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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 253 records · Page 14
All sourcesNASA NTRSDOE OSTI
NASA NTRS1994

Multilayer Microstrip Slot And Dipole Array Antenna

Multilayer antenna structure contains interleaved linear subarrays of microstrip dipole and slot radiating antenna elements to provide compact, dual-band antenna. Structure also contains associated microstrip transmission lines, plus high-power amplifiers for transmission and low-noise amplifiers for reception. Overall function is to transmit in horizontal polarization at frequency of 29.634 GHz and receive in vertical polarization at 19.914 GHz, in direction 44 degrees from broadside to antenna. Antenna structure is part of apparatus described in "Steerable K/Ka-band Antenna for Land-Mobile Satellite Applications," NPO-18772.

Tulintseff, Ann N.↗
NASA NTRS1994

Microwave Frequency Discriminator With Sapphire Resonator

Cooled sapphire resonator provides ultralow phase noise. Apparatus comprises microwave oscillator operating at nominal frequency of about 8.1 GHz, plus frequency-discriminator circuit measuring phase fluctuations of oscillator output. One outstanding feature of frequency discriminator is sapphire resonator serving as phase reference. Sapphire resonator is dielectric ring resonator operating in "whispering-gallery" mode. Functions at room temperature, but for better performance, typically cooled to operating temperature of about 80 K. Similar resonator described in "Sapphire Ring Resonator for Microwave Oscillator" (NPO-18082).

Santiago, David G.↗
NASA NTRS1994

Dual-Element Tunneling Accelerometer

Improved micromachined tunneling accelerometer contains two deflecting transducer elements: One an elastically supported proof mass having relatively low resonant frequency; other cantilever tunneling transducer that tracks displacement of proof mass and has relatively high resonant frequency ({sup a} 10 kHz). Deflection voltage generated by circuit like described in "Wideband Feedback Circuit for Tunneling Sensor" (NPO-18866). Accelerometers of this type suited for underwater acoustic measurements, detecting vibrations associated with malfunctions in vehicles, detecting seismic signals, monitoring and controlling vibrations in structures, and other applications.

Kaiser, William J.↗
NASA NTRS1994

Making Porous Luminescent Regions In Silicon Wafers

Regions damaged by ion implantation stain-etched. Porous regions within single-crystal silicon wafers fabricated by straightforward stain-etching process. Regions exhibit visible photoluminescence at room temperature and might constitute basis of novel class of optoelectronic devices. Stain-etching process has advantages over recently investigated anodic-etching process. Process works on both n-doped and p-doped silicon wafers. Related development reported in article, "Porous Si(x)Ge(1-x) Layers Within Single Crystals of Si," (NPO-18836).

Fathauer, Robert W.↗
NASA NTRS1993

Production and application of chemical fibers with special properties for manufacturing composite materials and goods of different usage

The development of modern technologies demands the creation of new nonmetallic, fibrous materials with specific properties. The fibers and materials developed by NII 'Chimvolokno', St. Petersburg, can be divided into two groups. The first group includes heat-resistant fibers, fire-resistant fibers, thermotropic fibers, fibers for medical application, and textile structures. The second group contains refractory fibers, chemoresistant and antifriction fibers, fibers on the basis of polyvinyl alcohol, microfiltering films, and paperlike and nonwoven materials. In cooperation with NPO 'Chimvolokno' MYTITSHI, we developed and started producing heat-resistant high-strength fibers on the base of polyhetarearilin and aromatic polyimides (SVM and terlon); heat-resistant fibers on the base of polyemede (aramid); fire-retardant fibers (togilen); chemoresistant and antifriction fibers on the basis of homo and copolymers of polytetrafluoroethylene (polyfen and ftorin); and water soluble, acetylated, and high-modulus fibers from polyvinyl alcohol (vylen). Separate reports will deal with textile structures and thermotropic fibers, as well as with medical fibers. One of the groups of refractory fibers carbon fibers (CF) and the corresponding paperlike nonwoven materials are discussed in detail. Also, composite materials (CM) and their base, which is the subject of the author's research since 1968, is discussed.

Levit, R.↗
NASA NTRS1994

Russian national time scale long-term stability

The Institute of Metrology for Time and Space NPO 'VNIIFTRI' generates the National Time Scale (NTS) of Russia -- one of the most stable time scales in the world. Its striking feature is that it is based on a free ensemble of H-masers only. During last two years the estimations of NTS longterm stability based only on H-maser intercomparison data gives a flicker floor of about (2 to 3) x 10(exp -15) for averaging times from 1 day to 1 month. Perhaps the most significant feature for a time laboratory is an extremely low possible frequency drift -- it is too difficult to estimate it reliably. The other estimations, free from possible inside the ensemble correlation phenomena, are available based on the time comparison of NTS relative to the stable enough time scale of outer laboratories. The data on NTS comparison relative to the time scale of secondary time and frequency standards at Golitzino and Irkutsk in Russia and relative to NIST, PTB and USNO using GLONASS and GPS time transfer links gives stability estimations which are close to that based on H-maser intercomparisons.

Alshina, A. P.↗
NASA NTRS1993

Soyuz-TM-based interim Assured Crew Return Vehicle (ACRV) for the Space Station Freedom

The concept of using the available Soyuz-TM Assured Crew Return Vehicle (ACRV) spacecraft for the assurance of the safety of the Space Station Freedom (SSF) crew after the departure of the Space Shuttle from SSF was proposed by the NPO Energia and was accepted by NASA in 1992. The ACRV will provide the crew with the capability to evacuate a seriously injured/ill crewmember from the SSF to a ground-based care facility under medically tolerable conditions and with the capability for a safe evacuation from SSF in the events SSF becomes uninhabitable or the Space Shuttle flights are interrupted for a time that exceeds SSF ability for crew support and/or safe operations. This paper presents the main results of studies on Phase A (including studies on the service life of ACRV; spacecraft design and operations; prelaunch processing; mission support; safety, reliability, maintenance and quality and assurance; landing, and search/rescue operations; interfaces with the SSF and with Space Shuttle; crew accommodation; motion of orbital an service modules; and ACRV injection by the Expendable Launch Vehicles), along with the objectives of further work on the Phase B.

Yu P Semenov↗
NASA NTRS1993

Condition monitoring requirements for the development of a space nuclear propulsion module

To facilitate the development of a space nuclear propulsion module for manned flights to Mars, requirements must be established early in the technology cycle. The long lead times for the acquisition of the engine system and nuclear test facilities demands that the engine system, size, performance, safety goals and condition monitoring philosophy be defined at the earliest possible time. These systems are highly complex and require a large multi-disciplinary systems engineering team to develop and track the requirements and to ensure that the as-built system reflects the intent of the mission. An effective methodology has been devised coupled with sophisticated computer tools to effectivly develop and interpret the functional requirements. These requirements can then be decomposed down to the specification level for implementation. This paper discusses the application of the methodology and the analyses to develop condition monitoring requirements under a contract with the National Aeronautics and Space Administration (NASA) Lewis Research Center (LeRC) Nuclear Propulsion Office (NPO).

Wagner, Robert C.↗
NASA NTRS1995

Circular-Loop-Element Microwave Frequency-Selective Reflectors

Double or single planar arrays of circular loops laminated with dielectric sheets. Reflectors designed for use in multiplexing signals at several frequencies in microwave antenna system. Well suited to both circularly and linearly polarized radiation. Transmission and reflection characteristics relatively insensitive to angle of incidence. Similar device described in "Triband Circular-Loop Frequency-Selective Microwave Reflector" (NPO-18714).

Huang, John↗
NASA NTRS1995

Direct Adaptive Impedance Control Of Redundant Manipulators

Method of controlling mechanical impedance of end effector of robotic manipulator related to method described in "Adaptive Impedance Control of Redundant Manipulators" (NPO-18606). Present method does not require detailed knowledge and computation of dynamics and inverse kinematic transformation of manipulator. Provides for control globally stable in presence of bounded disturbances. Applicable to both nonredundant and redundant manipulators performing tasks involving impacts between manipulator and objects in its environment, and controlled contact between end effector and object, such as deburring.

Seraji, Homayoun↗
NASA NTRS1995

Higher-Sensitivity Ionization Trace-Species Detector

Electron source and electron optics of reversal electron-attachment detector modified to increase sensitivity. Original version described in "High-Sensitivity Ionization Trace-Species Detector" (NPO-17596). Used to detect molecules of particular chemical species of interest (e.g., narcotics, explosives, or organic wastes) present in air at low concentrations, and known to attach extremely low-energy electrons. Apparatus does this by ionizing molecules from sampled atmosphere, then detecting ions of species of interest. Detector features indirectly heated spherical cathode and redesigned electron optics, together, deliver more electrons at low kinetic energy to reversal plane, R. Greater electron current generates more ions for detection.

Boumsellek, Said↗
NASA NTRS1995

Detecting Faults By Use Of Hidden Markov Models

Frequency of false alarms reduced. Faults in complicated dynamic system (e.g., antenna-aiming system, telecommunication network, or human heart) detected automatically by method of automated, continuous monitoring. Obtains time-series data by sampling multiple sensor outputs at discrete intervals of t and processes data via algorithm determining whether system in normal or faulty state. Algorithm implements, among other things, hidden first-order temporal Markov model of states of system. Mathematical model of dynamics of system not needed. Present method is "prior" method mentioned in "Improved Hidden-Markov-Model Method of Detecting Faults" (NPO-18982).

Smyth, Padhraic J.↗
NASA NTRS1995

Assessment Of C60 As A Propellant Material For Ion Thrusters

Report presents analyses and data to support proposed use of C60 (buckminsterfullerene) as alternative to Xe, current propellent material of choice for use in ion thrusters. Concept of using C60 for this purpose described in "Electrostatic Propulsion Using C60 Molecules" (NPO-18526).

Rapp, Don↗
NASA NTRS1995

Uses And Characteristics Of Dynamic Tradeoff Evaluation

Report discusses basic concepts, some applications, and performance characteristics of dynamic tradeoff evaluation (DTE). Basic concepts of DTE also described in "Dynamic Restructuring of Problems in Artificial Intelligence" (NPO-18488). DTE is method of enhancing real-time performance of artificial-intelligence system such as might be used to monitor data from multiple sensors in factory, aircraft, spacecraft, or other complex system of equipment. Report presents evaluation of DTE as applied to spacecraft-monitoring problems.

Schwuttke, Ursula M.↗
NASA NTRS1995

Analysis Of Performance Of A Thick Dichroic Microwave Panel

Report describes theoretical and experimental studies of performance of thick dichroic microwave panel comprising honeycomblike planar array of cross-shaped, waveguidelike apertures separated by thin metal walls. Except for small changes in dimensions, design of panel identical to one of designs described in "Two Thick Microwave Dichroic Panels" (NPO-18887).

Epp, Larry W.↗
NASA NTRS1995

Improved Dichroics For Microwave Reflector Antenna Systems

Panel contains array of grid and square conductive loops as array elements designed to reflect most of incident electromagnetic radiation in K(subu) band (13.5 to 15.5 GHz) and to pass that in X band (7 to 9 GHz). Designed to exhibit this dichroic property at angles of incidence up to 40 degrees in transverse electric, transverse magnetic, or circular polarization. Concept of gridded-square-loop dichroic array related to double-loop dichroic arrays described in "Frequency-Selective Microwave Reflectors" (NPO-18701). Improved version exhibits smaller shift of resonant frequency with angle of incidence.

Wu, Te-Kao↗
NASA NTRS1995

Prototype Focal-Plane-Array Optoelectronic Image Processor

Prototype very-large-scale integrated (VLSI) planar array of optoelectronic processing elements combines speed of optical input and output with flexibility of reconfiguration (programmability) of electronic processing medium. Basic concept of processor described in "Optical-Input, Optical-Output Morphological Processor" (NPO-18174). Performs binary operations on binary (black and white) images. Each processing element corresponds to one picture element of image and located at that picture element. Includes input-plane photodetector in form of parasitic phototransistor part of processing circuit. Output of each processing circuit used to modulate one picture element in output-plane liquid-crystal display device. Intended to implement morphological processing algorithms that transform image into set of features suitable for high-level processing; e.g., recognition.

Fang, Wai-Chi↗
NASA NTRS1995

Improved Adjoint-Operator Learning For A Neural Network

Improved method of adjoint-operator learning reduces amount of computation and associated computational memory needed to make electronic neural network learn temporally varying pattern (e.g., to recognize moving object in image) in real time. Method extension of method described in "Adjoint-Operator Learning for a Neural Network" (NPO-18352).

Toomarian, Nikzad↗