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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 577 records · Page 32
All sourcesNASA NTRSDOE OSTI
NASA NTRS1981

Electron and ion acceleration by strong electrostatic turbulence

It is noted that, for waves observed on auroral field lines, ion trapping may be important, affecting models of transverse ion acceleration. The strength of the electrostatic ion cyclotron turbulence observed in the auroral zone may be attributed to the large convective growth rate that is associated with this mode. These waves may be destabilized by the enhancement in the field-aligned current that results from the onset of a magnetospheric substorm. The rise in the field-aligned current is associated with the passage of shear mode Alfven waves between the magnetosphere and ionosphere. When these Alfven waves have a perpendicular wavelength comparable to the ion gyroradius, they carry a parallel electric field that can accelerate the plasma in the topside auroral ionosphere, destabilizing the electrostatic ion cyclotron mode.

Lysak, R. L.↗
NASA NTRS1982

IUE observations of NGC 4649, an elliptical galaxy with a strong ultraviolet flux

As in the previously studied elliptical galaxies, the flux f(lambda) in NGC 4649 has a minimum at 2500 A followed by a rapid increase towards shorter wavelengths. In NGC 4649, the flux level of this rising branch is the highest so far observed and seems not to be correlated with the luminosity or activity in the galaxy. The excess shortward of 4000 A, observed in M87, another high level rising branch galaxy, is not present in NGC 4649. The UV spectrum of NGC 4649 down to 2500 A matches closely those of NGC 3379 and NGC 4472. The implications of the UV properties of elliptical galaxies on the stellar content as well as on magnitudes and colors of distant galaxies are discussed

Bertola, F.↗
NASA NTRS1981

Analysis and computation of three-dimensional flow in strongly curved ducts

Numerical solutions are presented for three-dimensional laminar and turbulent flow in curved ducts of rectangular cross section and significant curvature. The analysis is based on a primary-secondary velocity decomposition in a given coordinate system, and leads to approximate governing equations which correct an a priori inviscid solution for viscous effects, secondary flows, total pressure distortion, heat transfer, and internal flow blockage and losses. Solution of the correction equations is accomplished as an initial-value problem in space using an implicit forward-marching technique. The overall solution procedure requires significantly less computational effort than Navier-Stokes algorithms. The present solution procedure is effective even with the extreme local mesh resolution which is necessary to resolve near-wall sublayer regions in turbulent flow calculations. Computed solutions for both laminar and turbulent flow compare very favorably with available analytical and experimental results.

Kreskovsky, J. P.↗
NASA NTRS1982

Tangential blowing for control of strong normal shock - Boundary layer interactions on inlet ramps

The use of tangential blowing from a row of holes in an aft facing step is found to provide good control of the ramp boundary layer, normal shock interaction on a fixed geometry inlet over a wide range of inlet mass flow ratios. Ramp Mach numbers of 1.36 and 1.96 are investigated. The blowing geometry is found to have a significant effect on system performance at the highest Mach number. The use of high-temperature air in the blowing system, however, has only a slight effect on performance. The required blowing rates are significantly high for the most severe test conditions. In addition, the required blowing coefficient is found to be proportional to the normal shock pressure rise.

Schwendemann, M. F.↗
NASA NTRS1981

Experimental investigation of tangential blowing for control of the strong shock boundary layer interaction on inlet ramps

A 0.165-scale isolated inlet model was tested in the NASA Lewis Research Center 8-ft by 6-ft Supersonic Wind Tunnel. Ramp boundary layer control was provided by tangential blowing from a row of holes in an aft-facing step set into the ramp surface. Testing was performed at Mach numbers from 1.36 to 1.96 using both cold and heated air in the blowing system. Stable inlet flow was achieved at all Mach numbers. Blowing hole geometry was found to be significant at 1.96M. Blowing air temperature was found to have only a small effect on system performance. High blowing levels were required at the most severe test conditions.

Schwendemann, M. F.↗
NASA NTRS1983

Development of tough, strong, iron-base alloy for cryogenic applications

The development of an iron-base alloy that combines the normally divergent properties of high toughness and high strength at cryogenic temperatures is discussed. Specifically, alloy properties were sought which at -196 C would exhibit a fracture toughness of 220 MPa-m(1/2) with a corresponding yield strength of 1.4 GPa (200 ksi). Early work showed that high toughness could be achieved in Fe-12Ni alloys containing reactive metal additions such as Al, Nb, Ti, and V. Further research emphasized strengthening of these tough alloys by thermomechanical processing and the addition of Cu. Results showed that high strength and high toughness could be achieved in a single alloy at temperatures as low as -196 C. An alloy with composition Fe-12Ni-9.5Al-2Cu exhibited a yield strength of 1.65 GPa with a corresponding fracture toughness of 220 MPa-m(1/2) at -196 C. Strengthening due to Cu additions to the Fe-12Ni base alloys results primarily from precipitation of Cu-rich epsilon particles approximately 20 nm in diameter. Strengthening mechanisms are discussed in terms of an elastic modulus hardening model and are supported by transimission electron microscopy examinations of selected test specimens.

Stephens, J. R.↗
NASA NTRS1983

Multiple energetic injections in a strong spike-like solar burst

An intense and fast spike-like solar burst was built up of short time scale structures superimposed on an underlying gradual emission, the time evolution of which shows remarkable proportionality between hard X-ray and microwave fluxes. The finer time structure were best defined at mm-microwaves. At the peak of the event, the finer structures repeat every 30x60ms. The more slowly varying component with a time scale of about 1 second was identified in microwave hard X-rays throughout the burst duration. It is suggested that X-ray fluxes might also be proportional to the repetition rate of basic units of energy injection (quasi-quantized). The relevant parameters of one primary energy release site are estimated both in the case where hard X-rays are produced primarily by thick-target bremsstrahlung, and when they are purely thermal. The relation of this figure to global energy considerations is discussed.

Kaufmann, P.↗
NASA NTRS1985

Strong, Lighweight Curved Panels

Sandwich construction gives panels structural efficiency. Large panels with compound curvatures are formed from a honeycomb core faced with sheets of graphite/epoxy cloth and tape. Developed for pod on Space Shuttle, construction readily adapted to curved skin panels on cars, trucks, and airplanes.

Molho, R.↗
NASA NTRS1983

The strong equivalence principle and its violation

Theoretical and observational aspects of an SEP violation are discussed. A two-times theory is presented as a possible framework to handle an SEP violation, and tests performed to check the compatibility of such violation with a host of data ranging from nucleosynthesis to geophysics are summarized. Also discussed are the dynamical equations needed to analyze radar ranging data to reveal an SEP violation and in particular the method employed by Shapiro and Reasenberg (1976).

Canuto, V. M.↗
NASA NTRS1984

The early-type strong emission-line supergiants of the Magellanic Clouds - A spectroscopic zoology

The results of a spectroscopic survey of 21 early-type extreme emission line supergiants of the Large and Small Magellanic Clouds using IUE and optical spectra are presented. The combined observations are discussed and the literature on each star in the sample is summarized. The classification procedures and the methods by which effective temperatures, bolometric magnitudes, and reddenings were assigned are discussed. The derived reddening values are given along with some results concerning anomalous reddening among the sample stars. The derived mass, luminosity, and radius for each star are presented, and the ultraviolet emission lines are described. Mass-loss rates are derived and discussed, and the implications of these observations for the evolution of the most massive stars in the Local Group are addressed.

Shore, S. N.↗
NASA NTRS1984

Multiple energetic injections in a strong spike-like solar burst

An intense and fast spike-like solar burst was built up of short time scale structures superimposed on an underlying gradual emission, the time evolution of which shows remarkable proportionality between hard X-ray and microwave fluxes. The finer time structures were best defined at mm-microwaves. At the peak of the event, the finer structures repeat every 30 x 60 ms. The more slowly varying component with a time scale of about 1 second was identified in microwave hard X-rays throughout the burst duration. It is suggested that X-ray fluxes might also be proportional to the repetition rate of basic units of energy injection (quasi-quantized). The relevant parameters of one primary energy release site are estimated both in the case where hard X-rays are produced primarily by thick-target bremsstrahlung, and when they are purely thermal. The relation of this figure to global energy considerations is discussed. Previously announced in STAR as N83-35983

Kaufmann, P.↗
NASA NTRS1985

Production Process for Strong, Light Ceramic Tiles

Proportions of ingredients and sintering time/temperature schedule changed. Production process for lightweight, high-strength ceramic insulating tiles for Space Shuttle more than just scaled-up version of laboratory process for making small tiles. Boron in aluminum borosilicate fibers allows fusion at points where fibers contact each other during sintering, thereby greatly strengthening tiles structure.

Holmquist, G. R.↗
NASA NTRS1985

CO adsorption on (111) and (100) surfaces of the Pt sub 3 Ti alloy. Evidence for parallel binding and strong activation of CO

The CO adsorption on a 40 atom cluster model of the (111) surface and a 36 atom cluster model of the (100) surface of the Pt3Ti alloy was studied. Parallel binding to high coordinate sites associated with Ti and low CO bond scission barriers are predicted for both surfaces. The binding of CO to Pt sites occurs in an upright orientation. These orientations are a consequence of the nature of the CO pi donation interactions with the surface. On the Ti sites the orbitals donate to the nearly empty Ti 3d band and the antibonding counterpart orbitals are empty. On the Pt sites, however, they are in the filled Pt 5d region of the alloy band, which causes CO to bond in a vertical orientation by 5 delta donation from the carbon end.

Mehandru, S. P.↗
NASA NTRS1985

Strong earthquakes, novae and cosmic ray environment

Observations about the relationship between seismic activity and astronomical phenomena are discussed. First, after investigating the seismic data (magnitude 7.0 and over) with the method of superposed epochs it is found that world seismicity evidently increased after the occurring of novae with apparent magnitude brighter than 2.2. Second, a great many earthquakes of magnitude 7.0 and over occurred in the 13th month after two of the largest ground level solar cosmic ray events (GLEs). The causes of three high level phenomena of global seismic activity in 1918-1965 can be related to these, and it is suggested that according to the information of large GLE or bright nova predictions of the times of global intense seismic activity can be made.

Yu, Z. D.↗
NASA NTRS1984

Nonthermal synchrotron radiation in a strong magnetic field

A synchrotron source model is presented for the origin of gamma-ray bursts from neutron stars. The field strength and length of time needed for electrons to lose sufficient energy in emitting the gamma rays are calculated, together with the efficiency of the process, limiting frequencies, and the energy output. A Monte Carlo simulation of the synchrotron radiation spectrum of an electron undergoing a self-consistent energy loss demonstrates that a process involving thermalized electrons can be sufficiently efficient to produce 30 keV gamma rays. Problems expected in using the current capabilities of detectors to scan for the projected energy spectra from fields of at least 3 x 10 to the 12th Gauss are discussed.

Bussard, R. W.↗
NASA NTRS1985

Are galaxies more strongly correlated than clusters?

Distributions of galaxies and of clusters of galaxies have been investigated using the correlation function, the excess probability over random that there are two objects separated by a distance r. It is shown here that if the amplitudes of the cluster-cluster correlation function are made dimensionless, systematic changes with cluster richness vanish, implying scale invariance in the cluster process. The dimensionless galaxy-galaxy correlation seems stronger, implying gravitational enhancement on smaller scales.

Szalay, A. S.↗