Technology Focus

Electronics/Computers

Software

Materials

Mechanics/Machinery

Manufacturing

Bio-Medical

Physical Sciences

Information Sciences

Books and Reports

10-13 October 2013

NASA Tech Briefs, October 2013 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.

Additional Information on NASA Tech Briefs and TSPs

Additional information announced herein may be obtained from the NASA Technical Reports Server:

http://ntrs.nasa.gov.

Please reference the control numbers appearing at the end of each Tech Brief. Information on NASA’s

Innovative Partnerships Program (IPP), its documents, and services is available on the World Wide Web

at http://www.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 listed below.

Ames Research Center

David Morse

(650) 604-4724

david.r.morse@nasa.gov

Dryden Flight Research Center

Ron Young

(661) 276-3741

ronald.m.young@nasa.gov

Glenn Research Center

Kimberly A. Dalgleish-Miller

(216) 433-8047

kimberly.a.dalgleish@nasa.gov

Goddard Space Flight Center

Nona Cheeks

(301) 286-5810

nona.k.cheeks@nasa.gov

Jet Propulsion Laboratory

Dan Broderick

(818) 354-1314

daniel.f.broderick@jpl.nasa.gov

Johnson Space Center

John E. James

(281) 483-3809

john.e.james@nasa.gov

Kennedy Space Center

David R. Makufka

(321) 867-6227

david.r.makufka@nasa.gov

Langley Research Center

Michelle Ferebee

(757) 864-5617

michelle.t.ferebee@nasa.gov

Marshall Space Flight Center

Terry L. Taylor

(256) 544-5916

terry.taylor@nasa.gov

Stennis Space Center

Ramona Travis

(228) 688-3832

ramona.e.travis@ssc.nasa.gov

NASA Headquarters

Daniel Lockney,

Technology Transfer Program Executive

(202) 358-2037

daniel.p.lockney@nasa.gov

Small Business Innovation Research

(SBIR) & Small Business Technology

Transfer (STTR) Programs

Rich Leshner, Program Executive

(202) 358-4920

rleshner@nasa.gov

NASA Field Centers and Program Offices

5 Technology Focus: Sensors

5 A Short-Range Distance Sensor with Exceptional Linearity

5 Miniature Trace Gas Detector Based on Microfabricated

Optical Resonators

6 Commercial Non-Dispersive Infrared Spectroscopy Sensors for

Sub-Ambient Carbon Dioxide Detection

7 Fast, Large-Area, Wide-Bandgap UV Photodetector for

Cherenkov Light Detection

9 Software

9 Mission Data System Java Edition Version 7

9 Adaptive Distributed Environment for Procedure

Training (ADEPT)

9 LEGEND, a LEO-to-GEO Environment Debris Model

11 Electronics/Computers

11 Millimeter-Wave Localizers for Aircraft-to-Aircraft

Approach Navigation

11 Impedance Discontinuity Reduction Between High-Speed

Differential Connectors and PCB Interfaces

12 SpaceCube Version 1.5

13 Manufacturing & Prototyping

13 High-Pressure Lightweight Thrusters

13 Non-Magnetic, Tough, Corrosion- and Wear-Resistant Knives

From Bulk Metallic Glasses and Composites

15 Materials & Coatings

15 Ambient Dried Aerogels

15 Applications for Gradient Metal Alloys Fabricated Using

Additive Manufacturing

17 Passivation of Flexible YBCO Superconducting Current

Lead With Amorphous SiO2 Layer

19 Mechanics/Machinery

19 Propellant-Flow-Actuated Rocket Engine Igniter

19 Lightweight Liquid Helium Dewar for High-Altitude

Balloon Payloads

20 Method to Increase Performance of Foil Bearings Through

Passive Thermal Management

21 Unibody Composite Pressurized Structure

23 Physical Sciences

23 JWST Integrated Science Instrument Module Alignment

Optimization Tool

23 Radar Range Sidelobe Reduction Using Adaptive Pulse

Compression Technique

24 Digitally Calibrated TR Modules Enabling Real-Time

Beamforming SweepSAR Architectures

25 Electro-Optic Time-to-Space Converter for Optical Detector

Jitter Mitigation

25 Partially Transparent Petaled Mask/Occulter for

Visible-Range Spectrum

27 Information Technology

27 Educational NASA Computational and Scientific Studies

(enCOMPASS)

27 Coarse-Grain Bandwidth Estimation Scheme for

Large-Scale Network

28 Detection of Moving Targets Using Soliton Resonance Effect

29 Books & Reports

29 High-Efficiency Nested Hall Thrusters for Robotic Solar

System Exploration

29 High-Voltage Clock Driver for Photon-Counting CCD

Characterization

29 Development of the Code RITRACKS

31 Bio-Medical

31 Enabling Microliquid Chromatography by Microbead Packing

of Microchannels

NASA Tech Briefs, October 2013 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.

10-13 October 2013

NASA Tech Briefs, October 2013 5

Technology Focus: Sensors

A Short-Range Distance Sensor with Exceptional Linearity

Potential uses exist in the areas of micromachining and nanotechnology.

John F. Kennedy Space Center, Florida

A sensor has been demonstrated that

can measure distance over a total range

of about 300 microns to an accuracy of

about 0.1 nm (resolution of about 0.01

nm). This represents an exceptionally

large dynamic range of operation —

over 1,000,000. The sensor is optical in

nature, and requires the attachment of a

mirror to the object whose distance is

being measured.

This work resulted from actively developing a white light interferometric system to be used to measure the depths of

defects in the Space Shuttle Orbiter windows. The concept was then applied to

measuring distance. The concept later

expanded to include spectrometer calibration.

In summary, broadband (i.e., white)

light is launched into a Michelson interferometer, one mirror of which is fixed

and one of which is attached to the object whose distance is to be measured.

The light emerging from the interferometer has traveled one of two distances: either the distance to the fixed

mirror and back, or the distance to the

moving mirror and back. These two light

beams mix and produce an interference

pattern where some wavelengths interfere constructively and some destructively. Sending this light into a spectrometer allows this interference pattern to

be analyzed, yielding the net distance

difference between the two paths.

The unique feature of this distance sensor is its ability to measure accurately distance over a dynamic range of more than

one million, the ratio of its range (about

300 microns) to its accuracy (about 0.1

nanometer). Such a large linear operating range is rare and arises here because

both amplitude and phase-matching algorithms contribute to the performance.

The sensor is limited by the need to attach

a mirror of some kind to the object being

tracked, and by the fairly small total

range, but the exceptional dynamic range

should make it of interest.

This work was done by Stephen Simmons and

Robert Youngquist of Kennedy Space Center. For

more information, contact the Kennedy Space

Center Technology Transfer Office at (321) 867-

7171. KSC-13382

The Distance Sensor is based on the wavelength variations of the light transfer through a Michelson

interferometer. Collimated white light is launched into an interferometer composed of a fixed mirror

and a translating mirror aligned with a beamsplitter. Light reflected from each mirror makes its way

to a small spectrometer where the optical intensity can be measured as a function of wavelength.

Fiber-Optic

White Light

Source Translating

Mirror

Fiber-Optic

Coupled 

Spectrometer

Fixed Mirror

Lens 

Lens

Beamsplitter

Michelson

Interferometer

While a variety of techniques exist to

monitor trace gases, methods relying on

absorption of laser light are the most

commonly used in terrestrial applications. Cavity-enhanced absorption techniques typically use high-reflectivity mirrors to form a resonant cavity, inside of

which a sample gas can be analyzed.

The effective absorption length is augmented by the cavity’s high quality factor, or Q, because the light reflects many

times between the mirrors. The sensitivity of such mirror-based sensors scales

with size, generally making them somewhat bulky in volume. Also, specialized

coatings for the high-reflectivity mirrors

have limited bandwidth (typically just a

few nanometers), and the delicate mirror surfaces can easily be degraded by

dust or chemical films.

As a highly sensitive and compact alternative, JPL is developing a novel trace

gas sensor based on a monolithic optical

resonator structure that has been modified such that a gas sample can be directly injected into the cavity. This device concept combines ultra-high Q

Miniature Trace Gas Detector Based on Microfabricated

Optical Resonators

Ultra-sensitive detection of molecules is available with a modified whispering

gallery mode resonator.

NASA’s Jet Propulsion Laboratory, Pasadena, California
6 NASA Tech Briefs, October 2013

Carbon dioxide produced through respiration can accumulate rapidly within

closed spaces. If not managed, a crew’s respiratory rate increases, headaches and hyperventilation occur, vision and hearing

are affected, and cognitive abilities decrease. Consequently, development continues on a number of CO2 removal technologies for human spacecraft and

spacesuits. Terrestrially, technology development requires precise performance

characterization to qualify promising air

revitalization equipment. On-orbit, instrumentation is required to identify and eliminate unsafe conditions. This necessitates

accurate in situ CO2 detection.

Recursive compensation algorithms

were developed for sub-ambient detection of CO2 with commercial off-theshelf (COTS) non-dispersive infrared

(NDIR) sensors. In addition, the source

of the exponential loss in accuracy is developed theoretically. The basis of the

loss can be explained through thermal,

Doppler, and Lorentz broadening effects that arise as a result of the temperature, pressure, and composition of the

gas mixture under analysis.

The objective was to develop a mathematical routine to compensate COTS

CO2 sensors relying on NDIR over pressures, temperatures, and compositions

far from calibration conditions. The

routine relies on a power-law relationship for the pressure dependency of

the sensors along with an equivalent

pressure to account for the composition dependency. A Newton-Raphson

iterative technique solves for actual carbon dioxide concentration based on

the reported concentration. Moreover,

first principles routines were established to predict mixed-gas spectra

based on sensor specifications (e.g.,

optical path length). The first principles model can be used to parametrically optimize sensors or sensor arrays

across a wide variety of pressures/temperatures/compositions.

In this work, heuristic scaling arguments were utilized to develop reasonable compensation techniques. Experimental results confirmed this approach

and provided evidence that composition

broadening significantly alters spectra

when pressure is reduced. Consequently,

a recursive compensation technique was

developed with the Newton-Raphson

method, which was subsequently verified

through experimentation.

This work was done by Michael J. Swickrath

and Molly S. Anderson of Johnson Space Center,

Summer McMillin of Jacobs Technology, and

Craig Broerman of Hamilton Sundstrand. Further information is contained in a TSP (see

page 1). MSC-25343-1

Commercial Non-Dispersive Infrared Spectroscopy Sensors for

Sub-Ambient Carbon Dioxide Detection

Lyndon B. Johnson Space Center, Houston, Texas

optical whispering gallery mode resonators (WGMR) with microfabrication

technology used in the semiconductor

industry. For direct access to the optical

mode inside a resonator, material can be

precisely milled from its perimeter, creating an open gap within the WGMR.

Within this open notch, the full optical

mode of the resonator can be accessed.

While this modification may limit the obtainable Q, calculations show that the reduction is not significant enough to outweigh its utility for trace gas detection.

The notch can be milled from the highQ crystalline WGMR with a focused ion

beam (FIB) instrument with resolution

much finer than an optical wavelength,

thereby minimizing scattering losses and

preserving the optical quality. Initial experimental demonstrations have shown

that these opened cavities still support

high-Q whispering gallery modes.

This technology could provide ultrasensitive detection of a variety of molecular species in an extremely compact and robust package. With this

type of modified WGMR, one can inject a gas sample into the open gap, allowing highly sensitive trace molecule

detection within a roughly 1-cm volume. Other critical components of the

instrument, such as the detector and a

semiconductor laser, could be directly

packaged with the resonator so as to

not significantly increase the size of

the device.

Besides its low mass, volume, and

power consumption, the monolithic design makes these resonators intrinsically

robust devices, capable of handling significant temperature excursions, without moving parts to wear out or delicate

coatings that can be easily damaged. A

sensor could integrate with microfluidics technology for a chip-scale device.

It could be mounted to the end of a deployable arm, or inserted into a borehole. Also, a network of individual sensors could be dispersed to monitor

conditions over a wide region.

This work was done by David C. Aveline,

Nan Yu, Robert J. Thompson, and Dmitry V.

Strekalov of Caltech for NASA’s Jet Propulsion

Laboratory. Further information is contained

in a TSP (see page 1). NPO-47173

The Trace Gas Detection System features a concentrated sample gas flowing to the free-space gap in

the microfabricated disc, packaged inside a compact sealed enclosure with external laser and detection electronics. Also shown is a SEM image of a high-Q calcium fluoride disc that has been augmented

with a notch using FIB.

Micro-Fabricated WGM Trace Gas Sensor System

Sealed Vacuum Enclosure

Vacuum

Feedthrough Vacuum

feedthrough

Free-Space Gap

Concentrated

Sample Gas

Optical Output

Detection

Frequency

Lock

Temp. Regulated Mount

AOM

Laser

Fiber Coupling

WGM
NASA Tech Briefs, October 2013 7

Due to limited resources available for

power and space for payloads, miniaturizing and integrating instrumentation is a

high priority for addressing the challenges of manned and unmanned deep

space missions to high Earth orbit

(HEO), near Earth objects (NEOs),

Lunar and Martian orbits and surfaces,

and outer planetary systems, as well as improvements to high-altitude aircraft safety.

New, robust, and compact detectors allow

future instrumentation packages more

options in satisfying specific mission goals.

A solid-state ultraviolet (UV) detector

was developed with a theoretical fast response time and large detection area intended for application to Cherenkov detectors. The detector is based on the

wide-bandgap semiconductor zinc

oxide (ZnO), which in a bridge circuit

can detect small, fast pulses of UV light

like those required for Cherenkov detectors. The goal is to replace the role of

photomultiplier tubes in Cherenkov detectors with these solid-state devices, saving on size, weight, and required power.

For improving detection geometry, a

spherical detector to measure high

atomic number and energy (HZE) ions

from any direction has been patented

as part of a larger space radiation detector system. The detector will require

the development of solid-state UV photodetectors fast enough (2 ns response

time or better) to detect the shockwave

of Cherenkov light emitted as the ions

pass through a quartz, sapphire, or

acrylic ball. The detector must be small

enough to fit in the detector system

structure, but have an active area large

enough to capture enough Cherenkov

light from the sphere.

The detector is fabricated on bulk

single-crystal undoped ZnO. Interdigitated finger electrodes and contact

pads are patterned via photolithography, and formed by sputtered metal of

silver, platinum, or other high-conductivity metal.

The detector is operated as a resistive

sensor, such as an RTD (resistance temperature detector) or strain gauge with a

supplied voltage/current, and monitoring resulting current/voltage. A common embodiment is as part of a bridge

circuit where a supplied voltage is divided between the detector and a

dummy resistor, in parallel with two

other resistors of similar values of the detector and dummy resistor. Directly observing the difference of the voltage

drop of the detector and its parallel resistor, a UV light measurement can be

made. The preferred embodiment is in

half-bridge configuration where the

dummy resistor is another interdigitated

finger electrode pattern on the same

ZnO substrate, but coated with a UV

blocking material.

When exposed to UV light (or any

light of sufficient energy), the electrons in valence bands of the semiconductor absorb sufficient energy to

jump into the conductive band and

freely move about the semiconductor.

Unless defined by an electric field, the

motions of these electrons are random,

and will lose enough energy to fall back

into a valence band. An applied electric field thus directs the drift of the

conductive electrons, and the addition

of conductive electrons by the absorption of UV light reduces the resistance

of the semiconductor.

The main feature of the detector is

the simplicity of design with the large

area and the fast response time necessary for detecting Cherenkov light in radiation detectors. The sensor can be fabricated using standard microfabrication

processes without doping, allowing extended use in space without loss of sensitivity. The response time is dependent

on electrode spacing, but the wavelength is not, allowing the detector to be

fabricated to tolerances specific to mission requirements.

This work was done by John D. Wrbanek

and Susan Y. Wrbanek 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: Steven Fedor, Mail

Stop 4–8, 21000 Brookpark Road, Cleveland, Ohio 44135. Refer to LEW-19040-1.

Fast, Large-Area, Wide-Bandgap UV Photodetector for

Cherenkov Light Detection

This detector can be used for monitoring fires, microbial sterilization/disinfection processing,

and spectrophotometry analysis.

John H. Glenn Research Center, Cleveland, Ohio

Interdigitated

Fingers

Pads

ZnO Substrate

Schematic of the UV Photodetector.

NASA Tech Briefs, October 2013 9

Software

Mission Data System Java

Edition Version 7

The Mission Data System framework

defines closed-loop control system abstractions from State Analysis including

interfaces for state variables, goals, estimators, and controllers that can be

adapted to implement a goal-oriented

control system. The framework further

provides an execution environment

that includes a goal scheduler, execution engine, and fault monitor that support the expression of goal network activity plans. Using these frameworks,

adapters can build a goal-oriented control system where activity coordination

is verified before execution begins

(plan time), and continually during execution. Plan failures including violations of safety constraints expressed in

the plan can be handled through automatic re-planning.

This version optimizes a number of

key interfaces and features to minimize

dependencies, performance overhead,

and improve reliability. Fault diagnosis

and real-time projection capabilities are

incorporated. This version enhances

earlier versions primarily through optimizations and quality improvements

that raise the technology readiness level.

Goals explicitly constrain system states

over explicit time intervals to eliminate

ambiguity about intent, as compared to

command-oriented control that only implies persistent intent until another

command is sent. A goal network scheduling and verification process ensures

that all goals in the plan are achievable

before starting execution. Goal failures

at runtime can be detected (including

predicted failures) and handled by

adapted response logic. Responses can

include plan repairs (try an alternate

tactic to achieve the same goal), goal

shedding, ignoring the fault, cancelling

the plan, or safing the system.

This work was done by William K. Reinholtz and David A. Wagner 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 Dan Broderick at

Daniel.F.Broderick@jpl.nasa.gov. Refer to

NPO-47804.

Adaptive Distributed Envi- ronment for Procedure

Training (ADEPT)

ADEPT (Adaptive Distributed Environment for Procedure Training) is designed to provide more effective, flexible, and portable training for NASA

systems controllers. When creating a

training scenario, an exercise author can

specify a representative rationale structure using the graphical user interface,

annotating the results with instructional

texts where needed. The author’s structure may distinguish between essential

and optional parts of the rationale, and

may also include “red herrings” — hypotheses that are essential to consider,

until evidence and reasoning allow them

to be ruled out.

The system is built from pre-existing

components, including Stottler Henke’s

SimVentive instructional simulation

authoring tool and runtime. To that, a

capability was added to author and exploit explicit control decision rationale

representations. ADEPT uses SimVentive’s Scalable Vector Graphics (SVG)-

based interactive graphic display capability as the basis of the tool for quickly

noting aspects of decision rationale in

graph form.

The ADEPT prototype is built in Java,

and will run on any computer using Windows, MacOS, or Linux. No special peripheral equipment is required.

The software enables a style of student/tutor interaction focused on the

reasoning behind systems control behavior that better mimics proven Socratic

human tutoring behaviors for highly

cognitive skills. It supports fast, easy, and

convenient authoring of such tutoring

behaviors, allowing specification of detailed scenario-specific, but content-sensitive, high-quality tutor hints and feedback. The system places relatively light

data-entry demands on the student to

enable its rationale-centered discussions, and provides a support mechanism for fostering coherence in the student/tutor dialog by including focusing,

sequencing, and utterance tuning mechanisms intended to better fit tutor hints

and feedback into the ongoing context.

This work was done by Eric Domeshek,

James Ong, and John Mohammed of Stottler

Henke Associates, Inc. for Johnson Space Center. Further information is contained in a

TSP (see page 1). MSC-24493-1

LEGEND, a LEO-to-GEO

Environment Debris Model

LEGEND (LEO-to-GEO Environment

Debris model) is a three-dimensional orbital debris evolutionary model that is capable of simulating the historical and future debris populations in the near-Earth

environment. The historical component

in LEGEND adopts a deterministic approach to mimic the known historical

populations. Launched rocket bodies,

spacecraft, and mission-related debris

(rings, bolts, etc.) are added to the simulated environment. Known historical

breakup events are reproduced, and fragments down to 1 mm in size are created.

The LEGEND future projection component adopts a Monte Carlo approach

and uses an innovative pair-wise collision

probability evaluation algorithm to simulate the future breakups and the growth

of the debris populations. This algorithm

is based on a new “random sampling in

time” approach that preserves characteristics of the traditional approach and

captures the rapidly changing nature of

the orbital debris environment.

LEGEND is a Fortran 90-based numerical simulation program. It operates

in a UNIX/Linux environment.

This work was done by Jer Chyi Liou and

Doyle T. Hall of Johnson Space Center. Further information is contained in a TSP (see

page 1). MSC-24805-1

NASA Tech Briefs, October 2013 11

Electronics/Computers

Aerial refueling technology for both

manned and unmanned aircraft is critical for operations where extended aircraft flight time is required. Existing refueling assets are typically manned

aircraft, which couple to a second aircraft through the use of a refueling

boom. Alignment and mating of the two

aircraft continues to rely on human control with use of high-resolution cameras.

With the recent advances in unmanned

aircraft, it would be highly advantageous

to remove/reduce human control from

the refueling process, simplifying the

amount of remote mission management

and enabling new operational scenarios.

Existing aerial refueling uses a camera,

making it non-autonomous and prone to

human error. Existing commercial localizer technology has proven robust and reliable, but not suited for aircraft-to-aircraft approaches like in aerial refueling

scenarios since the resolution is too

coarse (approximately one meter). A localizer approach system for aircraft-to-aircraft docking can be constructed using

the same modulation with a millimeterwave carrier to provide high resolution.

One technology used to remotely

align commercial aircraft on approach

to a runway are ILS (instrument landing

systems). ILS have been in service within

the U.S. for almost 50 years. In a commercial ILS, two partially overlapping

beams of UHF (109 to 126 MHz) are

broadcast from an antenna array so that

their overlapping region defines the

centerline of the runway. This is called a

localizer system and is responsible for

horizontal alignment of the approach.

One beam is modulated with a 150-Hz

tone, while the other with a 90-Hz tone.

Through comparison of the modulation

depths of both tones, an autopilot system aligns the approaching aircraft with

the runway centerline. A similar system

called a glide-slope (GS) exists in the

320-to-330MHz band for vertical alignment of the approach. While this technology has been proven reliable for millions of commercial flights annually, its

UHF nature limits its ability to operate

beyond the 1-to-2-meter precisions associated with commercial runway width.

A prototype ILS-type system operates

at millimeter-wave frequencies to provide automatic and robust approach

control for aerial refueling. The system

allows for the coupling process to remain completely autonomous, as a

boom operator is no longer required.

Operating beyond 100 GHz provides

enough resolution and a narrow enough

beamwidth that an approach corridor of

centimeter scales can be maintained.

Two modules were used to accomplish

this task. The first module is a

localizer/glide-slope module that can be

fitted on a refueling aircraft. This module provides the navigation beams for

aligning the approaching aircraft. The

second module is navigational receiver

fitted onto the approaching aircraft to be

refueled that can detect the approach

beams. Since unmanned aircraft have a

limited payload size and limited electrical power, the receiver portion was implemented in CMOS (complementary

metal oxide semiconductor) technology

based on a super-regenerative receiver

(SRR) architecture. The SRR achieves

mW-level power consumption and chip

sizes less than l mm2. While super-regenerative techniques have small bandwidths that limit use in communication

systems, their advantages of high sensitivity, low complexity, and low power make

them ideal in this situation where modulating tones of less than 1 kHz are used.

This work was done by Adrian J. Tang of Caltech for NASA’s Jet Propulsion Laboratory. For

more information, contact iaoffice@jpl.nasa.gov.

NPO-48868

Millimeter-Wave Localizers for Aircraft-to-Aircraft

Approach Navigation

Beyond aircraft refueling, this system can be used in automotive navigation and unmanned

aerial vehicle refueling.

NASA’s Jet Propulsion Laboratory, Pasadena, California

High-speed serial communication

(i.e., Gigabit Ethernet) requires differential transmission and controlled impedances. Impedance control is essential throughout cabling, connector, and

circuit board construction.

An impedance discontinuity arises at

the interface of a high-speed quadrax and

twinax connectors and the attached

printed circuit board (PCB). This discontinuity usually is lower impedance since

the relative dielectric constant of the

board is higher (i.e., polyimide ≈4) than

the connector (Teflon ≈2.25). The discontinuity can be observed in transmit or receive eye diagrams, and can reduce the effective link margin of serial data networks.

High-speed serial data network transmission improvements can be made at the

connector-to-board interfaces as well as improving differential via hole impedances.

The impedance discontinuity was improved by 10 percent by drilling a 20-mil

(≈0.5-mm) hole in between the pin of a differential connector spaced 55 mils (≈1.4

mm) apart as it is attached to the PCB.

The effective dielectric constant of

the board can be lowered by drilling

holes into the board material between

the differential lines in a quadrax or

Impedance Discontinuity Reduction Between High-Speed

Differential Connectors and PCB Interfaces

Lyndon B. Johnson Space Center, Houston, Texas
12 NASA Tech Briefs, October 2013

twinax connector attachment points.

The differential impedance is inversely

proportional to the square root of the

relative dielectric constant. This increases the differential impedance and

thus reduces the above described impedance discontinuity. The differential

via hole impedance can also be increased in the same manner. This technique can be extended to multiple

smaller drilled holes as well as tapered

holes (i.e., big in the middle followed by

smaller ones diagonally).

This work was done by Sal Navidi, Rodell

Agdinaoay, and Keith Walter of Honeywell

Aerospace for Johnson Space Center. For further information, contact the JSC Innovation

Partnerships Office at (281) 483-3809.

Title to this invention has been waived

under the provisions of the National Aeronautics and Space Act {42 U.S.C. 2457(f)},

to Honeywell Aerospace. Inquiries concerning

licenses for its commercial development should

be addressed to:

Honeywell Aerospace

P.O. Box 52199

Phoenix, AZ 85072

Refer to MSC-24855-l, volume and number of this NASA Tech Briefs issue, and the

page number.

SpaceCube 1.5 is a high-performance

and low-power system in a compact

form factor. It is a hybrid processing system consisting of CPU (central processing unit), FPGA (field-programmable

gate array), and DSP (digital signal

processor) processing elements. The

primary processing engine is the Virtex5 FX100T FPGA, which has two embedded processors. The SpaceCube 1.5 System was a bridge to the SpaceCube 2.0

and SpaceCube 2.0 Mini processing systems. The SpaceCube 1.5 system was the

primary avionics in the successful

SMART (Small Rocket/Spacecraft Technology) Sounding Rocket mission that

was launched in the summer of 2011.

For SMART and similar missions, an

avionics processor is required that is reconfigurable, has high processing capability, has multi-gigabit interfaces, is low

power, and comes in a rugged/compact

form factor. The original SpaceCube 1.0

met a number of the criteria, but did not

possess the multi-gigabit interfaces that

were required and is a higher-cost system.

The SpaceCube 1.5 was designed with

those mission requirements in mind.

The SpaceCube 1.5 features one Xilinx Virtex-5 FX100T FPGA and has excellent size, weight, and power characteristics [4×4×3 in. (≈10×10×8 cm), 3 lb

(≈1.4 kg), and 5 to 15 W depending on

the application]. The estimated computing power of the two PowerPC 440s in

the Virtex-5 FPGA is 1100 DMIPS each.

The SpaceCube 1.5 includes two Gigabit

Ethernet (1 Gbps) interfaces as well as

two SATA-I/II interfaces (1.5 to 3.0

Gbps) for recording to data drives. The

SpaceCube 1.5 also features DDR2

SDRAM (double data rate synchronous

dynamic random access memory); 4-

Gbit Flash for storing application code

for the CPU, FPGA, and DSP processing

elements; and a Xilinx Platform Flash

XL to store FPGA configuration files or

application code.

The system also incorporates a 12 bit

analog to digital converter with the ability to read 32 discrete analog sensor inputs. The SpaceCube 1.5 design also has

a built-in accelerometer. In addition, the

system has 12 receive and transmit RS422 interfaces for legacy support. The

SpaceCube 1.5 processor card represents

the first NASA Goddard design in a compact form factor featuring the Xilinx Virtex-5. The SpaceCube 1.5 incorporates

backward compatibility with the SpaceCube 1.0 form factor and stackable architecture. It also makes use of low-cost

commercial parts, but is designed for operation in harsh environments.

This work was done by Alessandro Geist,

Michael Lin, Tom Flatley, and David Petrick

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

GSC-15936-1

SpaceCube Version 1.5

This processing system is suited for any sub-orbital application that requires a compact solution

with high-data-rate storage capability and high-performance processing.

Goddard Space Flight Center, Greenbelt, Maryland
NASA Tech Briefs, October 2013 13

Quality knives are typically fabricated

from high-strength steel alloys. Depending on the application, there are different

requirements for mechanical and physical

properties that cause problems for steel

alloys. For example, diver’s knives are generally used in salt water, which causes rust

in steel knives. Titanium diver’s knives are

a popular alternative due to their salt

water corrosion resistance, but are too soft

to maintain a sharp cutting edge. Steel

knives are also magnetic, which is undesirable for military applications where the

knives are used as a tactical tool for diffusing magnetic mines. Steel is also significantly denser than titanium (8 g/cm3 vs.

4.5 g/cm3), which results in heavier

knives for the same size. Steel is hard and

wear-resistant, compared with titanium,

and can keep a sharp edge during service.

A major drawback of both steel and titanium knives is that they must be ground

or machined into the final knife shape

from a billet. Since most knives have a

mirrored surface and a complex shape,

manufacturing them is complex. It would

be more desirable if the knife could be

cast into a net or near-net shape in a single step.

The solution to the deficiencies of titanium, steel, and ceramic knives is to fabricate them using bulk metallic glasses

(or composites). These alloys can be cast

Manufacturing & Prototyping

Non-Magnetic, Tough, Corrosion- and Wear-Resistant Knives

From Bulk Metallic Glasses and Composites

High-performance knives are used in hunting, fishing, sailing, diving, industrial, and

military applications.

NASA’s Jet Propulsion Laboratory, Pasadena, California

High-Pressure Lightweight Thrusters

Carbon/carbon composite structures are braided over iridium-lined mandrels and densified by

chemical vapor infiltration.

Marshall Space Flight Center, Alabama

Returning samples of Martian soil and

rock to Earth is of great interest to scientists. There were numerous studies to evaluate Mars Sample Return (MSR) mission

architectures, technology needs, development plans, and requirements. The largest

propulsion risk element of the MSR mission is the Mars Ascent Vehicle (MAV).

Along with the baseline solid-propellant

vehicle, liquid propellants have been considered. Similar requirements apply to

other lander ascent engines and reaction

control systems.

The performance of current state-ofthe-art liquid propellant engines can be

significantly improved by increasing

both combustion temperature and pressure. Pump-fed propulsion is suggested

for a single-stage bipropellant MAV.

Achieving a 90-percent stage propellant

fraction is thought to be possible on a

100-kg scale, including sufficient thrust

for lifting off Mars.

To increase the performance of storable

bipropellant rocket engines, a high-pressure, lightweight combustion chamber was

designed. Iridium liner electrodeposition

was investigated on complex-shaped

thrust chamber mandrels. Dense, uniform

iridium liners were produced on chamber

and cylindrical mandrels. Carbon/carbon

composite (C/C) structures were braided

over iridium-lined mandrels and densified

by chemical vapor infiltration. Niobium

deposition was evaluated for forming a

metallic attachment flange on the carbon/carbon structure. The new thrust

chamber was designed to exceed state-ofthe-art performance, and was manufactured with an 83-percent weight savings.

High-performance C/Cs possess a

unique set of properties that make them

desirable materials for high-temperature

structures used in rocket propulsion

components, hypersonic vehicles, and

aircraft brakes. In particular, more attention is focused on 3D braided C/Cs due

to their mesh-work structure. Research

on the properties of C/Cs has shown that

the strength of composites is strongly affected by the fiber-matrix interfacial

bonding, and that weakening interface

realizes pseudo-plastic behavior with significant increase in the tensile strength.

The investigation of high-temperature

strength of C/Cs under high-rate heating (critical for thrust chambers) shows

that tensile and compression strength increases from 70 MPa at room temperature to 110 MPa at 1,773 K, and up to 125

MPa at 2,473 K.

Despite these unique properties, the

use of C/Cs is limited by its high oxidation rate at elevated temperatures. Lining

carbon/carbon chambers with a thin

layer of iridium or iridium and rhenium

is an innovative way to use proven refractory metals and provide the oxidation

barrier necessary to enable the use of carbon/carbon composites. Due to the

lower density of C/Cs as compared to

SiC/SiC composites, an iridium liner can

be added to the C/C structure and still be

below the overall thruster weight. Weight

calculations show that C/C, C/C with 50

microns of Ir, and C/C with 100 microns

of Ir are of less weight than alternative

materials for the same construction.

This work was done by Richard Holmes of

Marshall Space Flight Center and Timothy

McKechnie, Anatoliy Shchetkovskiy, and

Alexander Smirnov of Plasma Processes, Inc.

For more information, contact Sammy

Nabors, MSFC Commercialization Assistance

Lead, at sammy.a.nabors@nasa.gov. Refer to

MFS-32883-1.
14 NASA Tech Briefs, October 2013

into net or near-net shaped knives with a

combination of properties that exceed

both titanium and steel. A commercially

viable BMG (bulk metallic glass) or composite knife is one that exhibits one or all

of the following properties: It is based on

titanium, has a self-sharpening edge, can

retain an edge during service, is hard, is

non-magnetic, is corrosion-resistant

against a variety of corrosive environments, is tough (to allow for prying), can

be cast into a net-shape with a mirror finish and a complex shape, has excellent

wear resistance, and is low-density. These

properties can be achieved in BMG and

composites through alloy chemistry and

processing. For each desired property for

knife fabrication and performance, there

is an alloy development strategy that optimizes behavior. Although BMG knives

have been demonstrated as far back as

1995, they never found commercial success because they had to be ground

(which presented problems because the

alloys contained beryllium), they weren’t

low cost (because they weren’t cast to a

net-shape), they were brittle (because

they were made with a low-quality commercial material), and they had extremely poor corrosion resistance (because corrosion was not well-understood

in these materials). Ultimately, these

shortcomings prevented the widespread

commercialization.

In the current work, the inventors have

applied more than a decade of research

on BMGs from Caltech and JPL to develop a better understanding of how to

make BMG knives that exhibit an optimal

combination of properties, processing

and cost. Alloys have been developed

based in titanium (and other metals),

that exhibit high toughness, high hardness, excellent corrosion resistance, no

ferromagnetism, edge-retaining selfsharpening, and the ability to be cast like

a plastic using commercially available

casting techniques (currently used by

commercial companies such as Liquidmetal Technologies and Visser Precision

Casting). The inventors argue that depending on the application (diving, military, tactical, utility, etc.) there is an optimal combination of design and alloy

composition. Moreover, with new casting

technologies not available at the inception of these materials, net-shaped knives

can be cast into complex shapes that require no aftermarket forming, except for

sharpening using water-cooled polishing

wheel. These combinations of discoveries

seek to make low-cost BMG knives commercially viable products that have no

equal among metal or ceramic knives.

Current work at JPL focuses on net-shape

casting of these alloys and testing their

mechanical properties versus commercially available knives to demonstrate

their benefits.

This work was done by Douglas C. Hofmann of Caltech and Benjamin Potter for

NASA’s Jet Propulsion Laboratory. For more

information, contact the inventors at

dch@jpl.nasa.gov. NPO-48850

A full tang Bulk Metallic Glass Tactical Knife with multi-faceted blade surface and carbon fiber grip

with titanium pins, fabricated by Benjamin Potter of Altadena, CA. The knife was fabricated by watergrinding from a larger plate as an illustration. In a commercial setup, the knife would be cast to a netshape using an auto-feed and eject system, similar to what is done in plastics.
NASA Tech Briefs, October 2013 15

Materials & Coatings

Ambient Dried Aerogels

NASA’s Jet Propulsion Laboratory, Pasadena, California

A method has been developed for

creating aerogel using normal pressure

and ambient temperatures. All spacecraft, satellites, and landers require the

use of thermal insulation due to the extreme environments encountered in

space and on extraterrestrial bodies.

Ambient dried aerogels introduce the

possibility of using aerogel as thermal

insulation in a wide variety of instances

where supercritically dried aerogels cannot be used. More specifically, thermoelectric devices can use ambient dried

aerogel, where the advantages are in

situ production using the cast-in ability

of an aerogel.

Previously, aerogels required supercritical conditions (high temperature

and high pressure) to be dried. Ambient dried aerogels can be dried at

room temperature and pressure. This

allows many materials, such as plastics

and certain metal alloys that cannot

survive supercritical conditions, to be

directly immersed in liquid aerogel

precursor and then encapsulated in

the final, dried aerogel. Additionally,

the metalized Mylar films that could

not survive the previous methods of

making aerogels can survive the ambient drying technique, thus making

multilayer insulation (MLI) materials

possible. This results in lighter insulation material as well.

Because this innovation does not require high-temperature or high-pressure

drying, ambient dried aerogels are

much less expensive to produce. The

equipment needed to conduct supercritical drying costs many tens of thousands

of dollars, and has associated running

expenses for power, pressurized gasses,

and maintenance. The ambient drying

process also expands the size of the

pieces of aerogel that can be made because a high-temperature, high-pressure

system typically has internal dimensions

of up to 30 cm in diameter and 60 cm in

height. In the case of this innovation,

the only limitation on the size of the

aerogels produced would be in the ability of the solvent in the wet gel to escape

from the gel network.

This work was done by Steven M. Jones

and Jong-Ah Paik of Caltech for NASA’s Jet

Propulsion Laboratory. For more information,

contact iaoffice@jpl.nasa.gov. NPO-49008

Applications for Gradient Metal Alloys Fabricated Using

Additive Manufacturing

A new roadmap for gradient metals that could be used in cars, optics, aircraft, and sporting goods.

NASA’s Jet Propulsion Laboratory, Pasadena, California

Recently, additive manufacturing

(AM) techniques have been developed

that may shift the paradigm of traditional metal production by allowing

complex net-shaped hardware to be

built up layer-by-layer, rather than

being machined from a billet. The AM

process is ubiquitous with polymers due

to their low melting temperatures, fast

curing, and controllable viscosity, and

3D printers are widely available as commercial or consumer products. 3D

printing with metals is inherently more

complicated than with polymers due to

their higher melting temperatures and

reactivity with air, particularly when

heated or molten. The process generally requires a high-power laser or other

focused heat source, like an electron

beam, for precise melting and deposition. Several promising metal AM techniques have been developed, including

laser deposition (also called laser engineered net shaping or LENS® and laser

deposition technology (LDT)), direct

metal laser sintering (DMLS), and electron beam free-form (EBF). These machines typically use powders or wire

feedstock that are melted and deposited using a laser or electron beam.

Complex net-shape parts have been

widely demonstrated using these (and

other) AM techniques and the process

appears to be a promising alternative to

machining in some cases.

Rather than simply competing with

traditional machining for cost and time

savings, the true advantage of AM involves the fabrication of hardware that

cannot be produced using other techniques. This could include parts with

“blind” features (like foams or trusses),

parts that are difficult to machine conventionally, or parts made from materials that do not exist in bulk forms. In

this work, the inventors identify that several AM techniques can be used to develop metal parts that change composition from one location in the part to another, allowing for complete control

over the mechanical or physical properties. This changes the paradigm for conventional metal fabrication, which relies

on an assortment of “post-processing”

methods to locally alter properties

(such as coating, heat treating, work

hardening, shot peening, etching, anodizing, among others). Building the

final part in an additive process allows

for the development of an entirely new

class of metals, so-called “functionally

graded metals” or “gradient alloys.” By

carefully blending feedstock materials

with different properties in an AM

process, hardware can be developed

with properties that cannot be obtained

using other techniques but with the

added benefit of the net-shaped fabrication that AM allows.

Functionally graded metal alloys have

been demonstrated previously using the

LENS® process but the technique has
16 NASA Tech Briefs, October 2013

not been used to develop functional

hardware because the fabrication of robust gradient compositions is not trivial.

In most cases, one cannot simply add a

feedstock metal to another and expect

to develop a new metal alloy free of

cracks and unwanted phases. Developing gradient metal alloys requires a significant amount of knowledge in phase

transformations to avoid compositions

where brittle intermetallic compounds

form (which may crack and, thus, destroy the hardware). To address this, the

inventors have developed a technique

where potential gradient compositions

can be simplified and transposed onto a

three-component (ternary) phase diagram (or a 3-dimensional hybrid phase

diagram, in some cases) and the desired

gradient composition can be “mapped”

to avoid unwanted phases (see figure).

This process is part of a broader

roadmap for gradient alloys that the inventors have developed to go from a desired combination of properties to a

final part. This process proceeds by (1)

identifying a combination of desired

properties and modeling a component,

(2) selecting metal alloys that satisfy the

desired mechanical or physical properties, (3) developing a composition map

to transition from one alloy to the other

without forming unwanted phases, (4)

selecting the desired AM building

process, and (5) fabricating the part. Although at the time of this reporting it

has not yet been demonstrated in the literature, the authors have identified a

number of AM techniques that can be

used to fabricate gradient metals, including laser deposition, laser sintering,

wire free-form, thermal spray coating,

metal dipping, among others. In any additive process involving metal feedstock,

gradient alloys are possible.

In the current program, funded by

NASA’s Jet Propulsion Laboratory, the

inventors use the gradient alloy

roadmap to explore several desirable

spacecraft applications. The LENS®

technique was selected to develop gradient compositions free of brittle phases

and those alloys were fabricated into

prototype hardware. In one application,

a gradient alloy mirror mount was developed that transitions between stainless

steel at the base and Invar (an FeNi

alloy) at the top. In space optics applications, glass mirrors are often bonded

with epoxy to metal mirror mounts,

a b c

d e

f g

Various Aspects of the Innovation: (a) An isothermal slice of the Fe-Ni-Cr ternary phase diagram showing how different gradient compositions can be

mapped. The lines represent composition gradients between 304L stainless steel and Invar 36, a simplified Inconel 625 alloy and a NiFeCr alloy. In some gradients, the path intersects brittle intermetallic phases, which can be avoided by changing the path to go through more desirable phases (the segmented

green line). (b) An isogrid mirror fabricated using a 3D plastic printer and (c) the same part fabricated using LENS after some finish machining. The mirror

surface is made of Invar 36 and the isogrid backing is a gradient alloy that transitions from Invar 36 to stainless steel. (d) A gradient alloy mirror assembly

with a metal-coated glass mirror attached to the Invar side of the assembly using epoxy. The mirror assembly transitions into stainless steel at the base. (e)

Test samples of a Ti-V gradient alloy being fabricated by LENS. (f) The compositions (as measured through electron dispersive XRD) of the gradient mirror

assembly in (d) showing the transition between Invar and stainless steel. (g) A plot of hardness and thermal expansion across the gradient mirror assembly. The intermediate phases of the gradient have been designed to be soft austenite (as demonstrated by the decreased hardness). The controllable thermal expansion makes this part alluring for optics applications. One side of the gradient has a near-zero thermal expansion while the other side matches

steel.
NASA Tech Briefs, October 2013 17

which are then bonded or fastened to an

optical bench. When the part is exposed

to extreme cold, the epoxy holding the

mirror can crack and the fasteners holding the mirror mount can shrink, shifting the position of the mirror. In the gradient alloy, the glass mirror can be

bonded to Invar, which has a near-zero

thermal expansion coefficient that

matches glass. However, the whole part

does not need to be made from Invar,

but rather it can be graded to stainless

steel and then welded to the optical

bench, eliminating thermal expansion

mismatch from dissimilar metals. The

gradient technique has also been used

in an optics application to fabricate an

Invar mirror with a high-stiffness isogrid

backing. Isogrids are extremely costly

and complicated to fabricate, but the

AM technique allows gradient compositions to be built up right on the backside

of the mirror. Other gradients have been

developed, including a stainless steel to

Inconel (a high-temperature Ni alloy)

gradient to be fabricated into a valve

stem for automotive applications. Invarcontaining metal inserts have been developed to eliminate low-temperature

pull-out in carbon fiber panels and lowdensity titanium alloys have been graded

to refractory metals (e.g. Nb and V) for

high-temperature applications (such as

rocket nozzles and engine components).

Ongoing work has focused on developing new types of gradient armor for defense applications as well as a wide assortment of commercial applications.

This work was done by Douglas C. Hofmann, John Paul C. Borgonia, Robert P. Dillon, Eric J. Suh, Jerry L. Mulder, and Paul B.

Gardner of Caltech for NASA’s Jet Propulsion

Laboratory. For more information, contact

iaoffice@jpl.nasa.gov.

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 321-123

4800 Oak Grove Drive

Pasadena, CA 91109-8099

E-mail: iaoffice@jpl.nasa.gov

Refer to NPO-48419, volume and number

of this NASA Tech Briefs issue, and the

page number.

Passivation of Flexible YBCO Superconducting Current Lead

With Amorphous SiO2 Layer

The aim of this project is to design and construct leads from YBCO composite conductors to

reduce the heat load to adiabatic demagnetization refrigerators.

Goddard Space Flight Center, Greenbelt, Maryland

Adiabatic demagnetization refrigerators (ADR) are operated in space to

cool detectors of cosmic radiation to a

few 10s of mK. A key element of the

ADR is a superconducting magnet operating at about 0.3 K that is continually

energized and de-energized in synchronism with a thermal switch, such that a

piece of paramagnetic salt is alternately

warm in a high magnetic field and cold

in zero magnetic field. This causes the

salt pill or refrigerant to cool, and it is

able to suck heat from an object, e.g.,

the sensor, to be cooled. Current has to

be fed into and out of the magnets from

a dissipative power supply at the ambient temperature of the spacecraft. The

current leads that link the magnets to

the power supply inevitably conduct a

significant amount of heat into the

colder regions of the supporting cryostat, resulting in the need for larger,

heavier, and more powerful supporting

refrigerators. The aim of this project

was to design and construct high-temperature superconductor (HTS) leads

from YBCO (yttrium barium copper

oxide) composite conductors to reduce

the heat load significantly in the temperature regime below the critical temperature of YBCO.

The magnet lead does not have to support current in the event that the YBCO

ceases to be superconducting. Customarily, a normal metal conductor in

parallel with the YBCO is a necessary

part of the lead structure to allow for

this upset condition; however, for this

application, the normal metal can be

dispensed with.

Amorphous silicon dioxide is deposited directly onto the surface of

YBCO, which resides on a flexible substrate. The silicon dioxide protects the

YBCO from chemically reacting with atmospheric water and carbon dioxide,

thus preserving the superconducting

properties of the YBCO. The customary

protective coating for flexible YBCO

conductors is silver or a silver/gold alloy,

which conducts heat many orders of

magnitude better than SiO2 and so limits the use of such a composite conductor for passing current across a thermal

gradient with as little flow of heat as possible to make an efficient current lead.

By protecting YBCO on a flexible substrate of low thermal conductivity with

SiO2, a thermally efficient and flexible

current lead can be fabricated. The technology is also applicable to current leads

for 4 K superconducting electronics current biasing.

A commercially available thin-film

YBCO composite tape conductor is first

stripped of its protective silver coating. It

is then mounted on a jig that holds the

sample flat and acts as a heat sink. Silicon dioxide is then deposited onto the

YBCO to a thickness of about 1 micron

using PECVD (plasma-enhanced chemical vapor deposition), without heating

the YBCO to the point where degradation occurs.

Since SiO2 can have good high-frequency electrical properties, it can be

used to coat YBCO cable structures used

to feed RF signals across temperature

gradients. The prime embodiment concerns the conduction of DC current

across the cryogenic temperature gradient. The coating is hard and electrically

insulating, but flexible.

This work was done by Daniel Johannes and

Robert Webber of Hypes for Goddard Space

Flight Center. Further information is contained in a TSP (see page 1). GSC-16732-1

Astrophysical observations at millimeter wavelengths require large (2-to-5-

meter diameter) telescopes carried to altitudes above 35 km by scientific

research balloons. The scientific performance is greatly enhanced if the telescope is cooled to temperatures below

10 K with no emissive windows between

the telescope and the sky. Standard liquid helium bucket dewars can contain a

suitable telescope for telescope diameter less than two meters. However, the

mass of a dewar large enough to hold a

3-to-5-meter diameter telescope would

exceed the balloon lift capacity.

The solution is to separate the functions of cryogen storage and in-flight

thermal isolation, utilizing the unique

physical conditions at balloon altitudes.

Conventional dewars are launched cold:

the vacuum walls necessary for thermal

isolation must also withstand the pressure gradient at sea level and are correspondingly thick and heavy. The pressure at 40 km is less than 0.3% of sea

level: a dewar designed for use only at 40

km can use ultra thin walls to achieve significant reductions in mass.

This innovation concerns new construction and operational techniques to

produce a lightweight liquid helium

bucket dewar. The dewar is intended

for use on high-altitude balloon payloads. The mass is low enough to allow

a large (3-to-5-meter) diameter dewar

to fly at altitudes above 35 km on conventional scientific research balloons

without exceeding the lift capability of

the balloon.

The lightweight dewar has thin (250-

micron) stainless steel walls. The walls

are too thin to support the pressure gradient at sea level: the dewar launches

warm with the vacuum space vented continuously during ascent to eliminate any

NASA Tech Briefs, October 2013 19

Mechanics/Machinery

Propellant-Flow-Actuated Rocket Engine Igniter

A pneumatically driven hammer initiates ignition.

Lyndon B. Johnson Space Center, Houston, Texas

A rocket engine igniter has been created that uses a pneumatically driven

hammer that, by specialized geometry, is

induced into an oscillatory state that can

be used to either repeatedly impact a

piezoelectric crystal with sufficient force

to generate a spark capable of initiating

combustion, or can be used with any

other system capable of generating a

spark from direct oscillatory motion.

This innovation uses the energy of

flowing gaseous propellant, which by

means of pressure differentials and kinetic motion, causes a hammer object

to oscillate. The concept works by mass

flows being induced through orifices on

both sides of a cylindrical tube with one

or more vent paths. As the mass flow enters the chamber, the pressure differential is caused because the hammer object is supplied with flow on one side

and the other side is opened with access

to the vent path. The object then

crosses the vent opening and begins to

slow because the pressure differential

across the ball reverses due to the geometry in the tube.

Eventually, the object stops because of

the increasing pressure differential on

the object until all of the kinetic energy

has been transferred to the gas via compression. This is the point where the object reverses direction because of the

pressure differential. This behavior excites a piezoelectric crystal via direct impact from the hammer object. The hammer strikes a piezoelectric crystal, then

reverses direction, and the resultant high

voltage created from the crystal is transferred via an electrode to a spark gap in

the ignition zone, thereby providing a

spark to ignite the engine. Magnets, or

other retention methods, might be employed to favorably position the hammer

object prior to start, but are not necessary to maintain the oscillatory behavior.

Various manifestations of the igniter

have been developed and tested to improve device efficiency, and some improved designs are capable of operation

at gas flow rates of a fraction of a gram

per second (0.001 lb/s) and pressure

drops on the order of 30 to 50 kilopascal

(a few psi).

An analytical model has been created

and tested in conjunction with a precisely calibrated reference model. The

analytical model accurately captures the

overall behavior of this innovation. The

model is a simple “volume-orifice” concept, with each chamber considered a

single temperature and pressure “node”

connected to adjacent nodes, or to vent

paths through flow control orifices. Mass

and energy balances are applied to each

node, with gas flow predicted using simple compressible flow equations.

This work was done by Mark Wollen of Innovative Engineering Solutions, Inc. for Johnson Space Center. 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 Engineering Solutions, Inc

26200 Adams Avenue

Murrieta, CA 92562-7060

Refer to MSC-25078-1, volume and number of this NASA Tech Briefs issue, and the

page number.

Lightweight Liquid Helium Dewar for High-Altitude

Balloon Payloads

A factor-of-five or better reduction in mass is achieved.

Goddard Space Flight Center, Greenbelt, Maryland
20 NASA Tech Briefs, October 2013

pressure gradient across the walls. A

commercial 500-liter storage dewar

maintains a reservoir of liquid helium

within a minimal (hence low mass) volume. Once a 40-km altitude is reached,

the valve venting the vacuum space of

the bucket dewar is closed to seal the

vacuum space. A vacuum pump then

evacuates the dewar vacuum space to

provide the necessary thermal isolation.

Liquid helium may then be transferred

from the storage dewar into the bucket

dewar to cool the telescope inside the

bucket dewar.

By splitting the functions of helium

storage and in-flight thermal isolation,

the parasitic mass associated with the

dewar pressure vessel is eliminated to

achieve factor-of-five or better reduction

in mass. The lower mass allows flight on

conventional scientific research balloons, even for telescopes 3 to 5 meters

in diameter.

This work was done by Alan Kogut, Bryan

James, and Dale Fixsen of Goddard Space

Flight Center. Further information is contained in a TSP (see page 1).GSC-16687-1

This invention is a new approach to

designing foil bearings to increase their

load capacity and improve their reliability through passive thermal management. In the present case, the bearing is

designed in such a way as to prevent the

carryover of lubricant from the exit of

one sector to the inlet of the ensuing

sector of the foil bearing. When such

passive thermal management techniques are used, bearing load capacity is

improved by multiples, and reliability is

enhanced when compared to current

foil bearings. This concept has recently

been tested and validated, and shows

that load capacity performance of foil

bearings can be improved by a factor of

two at relatively low speeds with potentially greater relative improvements at

higher speeds. Such improvements in

performance with respect to speed are

typical of foil bearings. Additionally, operation of these newly conceived bearings shows much more reliability and repeatable performance. This trait can be

exploited in machine design to enhance

safety, reliability, and overall performance. Finally, lower frictional torque has

been demonstrated when operating at

lower (non-load capacity) loads, thus

providing another improvement above

the current state of the art.

The objective of the invention is to incorporate features into a foil bearing that

both enhance passive thermal management and temperature control, while at

the same time improve the hydrodynamic

(load capacity) performance of the foil

bearing. Foil bearings are unique antifriction devices that can utilize the working

fluid of a machine as a lubricant (typically

air for turbines and motors, liquids for

pumps), and as a coolant to remove excess energy due to frictional heating. The

current state of the art of foil bearings utilizes forced cooling of the bearing and

shaft, which represents poor efficiency

and poor reliability.

This invention embodies features that

utilize the bearing geometry in such a

manner as to both support load and provide an inherent and passive cooling

mechanism. This cooling mechanism

functions in such a way as to prevent

used (higher temperature) lubricant

from being carried over from the exit of

one sector into the entry of the next sector of the foil bearing.

The disclosed innovation is an improved foil bearing design that reduces

or eliminates the need for force cooling

of the bearing, while at the same time improving the load capacity of the bearing

by at least a factor of two. These improvements are due to the elimination of lubricant carryover from the trailing edge

of one sector into the leading edge of the

next, and the mixing of used lubricant

with the surrounding ambient fluid.

This work was done by Robert Bruckner 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: Steven Fedor, Mail

Stop 4–8, 21000 Brookpark Road, Cleveland, Ohio 44135. Refer to LEW-18789-1

Method to Increase Performance of Foil Bearings Through

Passive Thermal Management

Bearing load capacity is improved by multiples and reliability is enhanced.

John H. Glenn Research Center, Cleveland, Ohio

Low-speed data showing the increased load capacity of the Foil Bearing Technology.

Load Capacity v. Shaft Speed at 325 oF

Shaft Speed (krpm)

Load Capacity (lbs)

TEE01 mt TEE02 mt TEE03 mt
NASA Tech Briefs, October 2013 21

Unibody Composite Pressurized Structure

John H. Glenn Research Center, Cleveland, Ohio

An integrated, generic unibody composite pressurized structure (UCPS)

combined with a positive expulsion device (PED), consisting of an elastomeric

bladder for monopropellant hydrazine,

has been quasi-standardized for spacecraft use. The combination functions as

an all-composite, non-metallic, propellant tank with bladder. The integrated

UCPS combines several previous innovations — specifically, the linerless, allcomposite cryogenic tank technology;

all-composite boss; resin formulation;

and integrated stringer system. The innovation combines the UCPS with an integrated propellant management device

(PMD), the PED or bladder, to create an

entirely unique system for in-space use.

The UCPS is a pressure vessel that incorporates skirts, stringers, and other

structures so that it is both an in-space

hydrazine tank, and also a structural

support system for a spacecraft in a single, all-composite unit. This innovation

builds on the progress in the development of a previous SBIR (Small Business Innovation Research) Phase I with

Glenn Research Center and an SBIR III

with Johnson Space Center that included the fabrication of two 42-in.

(≈107-cm) diameter all-composite cryogenic (LOX and liquid methane)

UCPS test tanks for a lunar lander. This

Phase II provides hydrazine compatibility testing of the elastomeric bladder, a

see-through PED to validate the expulsion process and model, and a complete UCPS-based PED with stringers

and skirts that will be used to conduct

initial qualification and expulsion tests.

This extends the UCPS technology to

include hydrazine-based, in-space propulsion applications and can also be

used for electric propulsion.

This innovation creates a system that,

in comparison to the traditional approach, is lower in weight, cost, volume,

and production time; is stronger; and is

capable of much higher pressures. It also

has fewer failure modes, and is applicable to both chemical and electric propulsion systems.

This work was done by Markus Rufer,

Robert Conger, Thomas Bauer, and John Newman of Microcosm, Inc. 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: Steven Fedor, Mail

Stop 4–8, 21000 Brookpark Road, Cleveland, Ohio 44135. Refer to LEW-19042-1.

NASA Tech Briefs, October 2013 23

Physical Sciences

JWST Integrated Science Instrument Module Alignment

Optimization Tool

Goddard Space Flight Center, Greenbelt, Maryland

During cryogenic vacuum testing of

the James Webb Space Telescope

(JWST) Integrated Science Instrument

Module (ISIM), the global alignment of

the ISIM with respect to the designed interface of the JWST optical telescope element (OTE) will be measured through

a series of optical characterization tests.

These tests will determine the locations

and orientations of the JWST science instrument projected focal surfaces and

entrance pupils with respect to their corresponding OTE optical interfaces. If

any optical performance non-compliances are identified, the ISIM will be adjusted to improve its performance. In

order to understand how to manipulate

the ISIM’s degrees of freedom properly

and to prepare for the ISIM flight model

testing, a series of optical-mechanical

analyses have been completed to develop and identify the best approaches

for bringing a non-compliant ISIM element into compliance.

In order for JWST to meet its observatory-level optical requirements and

ambitious science goals, the ISIM element has to meet approximately 150

separate optical requirements. Successfully achieving many of those optical requirements depends on the

proper alignment of the ISIM element

with respect to the OTE. To verify that

the ISIM element will meet its optical

requirements, a series of cryogenic vacuum tests will be conducted with an

OTE Simulator (OSIM).

An optical Ray Trace and Geometry

Model tool was developed to help solve

the multi-dimensional alignment problem. The tool allows the user to determine how best to adjust the alignment of

the JWST ISIM with respect to the ideal

telescope interfaces so that the approximately 150 ISIM optical performance requirements can be satisfied. This capability has not existed previously.

This work was done by Brent Bos of Goddard Space Flight Center. Further information

is contained in a TSP (see page 1). GSC16698-1

Radar Range Sidelobe Reduction Using Adaptive Pulse

Compression Technique

There is significant improvement on sidelobe performance.

Goddard Space Flight Center, Greenbelt, Maryland

Pulse compression has been widely used

in radars so that low-power, long RF pulses

can be transmitted, rather than a highpower short pulse. Pulse compression

radars offer a number of advantages over

high-power short pulsed radars, such as no

need of high-power RF circuitry, no need

of high-voltage electronics, compact size

and light weight, better range resolution,

and better reliability. However, range sidelobe associated with pulse compression

has prevented the use of this technique on

spaceborne radars since surface returns

detected by range sidelobes may mask the

returns from a nearby weak cloud or precipitation particles. Research on adaptive

pulse compression was carried out utilizing a field-programmable gate array

(FPGA) waveform generation board and a

radar transceiver simulator. The results

have shown significant improvements in

pulse compression sidelobe performance.

Microwave and millimeter-wave radars

present many technological challenges

for Earth and planetary science applications. The traditional tube-based radars

use high-voltage power supply/modulators and high-power RF transmitters;

therefore, these radars usually have large

size, heavy weight, and reliability issues

for space and airborne platforms. Pulse

compression technology has provided a

path toward meeting many of these radar

challenges. Recent advances in digital

waveform generation, digital receivers,

and solid-state power amplifiers have

opened a new era for applying pulse

compression to the development of compact and high-performance airborne

and spaceborne remote sensing radars.

The primary objective of this innovative

effort is to develop and test a new pulse

compression technique to achieve ultrarange sidelobes so that this technique can

be applied to spaceborne, airborne, and

ground-based remote sensing radars to

meet future science requirements. By

using digital waveform generation, digital

receiver, and solid-state power amplifier

technologies, this improved pulse compression technique could bring significant impact on future radar development.

The novel feature of this innovation

is the non-linear FM (NLFM) waveform

design. The traditional linear FM has

the limit (–20 log BT –3 dB) for achieving ultra-low-range sidelobe in pulse

compression. For this study, a different

combination of 20- or 40-microsecond

chirp pulse width and 2- or 4-MHz chirp

bandwidth was used. These are typical

operational parameters for airborne or

spaceborne weather radars. The NLFM

waveform design was then implemented on a FPGA board to generate a

real chirp signal, which was then sent to

the radar transceiver simulator. The

final results have shown significant improvement on sidelobe performance

compared to that obtained using a traditional linear FM chirp.

This work was done by Lihua Li, Michael

Coon, and Matthew McLinden of Goddard

Space Flight Center. Further information is contained in a TSP (see page 1). GSC-16458-1
24 NASA Tech Briefs, October 2013

Digitally Calibrated TR Modules Enabling Real-Time

Beamforming SweepSAR Architectures

Civilian and military remote sensing instruments could benefit from this work, as well as

military intelligence applications.

NASA’s Jet Propulsion Laboratory, Pasadena, California

SweepSAR, a novel radar architecture

that depends on a DBF (digital beamforming) array, requires calibration accuracies that are order(s) of magnitude

greater than is possible with traditional

techniques, such as a priori characterization of TR (transmit/receive) modules

in thermal vacuum chambers, or simple

loop-back of the calibration signal. The

advantages of a SweepSAR architecture

are so great that it is worth applying significant resources to calibration efforts.

Due to the nature of the DBF, each

channel contains a digitizer and very

powerful digital processor. Each channel

can independently digitize (with the digitizer) and analyze (with the processor)

its channel’s unique calibration signal,

and extract the relevant calibration parameters, namely channel gain and

channel phase delay commonly referred

to as the gain (or amplitude) and phase

of the channel. Using the processor,

each channel’s gain and phase can theoretically be estimated with arbitrary precision through averaging a sufficiently

large number of samples. Systematic errors and the changing gain and phase of

the channels, typically due to temperature drifts, limits how long the averaging

can occur, which limits the precision of

the calibration estimate. However, results indicate that calibration knowledge

of both the transmit and receive chains

of each TR module can be improved by

one or two orders of magnitude. Due to

the digital nature of the receiver data,

the channel’s gain and phase may be

corrected by a similar amount, while the

transmit chain can only be corrected in

a traditional manner. To implement

SweepSAR, the order of magnitude improvement in the knowledge of the

channel’s gain and phase is needed, and

the control of the receiver to a similar

level is required.

Inherent to the DBF array is the individual digitization of each of the array’s receiver channels. Current systems typically

combine all of the analog signals in the

array into one or two analog channels,

which are then digitized and processed.

All signal conditioning performed prior

to digitization is done using analog hardware (which is less precise than digital signal conditioning and dependent on temperature). The DBF digitizes every signal

prior to combining, and can therefore analyze and correct received signals, as well

as analyze signals that are being transmitted through analog hardware (by sampling a copy and digitizing). Each channel of a DBF also has a powerful

processor. With this combination, one is

able to digitize, analyze, and correct each

channel prior to its being combined.

A unique factor is the ability to digitize and analyze (in real time) each of

the array’s channels independently, allowing one to achieve unprecedented

knowledge of each channel’s performance (gain and phase), and since the

combining is done digitally, each receive

channel can be corrected prior to combining. This enables an unprecedented

level of accuracy and control through

onboard processing.

SweepSAR promises significant increases in instrument capability for solid

earth and biomass remote sensing, while

reducing mission mass and cost. This

new instrument concept requires new

methods for calibrating the multiple

channels, which must be combined onboard, in real time. New methods are

being developed for digitally calibrating

digital beam-forming arrays to reduce

development time, risk, and cost of precision calibrated TR modules for array

architectures by accurately tracking modules’ characteristics through closed-loop

digital calibration, thus tracking systematic changes regardless of temperature.

This work was done by James P. Hoffman,

Louise A. Veilleux, Eva Peral, Chung-Lun

Chuang, and Scott J. Shaffer of Caltech for

NASA’s Jet Propulsion Laboratory. Further

information is contained in a TSP (see page

1). NPO-48310

The SweepSAR Transmit and Receive swaths. Transmit requires illumination of a large swath (small

aperture), while Receive requires multiple small swaths (large apertures).

Range direction

Azimuth direction

Radar swath

Transmit

Radar antenna

Radar flight path

radar

pulse

in air

Scanning Receive

Radar antenna

ground echo

Beam scans

to track echoes

Multiple pulse echoes to track

Note: Transmit and Scanning Receive

events are colocated in space and time!

Along-track offset shown is for clarity

of presentation only!
NASA Tech Briefs, October 2013 25

Electro-Optic Time-to-Space Converter for Optical Detector

Jitter Mitigation

The ability to more precisely measure the arrival time of an optical pulse is valuable in free

space optical communications, lidar, and quantum key distribution.

NASA’s Jet Propulsion Laboratory, Pasadena, California

A common problem in optical detection is determining the arrival time of a

weak optical pulse that may comprise

only one to a few photons. Currently, this

problem is solved by using a photodetector to convert the optical signal to an

electronic signal. The timing of the electrical signal is used to infer the timing of

the optical pulse, but error is introduced

by random delay between the absorption

of the optical pulse and the creation of

the electrical one. To eliminate this

error, a time-to-space converter separates

a sequence of optical pulses and sends

them to different photodetectors, depending on their arrival time.

The random delay, called jitter, is at

least 20 picoseconds for the best detectors capable of detecting the weakest optical pulses, a single photon, and can be

as great as 500 picoseconds. This limits

the resolution with which the timing of

the optical pulse can be measured.

The time-to-space converter overcomes this limitation. Generally, the

time-to-space converter imparts a timedependent momentum shift to the incoming optical pulses, followed by an

optical system that separates photons of

different momenta. As an example, an

electro-optic phase modulator can be

used to apply longitudinal momentum

changes (frequency changes) that vary

in time, followed by an optical spectrometer (such as a diffraction grating),

which separates photons with different

momenta into different paths and directs them to impinge upon an array of

photodetectors. The pulse arrival time

is then inferred by measuring which

photodetector receives the pulse.

The use of a time-to-space converter

mitigates detector jitter and improves

the resolution with which the timing of

an optical pulse is determined. Also, the

application of the converter enables the

demodulation of a pulse position modulated signal (PPM) at higher bandwidths than using previous photodetector technology. This allows the creation

of a receiver for a communication system with high bandwidth and high

bits/photon efficiency.

This work was done by Kevin Birnbaum

and William Farr of Caltech for NASA’s Jet

Propulsion Laboratory. Further information is

contained in a TSP (see page 1). NPO-45799

Partially Transparent Petaled Mask/Occulter for

Visible-Range Spectrum

The intensity along the optical axis can be suppressed up to ten orders of magnitude.

Goddard Space Flight Center, Greenbelt, Maryland

The presence of the Poisson Spot, also

known as the spot of Arago, has been

known since the 18th century. This spot

is the consequence of constructive interference of light diffracted by the edge of

the obstacle where the central position

can be determined by symmetry of the

object. More recently, many NASA missions require the suppression of this spot

in the visible range. For instance, the exoplanetary missions involving space telescopes require telescopes to image the

planetary bodies orbiting central stars.

For this purpose, the starlight needs to

be suppressed by several orders of magnitude in order to image the reflected

light from the orbiting planet. For the

Earth-like planets, this suppression needs

to be at least ten orders of magnitude.

One of the common methods of suppression involves sharp binary petaled occulters envisioned to be placed many thousands of miles away from the telescope

blocking the starlight.

The suppression of the Poisson Spot

by binary sharp petal tips can be problematic when the thickness of the tips

becomes smaller than the wavelength of

the incident beam. First they are difficult to manufacture and also it invalidates the laws of physical optics. The

proposed partially transparent petaled

masks/occulters compensate for this

sharpness with transparency along the

surface of the petals. Depending on the

geometry of the problem, this transparency can be customized such that

only a small region of the petal is transparent and the remaining of the surface

is opaque. This feature allows easy fabrication of this type of occultation device

either as a mask or occulter.

A partially transparent petaled mask/

occulter has been designed for the visible spectrum range. The mask/occulter

can suppress the intensity along the optical axis up to ten orders of magnitude.

The design process can tailor the mask

shape, number of petals, and transparency level to the near-field and farfield diffraction region. The mask/occulter can be used in space astronomy,

ground-based telescope, and high-energy laser systems, and optical lithography to eliminate the Poisson Spot.

This work was done by Ron Shahram Shiri

of Goddard Space Flight Center, and Wasyl

Wasylkiwskyj of The George Washington University. Further information is contained in a

TSP (see page 1). GSC-16588-1

NASA Tech Briefs, October 2013 27

Information Technology

Educational NASA Computational and Scientific Studies

(enCOMPASS)

This project bridges the gap between computational objectives and needs of NASA’s scientific

research, missions, and projects, and academia’s latest advances in applied mathematics and

computer science.

Goddard Space Flight Center, Greenbelt, Maryland

Educational NASA Computational and

Scientific Studies (enCOMPASS) is an educational project of NASA Goddard

Space Flight Center aimed at bridging the

gap between computational objectives

and needs of NASA’s scientific research,

missions, and projects, and academia’s

latest advances in applied mathematics

and computer science. enCOMPASS

achieves this goal via bidirectional collaboration and communication between

NASA and academia. Using developed

NASA Computational Case Studies in university computer science/engineering

and applied mathematics classes is a way

of addressing NASA’s goals of contributing to the Science, Technology, Education, and Math (STEM) National Objective. The enCOMPASS Web site at

http://encompass.gsfc.nasa.gov provides

additional information.

There are currently nine enCOMPASS case studies developed in areas of

earth sciences, planetary sciences, and

astrophysics. Some of these case studies

have been published in AIP and IEEE’s

Computing in Science and Engineering

magazines. A few university professors

have used enCOMPASS case studies in

their computational classes and contributed their findings to NASA scientists. In these case studies, after introducing the science area, the specific

problem, and related NASA missions,

students are first asked to solve a known

problem using NASA data and past approaches used and often published in a

scientific/research paper. Then, after

learning about the NASA application

and related computational tools and approaches for solving the proposed problem, students are given a harder problem as a challenge for them to research

and develop solutions for.

This project provides a model for

NASA scientists and engineers on one

side, and university students, faculty,

and researchers in computer science

and applied mathematics on the other

side, to learn from each other’s areas of

work, computational needs and solutions, and the latest advances in research and development. This innovation takes NASA science and

engineering applications to computer

science and applied mathematics university classes, and makes NASA objectives part of the university curricula.

There is great potential for growth and

return on investment of this program to

the point where every major university

in the U.S. would use at least one of

these case studies in one of their computational courses, and where every

NASA scientist and engineer facing a

computational challenge (without having resources or expertise to solve it)

would use enCOMPASS to formulate

the problem as a case study, provide it to

a university, and get back their solutions

and ideas.

This work was done by Nargess

Memarsadeghi of Goddard Space Flight Center. Further information is contained in a

TSP (see page 1). GSC-16288-1

Coarse-Grain Bandwidth Estimation Scheme for

Large-Scale Network

A new analytical approach, called the “leveling scheme,” was developed to model the

mechanism of the network data flow.

NASA’s Jet Propulsion Laboratory, Pasadena, California

A large-scale network that supports a

large number of users can have an aggregate data rate of hundreds of Mbps at

any time. High-fidelity simulation of a

large-scale network might be too complicated and memory-intensive for typical

commercial-off-the-shelf (COTS) tools.

Unlike a large commercial wide-area-network (WAN) that shares diverse network

resources among diverse users and has a

complex topology that requires routing

mechanism and flow control, the ground

communication links of a space network

operate under the assumption of a guaranteed dedicated bandwidth allocation

between specific sparse endpoints in a

star-like topology. This work solved the

network design problem of estimating

the bandwidths of a ground network architecture option that offer different

service classes to meet the latency requirements of different user data types.

In this work, a top-down analysis and

simulation approach was created to size

the bandwidths of a store-and-forward

network for a given network topology, a

mission traffic scenario, and a set of data

types with different latency requirements.

These techniques were used to estimate

the WAN bandwidths of the ground links

for different architecture options of the

proposed Integrated Space Communication and Navigation (SCaN) Network.

A new analytical approach, called the

“leveling scheme,” was developed to

model the store-and-forward mechanism
28 NASA Tech Briefs, October 2013

of the network data flow. The term “leveling” refers to the spreading of data

across a longer time horizon without violating the corresponding latency requirement of the data type. Two versions

of the leveling scheme were developed:

1. A straightforward version that simply

spreads the data of each data type

across the time horizon and doesn’t

take into account the interactions

among data types within a pass, or between data types across overlapping

passes at a network node, and is inherently sub-optimal.

2. Two-state Markov leveling scheme

that takes into account the second

order behavior of the store-and-forward mechanism, and the interactions

among data types within a pass.

The novelty of this approach lies in

the modeling of the store-and-forward

mechanism of each network node. The

term store-and-forward refers to the

data traffic regulation technique in

which data is sent to an intermediate

network node where they are temporarily stored and sent at a later time to the

destination node or to another intermediate node. Store-and-forward can

be applied to both space-based networks that have intermittent connectivity, and ground-based networks with deterministic connectivity. For groundbased networks, the store-and-forward

mechanism is used to regulate the network data flow and link resource utilization such that the user data types can be

delivered to their destination nodes

without violating their respective latency requirements.

This work was done by Kar-Ming Cheung,

Esther H. Jennings, and John S. Segui of Caltech

for NASA’s Jet Propulsion Laboratory. For more

information, contact iaoffice@jpl.nasa.gov.

The software used in this innovation is available for commercial licensing. Please contact Dan

Broderick at Daniel.F.Broderick@jpl.nasa.gov.

Refer to NPO-48426.

The objective of this research was to

develop a fundamentally new method

for detecting hidden moving targets

within noisy and cluttered data-streams

using a novel “soliton resonance” effect

in nonlinear dynamical systems.

The technique uses an inhomogeneous Korteweg de Vries (KdV) equation containing moving-target information. Solution of the KdV equation will

describe a soliton propagating with the

same kinematic characteristics as the target. The approach uses the time-dependent data stream obtained with a

sensor in form of the “forcing function,”

which is incorporated in an inhomogeneous KdV equation. When a hidden

moving target (which in many ways resembles a soliton) encounters the natural “probe” soliton solution of the KdV

equation, a strong resonance phenomenon results that makes the location and

motion of the target apparent.

Soliton resonance method will amplify the moving target signal, suppressing the noise. The method will be a

very effective tool for locating and

identifying diverse, highly dynamic targets with ill-defined characteristics in a

noisy environment.

The soliton resonance method for

the detection of moving targets was developed in one and two dimensions.

Computer simulations proved that the

method could be used for detection of

singe point-like targets moving with

constant velocities and accelerations in

1D and along straight lines or curved

trajectories in 2D. The method also allows estimation of the kinematic characteristics of moving targets, and reconstruction of target trajectories in

2D. The method could be very effective for target detection in the presence of clutter and for the case of target obscurations.

This work was done by Igor K. Kulikov of

Caltech and Michail Zak of Raytheon for

NASA’s Jet Propulsion Laboratory. Further

information is contained in a TSP (see page

1). NPO-48785

Detection of Moving Targets Using Soliton Resonance Effect

NASA’s Jet Propulsion Laboratory, Pasadena, California
NASA Tech Briefs, October 2013 29

High-Efficiency Nested Hall

Thrusters for Robotic Solar

System Exploration

This work describes the scaling and

design attributes of Nested Hall

Thrusters (NHT) with extremely large

operational envelopes, including a wide

range of throttleability in power and specific impulse at high efficiency (>50%).

NHTs have the potential to provide the

game changing performance, powerprocessing capabilities, and cost effectiveness required to enable missions that

cannot otherwise be accomplished.

NHTs were first identified in the electric

propulsion community as a path to 100-

kW class thrusters for human missions.

This study aimed to identify the performance capabilities NHTs can provide

for NASA robotic and human missions,

with an emphasis on 10-kW class

thrusters well-suited for robotic exploration. A key outcome of this work has

been the identification of NHTs as

nearly constant-efficiency devices over

large power throttling ratios, especially

in direct-drive power systems. NHT systems sized for robotic solar system exploration are predicted to be capable of

high-efficiency operation over nearly

their entire power throttling range.

A traditional Annular Hall Thruster

(AHT) consists of a single annular discharge chamber where the propellant is

ionized and accelerated. In an NHT,

multiple annular channels are concentrically stacked. The channels can be operated in unison or individually depending on the available power or required

performance. When throttling an AHT,

performance must be sacrificed since a

single channel cannot satisfy the diverse

design attributes needed to maintain

high thrust efficiency. NHTs can satisfy

these requirements by varying which

channels are operated and thereby offer

significant benefits in terms of thruster

performance, especially under deep

power throttling conditions where the

efficiency of an AHT suffers since a single channel can only operate efficiently

(>50%) over a narrow power throttling

ratio (3:1).

Designs for 10-kW class NHTs were developed and compared with AHT systems. Power processing systems were

considered using either traditional

Power Processing Units (PPU) or Direct

Drive Units (DDU). In a PPU-based system, power from the solar arrays is transformed from the low voltage of the arrays

to the high voltage needed by the

thruster. In a DDU-based system, power

from the solar arrays is fed to the thruster

without conversion. DDU-based systems

are attractive for their simplicity since

they eliminate the most complex and expensive part of the propulsion system.

The results point to the strong potential of NHTs operating with either PPUs

or DDUs to benefit robotic and human

missions through their unprecedented

power and specific impulse throttling capabilities. NHTs coupled to traditional

PPUs are predicted to offer high-efficiency (>50%) power throttling ratios

320% greater than present capabilities,

while NHTs with direct-drive power systems (DDU) could exceed existing capabilities by 340%. Because the NHT-DDU

approach is implicitly low-cost, NHT-DDU

technology has the potential to radically

reduce the cost of SEP-enabled NASA

missions while simultaneously enabling

unprecedented performance capability.

This work was done by Richard R. Hofer of

Caltech for NASA’s Jet Propulsion Laboratory.

Further information is contained in a TSP

(see page 1). NPO-48400

High-Voltage Clock Driver

for Photon-Counting CCD

Characterization

A document discusses the CCD97 from

e2v technologies as it is being evaluated

at Goddard Space Flight Center’s Detector Characterization Laboratory (DCL)

for possible use in ultra-low background

noise space astronomy applications, such

as Terrestrial Planet Finder Coronagraph

(TPF-C). The CCD97 includes a photoncounting mode where the equivalent output noise is less than one electron. Use of

this mode requires a clock signal at a voltage level greater than the level achievable

by the existing CCD (charge-coupled-device) electronics.

A high-voltage waveform generator

has been developed in code 660/601 to

support the CCD97 evaluation. The unit

generates required clock waveforms at

voltage levels from –20 to +50 V. It deals

with standard and arbitrary waveforms

and supports pixel rates from 50 to 500

kHz. The system is designed to interface

with existing Leach CCD electronics.

This work was done by Robert Baker of Goddard Space Flight Center. Further information

is contained in a TSP (see page 1). GSC15059-1

Development of the Code

RITRACKS

A document discusses the code RITRACKS (Relativistic Ion Tracks), which

was developed to simulate heavy ion

track structure at the microscopic and

nanoscopic scales. It is a Monte-Carlo

code that simulates the production of radiolytic species in water, event-by-event,

and which may be used to simulate

tracks and also to calculate dose in targets and voxels of different sizes. The

dose deposited by the radiation can be

calculated in nanovolumes (voxels).

RITRACKS allows simulation of radiation tracks without the need of extensive

knowledge of computer programming

or Monte-Carlo simulations. It is installed as a regular application on Windows systems. The main input parameters entered by the user are the type and

energy of the ion, the length and size of

the irradiated volume, the number of

ions impacting the volume, and the number of histories. The simulation can be

started after the input parameters are entered in the GUI. The number of each

kind of interactions for each track is

shown in the result details window. The

tracks can be visualized in 3D after the

simulation is complete. It is also possible

to see the time evolution of the tracks

and zoom on specific parts of the tracks.

The software RITRACKS can be very

useful for radiation scientists to investigate various problems in the fields of radiation physics, radiation chemistry, and

radiation biology. For example, it can be

used to simulate electron ejection experiments (radiation physics).

This work was done by Ianik Plante and

Francis A. Cucinotta of Johnson Space Center.

Further information is contained in a TSP

(see page 1). MSC-25076-1

Books & Reports

NASA Tech Briefs, October 2013 31

Bio-Medical

Enabling Microliquid Chromatography by Microbead Packing

of Microchannels

Goddard Space Flight Center, Greenbelt, Maryland

The microbead packing is the critical

element required in the success of onchip microfabrication of critical microfluidic components for in-situ analysis and

detection of chiral amino acids. In order

for microliquid chromatography to

occur, there must be a stationary phase

medium within the microchannel that interacts with the analytes present within

flowing fluid. The stationary phase media

are the microbeads packed by the process

discussed in this work. The purpose of

the microliquid chromatography is to

provide a lightweight, low-volume, and

low-power element to separate amino

acids and their chiral partners efficiently

to understand better the origin of life.

In order to densely pack microbeads

into the microchannels, a liquid slurry of

microbeads was created. Microbeads

were extracted from a commercially available high-performance liquid chromatography column. The silica beads extracted were 5 microns in diameter, and

had surface coating of phenyl-hexyl.

These microbeads were mixed with a 200-

proof ethanol solution to create a microbead slurry with the right viscosity for

packing. A microfilter is placed at the

outlet via of the microchannel and the

slurry is injected, then withdrawn across a

filter using modified syringes. After each

injection, the channel is flushed with

ethanol to enhance packing. This cycle is

repeated numerous times to allow for a

tightly packed channel of microbeads.

Typical microbead packing occurs in

the macroscale into tubes or channels by

using highly pressurized systems. Moreover, these channels are typically long

and straight without any turns or curves.

On the other hand, this method of microbead packing is completed within a

microchannel 75 micrometers in diameter. Moreover, the microbead packing is

completed into a serpentine type microchannel, such that it maximizes microchannel length within a microchip.

Doing so enhances the interactions of

the analytes with the microbeads to separate efficiently amino acids and amino

acid enantiomers.

This work was done by Manuel Balvin

and Yun Zheng of Goddard Space Flight Center. Further information is contained in a

TSP (see page 1). GSC-16514-1


National Aeronautics and

Space Administration