December 2001

Briefs : Physical Sciences
Development of Sensors for Detecting Leaks of O2 and H2

The Propulsion group at Dryden Flight Research Center is performing analyses of the effectiveness of chemical-species sensors for detecting and assessing leakage. The group is also studying relationships between (1) rates at which high-energy species leak from the propellant-feed systems of...

Briefs : Physical Sciences
Micromachined Emitter/Bolometer Structures for Infrared Gas Sensors

Infrared gas sensors that could be mass-produced at relatively low cost have been proposed for a variety of applications — for example, detecting carbon monoxide in air inside houses. A sensor of this type would include a housing into which ambient air could diffuse. The gas...

Briefs : Electronics & Computers
Radiation-Tolerant CMOS Image Sensors

Complementary metal oxide semiconductor (CMOS) integrated-circuit image sensors that are highly tolerant of high-energy radiation ("radiation hard") are undergoing development. These devices are sensitive to visible light, yet are insensitive to diverse types of highly energetic radiation, including protons...

Briefs : Physical Sciences
Deployable Shell Structures With Shape-Control Actuators

Advanced control systems that include built-in smart-material elastic-deformation structural actuators have been proposed for deployable thin-shell structures that are required to be maintained in precise shapes once deployed. This approach to structural shape control was conceived to...

Briefs : Mechanical & Fluid Systems
"Smart" Actuators for Alleviating Buffet of Aircraft

An active-control surface modal (ACSM) device has been developed as an improved means of alleviating buffet of an aircraft. The ACSM device is a "smart" actuator system that includes an array of antagonistic piezoelectric actuators installed within a rudder or other aircraft control surface...

Briefs : Electronics & Computers
Low-Sidelobe Microwave Reflector Antennas and Dichroic Plate

The figure depicts the basic geometric features of an antenna system designed to be part of a miniature atmosphere-sounding passive microwave radiometer to be flown at high altitude aboard a remotely piloted aircraft. The system includes (1) a scanning flat reflector; (2) a dichroic...

Briefs : Electronics & Computers
Simple Phase Shifter for a Scanning-Beam Antenna

A simple, inexpensive device has been conceived for shifting the phase of a signal in a feed line of a scanning-beam microstrip antenna in order to change the direction of the beam. Heretofore, phase shifters used for this purpose have been relatively bulky and expensive.

Briefs : Electronics & Computers
High-Capacity Nickel-Hydrogen Cells

Nickel-hydrogen electrochemical cells with capacities of 350 ampere-hours have been developed. These cells are intended primarily for use in government and commercial satellites; they have been fully qualified to satisfy performance requirements for operation in geosynchronous satellites for as long as 15...

Briefs : Electronics & Computers
Ka-Band Solid-State Power Amplifier Module

A compact Ka-band power amplifier has been built with GaAs field-effect transistors (FETs) and microstrip conductors on a quartz substrate. Prior to the development of this amplifier, Ka-band solid-state amplifiers with useful output power levels (of the order of 1 W or more) were...

Briefs : Electronics & Computers
Skutterudite Thermoelectric Unicouples for Generating Power

A report presents some results of continuing efforts to develop advanced thermoelectric devices and, more particularly, thermoelectric unicouples for generating electric power from diverse thermal sources, including automotive exhausts and other waste-heat sources. The basic principles...

Briefs : Electronics & Computers
Miniature Proportional Temperature Controllers

Miniature proportional + integral + derivative (PID) temperature controllers that would be implemented as hybrid microcircuits have been proposed to satisfy special requirements to minimize size and mass and to maintain g-ray-detector modules at temperatures of 10±0.5 °C. These temperature...

Briefs : Information Technology
External Data and Attribute Hyperlink Programs for Promis•e®

External Data and Attribute Hyperlink are computer programs that can be added to Promis•e®, which is a commercial software system that automates routine tasks in the design (including drawing schematic diagrams) of electrical control systems. The programs were...

Briefs : Software
Software for Parallel Computation of 3D Thermal Convection

A computer program solves the differential equations of three-dimensional (3D) thermal convection of an incompressible fluid by use of a parallel-processing, finite volume numerical scheme. The equations of conservation of momentum, and energy are integrated over macroscopic...

Briefs : Physical Sciences
Software for Simulating Two-Phase Systems

Møtran (signifying "multi-phase transient") is a package of software for simulating flows in two-phase (gas/liquid) fluid systems like networks of such components as pipes, T junctions, pumps, evaporators, and condensers. The software is based on a two-fluid formulation that can accommodate unequal...

Briefs : Software
Fourth-Generation Software for SEU Testing

RBK4 is a computer program for testing electronic components for susceptibility to single-event upsets (SEUs). RBK4 controls the computer on which it is executed to communicate with both the board holding the device under test (DUT), a power supply, and other laboratory instruments including...

Briefs : Physical Sciences
Software for Improved Processing of DRWP Signals

The Automated Adaptive Signal Processing (AASP) computer program extracts wind data from the outputs of Doppler-radar wind profilers (DRWPs). Unlike prior software used for this purpose, AASP does not rely on manual intervention to prevent a DRWP system from locking onto and tracking...

Briefs : Materials
Refrigerant Blends Containing Trifluoroiodomethane

Blends of refrigerant fluids have been developed as improved alternatives to conventional chlorofluorocarbon (CFC) and hydrochlorofluorocarbon (HCFC) refrigerants, which contribute to depletion of stratosphere ozone. Each blend of this type is a zeotropic or nearly azeotropic mixture of...

Briefs : Materials
Heat-Exchanger Rocket Engine

The proposed rocket engine includes a combustion chamber actively cooled by liquid oxygen: Heat from the combustion chamber vaporizes the flowing liquid oxygen, and the absorption of latent heat of vaporization contributes to cooling of the combustion-chamber wall. The resulting high-vapor-quality (mostly vapor)...

Briefs : Materials
Stable Ohmic Contacts on SiC Devices for High Temperatures

Ti3SiC2 has been proposed as a mate- rial for ohmic contacts on SiC-based electronic and microelectromechanical devices intended to operate at temperatures >600 °C and/or in corrosive environments. Although SiC is stable and devices made of SiC are capable of...

Briefs : Mechanical & Fluid Systems
Improved Lightweight Freeze-Tolerant Tubes

Improved designs have been conceived for lightweight tubes that can withstand the large (as much as 8 or 9 volume percent) freeze/thaw expansions and contractions of typical heat-transfer fluids like water and ammonia. Intended originally for radiators for rejecting waste heat from spacecraft, these...

Briefs : Mechanical & Fluid Systems
Mechanisms Facilitate Blowdown of Large Diesel Engines

Simple mechanisms have been devised to facilitate the blowdown of large diesel engines. As explained below, these mechanisms reduce the amount of time and effort that must be expended to test engines before operating them.

Briefs : Mechanical & Fluid Systems
Uncertainty Models From Ground Vibration Testing

Structural dynamics are often an important consideration when evaluating system characteristics. A concern related to structural dynamics is the analysis of flutter for a flight vehicle. The instability associated with flutter can be quite sensitive to the structural dynamics; therefore, analysis...

Briefs : Information Technology
Compressed Symbology — Making Its Mark at NASA

Compressed symbology is a product-identification method that was pioneered by NASA for tracking space-shuttle parts and is now being used to mark everything from groceries to automobile parts. Based on a system of two-dimensional marks applied to parts, compressed symbology was developed at NASA's...

Briefs : Physical Sciences
Large-Aperture Telescope Synthesized From Small Mirrors

A report proposes a design concept for synthesizing a reflecting telescope with a large-aperture (diameter ≈100 m) primary mirror from a sparse arrangement of four smaller (diameter ≈10 m) primary mirrors. The telescope would be placed in orbit for viewing Earth with high...

Briefs : Mechanical & Fluid Systems
Spacecraft Nuclear Reactor Would Be Fueled in Orbit

Two reports summarize progress thus far in the continuing development of a spacecraft nuclear reactor, some or all of the fuel rods of which would not be loaded until the spacecraft was in orbit. (Keeping the fuel rods out of the reactor core before and during launch is intended to...

Briefs : Mechanical & Fluid Systems
Designs for Safer Launching of Spacecraft Fission System

A report proposes the development of two different mechanisms that would prevent inadvertent startup of reactors in nuclear-fission-based propulsion and power systems in future spacecraft. The purpose of this development is to contribute to safety by ensuring that radioactivity is kept...

Briefs : Information Technology
Automated Planning and Scheduling for a Large Interferometer

A report discusses the potential application of artificial intelligence (AI) to planning, scheduling, and control of the optical configuration and other aspects of the operations of a large astronomical interferometer. Scientific demand and technical requirements necessitate...

Briefs : Electronics & Computers
Cooperative Communication by Low-Power Radio Transmitters

A report proposes a method of cooperative modulation between (1) low-power radio transceivers associated with sensors geographically dispersed on a remote planet for relaying information between the sensors and an Earth station. The method, denoted node selection on orthogonal...

Briefs : Physical Sciences
Uplink/Downlink Spacecraft Radio Occultation Measurements

A report proposes a method to increase the accuracy of Doppler measurements made at the beginnings and endings of Earth/spacecraft radio occultations. Such measurements can reveal structural details of occulting objects in outer space. Heretofore, one-way measurements have been...

Briefs : Materials
Development of Alternatives to Hydrazines as Propellants

A brief report summarizes an investigation of less-toxic alternatives to toxic monopropellant fluids used in launch vehicles, upper stages, and spacecraft propulsion. The toxic fluids in question are (1) hydrazine and its derivatives, used, variously, as fuels or by themselves as...

Briefs : Electronics & Computers
ASIC for Controlling a Power-Switching MOSFET

A report describes an application-specific integrated circuit (ASIC) for controlling a power-switching metal oxide semiconductor field-effect transistor (MOSFET) in a spacecraft power-supply system. Denoted an SCA (for switch-control ASIC), this ASIC is designed to be radiation-hard and to...

Briefs : Motion Control
Equipment for Removal of EDM Water Filters

An assembly of lifting equipment has been devised to enable the safe removal of water filters used in electrical-discharge machining (EDM). As explained below, this equipment prevents injuries of a type formerly associated with changing the filters.

Briefs : Robotics, Automation & Control
Measuring Turbomachine-Blade Deflections in Two Dimensions

A report describes a method of simultaneously measuring steady-state axial and tangential turbomachine-blade deflections by use of fiber-optic probes and probe actuators designed specifically for this purpose. Each fiber-optic probe illuminates a small spot and, by measuring a change in...

Briefs : Motion Control
Motorized Rotator for an Ultrasonic Probe

An apparatus has been devised to enable accurate, reproducible angular positioning of an ultrasonic probe used to diagnose the carotid artery. More specifically, the apparatus is intended for use in a clinical setting in which the intima-media thickness (IMT) of the carotid artery is measured by use of...

Briefs : Motion Control
Progress in Magnetoelastic Vibration Dampers

A report describes uniaxial-stress-versus-strain experiments that were performed on polycrystalline Tb76Dy24 alloy specimens. [Also see "Magnetoelastic Vibration Dampers" (NPO-20988) on page 56 of this issue.] The proposal is to use Tb-Dy alloys as vibration-damping materials at...

Briefs : Motion Control
Software for Analyzing Traversability of Terrain

Grid-Based Estimation of Surface Traversability Applied to Local Terrain (GESTALT) is a software library that helps a robotic wheeled vehicle choose a safe path across nearby terrain. The input to GESTALT consists mainly of three-dimensional range measurements of the nearby terrain taken by...

Briefs : Motion Control
Six-Legged Experimental Robot

The figure depicts the Legged Excursion Mechanical Utility Robot (LEMUR) - a six-legged robot for demonstrating robotic capabilities for assembly, maintenance, and inspection. LEMUR is designed to be capable of walking autonomously along a truss structure and to perform other operations.

Briefs : Motion Control
Three-Fingered Robot Hand With Self-Adjusting Grip

The figure depicts a tendon-driven, three-fingered robot hand (or foot, depending on one's perspective) designed to be installed on the end of the left front leg of the six-legged robot described in the preceding article. This hand, which was undergoing development at the time of reporting the...

Briefs : Motion Control
Magnetoelastic Vibration Dampers

Magnetoelastic dampers have been proposed for use in suppressing vibrations of large motors and transformers that operate at temperatures below 100 K. [Also see "Progress in Magnetoelastic Vibration Dampers," (NPO-20887) on page 57 of this issue.] These dampers would be made of magnetostrictive materials -...

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