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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 1,567 records · Page 87
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NASA NTRS1985

Heat transfer and fluid mechanics measurements in transitional boundary layer flows

Experimental results are presented to document hydrodynamic and thermal development of flat-plate boundary layers undergoing natural transition. Local heat transfer coefficients, skin friction coefficients and profiles of velocity, temperature and Reynolds normal and shear stresses are presented. A case with no transition and transitional cases with 0.68 percent and 2.0 percent free-stream disturbance intensities were investigated. The locations of transition are consistent with earlier data. A late-laminar state with significant levels of turbulence is documented. In late-transitional and early-turbulent flows, turbulent Prandtl number and conduction layer thickness values exceed, and the Reynolds analogy factor is less than, values previously measured in fully turbulent flows.

Wang, T.↗
NASA NTRS1985

Very high potassium (VHK) basalt - Complications in mare basalt petrogenesis

The first comprehensive report on the petrology and geochemistry of Apollo 14 VHK (Very High Potassium) basalts and their implications for lunar evolution is presented. The reported data are most consistent with the hypothesis that VHK basalts formed through the partial assimilation of granite by a normal low-Ti, high-Al mare basalt magma. Assimilation was preceded by the diffusion-controlled exchange of alkalis and Ba between basalt magma and the low-temperature melt fraction of the granite. Hypotheses involving volatile/nonvolatile fractionations or long-term enrichment of the source regions in K are inconsistent with the suprachondritic Ba/La ratios and low initial Sr-87/Sr-86 ratios of VHK basalt. An important implication of this conclusion is that granite should be a significant component of the lunar crust at the Apollo 14 site.

Shervais, J. W.↗
NASA NTRS1986

Optical modeling of stratopheric aerosols - Present status

A stratospheric aerosol optical model is developed which is based on a size distribution conforming to direct measurements. Additional constraints are consistent with large data sets of independently measured macroscopic aerosol properties such as mass and backscatter. The period under study covers background as well as highly disturbed volcanic conditions and an altitude interval ranging from the tropopause to about 30 km. The predictions of the model are used to form a basis for interpreting and intercomparing several diverse types of stratospheric aerosol measurement.

Rosen, J. M.↗
NASA NTRS1986

Discovery of a new short-period, eclipsing cataclysmic variable

Photometry and spectroscopy of a newly recognized 14th mag eclipsing cataclysmic variable, KPD 1911 + 1212 (= SVS 8130, V1315 Agl) are reported. The system exhibits deep (1.7 mag) eclipses with period 0.1397 day. The spectrum is that of a high-excitation old nova and shows dramatic variability of the emission line strengths through the eclipse. The profiles of the Balmer emission lines are also phase-dependent, with prominent absorption cores appearing briefly near the inferior conjunction of the emission line source. There is no direct evidence for the secondary. A preliminary determination of radial velocity variations at modest spectral resolution yields K = 132 + or - 26 km/s for the Balmer emission lines. A model is presented for the system consistent with current data, which implies a mass for the primary and secondary stars of 0.9 and 0.4 solar mass respectively and in inclination of i = 78 deg.

Downes, R. A.↗
NASA NTRS1986

The excitation of the iron K-alpha feature in solar flares

The relationship between the hard X-ray photon spectrum and the flux of iron K-alpha emission in a thick-target electron bombardment model is evaluated. Results are presented for various power-law hard X-ray spectra. These results are applied to two events observed with the Hard X-Ray Burst Spectrometer and the K-alpha channel of the X-Ray Polychromator Bent Crystal Spectrometer on the Solar Maximum Mission satellite. For one of the events, on March 29, 1980, at 09:18 UT, the K-alpha flux predicted for a thick-target nonthermal process is significant compared to the background fluorescent component, and the data are indeed consistent with an enhancement of the predicted amount. For the other event, on October 14, 1980 at 0.6:09 UT, the hard X-ray spectrum is so steep that no significant K-alpha flux is predicted for this process, and no enhancement is seen. It is concluded that the agreement between the predicted K-alpha flux and the observed magnitude of the K-alpha enhancement above the fluorescent background at the time of the large hard X-ray bursts lends support to a thick-target nonthermal interpretation of impulsive hard X-ray emission in solar flares.

Emslie, A. G.↗
NASA NTRS1986

Flared landing approach flying qualities. Volume 1: Experiment design and analysis

An inflight research study was conducted utilizing the USAF Total Inflight Simulator (TIFS) to investigate longitudinal flying qualities for the flared landing approach phase of flight. The purpose of the experiment was to generate a consistent set of data for: (1) determining what kind of commanded response the pilot prefers in order to flare and land an airplane with precision, and (2) refining a time history criterion that took into account all the necessary variables and their characteristics that would accurately predict flying qualities. The result of the first part provides guidelines to the flight control system designer, using MIL-F-8785-(C) as a guide, that yield the dynamic behavior pilots perfer in flared landings. The results of the second part provides the flying qualities engineer with a newly derived flying qualities predictive tool which appears to be highly accurate. This time domain predictive flying qualities criterion was applied to the flight data as well as six previous flying qualities studies, and the results indicate that the criterion predicted the flying qualities level 81% of the time and the Cooper-Harper pilot rating, within + or - 1, 60% of the time.

Weingarten, Norman C.↗
NASA NTRS1986

Flared landing approach flying qualities. Volume 2: Appendices

An in-flight research study was conducted utilizing the USAF/Total In-Flight Simulator (TIFS) to investigate longitudinal flying qualities for the flared landing approach phase of flight. A consistent set of data were generated for: determining what kind of command response the pilot prefers/requires in order to flare and land an aircraft with precision, and refining a time history criterion that took into account all the necessary variables and the characteristics that would accurately predict flying qualities. Seven evaluation pilots participated representing NASA Langley, NASA Dryden, Calspan, Boeing, Lockheed, and DFVLR (Braunschweig, Germany). The results of the first part of the study provide guidelines to the flight control system designer, using MIL-F-8785-(C) as a guide, that yield the dynamic behavior pilots prefer in flared landings. The results of the second part provide the flying qualities engineer with a derived flying qualities predictive tool which appears to be highly accurate. This time-domain predictive flying qualities criterion was applied to the flight data as well as six previous flying qualities studies, and the results indicate that the criterion predicted the flying qualities level 81% of the time and the Cooper-Harper pilot rating, within + or - 1%, 60% of the time.

Weingarten, Norman C.↗
NASA NTRS1986

Origins of the solar wind in the corona

The coronal origins of the solar wind are considered. Potential sources of low-speed wind which are consistent with current data, including streamers and the interfaces between them and other coronal regions, await mass flow measurements for confirmation. A Doppler-dimming technique utilizing a white-light coronagraph and UV coronal spectrometer is to be employed aboard the Space Shuttle SPARTAN program, and its usage on Ulysses may provide information on mass flows in streamers and their surroundings.

Withbroe, G. L.↗
NASA NTRS1987

Comet-solar wind interaction as viewed from the International Cometary Explorer Mission (ICE) and from the earth

An overview of large-scale plasma phenomena is presented based on results of the ICE spacecraft probing of comet Giacobini-Zinner and on worldwide submissions to the Large-Scale Phenomena Discipline Specialist Team of the International Halley Watch. Results indicate that the magnetic field capture and draping model, originated by Alfven, is correct. Examples of tail 'turn on' and evolution are presented with emphasis on the observed Disconnection Events (DEs). The sector boundary model of DEs is consistent with the data and a dramatic example of synergism between in situ data from the VEGAs and ground-based imagery for the DE originating March 8.6, 1986 is presented.

Brandt, John C.↗
NASA NTRS1986

Seven years of total ozone from the TOMS instrument - A report on data quality

Seven years of TOMS total ozone data are currently available. Recently a new ozone retrieval algorithm based on improved ozone absorption cross section was implemented that has introduced 6-7 percent discontinuity in the archived data sets at the end of the fifth year of instrument operation. Until all data are reprocessed with the new algorithm users can use a table of correction factors given in this paper to make the data set internally consistent. This paper also presents a comparison of TOMS results with Amundsen Scott Dobson station. Though the agrement in most years is good, in 1983-84 the Dobson station reported unusually high values of ozone while TOMS saw the very low ozone values associated with the Antarctica ozone hole.

Fleig, Albert J.↗
NASA NTRS1986

Evidence for global processing of complex visual displays

'Polar graphic' displays, in which changes in system status are represented by distortions in the form of a geometric figure, were presented to subjects, and reaction time (RT) to discriminate system status was recorded. Of interest was the extent to which reaction time showed evidence of global processing of these displays as the number of nodes and difficulty of discrimination were varied. When discrimination of system status was easy, RT showed no increase with increasing number of nodes, providing evidence of global processing. When discrimination was difficult, systematic differences in RT as a function of the number of nodes suggested the invocation of other (local) processes, although the data were not consistent with a node-by-node search process.

Munson, Robert C.↗
NASA NTRS1987

Atomic hydrogen in planetary nebulae

The authors searched for neutral atomic hydrogen associated with 22 planetary nebulae and three evolved stars in the 21 cm line at the Arecibo Observatory. Objects whose radial velocities permitted discrimination from Galactic H I were chosen for observation. Hydrogen was detected in absorption from IC 4997. From the measurements new low limits are derived to the mass of atomic hydrogen associated with the undetected nebulae. Radio continuum observations were also made of several of the nebulae at 12.6 cm. The authors reexamine previous measurements of H I in planetary nebulae, and present the data on a consistent footing. The question of planetary nebula distances is considered at length. Finally, implications of the H I measurements for nebular evolution are discussed and it is suggested that atomic hydrogen seen in absorption was expelled from the progenitor star during the final 1000 yr prior to the onset of ionization.

Schneider, Stephen E.↗
NASA NTRS1987

Evidence for variations in magma production along oceanic spreading centers - A critical appraisal

Recent geologic, geophysical, and geochemical studies of the oceanic lithosphere near fracture zones have resulted in the proposal that the 'magma budget,' defined as the amount of magma delivered to magma chambers or conduits beneath a spreading center for a given amount of spreading, decreases as fracture zones are approached. Seismic reflection and refraction studies indicate that the crust becomes anomalously thin near fracture zones, but reference must be made to the boundary between residual upper mantle peridotites and overlying cumulate rocks in order to assess potential variations in the magma budget. The position of this interface, however, generally is not constrained by geophysical studies. Geochemical variations in basaltic glasses collected near fracture zones are consistent with a decrease in partial melting as fracture zones are approached, but they could also be produced by variations in open-system magmatic processes with no change in the extent of partial melting. Although a decrease in the magma budget as fracture zones are approached is consistent with these data, so are alternative models that incorporate a constant magma budget.

Karson, J. A.↗
NASA NTRS1987

Evidence for variations in magma production along oceanic spreading centers - A critical appraisal

Recent studies of the oceanic lithosphere near fracture zones have resulted in the proposal that the 'magma budget', defined as the amount of magma delivered to magma chambers or conduits beneath a spreading center for a given amount of spreading, decreases as fracture zones are approached. Geochemical variations in basaltic glasses collected near fracture zones are consistent with a decrease in partial melting as fracture zones are approached, but they could also be produced by variations in open-system magmatic processes with no change in the extent of partial melting. Although a decrease in the magma budget as fracture zones are approached is consistent with these data, so are alternative models that incorporate a constant magma budget.

Karson, J. A.↗
NASA NTRS1982

Ion beam deposition of amorphous carbon films with diamond like properties

Carbon films were deposited on silicon, quartz, and potassium bromide substrates from an ion beam. Growth rates were approximately 0.3 micron/hour. The films were featureless and amorphous and contained only carbon and hydrogen in significant amounts. The density and carbon/hydrogen ratio indicate the film is a hydrogen deficient polymer. One possible structure, consistent with the data, is a random network of methylene linkages and tetrahedrally coordinated carbon atoms.

Angus, John C.↗
NASA NTRS1987

Shock overshoots revisited

The ISEE 1 and 2 magnetometer and solar wind data for about 65 quasi-perpendicular bow shocks were used to investigate the role played by low-frequency turbulence in the determination of magnetic field overshoots in collisionless shock waves. Overshoots calculated from both high-resolution data and data averaged to eliminate the effects of turbulence exhibited similar behavior, but the overshoots calculated from the averaged data were generally lower by a factor of 2. Moreover, the size of overshoots calculated from the high-resolution data increased much more strongly with Mach number than that of overshoots calculated from averaged data. The difference between overshoots measured by the two sets of data was generally consistent with the presence of a component of overshoot magnitude due to low-frequecy turbulence.

Mellott, M. M.↗
NASA NTRS1987

On the relationship of flare size and particle anisotropy in solar gamma-ray flares

The effects of radiation directivity on the interpretation of SMM gamma-ray flare observations. If the electron anisotropy is independent of flare size, the size distribution of 300 keV-1 Mev flare is much flatter than that of X-ray flares. This implies that larger flares have, on average, harder electron spectra. Distributions of electrons strongly peaked downward into the solar photosphere are not consistent with the data.

Dermer, Charles D.↗
NASA NTRS1987

PG 1346+082 - An interacting binary white dwarf system

PG 1346+082 is both a photometric and a spectroscopic variable, spanning the B-magnitude range 13.6-17.2. High-speed photometric data reveal rapid flickering in the low-state light curve. The system also shows spectroscopic variations, displaying broad shallow He I absorption lines at maximum light and a weak emission feature at He I (4471 A) at minimum light. Hydrogen lines are conspicuous by their absence. Is is concluded that PG 1346+082 is an interacting binary white dwarf system. Furthermore, because continuum fits to IUE high-state data suggest temperatures consistent with membership in the DB white dwarf instability strip, it is suggested that some of the photometric variations may arise from pulsations.

Wood, M. A.↗