April 1999

Briefs : Physical Sciences
Foam Heat Exchangers

Experiments have demonstrated the feasibility of heat exchangers with flow channels containing open-cell metallic foams. Nonmetallic foams could also be used. One proposed design calls for an open-cell foam in the annular region between an inner and an outer tube, with a heat-transfer fluid flowing along the annular region...

Briefs : Robotics, Automation & Control
Human-Powered Centrifuges and Stationary Exercise Stations

Human-powered machines that can be operated as centrifuges or as stationary exercise stations have been invented. These machines are suitable for a variety of terrestrial and outer-space applications that involve physical therapy, maintenance of physical fitness, centrifugal simulation...

Briefs : Mechanical & Fluid Systems
High-Altitude Flight Test of the Perseus B Airplane

The Perseus B remotely piloted vehicle (RPV) has achieved a record altitude for a single-engine, propeller-driven airplane of 60,260 ft (18,367 m) on June 27, 1998. The Perseus B is one of the test-bed aircraft developed under NASA's Environmental Research Aircraft and Sensor Technology (ERAST)...

Briefs : Electronics & Computers
Interlayer Stripline Transition

A proposed multilayer metal-film/dielectric-plate laminate would serve as a passive radio-frequency (RF) interlayer stripline transition. This device is designed to provide RF coupling from (a) an input transmission line of the stripline type spanning the first through third metal layers, with characteristic...

Briefs : Materials
Another Improved Method for Making Fuel-Cell Electrodes

An improved method of fabricating membrane electrode structures for methanol fuel cells is similar to the method described in the preceding article, except that in this method, the catalytic ink is poured and spread onto the membrane instead of sprayed. The development of both improved...

Briefs : Electronics & Computers
Circuit for Automatic Tunneling-Controlled Golay Cell

An automatic tunneling-controlled, micromachined Golay cell has been implemented in a multichip integrated-circuit module. The module is designed specifically for sensing infrared radiation indicative of the concentration of glucose in blood, but its low noise, high gain, and low power...

Briefs : Physical Sciences
Thermal and Mechanical Effects in Graded Composite Cylinders

"HOTCFGM-1D" denotes a collection of four computer programs, plus the underlying theory, for calculating thermomechanical and inertial effects in axisymmetric cylindrical multiphase-composite-material objects that are functionally graded along their radial coordinates. The theory and...

Briefs : Electronics & Computers
Vertical-Bloch-Line Memories Containing Stacked Chips

Vertical-Bloch-line (VBL) memory devices of a proposed type would include stacks of VBL memory chips plus other components (see figure on next page). Each chip would be square, approximately 15 mm on each side. Each chip would have two input/output (I/O) lines connected to 16 I/O pads on each...

Briefs : Physical Sciences
Details of Apparatus for Advanced Ultrasonic C-Scan Imaging

A report comprising the main contents of U. S. Patent 5,750,895 presents detailed information on the subject of "Apparatus for Advanced Ultrasonic C-Scan Imaging (GSC-13524), NASA Tech Briefs, Vol. 21, No. 4 (April 1997), page 34. The apparatus is a computer-controlled ultrasonic C-scan...

Briefs : Information Technology
Neural-Network Modeling of Flow Properties of an Object

A method of computational simulation of the aerodynamic- or hydrodynamic-flow performance features of objects involves the use of neural-network mathematical models implemented in computer hardware and software. The method can be applied in conjunction with wind-tunnel, water-tunnel, or...

Briefs : Physical Sciences
Segmented-Aperture Michelson Interferometer

In a proposed modification of the basic design of a Michelson interferometer, the beam aperture would be split into a number (N ≧ 2) of smaller areas and the optics arranged so that the beam in each area would generate a distinct segment of the overall desired interferogram. Each segment of the...

Briefs : Materials
Electric-Arc and Electrochemical Texturing of Surfaces

Electric arcs and electrochemical etching can be used to impart microscopic textures to surfaces of metals. In electric-arc texturing, one strikes an arc between a water-cooled electrode and a substrate that one seeks to texture. As the arc is moved across the substrate surface, a...

Briefs : Robotics, Automation & Control
Miniature Lambda Sensors for Engine-Control Systems

Small, lightweight sensors that exploit the unique characteristics of nanoceramics are being developed for use in measuring air/fuel ratios in the exhaust gas flows of advanced aircraft engines. Adaptive control systems would process the readings from these sensors, along with other sensory and...

Briefs : Software
Software for Operating a Forward-Link-Simulator Card

A computer program has been developed to serve as the means for setting up, controlling, and receiving information on the status of a forward-link-simulator card in a Digital Equipment Corporation (DEC) Alpha computer that runs the Digital UNIX operating system. The program performs functions...

Briefs : Electronics & Computers
Improvements in Fabrication of HgCdTe Photodetectors

Two improvements have been made to solve two problems that arise in conjunction with a fabrication process in which an HgCdTe photodetector is mounted on an alumina substrate with epoxy. Although most of the HgCdTe-photodetector industry has abandoned this process in favor of epitaxial...

Briefs : Electronics & Computers
Broad-Band GaAs/AlₓGa₁₋ₓAs QWIPs

GaAs/AlxGa1-xAs quantum-well infrared photodetectors (QWIPs) with broad-band responses are undergoing development. The broad-band responses are obtained by varying the depths and widths of the wells and the thicknesses of the barriers between the wells, as explained below.

Briefs : Physical Sciences
Sensor for Monitoring Concentration of Methanol in Water

A robust sensor based on the electrochemical oxidation of methanol has been developed for use in measuring the concentration of methanol dissolved in water. The sensor is expected to be particularly useful in continuous monitoring and control of the concentration of an aqueous solution of...

Briefs : Mechanical & Fluid Systems
Model-Based Monitoring for Spacecraft Thruster Leakage

A report describes a method of detecting leakage in one of the 16 thrusters of the Cassini spacecraft. The detection method, implemented as part of the spacecraft flight software, is based on the fact that the three-axis rotational motion of a spacecraft is governed by the Euler's equation....

Briefs : Electronics & Computers
InₓGa₁₋ₓP/InₓGa₁₋ₓAs-on-Ge Solar Photovoltaic Cells

Monolithic, tandem two-junction InxGa1-xP/InxGa1-x As-on-Ge Solar Photovoltaic Cells are being developed. The cells are designed to be used with solar concentrators to generate electric power aboard spacecraft. The theoretically...

Briefs : Electronics & Computers
Mobile System for Control of a Remote Rocket-Launching Range

The Wallops Flight Facility of the Goddard Space Flight Center has designed and built in-house a Mobile Range Control System (MRCS), which is a self-contained system to be deployed in support of rocket launches at remote ranges in cases in which termination of flight may be required...

Briefs : Robotics, Automation & Control
Thermal Batteries Made With Nanostructured Material

Early experiments in a continuing research program have demonstrated that thermal batteries made from powdered solid electrode and electrolyte materials can be improved by use of smaller (nanometer vs. micrometer size) cathode powder grains. The improvements include the possibility of...

Briefs : Information Technology
Algorithm Accelerates Solution of Digraph Reliability Models

The SourceDoubls algorithm efficiently solves for singletons and doubletons of a digraph reliability model (defined below). In the case of a complex system of hardware and/or software represented by a correspondingly complex digraph reliability model, it can take as long as days to...

Briefs : Electronics & Computers
Lead Bromide Crystals Doped With Silver Bromide

Doping with silver bromide has been found to be an effective technique for enhancing the optical homogeneity and other qualities of single crystals of lead bromide. These crystals are grown from melts by directional solidification. The doping suppresses cleavage that would otherwise occur during...

Briefs : Robotics, Automation & Control
Solar Heating of Batteries in Cold Environments

According to a proposal for small electric-power systems that must operate in cold environments, heat released in the operation of solar photovoltaic arrays with solar concentrators would be utilized to maintain batteries at operating temperatures. The proposal is straightforward and does not...

Briefs : Physical Sciences
Programmable Multizone Directional-Solidification Furnaces

Programmable multizone furnaces with enhanced designs have been proposed for use in processing materials by directional solidification or, optionally, by related techniques of float-zone or isothermal solidification. Like some other directional-solidification furnaces reported previously...

Briefs : Electronics & Computers
High-Performance HgCdTe Detectors for Remote Sensing: Part 2

The split-geometry design for arrays of photoconductive HgCdTe infrared photodetectors described in the preceding article can also be used to mitigate the deleterious effect of a phenomenon called "sweepout," which degrades performance. Sweepout occurs in conventional small HgCdTe...

Briefs : Information Technology
Diagnosing Rotating Machinery Using Spectral Distribution Functions

A method for detecting and characterizing faults in a rotating machine involves analysis of selected aspects of the evolution of the spectral distribution function (SDF) of its vibrations. The method is based on the proposition that long-term accumulation of damage (e.g.,...

Briefs : Manufacturing & Prototyping
Software for Minimizing and Removing Burrs in Manufacturing

An integrated suite of computer programs is undergoing development to address issues pertaining to the formation of burrs — undesired projections of metal that are generated on edges of workpieces in most metal-cutting operations. Burrs must be removed prior to assembly of machined...

Briefs : Robotics, Automation & Control
Liquid-Circulation System Keeps Aircrew Members Cool

Each member of the aircrew of an advanced fighter airplane wears a complex, multilayered ensemble that imposes a significant thermal burden by inhibiting normal transport of heat from the body. The thermal burden may be aggravated by the use of nuclear, biological, and chemical (NBC)...

Briefs : Electronics & Computers
Improved Electrical Connections for Thin-Film Thermocouples

Improved electrical connections have been developed for thin-film thermocouples used to measure temperatures on the surfaces of ceramic-matrix composite-material specimens during high-temperature tests. In a test, specimens are arranged in a four-sided configuration in a test rig, where...

Briefs : Electronics & Computers
High-Performance HgCdTe Detectors for Remote Sensing: Part 1

Focal-plane arrays of HgCdTe photoconductors have been designed and fabricated to satisfy special requirements for high-performance long-wavelength infrared (LWIR) photodetectors. The special requirements are the following:

Briefs : Materials
Improved Fabrication of Electrodes for Methanol Fuel Cells

A method of fabricating membrane electrode structures for methanol fuel cells involves, among other things, the use of improved sprayers to deposit inks containing catalytic metals on membranes of Nafion™ (or equivalent) perfluorosulfonic acid-based hydrophilic, proton-conducting...

Briefs : Physical Sciences
Scanning Surface-Plasmon Filters for Miniature Spectrometers

Scanning filters based on surface plasmons would be used as the adjustable wavelength-selective (band-pass) devices in a class of proposed miniature spectrometers. These filters would occupy much less space and weigh much less than do the diffraction gratings and other...