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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 757 records · Page 42

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NASA NTRS1977

Annual Conference on Nuclear and Space Radiation Effects, 14th, College of William and Mary, Williamsburg, Va., July 12-15, 1977, Proceedings

Topics related to processing and hardness assurance are considered, taking into account the radiation hardening of CMOS technologies, technological advances in the manufacture of radiation-hardened CMOS integrated circuits, CMOS hardness assurance through process controls and optimized design procedures, the application of operational amplifiers to hardened systems, a hard off-the-shelf SG1524 pulse width modulator, and the gamma-induced voltage breakdown anomaly in a Schottky diode. Basic mechanisms are examined, giving attention to chemical and structural aspects of the irradiation behavior of SiO2 films on silicon, experimental observations of the chemistry of the SiO2/Si interface, leakage current phenomena in irradiated SOS devices, the avalanche injection of holes into SiO2, the low-temperature radiation response of Al2O3 gate insulators, and neutron damage mechanisms in silicon at 10 K. Other subjects discussed are related to radiation effects in devices and circuits, space radiation effects, and aspects of simulation, energy deposition, and dosimetry.

Stahl, R. H.↗

NASA NTRS1977

Ceramics in gas turbines - Powder and process characterization

The role of powder and process characterization in producing high quality silicon nitride and silicon carbide components, for gas turbine applications, is described. Some of the intrinsic properties of various forms of Si3N4 and SiC are listed and limitations of such materials' availability have been pointed out. The essential features/parameters to characterize a batch of powder have been discussed including the standard techniques for such characterization. In process characterization, parameters in sintering, reaction sintering, and hot pressing processes are discussed including the factors responsible for strength limitations in ceramic bodies. It is inevitable that significant improvements in material properties can be achieved by reducing or eliminating the strength limiting factors with consistent powder and process characterization along with process control.

Dutta, S.↗

NASA NTRS1978

Cost-effective use of minicomputers to solve structural problems

Minicomputers are receiving increased use throughout the aerospace industry. Until recently, their use focused primarily on process control and numerically controlled tooling applications, while their exposure to and the opportunity for structural calculations has been limited. With the increased availability of this computer hardware, the question arises as to the feasibility and practicality of carrying out comprehensive structural analysis on a minicomputer. This paper presents results on the potential for using minicomputers for structural analysis by (1) selecting a comprehensive, finite-element structural analysis system in use on large mainframe computers; (2) implementing the system on a minicomputer; and (3) comparing the performance of the minicomputers with that of a large mainframe computer for the solution to a wide range of finite element structural analysis problems.

Storaasli, O. O.↗

NASA NTRS1980

Window comparator for voltages

Circuit determines whether voltage is within preselected range of voltage levels.Device requires fewer components than previous window comparators and is less susceptible to errors from reference drift. Comparator is useful in process-control circuitry, measuring instruments, and checkout equipment.

Black, J. M.↗

NASA NTRS1980

Stitch-bond parallel-gap welding for IC circuits

Stitch-bonded flatpacks are superior to soldered dual-in-lines where size, weight, and reliability are important. Results should interest designers of packaging for complex high-reliability electronics, such as that used in security systems, industrial process control, and vehicle electronics.

Chvostal, P.↗

NASA NTRS1977

Driver steering dynamics measured in car simulator under a range of visibility and roadmaking conditions

A simulation experiment was conducted to determine the effect of reduced visibility on driver lateral (steering) control. The simulator included a real car cab and a single lane road image projected on a screen six feet in front of the driver. Simulated equations of motion controlled apparent car lane position in response to driver steering actions, wind gusts, and road curvature. Six drivers experienced a range of visibility conditions at various speeds with assorted roadmaking configurations (mark and gap lengths). Driver describing functions were measured and detailed parametric model fits were determined. A pursuit model employing a road curvature feedforward was very effective in explaining driver behavior in following randomly curving roads. Sampled-data concepts were also effective in explaining the combined effects of reduced visibility and intermittent road markings on the driver's dynamic time delay. The results indicate the relative importance of various perceptual variables as the visual input to the driver's steering control process is changed.

Allen, R. W.↗

NASA NTRS1979

Diode step stress program for JANTX1N649-1

The effect of power/temperature step stress when applied to a variety of semiconductor devices is evaluated. A total of 48 samples were submitted to be processed. Control sample units were maintained for verification of the electrical parametric testing. The test circuit was used to power all of the test devices during the power/temperature stress conditions.

Source record↗

NASA NTRS1979

Development of a beam builder for automatic fabrication of large composite space structures

The composite material beam builder which will produce triangular beams from pre-consolidated graphite/glass/thermoplastic composite material through automated mechanical processes is presented, side member storage, feed and positioning, ultrasonic welding, and beam cutoff are formed. Each process lends itself to modular subsystem development. Initial development is concentrated on the key processes for roll forming and ultrasonic welding composite thermoplastic materials. The construction and test of an experimental roll forming machine and ultrasonic welding process control techniques are described.

Bodle, J. G.↗

NASA NTRS1979

NASA JSC water monitor system: City of Houston field demonstration

A water quality monitoring system with on-line and real time operation similar to the function in a spacecraft was investigated. A system with the capability to determine conformance to future high effluent quality standards and to increase the potential for reclamation and reuse of water was designed. Although all system capabilities were not verified in the initial field trial, fully automated operation over a sustained period with only routine manual adjustments was accomplished. Two major points were demonstrated: (1) the water monitor system has great potential in water monitoring and/or process control applications; and (2) the water monitor system represents a vast improvement over conventional (grab sample) water monitoring techniques.

Taylor, R. E.↗

NASA NTRS1979

Phased models for evaluating the performability of computing systems

A phase-by-phase modelling technique is introduced to evaluate a fault tolerant system's ability to execute different sets of computational tasks during different phases of the control process. Intraphase processes are allowed to differ from phase to phase. The probabilities of interphase state transitions are specified by interphase transition matrices. Based on constraints imposed on the intraphase and interphase transition probabilities, various iterative solution methods are developed for calculating system performability.

Wu, L. T.↗

NASA NTRS1979

Analysis of visual estimation of system state from arbitrary displays

A method is presented for implementing the state estimator of the manual control model when the system output is a visual display of arbitrary form; that is, the display may be pictorial, including real world, or made up of dials and pointers. The method is used to provide error criteria for a look-point controller that appears to be capable of modeling human scanning behavior. This model, if combined with a model of the control process, should be useful in predicting effects of changes in displays on performance of flight tasks.

Gainer, P. A.↗

NASA NTRS1977

New processes and materials for ultraviolet detection with solid state devices

The three major effects that degrade external responsivity of silicon from the 1/lambda theoretical curve for a quantum detector are: surface reflectance, surface recombination, and junction depth. Since the p-n junction must be very shallow, problems relating to surface are further enhanced. MOS type of processing is necessary. HCl oxides and numerous acid clean-ups are utilized in order to obtain a contamination free surface with low Qss levels. Stringent process controls such as CV shifts, spreading resistance measurements, thickness monitoring etc., are used to analyze the surface contaminations, surface mobile charges, surface concentrations, junction depth, oxide thickness etc. Low surface concentrations of 10 to the 18th atoms/cu cm are achieved by low temperature boron nitride depositions. Shallow junction depths of the order of a few tenths of a micron are achieved by low temperature controlled diffusions. In order to improve breakdown characteristics of these shallow junction devices, field plate and deep diffused p(+) ring geometries are used.

Chopra, D.↗

NASA NTRS1979

Spatial-frequency response of the Limb Infrared Monitor of the Stratosphere /LIMS/ radiometer

The Limb Infrared Monitor of the Stratosphere (LIMS), an experiment on the Nimbus-7 satellite, is designed to scan the earth's limb vertically and measure spectral emission profiles of trace atmospheric gases believed to be important in processes controlling the stratospheric ozone distribution. Experiment objectives are reviewed and several analyses and measurements are described which were performed to determine the adequacy of the system for satisfying these objectives. Adequate spatial-frequency response for all the spectral channels is required to provide, through inversion of the measured limb-radiance profiles, important information about the temperature, structure, and composition of the atmosphere. From the LIMS design-model data, the MTF was calculated for the optical system, the detector field mask, the electronics, and the overall system, for each channel. The signal output performance of the instrument was predicted from the system MTF data model input radiance data for each channel. MTF measurements made on the flight sensor confirmed the analytical results. The predictions indicate that the instrument can satisfy the basic measurement objectives of the experiment.

Wilson, R. G.↗

NASA NTRS1980

Investigation of electrical noise in selenium-immersed thermistor bolometers

The selenium immersed, thermistor bolometer, IR detector failed due to spurious and escalating electrical noise outburst as a function of time at elevated temperatures during routine ground based testing in a space simulated environment. Spectrographic analysis of failed bolometers revealed selenium pure zones in the insulating selenium arsenic (Se-As) glass film which surrounds the active sintered Mn, Ni, Co oxide flake. The selenium pure film was identified as a potentially serious failure mechanism. Significant changes were instituted in the manufacturing techniques along with more stringent process controls which eliminated the selenium pure film and successfully produced 22study bolometers.

Tarpley, J. L.↗

NASA NTRS1979

Dust-magnetospheric interactions

The important processes controlling the electrical potentials of dust grains in planetary magnetospheres are considered, and the quasi-equilibrium electric potentials acquired by them in the different plasma and radiative environments encountered are evaluated. The orbital dynamics of such charged grains is discussed, and their interaction with satellites within the planetary magnetospheres is considered. The possibility of magneto-gravitational capture of these gains by magnetospheres, to form dust rings around the planets, is also discussed. Finally, the possible break-up of grains charged to large electrical potentials and its consequences are briefly addressed.

Mendis, D. A.↗

NASA NTRS1979

Commercial use of materials processing in space

The paper examines the scientific and commercial aspects of Materials Processing in the Space program. The elimination of gravity driven convection in molten materials can preclude undesirable stirring and mixing during crystal growth, and improve the casting of alloys and composites, chemical reactions, and the separation of biological materials. The elimination of hydrostatic pressure will allow alloy heat-treatment without distortion and growth of heavy crystals, such as thorium oxide, and containerless processing of liquids and molten materials. On the other hand, more sophisticated process control and diagnostic methods in sample preparation and temperature control must be developed, concluding that space made products of commercial interest are likely to be low volume, high value items.

Zoller, L. K.↗

NASA NTRS1980

The National Transonic Facility - Status and operational planning

The National Transonic Facility is scheduled to be completed in 1982. Several technical concerns remain, including thermal stress constraints which may limit the rate at which temperatures can be changed, seal performance in the cryogenic environment, and the tunnel process controls which could affect data acquisition rate. The current design affords the capability of dealing with all these concerns if they become problems. The outstanding instrument need is a real-time model surface deformation measurement system. Finally, an examination of the occupancy cost and the cost of liquid nitrogen for high Reynolds number tests indicates that operating costs should not be an inhibiting factor in the use of the facility.

Howell, R. R.↗

NASA NTRS1982

Self-Correcting Electronically-Scanned Pressure Sensor

High-data-rate sensor automatically corrects for temperature variations. Multichannel, self-correcting pressure sensor can be used in wind tunnels, aircraft, process controllers and automobiles. Offers data rates approaching 100,000 measurements per second with inaccuracies due to temperature shifts held below 0.25 percent (nominal) of full scale over a temperature span of 55 degrees C.

Gross, C.↗