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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 397 records · Page 22

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NASA NTRS1980

High-altitude resolution stratospheric measurements with the Arecibo 430-MHz radar

Instrumental modification at the Arecibo Observatory are described, which make possible a resolution of 150 m, the maximum allowed by the transmitter bandwidth. Attention is given to digital decoding, the radar controller, and the fact that a complementary coded pulse scheme generating no pulse side lobes has been used for the first time. It is noted that power spectra of the signals corresponding to 256 altitudes are evaluated on line by means of an array processor. A profile of the E-W component of the wind as a function of altitude has been observed, as well as the discrete layered structure of turbulence, especially at higher altitudes; in addition, the maximum range at which an echo has been detected is about 31 km. The results obtained show the importance for stratospheric studies of high resolution when using radar to obtain wind information from the Doppler shift of turbulence echoes.

Woodman, R. F.↗

NASA NTRS1980

Oxidation state of the atmosphere and crust of Venus from Pioneer Venus results

Recent spacecraft observations of Venus permit a detailed model of sulfur chemistry in the atmosphere-lithosphere system. Pioneer Venus experiments confirm that, as predicted, COS and H2S are dominant over SO2 in the lower atmosphere, and that the equilibrium concentrations of S2 and S3 are significant. Many criteria serve to bracket the oxidation state of the crust: it is nearly certain that the S2(2-)/SO4(2-) buffer regulates the oxygen fugacity, and that FeO is at least as abundant as F2O3 in crustal silicates. A highly oxidized crust (as, for example, would result from O2 absorption complementary to escape of vast amounts of H2) is incompatible with the gas-phase sulfur chemistry. If the Pioneer Venus mass spectrometer estimates of the abundance of sulfur gases are correct, earth-like models for the bulk composition of Venus are seriously in error, and a far lower FeO content is required for Venus.

Lewis, J. S.↗

NASA NTRS1980

Transonic rotor noise: Theoretical and experimental comparisons

Two complementary methods of describing the high speed rotor noise problem are discussed. The first method uses the second order transonic potential equation to define and characterize the nature of the aerodynamic and acoustic fields and to explain the appearance of radiating shock waves. The second employs the Ffowcs Williams and Hawkings equation to successfully calculate the acoustic far field. Good agreement between theoretical and experimental waveforms is shown for transonic hover tip Mach numbers from 0.8 to 0.9.

Schmitz, F. H.↗

NASA NTRS1980

Effects of boundary-layer treatment on cryogenic wind-tunnel controls

Various techniques of realizing the desired boundary layer wall mass removal are considered in order to obtain the desired flow field over the model for various airfoils. The complementary problem of overall thermodynamic equilibrium maintenance created by the side wall boundary layer bleed is also addressed.

Balakrishna, S.↗

NASA NTRS1978

C-MOS array design techniques

The entire complement of standard cells and components, except for the set-reset flip-flop, was completed. Two levels of checking were performed on each device. Logic cells and topological layout are described. All the related computer programs were coded and one level of debugging was completed. The logic for the test chip was modified and updated. This test chip served as the first test vehicle to exercise the standard cell complementary MOS(C-MOS) automatic artwork generation capability.

Feller, A.↗

NASA NTRS1981

Effect of load introduction on graphite epoxy compression specimens

Compression testing of modern composite materials is affected by the manner in which the compressive load is introduced. Two such effects are investigated: (1) the constrained edge effect which prevents transverse expansion and is common to all compression testing in which the specimen is gripped in the fixture; and (2) nonuniform gripping which induces bending into the specimen. An analytical model capable of quantifying these foregoing effects was developed which is based upon the principle of minimum complementary energy. For pure compression, the stresses are approximated by Fourier series. For pure bending, the stresses are approximated by Legendre polynomials.

Reiss, R.↗

NASA NTRS1981

Satellite altimetric measurements of the ocean. Report of the TOPEX Science Working Group

The scientific usefulness of satellite measurements of ocean topography for the study of ocean circulation was investigated. The following topics were studied: (1) scientific problems which use altimetric measurements of ocean topography; (2) the extent in which in situ measurements are complementary or required; (3) accuracy, precision, and spatial and temporal resolutions which are required of the topographic measurements; (4) errors associated with measurement techniques; and (5) influences of these errors on scientific problems. An operational system for measuring ocean topography, was defined and the cost of conducting such a topographic experiment, was estimated.

Stewart, R.↗

NASA NTRS1981

NASA-OAST/JPL high efficiency thermionic conversion studies

Efforts were made to develop a thermionic energy conversion TEC technology appropriate for nuclear electric propulsion missions. This space TEC effort was complementary to the terrestrial TEC studies sponsored by the Department of Energy which had the goal of topping fossil fuel power plants. Thermionic energy conversion was a primary conversion option for space reactors because of its: (1) high operating temperature; (2) lack of moving parts; (3) modularity; (4) established technology; and (5) development potential.

Source record↗

NASA NTRS1981

An IUE's eye view of cool-star outer atmospheres

Three topics are discussed which together demonstrate the power of the IUE to probe the occurrences of chromospheres and coronas in the cool half of the HR diagram. These are: (1) the complementary low dispersion and echelle observing modes; (2) Mg II h and k: chromospheric cooling and width luminosity correlation; and (3) empirical correlations among chromospheric, transition region, and coronal emission. The spectra of alpha Centauri (G2 V + K1 V) and Capella (G6 III + F9 III) are compared with that of the Sun and recent low dispersion surveys of cool star emission in the 1150 A to 2000 A short wavelength region are summarized.

Ayres, T. R.↗

NASA NTRS1981

Development of an orthotropic hole element

A finite element was developed which adequately represents the state of stress in the region around a circular hole in orthotropic material experiencing reasonably general loading. This was achieved with a complementary virtual work formulation of the stiffness and stress matrices for a square element with center circular hole. The assumed stress state provides zero shearing stress on the hole boundary, so the element is suitable for problems involving load transfer without friction. The element has been implemented in the NASTRAN computer program, and sample problem results are presented.

Smith, C. V.↗

NASA NTRS1981

The outlook for precipitation measurements from space

To provide useful precipitation measurements from space, two requirements must be met: adequate spatial and temporal sampling of the storm and sufficient accuracy in the estimate of precipitation intensity. Although presently no single instrument or method completely satisfies both requirements, the visible/IR, microwave radiometer and radar methods can be used in a complementary manner. Visible/IR instruments provide good temporal sampling and rain area depiction, but recourse must be made to microwave measurements for quantitative rainfall estimates. The inadequacy of microwave radiometer measurements over land suggests, in turn, the use of radar. Several recently developed attenuating-wavelength radar methods are discussed in terms of their accuracy, dynamic range and system implementation. Traditionally, the requirements of high resolution and adequate dynamic range led to fairly costly and complex radar systems. Some simplications and cost reduction can be made; however, by using K-band wavelengths which have the advantages of greater sensitivity at the low rain rates and higher resolution capabilities. Several recently proposed methods of this kind are reviewed in terms of accuracy and system implementation. Finally, an adaptive-pointing multi-sensor instrument is described that would exploit certain advantages of the IR, radiometric and radar methods.

Atlas, D.↗

NASA NTRS1980

Initial coastal zone color scanner imagery

The characteristics of the Nimbus-7 Coastal Zone Color Scanner are presented and the atmospheric correction and bio-optical algorithms are reviewed. Comparison of imagery before and after atmospheric correction shows that water features such as color fronts and small scale eddies can be retrieved even through a hazy and horizontally inhomogeneous atmosphere. Imagery is also presented to show that features revealed in color are sometimes completely absent from simultaneous thermal imagery implying that color and thermal imagery can provide complementary rather than redundant information.

Gordon, H. R.↗

NASA NTRS1980

Early lunar petrogenesis, oceanic and extraoceanic

An attempt is made to ascertain which (if any) pristine nonmare rocks, other than KREEPy ones, are not cumulates from the magma ocean. It is noted that the only pristine rocks having bulk densities low enough to have formed by floating above the magma ocean are the ferroan anorthosites, which are easily recognizable as a discrete subset of pristine rocks in general, on the basis of mineral composition relationships. The other class of pristine nonmare rocks, the Mg-rich rocks, did not form from the same magma that produced the ferroan anorthosites. It is suggested that they were formed in layered noritic-troctolitic plutons. These plutons, it is noted, were apparently intruded at, or slightly above, the boundary between the floated ferroan anorthosite crust and the underlying complementary mafic cumulates. It is thought that the parental magmas of the plutons may have arisen by partial melting of either deep mafic cumulates from the magma ocean or a still deeper, undifferentiated primordial layer that was not molten during the magma ocean period.

Warren, P. H.↗

NASA NTRS1980

Radio occultation measurements of turbulence in the Venus atmosphere by Pioneer Venus

As in the cases of Mariner 5 and 10 and Venera 9, the Pioneer Venus radio occultation measurements of Venus show an upper region of turbulence located in the vicinity of 60 km. Estimates of the deduced intensity of turbulence are consistent with the upper bound obtained earlier from the complementary Pioneer Venus probe measurements. Comparison with the Pioneer Venus in situ temperature measurements of 1 km scale size also shows very good agreement. It is clear that for scale sizes smaller than the Fresnel size (approximately 1 km), the refractive index irregularities are represented by a continuum of scale sizes having a spatial wave number spectrum that is power law and close to Kolmogorov. These irregularities are elongated in the horizontal direction (axial ratios are large, greater than approximately 10). The fact that the upper region of turbulence coincides with a region of high stability marked by one or more peaks in the stability profile suggests that the turbulence is associated with trapped gravity waves. The amplitude scintillations appear to increase poleward of about 70 deg which is interpreted as an increase in turbulence level with latitude.

Woo, R.↗

NASA NTRS1981

Planetary science with Space Telescope

The capabilities of the Space Telescope observatory which will comprise a 2.4 m primary mirror scheduled for launch into low earth orbit in late 1983 by the Shuttle are discussed. Attention is given to the first generation of science instruments, including two imaging systems, two complementary spectrographs, a high-speed photometer, and a fine guidance/astrometry system. A specific observing program, an intercomparison of Uranus and Neptune, is examined in detail.

Caldwell, J.↗

NASA NTRS1981

Spatial distribution of energetic particles in the distant magnetotail

The spatial distribution of energetic particles in the distant magnetotail is analyzed by using identical sets of two complementary energetic particle experiments aboard the IMP 7 and 8 spacecraft. It is noted that the combined IMP 7 and 8 data set provides nearly 10 years of satellite observation. The quantitative distributions of energetic electrons in two energy ranges and energetic protons are given in terms of occurrence frequency and the average particle flux intensity over an 80 earth radii x 70 earth radii plane perpendicular to the sun-earth line. A particle distribution in the shape of an O with a crossbar over the solar magnetospheric YZ plane in the antisolar direction is clearly demonstrated at all energies and for both species. It is pointed out that the O part of the distribution corresponds to the magnetosheath region and that the crossbar is the average plasma sheet configuration. A distinct, species dependent, dawn-dusk asymmetry in particle distribution is observed in the plasma sheet and, to a lesser extent, in the magnetosheath.

Meng, C.-I.↗

NASA NTRS1981

Use of imaging radar for geology and archeology

Imaging radar is shown to be a useful sensor for geological analysis as a standal one sensor in clouded regions or as a complementary data source with visible NIR systems. Radar image tone is a function of the radar system parameters (imaging geometry, frequency, polarization) and a function of the target (local slope, electrical properties, and surface roughness). Substantial topographic texture enhancement can be achieved for large scale features by using specular returns associated with steep-incidence radars or shadows associated with grazing-incidence systems. Texture enhancement also allows radar to image lineaments and archeological features, such as canals and causeways. Future multispectral radars may achieve better discrimination of subresolution structures. Seasat radar images of several geographic locations are provided.

Daily, M.↗

NASA NTRS1981

Boron and beryllium in Gamma Geminorum

Observations have been made of the B II resonance line at 1362 A in the A0 IV star Gamma Gem with the Princeton spectrometer on the Copernicus satellite at a spectral resolution of 0.05 A. Complementary ground-based observations of the Be II resonance lines at 3130 and 3131 A have been made at Mauna Kea Observatory with a comparable resolution. A model-atmosphere abundance analysis has been done which includes the effects of the lines that blend with the B II and Be II lines. Previous data on Alpha Lyr and Alpha CMa for B II (which blends with a V III feature) have been reanalyzed with the help of new photographic and Reticon data from Mauna Kea which enable the determination of the V abundance. The results show that Gamma Gem is depleted in B by a factor of 5-10 relative to Alpha Lyr and other normal B stars and depleted in Be by at least a factor of four. By comparison, the hot Am star Alpha CMa is B-deficient by about three orders of magnitude and Be-deficient by at least fifteen times. It is suggested that the abundance deficiencies are due to diffusion, and that Alpha CMa is intrinsically a slow rotator, and Gamma Gem is a slightly evolved slow rotator where some, but not all, of the B and Be has resurfaced.

Boesgaard, A. M.↗