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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 883 records · Page 49
All sourcesNASA NTRSDOE OSTI
NASA NTRS1989

Design of a thrust stand for high power electric propulsion devices

A thrust stand for use with high power electric propulsion devices has been designed and tested. The thrust stand was specifically tailored to the needs of a 0.1 to 0.25 MW magnetoplasmadynamic (MPD) thruster program currently in progress at the NASA Lewis Research Center. The thrust stand structure was built as an inverted pendulum arrangement, supported at the base by water-cooled electrical power flexures. Thrust stand tares due to thruster discharge current were demonstrated to be negligible. Tares due to an applied field magnet current, after considerable effort, were reduced to less than 3.0 percent of measured thrust. These tares, however, could be determined independently and subtracted from the indicated thrust measurement. The paper gives a detailed description of the thrust stand design and operation with a 0.1 MW class MPD device. Other thrust stand tares due to vibration and thermal effects are discussed, along with issues of accuracy and repeatability.

Haag, Thomas W.↗
NASA NTRS1990

Borescope Device Takes Impressions In Ducts

Maneuverable device built around borescope equipped to make impression molds of welded joints in interior surfaces of ducts. Molds then examined to determine degress of mismatch in welds. Inserted in duct, and color-coded handles on ends of cables used to articulate head to maneuver around corners. Use of device fairly easy and requires little training.

Walter, Richard F.↗
NASA NTRS1990

Nonvolatile Ionic Two-Terminal Memory Device

Conceptual solid-state memory device nonvolatile and erasable and has only two terminals. Proposed device based on two effects: thermal phase transition and reversible intercalation of ions. Transfer of sodium ions between source of ions and electrical switching element increases or decreases electrical conductance of element, turning switch "on" or "off". Used in digital computers and neural-network computers. In neural networks, many small, densely packed switches function as erasable, nonvolatile synaptic elements.

Williams, Roger M.↗
NASA NTRS1990

Optically-Tuned Far-Infrared Device

Spacing of visible interference pattern determines frequency of infrared radiation. Variable photoconductivity grating formed by interference of two visible laser beams intersecting on surface of proposed AlGaAs device substituted for fixed metal grating. Proposed device provides higher output-power density and greater tunability.

Katz, Joseph↗
NASA NTRS1990

Fast, Capacious Disk Memory Device

Device for recording digital data on, and playing back data from, memory disks has high recording or playback rate and utilizes available recording area more fully. Two disks, each with own reading/writing head, used to record data at same time. Head on disk A operates on one of tracks numbered from outside in; head on disk B operates on track of same number in sequence from inside out. Underlying concept of device applicable to magnetic or optical disks.

Muller, Ronald M.↗
NASA NTRS1990

Spring-Loaded-Bolt Locking Device

Locking device designed to clamp small objects temporarily onto object or vehicle that accelerates. Intended to be used in place of toggle clamp, which can snap out of lock during excessive shock or vibration or because of accidental contact of person or object with toggle locking handle. Device looks and operates somewhat like spring-loaded door bolt. Moderate vibrations do not cause accidental unlocking.

Calco, Frank S.↗
NASA NTRS1989

Design of a thrust stand for high power electric propulsion devices

A thrust stand for use with high power electric propulsion devices was designed and tested. The thrust stand was specifically tailored to the needs of a 100 to 250 kW magnetoplasmadynamic (MPD) thruster program currently in progress at the NASA Lewis Research Center. The thrust stand structure was built as an inverted pendulum arrangement, supported at the base by water-cooled electrical power flexures. Thrust stand tares due to thruster discharge current were demonstrated to be negligible. Tares due to an applied field magnet current, after considerable effort, were reduced to less than 3.0 percent of measured thrust. These tares, however, could be determined independently and subtracted from the indicated thrust measurement. A detailed description is given for the thrust stand design and operation with a 100 kW class MPD device. Other thrust stand tares due to vibration and thermal effects are discussed, along with issues of accuracy and repeatability.

Haag, Thomas W.↗
NASA NTRS1989

Stand Alone Pressure Measurement Device (SAPMD) for the space shuttle Orbiter, part 1

The specifications for the Stand Alone Pressure Measurement Device (SAPMD) are as follows: the SAPMD shall measure ambient pressure at the surface of the Orbiter TPS in the range of 0 to 15 pounds per square inch absolute (PSIA). Measurement will begin at solid rocket booster (SRB) ignition as sensed by appropriate vibration sensing elements in the SAPMD. Pressure and corresponding real-time data are to be recorded every one tenth second for 140 seconds and at the end of the recording period, the operation will be discontinued with the data preserved for interrogation subsequent to Orbiter re-entry and landing. The type and size of the battery shall be such as to allow the vibration sensing elements and a real-time clock to be initialized a minimum of 30 day prior to launch and still provide power as necessary to perform the 140 second data recording period after SRB ignition. Battery installation shall be in such a manner as to allow battery replacement without removing the SAPMD from its position or removing more than one TPS tile. The SAPMD must be mounted in specific locations under tile of the TPS. To accommodate such mounting, the absolute maximum physical dimensions much not exceed 6.0 inches in length, 1.5 inches in width, and 0.4 inches in height, and the device shall be of such configuration that it can be bonded to the Orbiter skin at the joint line of two TPS tiles with the pressure sensing port at the surface of the tile. The SAPMD must remain operational in the temperature range of -40 to +85 C and survive storage temperature of -55 to +125 C. The pressure port must withstand 934 C without causing damage to the TPS during entry and must remain functional at 262 C during ascent. The accuracy of the pressure measurement must be plus or minus one-half PSIA over a temperature range of 0 to +36 C. All the specifications were met and verified by prototype testing and documented in the enclosed test data. Four flight-qualified models were fabricated and of these, two were delivered and successfully flown in the cargo bay of STS-26.

Tomlinson, Bill↗
NASA NTRS1990

Silicon carbide semiconductor device fabrication and characterization

A number of basic building blocks i.e., rectifying and ohmic contacts, implanted junctions, MOS capacitors, pnpn diodes and devices, such as, MESFETs on both alpha and beta SiC films were fabricated and characterized. Gold forms a rectifying contact on beta SiC. Since Au contacts degrade at high temperatures, these are not considered to be suitable for high temperature device applications. However, it was possible to utilize Au contact diodes for electrically characterizing SiC films. Preliminary work indicates that sputtered Pt or Pt/Si contacts on beta SiC films are someways superior to Au contacts. Sputtered Pt layers on alpha SiC films form excellent rectifying contacts, whereas Ni layers following anneal at approximately 1050 C provide an ohmic contact. It has demonstrated that ion implantation of Al in substrates held at 550 C can be successfully employed for the fabrication of rectifying junction diodes. Feasibility of fabricating pnpn diodes and platinum gated MESFETs on alpha SiC films was also demonstrated.

Davis, R. F.↗
NASA NTRS1989

AlGaAs/InGaAs heterostructures with doped channels for discrete devices and monolithic amplifiers

AlGaAs/InGaAs/GaAs-type heterostructure with one or two doped channels have been used to fabricate both discrete devices and monolithic amplifiers for millimeter-wave operation. Maximum current densities of 1 A/mm and maximum transconductances of 530 mS/mm were obtained. 0.25 x 50 micron discrete devices delivered a power density of 1 W/mm with 2.9-dB gain and 25 percent efficiency at 60 GHz. A 100-micron monolithic one-stage amplifier demonstrated 93 mW (0.93-W/mm power density) at 31.5 GHz with 4.2-dB gain and 29 percent efficiency. A record 34 percent efficiency was achieved with a 53.7-mW output power and 4.8-dB gain.

Saunier, Paul↗
NASA NTRS1990

A device for introducing helical perturbations into a trailing line vortex

A perturbation generator has been designed which can be attached to the centerbody of a matched airfoil type vortex generator. The device was desired to enable the introduction of helical-wave, velocity perturbations into a vortex core to permit experimental verification of theoretical vortex stability predictions. Evaluation of the perturbation generator performance, prior to vortex stability studies, has been reported here. Controlled perturbations with frequencies above 200 hz have been produced, but visual observations were insufficient to confirm their helical character. Hot wire velocity spectrum data have confirmed the device's ability to introduce controlled frequency fluctuations. In addition, other flow oscillations have been discussed which can influence the controllability of vortex perturbations.

Ash, Robert L.↗
NASA NTRS1990

Programmable synaptic devices for electronic neural nets

The architecture, design, and operational characteristics of custom VLSI and thin film synaptic devices are described. The devices include CMOS-based synaptic chips containing 1024 reprogrammable synapses with a 6-bit dynamic range, and nonvolatile, write-once, binary synaptic arrays based on memory switching in hydrogenated amorphous silicon films. Their suitability for embodiment of fully parallel and analog neural hardware is discussed. Specifically, a neural network solution to an assignment problem of combinatorial global optimization, implemented in fully parallel hardware using the synaptic chips, is described. The network's ability to provide optimal and near optimal solutions over a time scale of few neuron time constants has been demonstrated and suggests a speedup improvement of several orders of magnitude over conventional search methods.

Moopenn, A.↗
NASA NTRS1990

The propagation of RF wave in a tandem mirror plasma propulsion device

The propagation of RF waves launched in the end and the central cell of the tandem mirror propulsion device has been investigated both theoretically and experimentally. It was found that the amplitude of the wave excited in the plasma peaked while approaching the resonance, but then damped out, indicating strong absorption of the wave by the plasma. The absorption took place near the axis and the midplane of the device. The experimental results confirmed the theoretical prediction of the resonance effect. A very important discovery of this experiment was the broadening of the ICRF Fourier spectrum in the presence of the plasma.

Yang, T. F.↗
NASA NTRS1989

Doped-channel heterojunction structures for millimeter-wave discrete devices and MMICs

AlGaAs/InGaAs/GaAs-type heterostructures with one or two channels have been used to fabricate both discrete devices and monolithic amplifiers for millimeter-wave operation. The authors report that 0.25-micron x 50-micron discrete devices delivered a power density of 1 W/mm with 2.9-dB gain and 25 percent efficiency at 60 GHz. A 100-micron monolithic single-stage amplifier demonstrated a record 40 percent efficiency at 32 GHz, and a two-stage monolithic amplifier achieved a record 31.3 percent efficiency with 72-mW power and 13-dB gain at 32 GHz.

Saunier, P.↗
NASA NTRS1990

The study of pressure measurement techniques and devices in the range of 10(exp -1) to 10(exp -5) torr (2 millipsi to 0.2 micropsi)

The atmospheric pressure range was studied in a region where conventional pressure sensing devices do not provide meaningful measurements. However, a hot filament gauge was developed and miniaturized which will measure the pressure in the 10(exp -1) to 10(exp -5) torr (2 millipsi to 0.2 micropsi) region, hence the name Micropsi gauge. Laboratory studies were made comparing the currently available devices with the newly developed miniature low power 'Micropsi' pressure sensor.

Hoffman, John H.↗
NASA NTRS1990

Method of fabricating germanium and gallium arsenide devices

A method of semiconductor diode fabrication is disclosed which relies on the epitaxial growth of a precisely doped thickness layer of gallium arsenide or germanium on a semi-insulating or intrinsic substrate, respectively, of gallium arsenide or germanium by either molecular beam epitaxy (MBE) or by metal-organic chemical vapor deposition (MOCVD). The method involves: depositing a layer of doped or undoped silicon dioxide on a germanium or gallium arsenide wafer or substrate, selectively removing the silicon dioxide layer to define one or more surface regions for a device to be fabricated thereon, growing a matched epitaxial layer of doped germanium or gallium arsenide of an appropriate thickness using MBE or MOCVD techniques on both the silicon dioxide layer and the defined one or more regions; and etching the silicon dioxide and the epitaxial material on top of the silicon dioxide to leave a matched epitaxial layer of germanium or gallium arsenide on the germanium or gallium arsenide substrate, respectively, and upon which a field effect device can thereafter be formed.

Jhabvala, Murzban↗
NASA NTRS1991

A spatial disorientation predictor device to enhance pilot situational awareness regarding aircraft attitude

An effort was initiated at the Armstrong Aerospace Medical Research Laboratory (AAMRL) to investigate the improvement of the situational awareness of a pilot with respect to his aircraft's spatial orientation. The end product of this study is a device to alert a pilot to potentially disorienting situations. Much like a ground collision avoidance system (GCAS) is used in fighter aircraft to alert the pilot to 'pull up' when dangerous flight paths are predicted, this device warns the pilot to put a higher priority on attention to the orientation instrument. A Kalman filter was developed which estimates the pilot's perceived position and orientation. The input to the Kalman filter consists of two classes of data. The first class of data consists of noise parameters (indicating parameter uncertainty), conflict signals (e.g. vestibular and kinesthetic signal disagreement), and some nonlinear effects. The Kalman filter's perceived estimates are now the sum of both Class 1 data (good information) and Class 2 data (distorted information). When the estimated perceived position or orientation is significantly different from the actual position or orientation, the pilot is alerted.

Chelette, T. L.↗
NASA NTRS1991

Development of silicon carbide semiconductor devices for high temperature applications

The semiconducting properties of electronic grade silicon carbide crystals, such as wide energy bandgap, make it particularly attractive for high temperature applications. Applications for high temperature electronic devices include instrumentation for engines under development, engine control and condition monitoring systems, and power conditioning and control systems for space platforms and satellites. Discrete prototype SiC devices were fabricated and tested at elevated temperatures. Grown p-n junction diodes demonstrated very good rectification characteristics at 870 K. A depletion-mode metal-oxide-semiconductor field-effect transistor was also successfully fabricated and tested at 770 K. While optimization of SiC fabrication processes remain, it is believed that SiC is an enabling high temperature electronic technology.

Matus, Lawrence G.↗