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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 361 records · Page 20
All sourcesNASA NTRSDOE OSTI
NASA NTRS1980

Some calculated effects of non-uniform inflow on the radiated noise of a large wind turbine

Far field computations were performed for a large wind turbine to evaluate the effects of non-uniform aerodynamic loading over the rotor disk. A modified version of the Farassat/Nystrom propeller noise prediction program was applied to account for the variations in loading due to inflow interruption by the upstream support tower. The computations indicate that for the uniform inflow case, relatively low noise levels are generated and the first rotational harmonic dominated the spectrum. For cases representing wake flow deficiences due to the tower structure, subtantially increased noise levels for all harmonics are indicated, the greatest increases being associated with the higher order harmonics.

Greene, G. C.↗
NASA NTRS1979

Initial results on 5 MHz quartz oscillators equipped with BVA resonators

The techniques of fabricating BVA resonators are discussed in terms of aging, amplitude-frequency effect, and acceleration sensitivity. Results on 5 MHz resonators concerning aging versus drive level, reduced amplitude-frequency effect, frequency and phase stability performance, and frequency retrace following power interruption are presented. It is indicated that a zero aging rate is possible at a drive level which depends on the qaurtz material used. For natural AT quartz, a level of 70 to 90 micro W appears to be optimum, and for SC quartz approximately 160 micro W.

Besson, R. J.↗
NASA NTRS1980

Effects of conversation interference on annoyance due to aircraft noise

The annoyance and interference effects of aircraft flyover noise on face to face conversation were investigated. Twenty 5 minute sessions, each composed of three flyovers, were presented to each of 20 pairs of female subjects in a simulated living room. Flyovers varied in peak noise level (55-79 dB, A-weighted) and spectrum (low or high frequency components). Subjects engaged in conversation for 10 sessions and in reverie for the other 10 sessions, and completed subjective ratings following every session. Annoyance was affected by noise level, but was not significantly different for the two activities of reverie and conversation. A noise level of 77 db was found unacceptable for conversation by 50 percent of the subjects. Conversation interference was assessed by incidence of increased vocal effort and/or interruption of conversation during flyovers. Although conversation interference increased with noise level, the conversation interference measures did not improve prediction of individual annoyance judgments.

Key, K. F.↗
NASA NTRS1980

Technique of electrical stimulation of the vestibular analyzer under clinical conditions

Vestibular reactions appear under the action of direct current (dc) on the labyrinth of man and animals. A decrease of the stimulation effect of dc on the extralabyrinthine nervous formations in the suggested method is achieved by the use of electric pulses with steep front and back parts, as well as by previous anesthetization of the skin in the electrode application area by means of novocain solution electrophoresis. For this purpose a pulse producer giving trapezoid pulses with smoothly changing fronts and duration was constructed. With the help of an interrupter it is possible to stop the current increase instantly, and stimulation is performed at the level of the pulse 'plateau'. To induce vestibular reactions under monopolar stimulation, it is necessary to apply the current twice as high as that with bipolar electrode position. The use of short pulses with steep front and back parts for electrode stimulation of the vestibular analyzer is considered to be inexpedient.

Khechinashvili, S. N.↗
NASA NTRS1980

Operation and maintenance cost data for residential photovoltaic modules/panels

Costs associated with the operation and maintenance of residential photovoltaic modules and arrays are studied. Six basic topics related to operation and maintenance to photovoltaic arrays are investigated: maintenance; cleaning; panel replacement; gasket repair/replacement; wiring repair/replacement; and termination repair/replacement. The effects of the mounting types (rack mount, stand off mount, direct mount and integral mount) and the installation/replacement type (sequential, partial interruption and independent) are identified and described. Methods of reducing maintenance costs are suggested.

Oster, J. R., Jr.↗
NASA NTRS1980

What is a magnetospheric substorm

The paper suggests that if the solar wind-magnetosphere energy coupling increases above about 10 to the 18th erg/sec, the magnetosphere suddenly develops a more efficient energy dissipation process than that operating during periods of less than 10 to the 18th erg/sec. Discussion covers the appearance that the magnetosphere achieves this enhanced energy dissipation by interrupting the cross-tail current in the magnetotail and diverting it into the ionosphere, causing an enhanced Joule heat production in the ionosphere.

Akasofu, S.-I.↗
NASA NTRS1980

Seasat-A satellite scatterometer instrument evaluation

The Seasat-A satellite scatterometer (SASS) was designed to measure ocean surface wind speed and direction in twenty-four independent cells over a 1000-km swath. It operated in the interrupted CW mode at a frequency of 14.6 GHz with four fan beam antennas and used Doppler filtering in the receiver for resolving the cells on the surface. The instrument began operating in space on July 6, 1978, and gathered normalized radar cross section data for approximately 2290 h. The purpose of this paper is to describe the in-orbit evaluation of the SASS hardware and its compatibility with the spacecraft. It has been determined that the scatterometer operated flawlessly throughout the mission, met all design requirements, and established a good data base for geophysical processing.

Johnson, J. W.↗
NASA NTRS1980

A modeling of magnetic field variations during magnetospheric substorms

Magnetic field variations in the noon-midnight plane during the magnetospheric substorm are studied in terms of changes of three current systems: the dynamo-driven current on the magnetopause, the cross-tail current and the field-aligned current-auroral electrojet system. The field-aligned current is assumed to be generated as a result of interruption and subsequent diversion of the cross-tail current to the ionosphere. It is concluded that the available observations are consistent with a large increase of the three currents.

Akasofu, S.-I.↗
NASA NTRS1980

Computer-based manuals for procedural information

Display of procedural information as found in aircraft operating manuals is discussed. The problem of converting hardcopy manuals to a computer-based presentation is considered. The trade-off of faster retrieval and display integration possible with a cathode-ray tube (CRT) versus the limited size of a CRT is emphasized. Nine subjects participated in an experimental study of the effectiveness of three alternative displays. Displays were evaluated for the task of retrieving and carrying out emergency procedures in an environment where task interruptions were prevalent. It was found that an on-line manual which provided considerable user assistance was superior to a hardcopy manual in terms of both task completion time and errors. However, an on-line manual without user assistance was inferior to a hardcopy manual in terms of errors.

Rouse, S. H.↗
NASA NTRS1982

New Algorithms Manage Fourfold Redundancy

Redundant sensors, actuators, and computers improve reliability of complex control systems, such as those in nuclear powerplants and aircraft. If one or more redundant elements fail, another takes over so that normal operation is not interrupted. Quad selection filter rejects data from null-failed and hardover-failed and hardover-failed units.

Gelderloos, H. C.↗
NASA NTRS1982

Automatically Reconfigurable Computer

Modular system changes its architecture to maximize either reliability or capacity. Reconfigurable computer is assembled from four kinds of modules: organizer/scheduler, memory, input/output processor, and central processor. Reconfiguration is initiated by a signal from a control panel or by fault interrupt from one of the modules.

Source record↗
NASA NTRS1980

Solar hot water system installed at Day's Lodge, Atlanta, Georgia

The solar energy hot water system installed in the Days Inns of America, Inc., Atlanta, Georgia is described. This system provides for 81 percent of the total hot water demand. There are two separate systems, each serving one building of the lodge (total of 65 suites). The entire system contains only potable city water. The 1024 square feet of Grumman Sunstream Model 332 liquid flat plate collectors and the outside piping drain whenever the collector plates approach freezing or when power is interrupted. Solar heated water from the two above ground cement lined steel tanks (1000 gallon tank) is drawn into the electric Domestic Hot Water (DHW) tanks as hot water is drawn. Electric resistance units in the DHW tanks top off the solar heated water, if needed, to reach thermostat setting.

Source record↗
NASA NTRS1980

P78-2 (SCATHA) satellite thermal balance test, a laboratory test

Space simulation test programs can be carried out with a high probability of being troublefree with a competent staff, a well-maintained test facility and attention to interfaces; however, full-up thermal balance tests using the solar simulator, temperature control of infrared sources, the gimbal, a large number of thermocouples, and other requirements for a high fidelity thermal balance are still a challenge. The P78-2 (Scatha) satellite was successfully tested with one interruption and a four-day abbreviated retest to verify a modification. This was accomplished in spite of the new test crew, a facility beset with several operational problems, and marginal interface control. These problems were addressed with very good results. Subsequent tests have been highly successful.

Parrish, R. P., Jr.↗
NASA NTRS1980

New methods to detect particle velocity and mass flux in arc-heated ablation/erosion facilities

Arc-heated flow facilities with injected particles are used to simulate the erosive and ablative/erosive environments encountered by spacecraft re-entry through fog, clouds, thermo-nuclear explosions, etc. Two newly developed particle diagnostic techniques used to calibrate these facilities are discussed. One technique measures particle velocity and is based on the detection of thermal radiation and/or chemiluminescence from the hot seed particles in a model ablation/erosion facility. The second technique measures a local particle rate, which is proportional to local particle mass flux, in a dust erosion facility by photodetecting and counting the interruptions of a focused laser beam by individual particles.

Brayton, D. B.↗
NASA NTRS1980

Improved refractory coatings

The adhesion, friction and wear properties of sputtered refractory coatings on substrates of materials that form stable nitrides are enhanced by placing each substrate directly below a titanium carbide target of a commercial radiofrequency diode apparatus in a vacuum chamber. Nitrogen is bled into the system through a nozzle resulting in a small partial pressure of about 0.5% to 2.5% during the first two minutes of deposition. The flow of nitrogen is then stopped, and the sputtering ambient is reduced to pure argon through a nozzle without interrupting the sputtering process. When nitrogen is deliberately introduced during the crucial interface formation, some of the titanium at the interface reacts to form titanium nitride while the metal of the substrate also forms the nitride. These two nitrides atomically mixed together in the interfacial region act to more strongly bond the growing titanium carbide coating as it forms on the substrate.

Brainard, W. A.↗
NASA NTRS1980

Examination of time series through randomly broken windows

The effect of irregular interruption of data collection (the breaking of the window function) on the spectrum determination of a time series is investigated. It is assumed that there is a uniform probability p that each interval of length tau, of the total interval of length T = tau, yields no data. For the linear case (Fourier transform) it is found that the noise to signal ratio has a (one sigma) value less than epsilon if N exceeds p(-1) (1-p) epsilon (-2). For the quadratic case, the same requirement is met by the less restrictive requirement that N exceed p(-1) (1-p) epsilon (-1). It appears that, if four observatories spaced around the Earth were to operate for 25 days, each for six hours a day (N = 100), and if the probability of cloud cover at any site on any day is 20% (p = 0.8), the r.m.s. noise to signal ratio is 0.25% for frequencies displaced from a sharp strong signal by 15 micro Hz. The noise to signal ratio drops off rapidly if the frequency offset exceeds 15 micro Hz.

Sturrock, P. A.↗
NASA NTRS1981

Common data buffer system

A high speed common data buffer system is described for providing an interface and communications medium between a plurality of computers utilized in a distributed computer complex forming part of a checkout, command and control system for space vehicles and associated ground support equipment. The system includes the capability for temporarily storing data to be transferred between computers, for transferring a plurality of interrupts between computers, for monitoring and recording these transfers, and for correcting errors incurred in these transfers. Validity checks are made on each transfer and appropriate error notification is given to the computer associated with that transfer.

Byrne, F.↗
NASA NTRS1981

Abradable dual-density ceramic turbine seal system

A plasma sprayed dual density ceramic abradable seal system for direct application to the HPT seal shroud of small gas turbine engines. The system concept is based on the thermal barrier coating and depends upon an additional layer of modified density ceramic material adjacent to the gas flow path to provide the desired abradability. This is achieved by codeposition of inert fillers with yttria stabilized zirconia (YSZ) to interrupt the continuity of the zirconia struture. The investigation of a variety of candidate fillers, with hardness values as low as 2 on Moh's scale, led to the conclusion that solid filler materials in combination with a YSZ matrix, regardless of their hardness values, have a propensity for compacting rather than shearing as originally expected. The observed compaction is accompanied by high energy dissipation in the rub interaction, usually resulting in the adhesive transfer of blade material to the stationary seal member. Two YSZ based coating systems which incorported hollow alumino silicate spheres as density reducing agents were surveyed over the entire range of compositions from 100 percent filler to 100 percent YSZ. Abradability and erosion characteristics were determined, hardness and permeability characterized, and engine experience acquired with several system configurations.

Clingman, D. L.↗