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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 811 records · Page 45
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

New interpretations of extraterrestrial Lyman-alpha observations.

The solar Lyman-alpha radiation pressure affects the orbits and the velocities of the interstellar particles entering the solar system. This leads to enhanced particle losses in the heliosphere, since particles spend a longer time crossing it. This causes a stronger decrease of the density with decreasing distances from the sun than had been calculated without accounting for the radiation pressure. Furthermore, the emission pattern of the solar Lyman-alpha radiation is anisotropic and rotates with the sun in a 27-day period. This causes a temporal change in the location of the intensity extrema. At the same time it produces hydrogen density anisotropies with extrema deviating in their directions from those which had been calculated without consideration of the radiation pressure.

Blum, P. W.↗
NASA NTRS1972

Mercury - Interpretation of optical observations.

The spectral reflectivity of Mercury has constant positive slope from 0.32 to 1.05 microns, except for the possibility of an absorption feature in the infrared. The reflectivity curve matches closely the curve for lunar upland and mare regions. Thus, the surface of Mercury is probably covered with lunar-like soil rich in dark glasses of high iron and titanium content. If the absorption band is real, pyroxene is the dominant mafic mineral.

Mccord, T. B.↗
NASA NTRS1973

Cosmic ray electrons of E greater than 1 Gev - Some new measurements and interpretations.

In the summer of 1971 new measurements were made of the primary electron spectrum from 1 to 20 GeV with an electron spectrometer telescope at Fort Churchill. This telescope has been calibrated by using electrons and pions of 0.5 to 15 GeV at the Stanford Linear Accelerator in early 1971 and again in 1972. The calibration results suggest that the events observed are due to interactions of high-energy protons. The measured primary electron spectrum is uncomfortably close to that calculated for secondary electrons produced by the interaction of cosmic ray nuclei with interstellar hydrogen in the Galaxy, and therefore the question of the origin of the high-energy electrons is reopened. The problem of the age of cosmic ray electrons must also be reexamined if the measured spectrum is found to extend to still higher energies.

Webber, W. R.↗
NASA NTRS1972

Analysis and interpretation of lunar laser altimetry.

About 4.5 revolutions of laser altimetry were obtained by Apollo 15. This altimetry indicates a 2-km displacement of the center of mass from the center of figure toward the earthside. The terrae are quite rough, with frequent changes of 1 km or more in successive altitudes at about 33-km intervals. The mean altitude of terrae above maria is about 3 km with respect to the center of mass, indicating a thickness of about 24 km for a high-alumina crust. The maria are extremely level, with elevations varying not more than plus or minus 150 m about the mean over some stretches of 200 to 600 km. However, different maria have considerably different mean elevations. The largest unanticipated feature found is a 1400 km wide depression centered at about 180 deg longitude, and 2 km deep with respect to a 1737-km sphere (about 6 km deep with respect to the surrounding terrae). This basin has the appearance of typical terrae, although there are indications of a ring structure of about 600-km radius in the Orbiter photography. Altitudes across circum-Orientale features suggest that Mare Orientale is also a deep basin. The data appear to corroborate a model of early large-scale differentiation of a crust, followed a considerable time later by short intense episodes of mare filling with low viscosity lavas.

Kaula, W. M.↗
NASA NTRS1973

Profiles of emission lines in Be stars. II - Interpretation of the long-period V/R variation.

Investigation of the long-period V/R variation in some Be stars studied by McLaughlin (1966) and others, based on the assumption that the variation is caused by the apsidal motion of an elliptical ring in which the emitting atoms revolve around the star according to Kepler's laws of motion. The results indicate that the behavior of the V/R variation depends upon both the eccentricity and the lateral extent of the gaseous ring. However, if the ring is narrower than a certain limit, the dependence on the width is negligible. In such a case, the eccentricity of the ring can be determined by the observed amplitude of the V/R variation. Based on this model, the radial-velocity curves of both emission edges and central absorption are derived. It is found that they all have the same amplitude, which also depends on the eccentricity, and that all are changing in phase with the V/R variation.

Huang, S.-S.↗
NASA NTRS1973

Pioneer 8 observations and interpretations of sixteen interplanetary shock waves observed in 1968.

A study has been made of 16 interplanetary shock waves observed in 1968 by Pioneer 8 at large distances from earth. A comparison with the shapes of interplanetary shock fronts obtained by De Young and Hundhausen (1971) suggests that in general the ejection of flare gas occurs within a cone of half-angle between 30 and 60 deg. For near-earth events a deflection of the shock front has been observed, possibly owing to an interaction with the bow shock. The average duration of the postshock perturbation is about 20 hours. Strong magnetic fields and rapid fluctuations occur during the first 6 to 12 hours. Electric field perturbations in the VLF band are also noted during these periods. There is limited evidence for one corotating shock in these data.

Bavassano, B.↗
NASA NTRS1973

Geometric interpretation of the ratio of overall diameter to rim crest diameter for lunar and terrestrial craters.

An empirical linear relationship has been established by Pike (1967) between the overall diameter and the rim crest diameter for rimmed, flat-floored as well as bowl-shaped, lunar and terrestrial craters formed by impact and explosion. A similar relationship for experimentally formed fluidization craters has been established by Siegal (1971). This relationship is examined in terms of the geometry of the crater and the slope angles of loose materials. The parameter varies from 1.40 to 1.65 and is found to be dependent on mean interior flat floor radius, exterior and interior rim slope angles, angle of aperture of the crater cone, and the volume fraction of crater void accounted for in the rim. The range of the observed parameter can be understood in terms of simple crater geometry by realistic values of the five parameters.

Siegal, B. S.↗
NASA NTRS1973

Thermal-bremsstrahlung interpretation of cluster X-ray sources.

Analysis of the X-ray data for the extended sources in Coma, Perseus, and Virgo in terms of an isothermal gas-sphere model emitting thermal-bremsstrahlung radiation. It is found that the gas distribution is somewhat less centrally condensed than the galaxies, and that the gas mass is generally a small fraction of the binding mass of each cluster. In the case of the Coma cluster, approximately one-eighth of the binding mass (with an uncertainty of about 50%) may be in the form of hot gas at 100,000,000 K if H sub zero = 50 km/sec/Mpc.

Lea, S. M.↗
NASA NTRS1973

An interpretation of the WC stars.

The difference in separation that is characteristic of WN and WC binaries is shown to provide an explanation for the observation that spectra of WC stars are apparently unaffected by the presence of a companion, whereas the spectra of WN stars in binary systems appear to be significantly different from those of single stars with a comparable degree of excitation. WC binaries are sufficiently widely separated for the WC atmosphere to remain unperturbed by the presence of the companion, while the companions of WN stars are closer and gravitational perturbation, reflection effects, and limitations of the atmosphere's extent by the Roche lobe may each have an effect.

Smith, L. F.↗
NASA NTRS1973

Observation of cosmic-ray particles with Z of 50 or greater and interpretation of the charge spectrum.

Large areas of plastic detectors and nuclear emulsions were exposed to the primary cosmic radiation on two high-altitude balloon flights in May 1968 and September 1969. From measurements on the tracks found in the scanning of the plastic detectors, events with charges Z greater than 50 were selected, and these data were consolidated with those from our earlier flights. Several conclusions can be drawn from the observed charge spectrum. The detection of trans-bismuth nuclei confirms earlier observations of these particles in the cosmic rays. However, no trans-uranium particles were observed. Detailed features of the charge spectrum cannot be explained by nuclei from r-process nucleosynthesis alone. Although the addition of particles following s-process abundances yields improved agreement, the spectrum appears more complicated than would result from a simple combination of r- and s-process abundances with identical propagation histories.

Blanford, G. E., Jr.↗