August 2001

Briefs : Electronics & Computers
The NASA Spacecraft Transponding Modem

A report describes the NASA Spacecraft Transponding Modem (STM) — a spacecraft transponder now under development for planned use on deep-space missions scheduled for launch in the year 2003. In comparison with a traditional deep-space transponder, the STM will be smaller and less power hungry; the...

Briefs : Electronics & Computers
Analog VLSI Circuits for Hebbian Learning in Neural Networks

An analog very-large-scale integrated (VLSI) circuit was designed and built to implement Hebbian synapses with an improved method of modifying and storing the synaptic weights, for use in neural-network circuits. (In Hebbian synapses, the synaptic weights are modified through Hebbian...

Briefs : Electronics & Computers
Design of a Highly Reliable Controller for an I2C Bus

The design of a highly reliable controller for a digital data bus incorporates improvements, in both hardware and software, over the basic design of a low-speed, low-power, serial bus known in the industry as "I2C." ("I2C" signifies "inter integrated circuit bus" — a...

Briefs : Information Technology
Advances in Parallel Computing on Adaptive Grids

Five papers address interrelated topics in parallel computing and the use of adaptive, unstructured computational grids. The titles of the papers and their general subject matters are the following:

Briefs : Electronics & Computers
Compact, Rugged Enclosure for PC-Based Electronic Circuits

Figure 1 depicts a compact enclosure enabling the operation of personal-computer (PC)-based electronic circuits in harsh environments. The electronic circuits in question are commercial off-the-shelf Industry Standard Architecture (ISA) and Extended Industry Standard Architecture (EISA)...

Briefs : Electronics & Computers
Full-Spectrum Arraying of Receiving Radio Antennas

A method of arraying of receiving radio antennas involves utilization of all of the signal information available across a broad spectral band that includes any signal(s) of interest. As used here, "arraying" signifies combining the signals received by multiple antennas at different locations in...

Briefs : Electronics & Computers
Array of Nanoklystrons for Frequency Agility or Redundancy

An array of monolithically fabricated nanoklystrons has been proposed as a frequency-agile and/or redundant source of electromagnetic radiation at frequencies ranging from about 0.3 to about 3 THz. Each nanoklystron would, as its name suggests, be a very small klystron. Like other...

Briefs : Electronics & Computers
Log-Ratio Circuit With Enhanced Temperature Stability

The figure illustrates a proposed analog amplifier circuit that would put out a voltage proportional to the logarithm of the ratio between two input signal currents, I1 and I2. In comparison with prior log-ratio amplifiers, this one would be relatively insensitive to...

Briefs : Electronics & Computers
Millimeter-Wave Dichroic Plates for High Angles of Incidence

Dichroic plates for cutoff wavelengths down to about a millimeter and high angles of incidence can be fabricated by numerically controlled milling of rectangular arrays of waveguide slots in half-wavelength-thick metal plates. A plate of this type is used to separate higher- and...

Briefs : Software
Computing Diffusion in High-Temperature Coating Layer

COSIM is a computer program that numerically simulates oxidation and diffusion in a metallic coating layer on substrates made of nickel-base alloys. COSIM is primarily useful for analyzing the gradual deterioration and predicting the lifetimes of the protective coating on turbine blades...

Briefs : Software
Software for 3D Graphics With Time- and Cost-Saving Features

Enigma version 4.4 is an integrated three-dimensional (3D)-graphics application program that includes multiple cost- and time-saving features. Enigma provides capabilities for building geometric models, key-frame animation, and video recording, and provides graphical front ends for use...

Briefs : Materials
Obtaining Consistent, Reliable Results in Elastomer Seal Testing

Compression Stress Relaxation (CSR) is an important factor in evaluating elastomer materials and seal configurations for their ability to provide sealing force retention under a variety of conditions. Increasing emphasis on the performance and longevity of elastomer seals, used...

Briefs : Materials
Making Ion-Accelerator Grids From Ti Instead of Mo

Titanium has been found to offer several advantages over molybdenum as the material used to construct electrostatic-accelerator and -screen grids for ion thrusters for spacecraft. These advantages could also be expected to extend to the manufacture of grids for ion accelerators used in...

Briefs : Mechanical & Fluid Systems
Quasi-Fractal Lenticular Booms

An improved configuration for large, thin-walled lenticular booms has been proposed to reduce their susceptibility to buckling. Lenticular booms have been used on spacecraft because they can be flattened and rolled onto drums for compact storage during transport, then deployed by unrolling them from the drums....

Briefs : Mechanical & Fluid Systems
Nonintrusive Pressure Gauges

The state of the art of pressure gauging has been advanced by the development of a new technique, and of a nonintrusive gauge based on the technique, for measuring the pressure of a fluid in the same segment of pipe in which the mass-flow rate of the fluid is also measured. NASA anticipates the first use of the...

Briefs : Mechanical & Fluid Systems
PVP-MP Method for Wrinkling Analysis of Space Membrane Structures

Parameter-Variation-Principle (PVP) based Mathematical Programming (MP) is the basis of a computational method of analyzing wrinkles in membranes. Devised for original application to lightweight membrane structures in outer space, the method can also be applied on Earth to similar...

Briefs : Mechanical & Fluid Systems
Vacuum Pumping Station

A proposed valve unit called a "vacuum pumping station" would be incorporated into a plumbing system that supplies a vacuum for vacuum insulated cryogenic equipment. The vacuum pumping station is intended to perform functions now performed by, and to be a simpler and more reliable alternative to, an assembly of components...

Briefs : Manufacturing & Prototyping
Digital Preassembly Process

Because the International Space Station is being assembled in orbit, there was a need to verify in advance that it could, indeed, be assembled there and that the various assembled parts would function as intended. A digital preassembly process was devised to satisfy this need for verification, without having to...

Briefs : Physical Sciences
Numerical Index for Quantifying Aircraft Icing Hazards

A new method for assessing and communicating aviation in-flight icing hazards has been proposed. This methodology creates a simple numerical index for quantifying hazard severity. The index is traceable to flight-level meteorology and aircraft-specific, icing-induced reductions in aircraft...

Briefs : Physical Sciences
DNS of Mixing of Supercritical Heptane and Nitrogen

A report discusses direct numerical simulations (DNS) of a developing mixing layer between nitrogen and heptane initially at different temperatures and initially flowing at different velocities under supercritical conditions. The usual conservation equations for a binary fluid, along with the...

Briefs : Mechanical & Fluid Systems
Gas Generator for Inflating Structures in Outer Space

A report proposes a system that would supply gas for inflating one or more inflatable structure(s) in outer space. The system would include a small tank of helium for initial inflation, plus a catalytic hydrazine gas generator that would supply makeup gas over the long term. After...

Briefs : Materials
Thermal Insulation Would Use CO2 in the Martian Environment

A report describes the development of a lightweight thermal insulation system for Martian surface applications. The ambient Martian atmosphere, which is predominantly carbon dioxide at a pressure of 10 torr, is used as the insulation medium with a modest multiple radiation shield...

Briefs : Mechanical & Fluid Systems
Martian Landing Balls

A report describes Martian landing balls, which are under development for use in delivering scientific payloads to Mars. Martian landing balls are related to other soft-landing devices that resemble beach balls and that have been described in several previous NASA Tech Briefs articles. They are also related to the...

Briefs : Motion Control
Self-Tuning Impact Dampers for Turbomachine Blades

Self-tuning impact dampers have been proposed as improved means for suppressing vibrations in the rotor blades of turbomachines (turbines and compressors). Dampers are needed because aeroelastic blade/flow interactions in a turbomachine cause the blades to vibrate intensely, with resultant...

Briefs : Motion Control
Double-Parallelogram Carriage for Spectrometer Mirrors

A double-parallelogram ("porch swing") carriage mechanism has been devised to provide for free linear motion of one or more retroreflector(s) in a Fourier-transform infrared spectrometer. Mechanisms like this one are particularly well suited for cryogenic high-resolution Fourier transform...

Briefs : Motion Control
Using Microwave Radiometers To Prevent Unstarts

Measurement and control systems based on microwave radiometers would be used to prevent unstarts in the next generation of high-speed (up to mach 2.4) civil-transport airplanes, according to a proposal. "Unstart" denotes a compressor stall in a supersonic aircraft engine, and is caused by a change...

Briefs : Motion Control
Non-Ablative Aeroshells

Two reports propose the development of non-ablative aeroshells for braking of spacecraft entering the atmospheres of Earth, Mars, and other planets. The primary advantages of non-ablative aeroshells, relative to ablative aeroshells, results from reduced mass and increased aerodynamic stability of the aeroshell occasioned...

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