Fig 2 ABPI 9-21-03 es

Weight

Weight

Drive Motor

and Indexer

Drive

Motor

and

Indexer
18 NASA Tech Briefs, January 2006

This type of buffeting has reduced

the airframe fatigue lives and the system reliabilities of several legacy aircraft. This situation has been brought

on largely because tail buffet loads

have generally been ignored in the design of twin-tailed fighter airplanes.

There are several reasons for this oversight: Fundamentally, tail buffet loads

have not been identified as a major

concern in designing fighter airframes.

More practical reasons are that, until

recently, (1) there was a lack of quantitative data on buffet forces; and (2) no

readily available and cohesive analysis

method could be used to predict buffet

loads during the design of fighter airplanes.

Now, there exists a new analysis capability for predicting buffet loads during

the earliest design phase of a fighter-aircraft program. In effect, buffet pressures

are applied to mathematical models in

the framework of a finite-element code,

complete with aeroelastic properties and

working knowledge of the spatiality of

the buffet pressures for all flight conditions. The results of analysis performed

by use of this capability illustrate those

vibratory modes of a tail fin that are

most likely to be affected by buffet loads.

Hence, the results help in identifying

the flight conditions during which to expect problems. Using this capability, an

aircraft designer can make adjustments

to the airframe and possibly the aerodynamics, leading to a more robust design.

This capability has been utilized in the

design of the Joint Strike Fighter, leading to better understanding of buffet

loads and to total redesign of the airframe to avoid fatigue-life issues.

This work was done by Robert W. Moses

and Anthony S. Pototzky of Langley Research Center. For further information,

contact the Intellectual Property Team at

(757) 864-3521. LAR-16515

Water Containment Systems for Testing High-Speed Flywheels 

Water-filled containers are stacked like bricks. 

John H. Glenn Research Center, Cleveland, Ohio

Water-filled containers are used as

building blocks in a new generation of

containment systems for testing highspeed flywheels. Such containment systems are needed to ensure safety by trapping high-speed debris in the event of

centrifugal breakup or bearing failure.

Traditional containment systems for testing flywheels consist mainly of thick steel

rings. While steel rings are effective for

protecting against fragments from conventional and relatively simple metal flywheels, they are also expensive. Moreover, it is difficult and expensive to

configure steel-ring containment systems for testing of advanced flywheel systems that can include flywheels made of

composite materials, counter-rotating

flywheels, and/or multiple flywheels rotating about different axes. In contrast,

one can quickly, easily, and inexpensively stack water-filled containers like

bricks to build walls, (and, if needed,

floors, and ceilings) of sufficient thickness to trap debris traveling in any possible direction at the maximum possible

kinetic energy that could be encountered in testing a given flywheel system. 

Water is remarkably effective in decelerating high-speed debris: In an analysis

performed in 1998, it was found that for

a fragment that has a characteristic dimension L and an initial kinetic energy

E0, the kinetic energy E after traveling a

distance d through water is approximated by E = E0e

–d/L. For typical fragment

sizes and speeds expected to be encountered in tests of advanced flywheel systems, this equation leads to the expectation that a wall of water only 0.6 m thick

would suffice to dissipate practically all

the kinetic energy. 

The effectiveness of this approach to

shielding against high-speed debris was

demonstrated in a series of tests, including one in which a bullet was fired into a

stack of two cubic cardboard boxes, 0.28

m on each side, containing water-filled

bladders (see figure). The bullet had a

mass of 9.7 g and an initial speed of 790

m/s. Upon impact, the first container was

split, the water in the container was

widely dispersed, and the bullet was deformed. The bullet did not reach the second container. In other words, the bullet

was stopped by less than 0.28 m of water.

Limited composite fragment testing was

also performed in the Ballistics Impact

Laboratory at Glenn Research Center,

which demonstrated the ability to stop a

2.5 × 2.5 × 1.0 cm fragment with a velocity of approximately 730 m/s within 30.5

cm of water.

This work was done by Larry Trase and

Dennis Thompson of Glenn Research

Center. Further information is contained in a TSP (see page 1).

Inquiries concerning rights for the commercial use of this invention should be addressed

to NASA Glenn Research Center, Innovative

Partnerships Office, Attn: Steve Fedor, Mail

Stop 4–8, 21000 Brookpark Road, Cleveland, Ohio 44135. Refer to LEW-17608-1.

A Bullet Was Fired from the left toward two

cubic water-filled containers. The bullet was

stopped by the first container. LEW-17608

ABPI

04-05-05 LE
NASA Tech Briefs, January 2006 19

Machinery/Automation

Multistage Electrophoretic Separators

Separations can be performed in preparative quantities and can be automated.

Lyndon B. Johnson Space Center, Houston, Texas

A multistage electrophoresis apparatus has been invented for use in the separation of cells, protein molecules, and

other particles and solutes in concentrated aqueous solutions and suspensions. The design exploits free electrophoresis but overcomes the

deficiencies of prior free-electrophoretic separators by incorporating

a combination of published advances in

mathematical modeling of convection,

sedimentation, electro-osmotic flow, and

the sedimentation and aggregation of

droplets. In comparison with other electrophoretic separators, these apparatuses are easier to use and are better

suited to separation in relatively large

quantities characterized in the art as

preparative (in contradistinction to

smaller quantities characterized in the

art as analytical).

In a multistage electrophoretic separator according to the invention, an applied vertical steady electric field draws

the electrically charged particles of interest from within a cuvette to within a collection cavity that has been moved into

position of the cuvette. There are multiple collection cavities arranged in a circle; each is aligned with the cuvette for a

prescribed short time. The multistage,

short-migration-path character of the invention solves, possibly for the first time,

the fluid-instability problems associated

with free electrophoresis.

The figure shows a prototype multistage electrophoretic separator that includes four sample stations and five

collection stages per sample. At each

sample station, an aqueous solution or

Paristalic

Pump

Top

Plate

Electrolyte

Compartment

Cuvette

Lower

Plate

Collection

Cavity

Base Unit

(Contains the Electronics)

25 cm

This Multistage Electrophoretic Separator contains four sample stations, of which one faces front in

this view.

Vapor-compression heat pumps (including both refrigerators and heat

pumps) of a proposed type would be capable of operating in microgravity and

would be safe to use in enclosed environments like those of spacecraft. The

designs of these pumps would incorporate modifications of, and additions to,

vapor-compression cycles of heat

pumps now used in normal Earth gravitation, in order to ensure efficiency and

reliability during all phases of operation, including startup, shutdown, nominal continuous operation, and peak

operation. Features of such a design

might include any or all of the following: 

(1) Configuring the compressor, condenser, evaporator, valves, capillary

tubes (if any), and controls to function in microgravitation; 

(2) Selection of a working fluid that satisfies thermodynamic requirements

and is safe to use in a closed crew

compartment;

(3) Incorporation of a solenoid valve

and/or a check valve to prevent influx of liquid to the compressor

upon startup (such influx could

damage the compressor); 

(4) Use of a diode heat pipe between

the cold volume and the evaporator

to limit the influx of liquid to the

compressor upon startup; and 

(5) Use of a heated block to vaporize

any liquid that arrives at the compressor inlet.

This work was done by Warren Ruemmele,

Eugene Ungar, and John Cornwell of Johnson

Space Center. For further information, contact

the Johnson Innovative Partnerships Office at

(281) 483-3809. MSC-23746

Vapor-Compression Heat Pumps for Operation Aboard

Spacecraft

Lyndon B. Johnson Space Center, Houston, Texas
20 NASA Tech Briefs, January 2006

Recovering Residual Xenon Propellant for an Ion Propulsion System

Most of the otherwise unusable xenon is recovered.

NASA’s Jet Propulsion Laboratory, Pasadena, California

Future nuclear-powered Ion-PropulsionSystem-propelled spacecraft such as

Jupiter Icy Moon Orbiter (JIMO) will

carry more than 10,000 kg of xenon propellant. Typically, a small percentage of

this propellant cannot be used towards

the end of the mission because of the

pressure drop requirements for maintaining flow. For large missions such as

JIMO, this could easily translate to over

250 kg of unusable xenon. 

A proposed system, the Xenon Recovery System (XRS), for recovering almost

all of the xenon remaining in the tank,

would include a cryopump in the form

of a condenser/evaporator that would

be alternatively cooled by a radiator,

then heated electrically. When the pressure of the xenon in the tank falls below

0.7 MPa (100 psia), the previously isolated XRS will be brought online and

the gas from the tank would enter the

cryopump that is initially cooled to a

temperature below saturation temperature of xenon. This causes xenon liquefaction and further cryopumping from

the tank till the cryopump is full of liquid xenon. At this point, the cryopump

is heated electrically by small heaters (70

to 80 W) to evaporate the liquid that is

collected as high-pressure gas (<7 MPa;

1,000 psia) in an intermediate accumulator. Check valves between the tank and

the XRS prevent the reverse flow of

xenon during the heating cycle. The accumulator serves as the high-pressure

source of xenon gas to the Xenon Feed

System (XFS) downstream of the XRS.

This cycle is repeated till almost all the

xenon is recovered. Currently, this system is being baselined for JIMO.

This work was done by Gani Ganapathi,

P. Shakkottai, and Jiunn Jenq Wu of Caltech for NASA’s Jet Propulsion Laboratory. Further information is contained in a

TSP (see page 1).

NPO-40613

A Proposed Xenon Recovery System promises to reduce waste of valuable cargo space on distant missions.

NPO40613 ABPI 8-4-04 CC

1.25-L Xenon

Accumulator

100 - 920 psia

0.25-L Condenser/Evaporator #1

0.25-L Condenser/Evaporator #2

Heater

300 K Evaporator

Radiator

Thermal Resistor

8% 40 PPI Aluminum Foam

Depleted

Xenon Fuel

Tank

<100 psia

suspension containing charged species

to be separated is loaded into a cuvette,

which is machined into a top plate.

The apparatus includes a lower plate,

into which 20 collection cavities have

been milled. Each cavity is filled with

an electrophoresis buffer solution. For

the collection of an electrophoretic

fraction, the lower plate is rotated to

move a designated collection cavity

into alignment with the opening of the

cuvette.

An electric field is then applied between a non-gassing electrode in the

collection cavity and an electrolyte

compartment, which is separated from

the cuvette by a semipermeable membrane. The electrolyte is refreshed by

circulation by use of a peristaltic

pump. In subsequent steps, the lower

plate is rotated to collect other electrophoretic fractions. Later, the collected fractions are removed from the

collection cavities through ports that

have threaded plugs.

The base of the apparatus contains

power supplies and a computer interface. The design includes provisions for

monitoring and feedback control of cavity position, electric field, and temperature. The operation of the apparatus can

easily be automated, as demonstrated by

use of software that has already been

written for this purpose.

This work was done by Nathan Thomas, John

F. Doyle, Andy Kurk, John C. Vellinger, and

Paul Todd of Space Hardware Optimization

Technology, Inc., for Johnson Space Center.

In accordance with Public Law 96-517,

the contractor has elected to retain title to this

invention. Inquiries concerning rights for its

commercial use should be addressed to:

Space Hardware Optimization Technology,

Inc.

7200 Highway 150

Greenville, IN 47124

Phone: (812) 923-9591

E-mail: info@SHOT.com

Refer to MSC-23208, volume and number

of this NASA Tech Briefs issue, and the

page number.
NASA Tech Briefs, January 2006 21

Manufacturing

A process for fabricating a precise, diffraction-limited, ultra-lightweight, composite-material (matrix/fiber) paraboloidal

telescope mirror has been devised. Unlike

the traditional process of fabrication of

heavier glass-based mirrors, this process involves a minimum of manual steps and

subjective judgment. Instead, this process

involves objectively controllable, repeatable steps; hence, this process is better

suited for mass production.

Other processes that have been investigated for fabrication of precise compositematerial lightweight mirrors have resulted

in “print-through” of fiber patterns onto

reflecting surfaces, and have not provided

adequate structural support for maintenance of stable, diffraction-limited surface

figures. In contrast, this process does not

result in “print-through” of the fiber pattern onto the reflecting surface and does

provide a lightweight, rigid structure capable of maintaining a diffraction-limited

surface figure in the face of changing temperature, humidity, and air pressure.

The process consists mainly of the following steps:

1. A precise glass mandrel is fabricated

by conventional optical grinding and

polishing.

2. The mandrel is coated with a release

agent and covered with layers of a carbon-fiber composite material.

3. The outer surface of the outer layer of

the carbon-fiber composite material is

coated with a surfactant chosen to provide for the proper flow of an epoxy

resin to be applied subsequently.

4. The mandrel as thus covered is

mounted on a temperature-controlled spin table.

5. The table is heated to a suitable temperature and spun at a suitable speed

as the epoxy resin is poured onto the

coated carbon-fiber composite material.

6. The surface figure of the optic is monitored and adjusted by use of traditional Ronchi, Focault, and interferometric optical measurement techniques while the speed of rotation and

the temperature are adjusted to obtain

the desired figure. The proper selection of surfactant, speed or rotation,

viscosity of the epoxy, and temperature

make it possible to obtain the desired

diffraction-limited, smooth (1/50th

wave) parabolic outer surface, suitable

for reflective coating.

7. A reflective coat is applied by use of

conventional coating techniques.

8. Once the final figure is set, a lightweight structural foam is applied to the

rear of the optic to ensure stability of

the figure.

This work was done by Frederick Thomas

Herrmann of Marshall Space Flight Center. Further information is contained in a

TSP (see page 1).

This invention is owned by NASA, and a

patent application has been filed. For further

information, contact Sammy Nabors, MSFC

Commercialization Assistance Lead, at

sammy.a.nabors@nasa.gov. Refer to MFS31595-1.

Manufacturing Precise, Lightweight Paraboloidal Mirrors

Success depends on the proper selection of materials and process conditions.

Marshall Space Flight Center, Alabama

A solvent-based welding process enables the joining of precise, cast polyimide

membranes at their edges to form larger

precise membranes. The process creates a

homogeneous, optical-quality seam between abutting membranes, with no overlap and with only a very localized area of

figure disturbance. The seam retains 90

percent of the strength of the parent material. The process was developed for original use in the fabrication of wide-aperture membrane optics, with areal

densities of less than 1 kg/m2

, for lightweight telescopes, solar concentrators, antennas, and the like to be deployed in

outer space. The process is just as well applicable to the fabrication of large precise

polyimide membranes for flat or inflatable solar concentrators and antenna reflectors for terrestrial applications.

The process is applicable to cast membranes made of CP1 (or equivalent) polyimide. The process begins with the precise fitting together and fixturing of two

membrane segments. The seam is

formed by applying a metered amount of

a doped solution of the same polyimide

along the abutting edges of the membrane segments. After the solution has

been applied, the fixtured films are allowed to dry and are then cured by convective heating. The weld material is the

same as the parent material, so that what

is formed is a homogeneous, strong joint

that is almost indistinguishable from the

parent material.

The success of the process is highly dependent on formulation of the seaming

solution from the correct proportion of

the polyimide in a suitable solvent. In addition, the formation of reliable seams

depends on the deposition of a precise

amount of the seaming solution along

the seam line. To ensure the required

precision, deposition is performed by

use of an automated apparatus comprising a modified commercially available,

large-format, ink-jet print head on an automated positioning table. The printing

head jets the seaming solution into the

seam area at a rate controlled in coordination with the movement of the positioning table.

This work was done by Robert Rood of

Marshall Space Flight Center and

James D. Moore, Chris Talley, and Paul A.

Gierow of SRS Technologies, Inc. Further

information is contained in a TSP (see

page 1).

MFS-32129

Automated Solvent Seaming of Large Polyimide Membranes

Success depends on precise control of all relevant process details.

Marshall Space Flight Center, Alabama
NASA Tech Briefs, January 2006 23

Bio-Medical

Noninvasive Diagnosis of Coronary Artery Disease Using 

12-Lead High-Frequency Electrocardiograms

Diagnostically significant signal features can be identified automatically by computational analysis.

Lyndon B. Johnson Space Center, Houston, Texas

A noninvasive, sensitive method of diagnosing certain pathological conditions

of the human heart involves computational processing of digitized electrocardiographic (ECG) signals acquired from

a patient at all 12 conventional ECG electrode positions. In the processing, attention is focused on low-amplitude, highfrequency components of those portions

of the ECG signals known in the art as

QRS complexes. The unique contribution of this method lies in the utilization

of signal features and combinations of

signal features from various combinations of electrode positions, not reported

previously, that have been found to be

helpful in diagnosing coronary artery

disease and such related pathological

conditions as myocardial ischemia, myocardial infarction, and congestive heart

failure.

The electronic hardware and software

used to acquire the QRS complexes and

perform some preliminary analyses of

their high-frequency components were

summarized in “Real-Time, High-Frequency QRS Electrocardiograph” (MSC23154), NASA Tech Briefs, Vol. 27, No. 7

(July 2003), pp. 26-28. To recapitulate,

signals from standard electrocardiograph electrodes are preamplified, then

digitized at a sampling rate of 1,000 Hz,

then analyzed by the software that detects R waves and QRS complexes and

analyzes them from several perspectives.

The software includes provisions for averaging signals over multiple beats and

for special-purpose nonrecursive digital

filters with specific low- and high-frequency cutoffs. These filters, applied to

the averaged signal, effect a band-pass

operation in the frequency range from

150 to 250 Hz. The output of the bandpass filter is the desired high-frequency

QRS signal. Further processing is then

performed in real time to obtain the

beat-to-beat root mean square (RMS)

voltage amplitude of the filtered signal,

certain variations of the RMS voltage,

and such standard measures as the heart

rate and R-R interval at any given time. 

A key signal feature analyzed in the

present method is the presence versus

the absence of reduced-amplitude zones

(RAZs). In terms that must be simplified

for the sake of brevity, an RAZ comprises

several cycles of a high-frequency QRS

signal during which the amplitude of the

high-frequency oscillation in a portion of

the signal is abnormally low (see figure).

A given signal sample exhibiting an inHigh-Frequency QTS Signal Potential

Time

100 ms

MSC23449

5 μV

RAZ

This High-Frequency QRS Signal was acquired from a patient having myocardial ischemia. The dip in

the amplitude envelope (the RAZ) is a key feature utilized in the present method.

Analysis of Membrane Lipids of Airborne Micro-Organisms

Lyndon B. Johnson Space Center, Houston, Texas

A method of characterization of airborne micro-organisms in a given location involves (1) large-volume filtration of

air onto glass-fiber filters; (2) accelerated

extraction of membrane lipids of the collected micro-organisms by use of pressurized hot liquid; and (3) identification and

quantitation of the lipids by use of gas

chromatography and mass spectrometry.

This method is suitable for use in both

outdoor and indoor environments; for example, it can be used to measure airborne

microbial contamination in buildings

(“sick-building syndrome”). The classical

approach to analysis of airborne micro-organisms is based on the growth of cultureable micro-organisms and does not provide an account of viable but

noncultureable micro-organisms, which

typically amount to more than 90 percent

of the micro-organisms present. In contrast, the present method provides an account of all micro-organisms, including

cultureable, noncultureable, aerobic, and

anaerobic ones. The analysis of lipids according to this method makes it possible

to estimate the number of viable airborne

micro-organisms present in the sampled

air and to obtain a quantitative profile of

the general types of micro-organisms present along with some information about

their physiological statuses.

This work was done by Sarah Macnaughton

of Microbial Insights, Inc., for Johnson Space

Center. For further information, contact the

Johnson Commercial Technology Office at

(281) 483-3809.

MSC-22984
24 NASA Tech Briefs, January 2006

terval of reduced amplitude may or may

not be classified as an RAZ, depending

on quantitative criteria regarding peaks

and troughs within the reduced-amplitude portion of the high-frequency QRS

signal. This analysis is performed in all

12 leads in real time.

Several RAZ criteria are used in this

method, including some, heretofore

used only by NASA, that involve the calculation of the kurtosis of the high-frequency QRS signal. (Kurtosis is a statistical measure of the degree to which the

distribution of data in a given set is

peaked or flat, relative to a normal distribution.) In this method, the various RAZ

criteria are applied to the ECG signals acquired from various combinations of

contiguous conventional ECG electrode

positions selected from among all 12

such positions. The sets of criteria and

electrode combinations were developed

from an analysis of ECG readings from

several young and healthy subjects and

from several patients with varying degrees of coronary artery disease and/or

heart failure.

Again, in terms that must be simplified

for brevity, a positive or negative diagnosis

is suggested, depending on whether or not

one of the RAZ criteria applied to the associated electrode combination is satisfied.

For example, the presence of a “kurtosis

RAZ” (characterized by a kurtosis value less

than about 2.6) in four or more contiguous electrode positions suggests a positive

diagnosis. A computer that runs software

that implements the sets of RAZ criteria

and electrode combinations can be incorporated into an ECG system to construct

an automated diagnostic system. Inasmuch

as electrocardiography is already a standard part of procedures for diagnosis of

cardiac conditions, this method has potential to increase productivity and accuracy

at minimal additional cost and without exposing patients to additional risks.

This work was done by Todd T. Schlegel of

Johnson Space Center and Brian Arenare

(self-employed).

This invention is owned by NASA, and a

patent application has been filed. Inquiries concerning nonexclusive or exclusive license for its

commercial development should be addressed to

the Patent Counsel, Johnson Space Center,

(281) 483-0837. Refer to MSC-23449.
NASA Tech Briefs, January 2006 25

Physical Sciences

Enhanced-Contrast Viewing of White-Hot Objects in Furnaces

Band-pass- and polarization-filtered laser light exceeds polarization-suppressed blackbody light.

Marshall Space Flight Center, Alabama

An apparatus denoted a laser image

contrast enhancement system (LICES)

increases the contrast with which one

can view a target glowing with blackbody radiation (a white-hot object)

against a background of blackbody radiation in a furnace at a temperature

as high as ≈1,500 °C. The apparatus

utilizes a combination of narrowband

illumination, along with band-pass filtering and polarization filtering to

pass illumination reflected by the target while suppressing blackbody light

from both the object and its background.

In a typical application, the target is

about 1 cm in size and located as far as

30 in. (≈76 cm) into the furnace. In the

absence of this or another contrast-enhancing apparatus, a white-hot target

in a furnace is nearly or totally indistinguishable from the white-hot background. Unlike a prior contrast-enhancing apparatus that utilizes two

intersecting optical axes for viewing

and illumination of the target and requires a furnace opening as wide as 3

in. (≈8 cm) the LICES provides for

both illumination and viewing of the

target along the same path. Hence, the

LICES makes it possible to utilize a narrower opening into the furnace: the

LICES can function with an illumination/viewing tube only about half an

inch (≈1.3 cm) wide.

The LICES (see figure) includes a

laser aimed perpendicularly to the optical path to the target. (Optionally, another source of narrowband illumination could be used.) The laser light

impinges on a polarizing beam splitter

that turns the light onto the optical

path to the target. The laser light passes

through a quarter-wave retardation

plate, which causes the light to become

Dual-Laser-Pulse Ignition

This scheme provides a more reliable ignition source and more efficient energy delivery than a

single-pulse format.

Marshall Space Flight Center, Alabama

A dual-pulse laser (DPL) technique

has been demonstrated for generating

laser-induced sparks (LIS) to ignite

fuels. The technique was originally intended to be applied to the ignition of

rocket propellants, but may also be applicable to ignition in terrestrial settings

in which electric igniters may not be suitable. Laser igniters have been sought as

alternatives to such conventional devices

as electrical spark plugs and torch igniters for the following main reasons:

1. A typical electric spark igniter generates sparks at its electrode near a

wall, which potentially quenches

combustion. Hence, more spark energy is needed to ensure ignition. A

large combustion chamber would require a torch igniter, which comprises an electric-spark source, a premixing chamber, and propellant

valves. In contrast, the laser igniter is

capable of creating sparks directly in

a main chamber at specific optimal

locations, which can be out away

from the chamber walls, and without

the need of other subsystems.

2. Laser igniters can generate LIS with

very precise timing, on the order of

nanoseconds. This accurate timing

precision may be helpful in certain ignition applications. Furthermore,

this ignition generates significantly

less electromagnetic emission noise

than electrical igniters. Such noise

can interfere with other electronic signals of engine sensors and control

components.

Years of research on laser ignition

have produced viable single-pulse laser

ignition concepts; however, the transmission of high laser energy through

fiber optics required by these singlepulse schemes has been problematic

due to potential fiber damage and reduction in transmission efficiency. In

comparison, optical energy for the DPL

method can be stretched out and transmitted through multiple fiber lines, effectively reducing the energy intensity.

In addition, the lifetime of the plasmas

generated by use of the DPL exceeds

those of plasmas generated by singlelaser pulses, which increases their efficacy as an ignition source.

In the present DPL technique, the

first pulse is used to generate a small

plasma kernel. The second pulse is subsequently used to irradiate the plasma

kernel. The transfer of laser energy into

the kernel is much more efficient because the radiation-absorption characteristics of the plasma kernel are greatly

enhanced, relative to the single-pulse

approach. Consequently, the kernel can

develop into a more effective ignition

source.

Comparative experiments on singleand dual-pulse laser ignition were performed in a small test-bed rocket

thrust chamber, at Marshall Space

Flight Center, using gaseous oxygen

and kerosene. Sapphire windows were

used for optical access to the chamber.

In the tests, the DPL technique was

found to provide a repeatable ignition

source for combustion with an optimal

energy level. 

This work was done by Huu Trinh of

Marshall Space Flight Center, James W.

Early of Los Alamos National Laboratory,

Matthew E. Thomas of CFD Research

Corp., and John A. Bossard, formerly of

CFD Research Corp. Further information

is contained in a TSP (see page 1).

MFS-31922
26 NASA Tech Briefs, January 2006

circularly polarized. The circularly polarized laser light passes undisturbed

through a vertical polarizer, then travels along the optical axis to the target.

Reflection from the target reverses the

circular polarization. The reflected

laser light passes again through the vertical polarizer and then through the

quarter-wave retardation plate, which

converts the reverse circular polarization to horizontal polarization.

The polarizing beam splitter passes

the horizontally polarized reflected laser

light, which then passes through a lens,

a field aperture (which helps to increase

contrast by blocking background light),

a horizontal polarizer, and a filter having

a 20-nm-wide wavelength pass band. The

reflected laser light ultimately comes to

focus in a charge-coupled-device (CCD)

camera. At the same time, the crossed

polarizers and the band-pass filter discriminate the wideband, randomly polarized blackbody light from both the

target and the background.

Because the intensity of blackbody

radiation is proportional to the fourth

power of absolute temperature, it

could be necessary to increase the

laser power to maintain adequate contrast at higher temperatures. A prototype LICES has been found to yield

high-contrast images at temperatures

1,500 °C.

This work was done by William K. Witherow and Richard R. Holmes of Marshall

Space Flight Center and Robert L. Kurtz

of Pace & Waite, Inc. 

This invention has been patented by NASA

(U.S. Patent No. 6,366,403). Inquiries concerning nonexclusive or exclusive license for its

commercial development should be addressed to

Sammy Nabors, MSFC Commercialization Assistance Lead, at sammy.a.nabors@nasa.gov.

Refer to MFS-31561-1.

CCD

Camera

Band-Pass

Filter

Horizontal

Polarizer

Lens

Laser or Other Narrowband

Light Source

Polarizing Beam Splitter

Quarter-Wave Retardation Plate

Vertical Polarizer

Target

Field

Aperture

MFS31561

4-19-02 bs

Only One Optical Path is used for both illuminating and viewing the target with laser light. Blackbody

radiation from the target is suppressed by the crossed (horizontal and vertical) polarizers.

Improved quantum-cascade lasers

(QCLs) are being developed as electrically tunable sources of radiation in the

far infrared spectral region, especially

in the frequency range of 2 to 5 THz.

(Heretofore, the wavelengths of QCLs

have been adjusted by changing temperatures, but not by changing applied

voltages or currents.) In comparison

with gas lasers now used as far-infrared

sources, these QCLs would have larger

wavelength tuning ranges, would be

less expensive, and would be an order

of magnitude less massive and powerhungry. It is planned to use the improved QCLs initially as the active components of local oscillators in

spaceborne heterodyne instruments

for studying infrared spectral lines of

molecules of scientific interest. On

Earth, the QCLs could be used as farinfrared sources for medical glucosemonitoring and heart-monitoring instruments, chemical-analysis and

spectral-imaging systems, and imaging

instruments that exploit the ability of

terahertz radiation to penetrate cloth

and walls for detection of contraband

weapons.

The structures of QCLs and the

processes used to fabricate them have

much in common with those of multiple-quantum-well infrared photodetectors described in numerous previous

NASA Tech Briefs articles. In one of four

approaches being followed in the present development effort, the focus is

upon designing and fabricating the

structures to obtain heterogeneous cascades for different electric fields and

different wavelengths in order to enable

electrical tuning of laser emission wavelengths. Both the variation of the emission wavelength and the targeted range

of the electric-field strength for each

cascade would be kept small so the spectral gains of adjacent cascades at any

given electric-field strength in the target

range would overlap. This approach is

expected to afford the desired variation

of the gain maximum with electric-field

strength, so that a change in applied

bias voltage would result in a wavelength change.

In the second approach, layers of a QCL

structure are to be graded to modify the

shapes and depths of quantum wells, such

that the electronic wave functions in the

quantum wells and the transition energies

between them would change with an intentional variation of the applied bias electrical field. A change of the bias applied to

such a structure would result in a change

in the energy and, hence, of the wavelength of the lasing transition.

In the third approach, the focus is on exploiting distributed-feedback and distributed-Bragg-reflector QCL architectures to

achieve wavelength tuning through variation of applied electric current.

In the fourth approach, which is complementary to the other three, the focus

Electrically Tunable Terahertz Quantum-Cascade Lasers

These devices would supplant gas lasers as far-infrared sources.

NASA’s Jet Propulsion Laboratory, Pasadena, California
NASA Tech Briefs, January 2006 27

Few-Mode Whispering-Gallery-Mode Resonators

Simple structures function similarly to single-mode optical fibers.

NASA’s Jet Propulsion Laboratory, Pasadena, California

Whispering-gallery-mode (WGM) optical resonators of a type now under development are designed to support few

well-defined waveguide modes. In the

simplest case, a resonator of this type

would support one equatorial family of

WGMs; in a more complex case, such a

resonator would be made to support

two, three, or some other specified finite number of modes. Such a resonator

can be made of almost any transparent

material commonly used in optics. The

nature of the supported modes does not

depend on which material is used, and

the geometrical dispersion of this resonator is much smaller than that of a

typical prior WGM resonator. Moreover,

in principle, many such resonators

could be fabricated as integral parts of a

single chip.

Basically, a resonator of this type consists of a rod, made of a suitable transparent material, from which protrudes

a thin circumferential belt of the same

material. The belt is integral with the

rest of the rod (see figure) and acts as a

circumferential waveguide. If the depth

(d) and width (w) of the belt are made

appropriately small, then the belt acts

as though it were the core of a singlemode optical fiber: the belt and its adjacent supporting rod material support a

single, circumferentially propagating

mode or family of modes.

It has been shown theoretically that

the fiber-optic-like behavior of the belton-rod resonator structure can be summarized, in part, by the difference, ∆n,

between (1) an effective index of refraction of an imaginary fiber core and

(2) the index of refraction (n) of the

transparent rod/belt material. It has

also been shown theoretically that for a

given required value of ∆n, the required depth of the belt can be estimated as d ≈ R ∆n, where R is the radius

of the rod. It must be emphasized that

this estimated depth is independent of

n and, hence, is independent of the

choice of rod material.

As in the cases of prior WGM resonators, input/output optical coupling involves utilization of evanescent

fields. In the present case, there are

two evanescent fields: one at the

belt/air interface and one in the

boundary region between the belt and

the rest of the rod.

This work was done by Anatoliy

Savchenkov, Dmitry Strekalov, Andrey

Matsko, Vladimir Iltchenko, and Lute

Maleki of Caltech for NASA’s Jet Propulsion Laboratory. Further information is

contained in a TSP (see page 1).

In accordance with Public Law 96-517,

the contractor has elected to retain title to this

invention. Inquiries concerning rights for its

commercial use should be addressed to:

Innovative Technology Assets Management

JPL

Mail Stop 202-233

4800 Oak Grove Drive

Pasadena, CA 91109-8099

(818) 354-2240

E-mail: iaoffice@jpl.nasa.gov

Refer to NPO-41256, volume and number

of this NASA Tech Briefs issue, and the

page number.

Transparent Rod

2R

d

w

NPO41256

ABPI

11-22-04 bs

An Integral Thin, Narrow Belt around a transparent rod acts as a circumferential optical waveguide. With suitable choice of d and w in conjunction with R, this structure can be made to act

as a single- or few-mode WGM resonator.

is on increasing maximum operating

temperatures and output power levels

in continuous-wave operation. In a

given QCL, this approach may involve

one or more of the following changes:

reducing the threshold current density,

improving mounting and packaging to

enhance removal of heat and reduce

stresses, and optimizing designs of the

active regions, injectors, and waveguide.

Moreover, optimization of design for increasing maximum operating temperature and output power must include

finding the most advantageous combination of the designs of the active regions and waveguide for optimal tuning

performance.

This work was done by Sarath Gunapala,

Alexander Soidel, and Kamjou Mansour of

Caltech for NASA’s Jet Propulsion Laboratory. Further information is contained in

a TSP (see page 1).

In accordance with Public Law 96-517,

the contractor has elected to retain title to this

invention. Inquiries concerning rights for its

commercial use should be addressed to:

Innovative Technology Assets Management

JPL

Mail Stop 202-233

4800 Oak Grove Drive

Pasadena, CA 91109-8099

(818) 354-2240

E-mail: iaoffice@jpl.nasa.gov

Refer to NPO-41611, volume and number

of this NASA Tech Briefs issue, and the

page number.
NASA Tech Briefs, January 2006 29

A new robust method of automated

real-time diagnosis of faults in an aircraft

engine or a similar complex system involves the use of a bank of Kalman filters.

In order to be highly reliable, a diagnostic

system must be designed to account for

the numerous failure conditions that an

aircraft engine may encounter in operation. The method achieves this objective

though the utilization of multiple Kalman

filters, each of which is uniquely designed

based on a specific failure hypothesis. A

fault-detection-and-isolation (FDI) system,

developed based on this method, is able to

isolate faults in sensors and actuators while

detecting component faults (abrupt

degradation in engine component performance). By affording a capability for

real-time identification of minor faults before they grow into major ones, the

method promises to enhance safety and

reduce operating costs. 

The robustness of this method is further enhanced by incorporating information regarding the aging condition of

an engine. In general, real-time fault diagnostic methods use the nominal performance of a “healthy” new engine as a

reference condition in the diagnostic

process. Such an approach does not account for gradual changes in performance associated with aging of an otherwise healthy engine. By incorporating

information on gradual, aging-related

changes, the new method makes it possible to retain at least some of the sensitivity and accuracy needed to detect incipient faults while preventing false alarms

that could result from erroneous interpretation of symptoms of aging as symptoms of failures. 

The figure schematically depicts an

FDI system according to the new

method. The FDI system is integrated

with an engine, from which it accepts two

Information Sciences

Real-Time Diagnosis of Faults Using a Bank of Kalman Filters 

Gradual changes associated with aging are taken into account in the diagnostic process. 

John H. Glenn Research Center, Cleveland, Ohio

A conflict-aware scheduling algorithm

is being developed to help automate the

allocation of NASA’s Deep Space Network (DSN) antennas and equipment

that are used to communicate with interplanetary scientific spacecraft. The current approach for scheduling DSN

ground resources seeks to provide an equitable distribution of tracking services

among the multiple scientific missions

and is very labor intensive. Due to the

large (and increasing) number of mission requests for DSN services, combined

with technical and geometric constraints,

the DSN is highly oversubscribed. To

help automate the process, and reduce

the DSN and spaceflight project labor effort required for initiating, maintaining,

and negotiating schedules, a new scheduling algorithm is being developed.

The scheduling algorithm generates a

“conflict-aware” schedule, where all requests are scheduled based on a dynamic

priority scheme. The conflict-aware

scheduling algorithm allocates all requests for DSN tracking services while

identifying and maintaining the conflicts

to facilitate collaboration and negotiation between spaceflight missions. These

contrast with traditional “conflict-free”

scheduling algorithms that assign tracks

that are not in conflict and mark the remainder as unscheduled. In the case

where full schedule automation is desired (based on mission/event priorities,

fairness, allocation rules, geometric constraints, and ground system capabilities/constraints), a conflict-free schedule

can easily be created from the conflictaware schedule by removing lower priority items that are in conflict.

Unlike most existing scheduling engines that require fixed length schedule

items in the request, the conflict-aware

schedule provides a dynamic scheduling

engine to determine allocation length

during the scheduling process. This is

made necessary by the variety of missiontracking request types faced by the DSN.

In addition to fixed track requests, missions may also need continuous coverage

or may need to segment a track related to

multiple ground assets to support a given

request for service. In these cases, the

schedule allocation length (time) will depend on the availability of each resource.

The conflict-aware scheduling algorithm combines scheduling heuristics,

optimization, a search algorithm, and

computational intelligence. At the beginning of the procedure, all requests

pass through a scoring system (chosen

from a simple mathematical equation or

fuzzy logic) that determines the priority

of each request on the basis of measures

of fairness of the allocation, importance

of the request, the type of request, and

the allocation length. Starting with the

highest priority request, all technical

and geometric constraints are combined

to determine the available “timeline/antenna groups” for scheduling. A scoring

system that considers items already in

the schedule and the request characteristics then identifies the best

timeline/antenna group and start times

for each request. This then continues

for each successive priority request (priority is recomputed dynamically) until

all requests are scheduled. 

The conflict-aware algorithm is not

limited to DSN application. It can also

be applicable to solution of scheduling

problems in areas such as manufacturing and traffic control.

This work was done by Yeou-Fang Wang

and Chester Borden for NASA’s Jet Propulsion Laboratory. Further information is

contained in a TSP (see page 1).

NPO-41320

Conflict-Aware Scheduling Algorithm

An algorithm is being developed to automate NASA’s Deep Space Network antenna allocation.

NASA’s Jet Propulsion Laboratory, Pasadena, California
30 NASA Tech Briefs, January 2006

sets of input signals: sensor readings and

actuator commands. Two main parts of

the FDI system are a bank of Kalman filters and a subsystem that implements

FDI decision rules. Each Kalman filter is

designed to detect a specific sensor or actuator fault. When a sensor or actuator

fault occurs, large estimation errors are

generated by all filters except the one

using the correct hypothesis. By monitoring the residual output of each filter, the

specific fault that has occurred can be

detected and isolated on the basis of the

decision rules.

A set of parameters that indicate the performance of the engine components is estimated by the “correct” Kalman filter for

use in detecting component faults. To reduce the loss of diagnostic accuracy and

sensitivity in the face of aging, the FDI system accepts information from a steadystate-condition-monitoring system. This information is used to update the Kalman

filters and a data bank of trim values representative of the current aging condition. 

This work was done by Takahisa

Kobayashi of QSS Group, Inc. and Donald L.

Simon of Army Research Laboratory for

Glenn Research Center. Further information is contained in a TSP (see page 1).

Inquiries concerning rights for the commercial use of this invention should be addressed

to NASA Glenn Research Center, Commercial

Technology Office, Attn: Steve Fedor, Mail

Stop 4-8, 21000 Brookpark Road, Cleveland,

Ohio 44135. Refer to LEW-17457.

This FDI System accepts information on gradual aging of an engine to retain its effectiveness in

fault diagnosis.

LEW-17457

ABPI 12-15-03 es

Bank of

Kalman

Filters

Updates of

Kalman

Filters or

Trim Values

FDI

Decision

Rules

Data Bank

of

Trim Values

+

+

–

–

Sensor

Readings

Actuator

Commands

Output:

Indication of a

Fault in a Sensor, or

Actuator, or Other

Engine Component

Information From

Steady-State-Condition-Monitoring

System
National Aeronautics and

Space Administration