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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 469 records · Page 26
All sourcesNASA NTRSDOE OSTI
NASA NTRS1978

Implementation of natural frequency analysis and optimality criterion design

A description is presented of an effective optimality criterion computer design approach for member size selection to improve frequency characteristics for moderately large structure models. It is shown that the implementation of the simultaneous iteration method within a natural frequency structural design optimization provides a method which is more efficient in isolating the lowest natural frequency modes than the frequently applied Stodola method. Additional computational advantages are derived by using previously converged eigenvectors at the start of the iterations during the second and the following design cycles. Vectors with random components can be used at the first design cycle, which, in relation to the entire computer time for the design program, results in only a moderate computational penalty.

Levy, R.↗
NASA NTRS1978

Residual glasses and melt inclusions in basalts from DSDP Legs 45 and 46 - Evidence for magma mixing

Microprobe analyses of natural glasses in basalts recovered by Legs 45 and 46 of the Deep Sea Drilling Project are reported and interpreted in the context of other geochemical, petrographic and experimental data on the same rocks (Rhodes et al., 1978). Residual glass compositions in the moderately evolved aphyritic and abundantly phyric basalts within each site indicate that none of the units is related to any other or to a common parent by simple fractional crystallization. The compositional trends, extensive disequilibrium textures in the plagioclase phenocrysts and the presence in evolved lavas of refractory plagioclase and olivine phenocrysts bearing primitive melt inclusions provide evidence that magma mixing had a major role in the genesis of the Leg 45 and 46 basalts. The magma parental to these basalts was most likely characterized by high Mg/(Mg + Fe/+2/), CaO/Al2O3, CaO/Na2O and low lithophile concentrations. A mixing model involving incremental enrichment of magmaphile elements by repeated episodes of mixing of relatively primitive and moderately evolved magmas, followed by a small amount of fractionation is consistent with the characteristics of the basalts studied.

Dungan, M. A.↗
NASA NTRS1980

Prepolymer dianhydrides

A process for preparing dianhydrides that are miscible with hydroxyl prepolymers at moderate temperatures and can cure hydroxyl prepolymers to elastomers at moderate temperatures is disclosed. The dianhydrides are prepared by solution reaction of a prepolymer diol with excess hydride followed by removal of unreacted dianhydride. The prepolymer dianhydrides are miscible with hydroxyl substituted hydrocarbon prepolymers and cure the prepolymers to polyester-linked elastomers.

Rhein, R. A.↗
NASA NTRS1979

Colorimetry and magnitudes of asteroids

In the present paper, 1500 UBV observations are analyzed by a new rather general multiple scattering theory which provided clear insight into previously poorly-recognized optical nature of asteroid surfaces. Thus, phase curves are shown to consist of a surface-texture controlled component, due to singly scattered light, and a component due to multiple scattering. Phase curve shapes can be characterized by a single parameter, the multiple scattering factor, Q. As Q increases, the relative importance of the opposition effect diminishes. Asteroid surfaces are particulate and strikingly similar to texture, being moderately porous and moderately rough on a scale greater than the wavelength of light. In concequence, Q (and also the phase coefficient) correlate well with geometric albedo, and there exists a purely photometric means of determining albedos and diameters.

Bowell, E.↗
NASA NTRS1979

Minimum-mass designs of stiffened graphite/polyimide compression panels

This study presents results from an analytic investigation to determine minimum-mass designs of stiffened Gr/Pi compression panels for a wide range of uniaxial compression loads. Four panel configurations are considered: (1) hat stiffened-laminated skin, (2) hat stiffened-honeycomb core sandwich skin, (3) blade stiffened-laminated skin and (4) blade stiffened-honeycomb core sandwich skin panels. Designs are generated by an automatic optimization computer code entitled PASCO (Panel Analysis and Sizing COde). The analysis portion of PASCO contains a generalized buckling analysis which calculates all critical modes without assuming any of them a priori. Mass-strength curves are presented for the four configurations along with specific designs generated for low, moderate and high values of compression load. A mass-strength curve for a titanium hat stiffened panel is provided for comparison. A 30% to 50% mass savings over titanium panels is shown for moderately and heavily loaded Gr/Pi panels.

Weaver, G. G., II↗
NASA NTRS1980

Nonlinear interaction of two waves in boundary-layer flows

First-order nonlinear interactions of Tollmien-Schlichting waves of different frequencies and initial amplitudes in boundary-layer flows are analyzed using the method of multiple scales. Numerical results for flow past a flat plate show that the spatial detuning wipes out resonant interactions unless the initial amplitudes are very large. Thus, a wave having a moderate amplitude has little influence on its subharmonic although it has a strong influence on its second harmonic. Moreover, two waves having moderate amplitudes have a strong influence on their difference frequency. The results show that the difference frequency can be very unstable when generated by the nonlinear interaction, even though it may be stable when introduced by itself in the boundary layer.

Nayfeh, A. H.↗
NASA NTRS1980

Variability of plasma sheet dynamics

IMP 7 observations of plasma sheet structure and dynamics made during a 24-h period in which the satellite traversed the tail plasma sheet at a radial distance of 35 earth radii and remained within 2 earth radii of the expected position at the neutral sheet and in which at least five substorms occured on the ground are presented. High-time-resolution measurements of the magnetic field, plasma flow and greater than 50-keV protons obtained by the satellite and ground-based magnetic measurements are discussed for a 4-hr interval in which two small substorms occurred, a 6-hr geomagnetically quiet interval in which moderate variable plasma flows were observed, a very rapid, smooth neutral sheet crossing and earthward plasma flow during the expansion phase of a small substorm, a moderate-size substorm in which a prolonged interval of field-aligned tailward flow commenced at onset, a strong tailward and dawnward flow burst in an interval between substorms and a large substorm in which strong tailward flow was observed. Observations indicate the significant distortion of the tail field, possibly by plasma flow stresses, a neutral sheet structure occasionally resembling the hydromagnetic rotational discontinuity and a high level of magnetic turbulence during an earthward plasma flow which may contribute towards plasma sheet dissipation.

Coroniti, F. V.↗
NASA NTRS1980

Numerical simulation of three-dimensional boattail afterbody flow fields

The thin shear layer approximations of the three-dimensional, compressible Navier-Stokes equations are solved for subsonic, transonic, and supersonic flow over axisymmetric boattail bodies at moderate angles of attack. The plume is modeled by a solid body configuration identical to those used in experimental tests. An implicit algorithm of second-order accuracy is used to solve the equations on the ILLIAC IV computer. The turbulence is expressed by an algebraic model applicable to three-dimensional flow fields with moderate separation. The computed results compare favorably with three different sets of experimental data reported by Reubush, Shrewsbury, and Benek, respectively

Deiwert, G. S.↗
NASA NTRS1980

Asymmetric trailing-edge flows at high Reynolds number

Results from an experimental investigation of asymmetric trailing-edge flows at high Reynolds numbers and subsonic Mach numbers are presented. Measurements include skin friction; surface and flow-field pressures; and mean-velocity, turbulent shear-stress, and turbulent kinetic-energy profiles in the trailing-edge region. Comparisons are made with computed solutions using Reynolds averaged Navier-Stokes and boundary-layer equations; two different turbulence models are used. Two attached flow are considered, one having a moderate adverse pressure gradient and the other a more severe gradient. From the comparisons, an evaluation is made of the predictions for these two pressure-gradient cases. Although the comparisons demonstrate reasonable agreement for the moderate pressure-gradient case, some differences are noted for the severe pressure-gradient case.

Cleary, J. W.↗
NASA NTRS1980

Advanced Technology Spark-Ignition Aircraft Piston Engine Design Study

The advanced technology, spark ignition, aircraft piston engine design study was conducted to determine the improvements that could be made by taking advantage of technology that could reasonably be expected to be made available for an engine intended for production by January 1, 1990. Two engines were proposed to account for levels of technology considered to be moderate risk and high risk. The moderate risk technology engine is a homogeneous charge engine operating on avgas and offers a 40% improvement in transportation efficiency over present designs. The high risk technology engine, with a stratified charge combustion system using kerosene-based jet fuel, projects a 65% improvement in transportation efficiency. Technology enablement program plans are proposed herein to set a timetable for the successful integration of each item of required advanced technology into the engine design.

Stuckas, K. J.↗
NASA NTRS1980

State of gas exchange in recumbent and orthostatic positions and under physical load in healthy persons of varying age, sex and body build

Age effect on gas exchange was studied in the recumbent and orthostatic positions and under physical load. In the case of the older age group and for normal as compared with hypersthenic persons, oxygen consumption during rest and during moderate physical overload diminishes. When the vertical position is assumed oxygen consumption in persons of various age groups is distinctly increased, particularly in the elderly group. There is a reduction in the amount of oxygen consumption, oxygen pulse, recovery coefficient, and work efficiency under moderate overload. In persons over 50, physical labor induces a large oxygen requirement and a sharp rise in the level of lactic acid and the blood's lactate/pyruvate ratio. No distinct difference was noted in the amount of oxygen consumed during rest and during physical overload in men and women of the same physical development and age.

Glezer, G. A.↗
NASA NTRS1981

Transonic wing design using potential-flow codes - Successes and failures

The state-of-the-art of transonic wing design by use of computer codes based on the potential flow-theory is presented. The capabilities and limitations of these codes are exemplified by several experiment-theory correlations, including an assessment of pressure distribution from isolated wing and wing-body codes. Computer codes using both conservative and nonconservative differencing schemes were used, and the effects of boundary-layer corrections were considered. Results showed that calculations from a full potential, isolated code correlate well with data from an isolated wing test, but may give poor predictions of the aerodynamic characteristics of some wing-body configurations. Boundary-layer correlations were found to have only moderate effects on experiment-theory correlation. Aeroelastic effects were considered important for high aspect ratio wings of low to moderate thickness, and viscous effects were minimal for typical cruise conditions, even for Reynold's numbers as low as two million. The effect of wind-tunnel walls on experiment-theory correlations remained inconclusive. A wing-body code was used to calculate the flow field about a wing-body configuration with body-mounted engines, typical of the transonic Biz-Jet aircraft.

Hicks, R. M.↗
NASA NTRS1982

Resource targets for advanced underground coal extraction systems

Resource targets appropriate for federal sponsorship of research and development of advanced underground coal mining systems are identified. A comprehensive examination of conventional and unconventional coals with particular attention to exceptionally thin and thick seams, steeply dipping beds, and multiple seam geometry was made. The results indicate that the resource of primary importance is flat lying bituminous coal of moderate thickness, under moderate cover, and located within the lower 48 states. Resources of secondary importance are the flat lying multiple seams and thin seams (especially those in Appalachia). Steeply dipping coals, abandoned pillars, and exceptionally thick western coals may be important in some regions of subregions, but the limited tonnage available places them in a position of tertiary importance.

Hoag, J. H.↗
NASA NTRS1983

Results of thermal environment measurements on the thermal cannister experiment and get away special enclosure

Because the OSS-1 pallet contained a variety of instruments with irregular surface geometry and properties which limited predictability, the total absorbed flux on thermal canister radiators was measured to determine heat rejection capability. The instrumentation and sensor cup design and locations for the thermal canister experiment are illustrated. Graphs show flux sensor history in hot and coal orbits. Kapton erosion is also considered. Results show that the flux levels measured in all STS attitudes are higher than predictions. In cold and moderate attitudes, flight results are a factor of two to three higher than predicts. In hot attitude, much better agreement occurred. It is concluded that in cold or moderate attitudes other sources may be contributing to added inputs (albedo, Earth shine, shuttle background). In hot attitude, smaller differences could be attributed to coatings assumptions or calculation uncertainty.

Ollendorf, S.↗
NASA NTRS1983

The spark-ignition aircraft piston engine of the future

The advanced technology, spark ignition, aircraft piston engine design study was conducted to determine the improvements that could be made by taking advantage of technology that could reasonably be expected to be made available for an engine intended for production by January 1, 1990. Two engines were proposed to account for levels of technology considered to be moderate risk and high risk. The moderate risk technology engine is a homogeneous charge engine operating on avgas and offers a 40% improvement in transportation efficiency over present designs. The high risk technology engine, with a stratified charge combustion system using kerosene-based jet fuel, projects a 65% improvement in transportation efficiency. Technology enablement program plans are proposed herein to set a timetable for the successful integration of each time of required advanced technology into the engine design.

Stuckas, K. J.↗
NASA NTRS1983

A survey of ultraviolet interstellar absorption lines

A telescope-spectrometer on the Copernicus spacecraft made possible the measurement of many ultraviolet absorption lines produced by the interstellar gas. The present survey provides data on ultraviolet absorption lines in the spectra of 88 early-type stars. The stars observed are divided into four classes, including reddened stars, unreddened bright stars, moderately reddened bright stars, and unreddened and moderately reddened faint stars. Data are presented for equivalent width, W, radial velocity V, and rms line width, D, taking into account some 10 to 20 lines of N I, O I, Si II, P II, S II, Cl I, Cl II, Mn II, Fe II, Ni II, Cu II, and H2. The data are based on multiple scans for each line. Attention is given to details of observations, the data reduction procedure, and the computation of equivalent width, mean velocity, and velocity dispersion.

Bohlin, R. C.↗
NASA NTRS1982

Vertical density and temperature structure over northern Europe

Vertical profiles of upper-atmosphere temperature and density over northern Europe constructed from data obtained in November and December 1980, as part of the Energy Budget Campaign, are presented and discussed. Temperature sondes, passive spheres, accelerometers, mass and IR spectrometers, and density gauges were rocket launched from ESRANGE, Sweden and Andoya, Norway; the data are combined with ground measurements to construct 20-120-km-altitude profiles for night periods of severe, moderate, and minimal geomagnetic storm activity. The profiles are compared with each other and with the 1976 U.S. Standard Atmosphere (USSA). In the temperature profiles, increased geomagnetic activity is associated with lower temperatures and flattened profiles in the stratopause region, and higher temperatures in the 70-90-km range. The density profiles show a variation of less than about 15 percent, except for a 25-percent range for the moderate-geomagnetic-activity period. The inferred wavelengths and periods are those expected for internal gravity waves at this altitude, and the divergence from USSA is accounted for by season and latitude dependence.

Philbrick, C. R.↗
NASA NTRS1983

Spacecraft-borne long life cryogenic refrigeration: Status and trends

The status of cryogenic refrigerator development intended for, or possibly applicable to, long life spacecraft-borne application is reviewed. Based on these efforts, the general development trends are identified. Using currently projected technology needs, the various trends are compared and evaluated. The linear drive, non-contacting bearing Stirling cycle refrigerator concept appears to be the best current approach that will meet the technology projection requirements for spacecraft-borne cryogenic refrigerators. However, a multiply redundant set of lightweight, moderate life, moderate reliability Stirling cycle cryogenic refrigerators using high-speed linear drive and sliding contact bearings may possibly suffice.

Johnson, A. L.↗