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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 1,621 records · Page 90
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

Quasi-one-dimensional compressible flow across face seals and narrow slots. 2: Computer program

A computer program is presented for compressible fluid flow with friction across face seals and through narrow slots. The computer program carries out a quasi-one-dimensional flow analysis which is valid for laminar and turbulent flows under both subsonic and choked flow conditions for parallel surfaces. The program is written in FORTRAN IV. The input and output variables are in either the International System of Units (SI) or the U.S. customary system.

Zuk, J.↗
NASA NTRS1974

Optimal controller design for high performance aircraft undergoing large disturbance angles

An examination of two aircraft controller structures applicable to on-line implementation was conducted. The two controllers, a linear regulator model follower and an inner-product model follower, were applied to the lateral dynamics of the F8-C aircraft. For the purposes of this research effort, the lateral dynamics of the F8-C aircraft were considered. The controller designs were evaluated for four flight conditions. Additionally, effects of pilot input, rapid variation of flight condition and control surface rate and magnitude deflection limits were considered.

Rhoten, R. P.↗
NASA NTRS1973

Earth and Ocean Physics Applications Program /EOPAP/

Abbreviated description of the objectives, experiments, spacecraft, and required schedules of a proposed NASA program blending geophysics, oceanography, and space technology in order to facilitate the prediction of earthquakes, storm surges, tidal waves, and the condition of ocean surfaces. Relevant measurements from space will be carried out by LAGEOS, SAESATS-1, GEOPAUSE, GRAVSAT, and SEASATS-2 satellites contributing data on earth dynamics, sea surface states, satellite dynamics, and earth gravity. The development of suitable mathematical models for predicting events on earth on the basis of satellite data is considered.

Vonbun, F. O.↗
NASA NTRS1974

Adhesive fracture mechanics

In studies of fracture mechanics the adhesive fracture energy is regarded as a fundamental property of the adhesive system. It is pointed out that the value of the adhesive fracture energy depends on surface preparation, curing conditions, and absorbed monolayers. A test method reported makes use of a disk whose peripheral part is bonded to a substrate material. Pressure is injected into the unbonded central part of the disk. At a certain critical pressure value adhesive failure can be observed. A numerical stress analysis involving arbitrary geometries is conducted.

Bennett, S. J.↗
NASA NTRS1974

Ground truth data for test sites (SL-4)

Field measurements performed simultaneous with Skylab overpass in order to provide comparative calibration and performance evaluation measurements for the EREP sensors are presented. Wavelength region covered include: solar radiation (400 to 1300 nanometer), and thermal radiation (8 to 14 micrometer). Measurements consisted of general conditions and near surface meteorology, atmospheric temperature and humidity vs altitude, the thermal brightness temperature, total and diffuse solar radiation, direct solar radiation (subsequently analyzed for optical depth/transmittance), and target reflectivity/radiance. The particular instruments used are discussed along with analyses performed. Detailed instrument operation, calibrations, techniques, and errors are given.

Source record↗
NASA NTRS1975

Detection of soil moisture and snow characteristics from Skylab

The author has identified the following significant results. The most significant result is the good response of the passive radiometers, particularly the L-band radiometer, to changing soil moisture conditions near the surface of the earth. Radiometer response was very good for the five complete data sets consisting of three passes across Texas and two passes across Kansas. When data from the five different passes were combined, the correlation between the S194 radiometric temperature and soil moisture content remained high with a value of -0.96. The performance of the S193 passive radiometer was less consistent; however, one data set gave a very high correlation of -0.95. The scatterometer response to soil moisture at incidence angles near 30 deg was not as good as for the radiometers.

Eagleman, J. R.↗
NASA NTRS1975

The escape of magnetic flux from a turbulent body of gas

Topological conditions on the surface of a turbulent body of highly conductive fluid under which escape of magnetic force lines would be impossible (Drobyshevski, Yuferev 1974) are studied with exact calculation of intermediate field configurations as a possible explanation of the decay of stellar magnetic fields via turbulent mixing. It is shown that upward escape of magnetic force lines in the regions between convective cells is possible through rapid reconnection of the force lines (studied as neutral point annihilation) such as occurs continually in rapidly evolving sunspot groups. It is concluded that there exists no topological barrier to the escape of magnetic flux from the sun or from the local galaxy.

Parker, E. N.↗
NASA NTRS1976

Scientific results of the Viking missions

The two Viking missions to Mars have been extraordinarily successful. Thirteen scientific investigations yielded information about the atmosphere and surface. Two orbiters and landers operating for several months photographed the surface extensively from 1500 kilometers and directly on the surface. Measurements were made of the atmospheric composition, the surface elemental abundance, the atmospheric water vapor, temperature of the surface, and meteorological conditions; direct tests were made for organic material and living organisms. The question of life on Mars remains unanswered. The Viking spacecraft are designed to continue the investigations for at least one Mars year.

Soffen, G. A.↗
NASA NTRS1976

High-explosive cratering analogs for bowl-shaped, central uplift, and multiring impact craters

The paper describes six experimental explosion craters in terms of their basic morphology, subsurface structural deformation, and surrounding ejecta blanket. These craters exhibit one or more of the following features: bowl shapes with underlying breccia lens, central uplifts, multirings, terraced walls, rim strata, zones of concentric rim deformation, inner continuous ground cover of ejecta blankets formed by overturned flaps, secondary cratering, and fused alluvium. These craters were formed by large shock wave energy transfers at or near zero heights-of-burst, and it is possible that impact craters with analogous morphologic and structural features may have formed under similar surface energy transfer conditions.

Roddy, D. J.↗
NASA NTRS1979

Nonequilibrium viscous flow over Jovian entry probes at high altitudes

The viscous chemical nonequilibrium flow around a Jovian entry body is investigated at high altitudes using two different methods. First method is only for the stagnation region and integrates the full Navier-Stokes equations from the body surface to the freestream. The second method uses viscous shock layer equations between the body surface and the shock. Due to low Reynolds numbers, both methods use surface slip boundary conditions and the second method also uses shock slip boundary conditions. The results of the two methods are compared at the stagnation point. It is found that the entire shock layer is under chemical nonequilibrium at higher altitudes and that the slip boundary conditions are important at these altitudes.

Kumar, A.↗
NASA NTRS1979

Materials and structural aspects of advanced gas-turbine helicopter engines

Advances in materials, coatings, turbine cooling technology, structural and design concepts, and component-life prediction of helicopter gas-turbine-engine components are presented. Stationary parts including the inlet particle separator, the front frame, rotor tip seals, vanes and combustors and rotating components - compressor blades, disks, and turbine blades - are discussed. Advanced composite materials are considered for the front frame and compressor blades, prealloyed powder superalloys will increase strength and reduce costs of disks, the oxide dispersion strengthened alloys will have 100C higher use temperature in combustors and vanes than conventional superalloys, ceramics will provide the highest use temperature of 1400C for stator vanes and 1370C for turbine blades, and directionally solidified eutectics will afford up to 50C temperature advantage at turbine blade operating conditions. Coatings for surface protection at higher surface temperatures and design trends in turbine cooling technology are discussed. New analytical methods of life prediction such as strain gage partitioning for high temperature prediction, fatigue life, computerized prediction of oxidation resistance, and advanced techniques for estimating coating life are described.

Freche, J. C.↗
NASA NTRS1980

On the swelling of rolled up vortex surfaces and the breakdown of the vortex core for slender wings

Simplified models of the vortex distribution over cylindrical surfaces are developed. The effect of a change of vortex strength was analyzed quantitatively by menas of potential theory. The considerable bulging of the cylindrical vortex sheet as a consequence of the change of the vortex strength is discussed. The coiling-up of the vortices rotation in opposite directions over the cylindrical surface renders the condition for instability and the subsequent large spreading of the vortex core. These processes occur without a positive pressure gradient being necessary in the field of flow surrounding the coiled up vortex sheet.

Das, A.↗
NASA NTRS1980

Bubble departure radii at solidification interfaces

A model has been developed for the prediction of bubble departure radii from flat solidification interfaces, including the effect of thermocapillary forces. Under normal gravity conditions, the necessary gas bubble radius required for departure from a CBr4 solidification interface is predicted to be approximately 1/2 mm in agreement with measured values. Under microgravity conditions, however, where surface forces predominate, the model predicts a seemingly prohibitive value of 40 mm. This result is at least in agreement with the microgravity tests conducted on the NASA SPAR I and SPAR III sounding rockets (1978) where the bubbles were not larger than 2 mm in radius and no bubble detachment was observed.

Cole, R.↗
NASA NTRS1980

Exploring the veiled planet

An overview of data obtained from various experiments which characterize geological features and atmospheric properties of Venus is presented. Data from the two Pioneer sounder probes (one located at Venus's equator and the other near the north pole) exhibit a reversal in the equator-to-pole temperature patterns at 60 km altitude which suggests that two circulation cells exist within the atmospheric region. However, the atmospheric temperature and pressure beneath the clouds are found to be nearly identical everywhere on Venus and both temperature and pressure conditions at the surface are lower than first expected. The identification of sulphur dioxide clouds which appear to coincide with Venus's characteristic global patterns of C- and Y-shaped dark markings support the hypothesis of a regular pattern of planet spanning breaks in the upper cloud layer. Explanations of a Venus sulphur cycle and of observed magnetic field structures are suggested

Source record↗
NASA NTRS1981

Validation of helicopter noise prediction techniques

The current techniques of helicopter rotor noise prediction attempt to describe the details of the noise field precisely and remove the empiricisms and restrictions inherent in previous methods. These techniques require detailed inputs of the rotor geometry, operating conditions, and blade surface pressure distribution. The purpose of this paper is to review those techniques in general and the Farassat/Nystrom analysis in particular. The predictions of the Farassat/Nystrom noise computer program, using both measured and calculated blade surface pressure data, are compared to measured noise level data. This study is based on a contract from NASA to Bolt Beranek and Newman Inc. with measured data from the AH-1G Helicopter Operational Loads Survey flight test program supplied by Bell Helicopter Textron.

Succi, G. P.↗
NASA NTRS1981

Improved liquid phase epitaxial GaAs for low series resistance Schottky barrier mixer diodes

Millimeter wave Schottky barrier mixer diodes are extremely important devices for radio astronomy. The performance of the Schottky diodes depends largely on the characteristics and quality of the GaAs epitaxial materials used. Systematic manipulation of the liquid phase epitaxial growth conditions and substrate surface treatments has yielded significantly improved surface morphology. Initial problems of high resistivity interfacial layers have been reduced without the use of an in situ etchback. Two-micron diameter Schottky diodes fabricated from epitaxial layers grown at 725 C exhibit a 9-ohm series resistance very near the theoretical minimum.

Binari, S. C.↗
NASA NTRS1981

Predictability of the tropical atmosphere

An examination of the deterministic predictability for tropics and middle-latitudes separately indicates that the theoretical upper limit of deterministic predictability for low latitudes is shorter than that for middle latitudes. Variability of time averages in low latitudes is mainly determined by the location and intensity of the large-scale Hadley and Walker circulations. Since these are largely influenced by the slowly varying boundary conditions of sea surface temperature and soil moisture, and since synoptic instabilities are not strong enough to change drastically the large scale flow, there is larger potential for predictability of monthly and seasonal means in low latitudes. It is conjectured that for short and medium range deterministic prediction, a prescribed diabatic heating field due to moist convection may be more useful than their explicit calculation from the evolving flow.

Shukla, J.↗