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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 271 records · Page 15
All sourcesNASA NTRSDOE OSTI
NASA NTRS1991

Microwave and physical properties of sea ice in the winter marginal ice zone

Surface-based active and passive microwave measurements were made in conjunction with ice property measurements for several distinct ice types in the Fram Strait during March and April 1987. Synthesis aperture radar imagery downlinked from an aircraft was used to select study sites. The surface-based radar scattering cross section and emissivity spectra generally support previously inferred qualitative relationships between ice types, exhibiting expected separation between young, first-year and multiyear ice. Gradient ratios, calculated for both active and passive data, appear to allow clear separation of ice types when used jointly. Surface flooding of multiyear floes, resulting from excessive loading and perhaps wave action, causes both active and passive signatures to resemble those of first-year ice. This effect could possibly cause estimates of ice type percentages in the marginal ice zone to be in error when derived from aircraft- or satellite-born sensors.

Tucker, W. B., III↗
NASA NTRS1991

The physical properties of double degenerate common proper motion binaries

Spectral types and spectrophotometry are presented for 21 double degenerate (DD) common proper motion binaries, along with estimates of their colors, absolute visual and bolometric magnitudes, and cooling ages. The oldest pairs in the sample are 9 x 10 to the 9th yr; the differential cooling ages range from 0.01 to 0.84. The median and mean separations of the DD pairs are 426 and 407 Au, respectively, both apparently smaller than the WD+MS values. The average UVW motions and velocity dispersions are significantly larger than the average velocities and dispersions associated with selected samples of single white dwarfs and MS+WD binaries when the latter are restricted to the same color/Mv range as the DD systems. This may be a result of the dynamical inflation of the velocity dispersion of DD systems due to their extremely ancient total stellar ages.

Sion, Edward M.↗
NASA NTRS1991

Magellan - Electrical and physical properties of Venus' surface

Magellan probes Venus'surface by 12.6-cm-wavelength vertical and oblique radar scattering and measures microwave thermal emission. Emissivity and root-mean-square slope maps between 330 deg and 30 deg E and 90 deg N and 80 deg S are dissimilar, although some local features are exceptions. Inferred surface emissivities typically are 0.85, but vary from 0.35 at Maxwell to 0.95 northeast of Gula Mons and other locations. Lowest emissivities appear in topographically high areas; this relation suggests that a phase change or differences in chemical weathering occur at about 6055-kilometer radius. Initial results indicate that there are significant variations in the surface scattering function.

Tyler, G. Leonard↗
NASA NTRS1991

Constraints on the physical properties of optical bullets in SS 433

The present study discusses possible mechanisms for continuously heating the H-alpha emitting bullets of SS 433 out to distances of 5 x 10 to the 14th cm and for turning off this emission at 10 to the 15th. Various observational contraints are used to establish bounds on permissible solutions in terms of the two key bullet parameters, mass, and angular radius seen from the central source. The analysis is carried out for the mathematically simplest case of uniform spherical bullets. For radiative heat of such bullets by starlight, solutions are found to exist only for the very massive bullets with about 0.03 radians, which are highly implausible on the grounds of the large implied mean kinetic luminosity of about 10 to the 41st ergs/s. It is concluded that collisional interaction is the most likely mechanism for heating the optical bullets of SS 433. The effects of these constraints being fragmented rather than uniform, and being elongated rather than spherical are discussed.

Brown, John C.↗
NASA NTRS1991

Physical properties of the regolith of Phobos

Results of two experiments performed onboard the Phobos spacecraft are presented: spectrophotometry in the 300-600 nm range and thermal radiometry, i.e., intrinsic thermal emission in the 6-50 micron range. The thermophysical characteristics of the Phobos regolith are indicated by a thermal inertia coefficient which is similar to that of the moon. The reflectivity of the regolith is inhomogeneous in the region investigated and depends mostly on the relief features, primarily craters and their age. The expected similarity of the reflection spectra with those of carbonacenous chondrites was not confirmed.

Ksanofomaliti, L.↗
NASA NTRS1991

Physical properties of cryovolcanic brines: Applications to the evolution of Ganymede

Carbonaceous chondrites contain abundant veins of water soluble salts, including carbonates and hydrated sulfates of Mg, Ca, Na, Ni, and Fe. These constitute over 1/4 of the mass of the meteorite Orgueil. Magnesium sulfate is the most abundant salt, constituting nearly half the mass of all salt components combined (anhydrous), and 73 pct. of the highly water soluble salts. The assumption that icy satellites and asteroids contain rock compositionally similar to carbonaceous chondrites suggests that salts may be important in the cryoigneous evolution of icy satellites and asteroids. Ordinary chondrites, an alternative rock component of icy satellites, lack abundant salts, although their anhydrous silicate assemblages are unstable with respect to water and would react to produce salts upon initial melting of ice. Some basic physiochemical properties are reviewed of likely cryovolcanic brines and how the existence of soluble salts in Ganymede might affect its structure and evolution is considered. Observations indicate late stage (post heavy bombardment and post tectonic) volcanism on Ganymede. The highly fluid character of Ganymedian volcanism is consistent with extrusions of either water or salt water brines.

Kargel, Jeffrey S.↗
NASA NTRS1991

Physical properties of lava flows on the southwest flank of Tyrrhena Patera, Mars

Tyrrhena Patera (TP) (22 degrees S, 253.5 degrees W), a large, low-relief volcano located in the ancient southern highlands of Mars, is one of four highland paterae thought to be structurally associated with the Hellas basin. The highland paterae are Hesperian in age and among the oldest central vent volcanoes on Mars. The morphology and distribution of units in the eroded shield of TP are consistent with the emplacement of pyroclastic flows. A large flank unit extending from TP to the SW contains well-defined lava flow lobes and leveed channels. This flank unit is the first definitive evidence of effusive volcanic activity associated with the highland paterae and may include the best preserved lava flows observed in the Southern Hemisphere of Mars. Flank flow unit averages, channelized flow, flow thickness, and yield strength estimates are discussed. Analysis suggests the temporal evolution of Martian magmas.

Crown, David A.↗
NASA NTRS1992

Measurement of surface physical properties and radiation balance for KUREX-91 study

Biophysical properties and radiation balance components were measured at the Streletskaya Steppe Reserve of the Russian Republic in July 1991. Steppe vegetation parameters characterized include leaf area index (LAI), leaf angle distribution, mean tilt angle, canopy height, leaf spectral properties, leaf water potential, fraction of absorbed photosynthetically active radiation (APAR), and incoming and outgoing shortwave and longwave radiation. Research results, biophysical parameters, radiation balance estimates, and sun-view geometry effects on estimating APAR are discussed. Incoming and outgoing radiation streams are estimated using bidirectional spectral reflectances and bidirectional thermal emittances. Good agreement between measured and modeled estimates of the radiation balance were obtained.

Walter-Shea, Elizabeth A.↗
NASA NTRS1992

Physical properties of Deucalionis, Eos, Xanthe-type units in the central equatorial region of Mars

Classification and mapping of surficial units in the central equatorial region of Mars (30 degrees N to 20 degrees S, 57 degrees E to 75 degrees W) using enhanced color images and Mars Consortium data, identified three distinct, high albedo, relatively red surficial units in regions with intermediate to high thermal inertias. These units have distinctive properties and morphologies, occur in different, well-defined areas, and show different seasonal and secular patterns of albedo change. Deucalionis units occupy the classical albedo area of Deucalionis Regio, south of Meridiani Sinus and Sabaeus Sinus, and adjacent areas. Eos forms a bright band that separates the dark, relatively blue Meridiani-type units that dominate the southern part of the study area from intermediate albedo, relatively red Oxia units common in the north. Xanthe forms moderately bright, relatively red, Type 1B crater-streaks and uniform sheet-deposits in and adjacent to parts of Chryse Planitia, including the Viking 1 landing site. Xanthe is always associated with Oxia deposits, and has significantly lower albedos than the Eos materials, which it can be confused with.

Strickland, Edwin L., III↗
NASA NTRS1992

Physical properties of Meridiani Sinus-type units in the central equatorial region of Mars

Classification and mapping of surficial units in the central equatorial region of Mars (30 degrees N to 20 degrees S, 57 degrees E to 75 degrees W) using enhanced color images and Mars Consortium data identified four major color/albedo units in the dark, reddish-gray regions that form the classical dark albedo markings of Mars, including Meridiani Sinus. The darkest, least red (relatively 'blue') materials form splotches (some with dune forms) in craters, inter-crater depressions, and part of Valles Marineris. These form the 'Dark Blue' Meridiani unit. Abundant materials that have higher albedos and are somewhat redder than the 'Dark Blue' unit have uniquely high green/(violet + red) color ratios in Viking Orbiter images. These materials, named 'Green-blue' Meridiani surround and mix with 'Dark Blue' Meridiani patches and are abundant on crater rims and local elevations. Discontinuous, patchy deposits with still higher albedos and much redder colors have morphologies classified of the Type Ib bright depositional dust streaks and sheets that were classified by Thomas et al. These dust deposits, which appear to be optically thin and patchy and are darker and not as red as other Type Ib dust deposits on Mars, and their Meridiani substrates, were designated the 'Red' Meridiani unit. Distinctive deposits that form highly eroded mesas and escarpments in northern Meridiani Sinus were named 'Light Blue' Meridiani, since they are not as red as other materials with moderately high albedos. Large areas dominated by these units form Meridiani Province in the central equatorial region of Mars.

Strickland, Edwin L., III↗
NASA NTRS1992

Physical properties of Oxia/Lunae Planum and Arabia-type units in the central equatorial region of Mars

Classification and mapping of surficial units in the central equatorial region of Mars Consortium data identified the relatively dark but 'red' materials that cover Lunae Planum and surround the Meridiani materials of Oxia Palus inertia region of Arabia. Oxia Province consists of the regions dominated by the characteristically dark 'red' Oxia materials, but it includes darker streaks and splotches of relatively 'blue' Meridiani materials and brighter 'red' deposits of dust belonging to Eos Province (the bright 'red' border between Oxia and regional Meridiani deposits to the south) and Xanthe Province (the moderately bright 'red' dust deposits in western Chryse Planitia and its vicinity, including the VL-1 landing site). Two Oxia units were recognized: a darker unit present on Lunae Planum and east of Oxia Palus that have intermediate to high inertias. Oxia Province surrounds the extremely low thermal inertia Arabia Province in the east part of the study area, and occurs as isolated patches within Arabia (often including splotches of Meridiani materials within the Oxia patches). Arabia Province's materials have been widely interpreted as unconsolidated dust deposits which are currently forming at this stage of Mars' precessional climate cycle, although the persistence of stable, moderately strong albedo contracts among Arabia materials has not been addressed in those models. A systematic interpretation of Oxia and Arabia Province materials based on currently available remote sensing data is given.

Strickland, Edwin L., III↗
NASA NTRS1992

Physical properties of concrete made with Apollo 16 lunar soil sample

This paper describes the first phase of the long-term investigation for the construction of concrete lunar bases. In this phase, petrographic and scanning electron microscope examinations showed that the morphology and elemental composition of the lunar soil made it suitable for use as a fine aggregate for concrete. Based on this finding, calcium aluminate cement and distilled water were mixed with the lunar soil to fabricate test specimens. The test specimens consisted of a 1-in cube, a 1/2-in cube, and three 0.12 x 0.58 x 3.15-in beam specimens. Tests were performed on these specimens to determine compressive strength, modulus of rupture, modulus of elasticity, and thermal coefficient of expansion. Based on examination of the material and test results, it is concluded that lunar soil can be used as a fine aggregate for concrete.

Lin, T. D.↗
NASA NTRS1993

Physical properties and evolutionary time scales of disks around solar-type and intermediate mass stars

Recent observations of circumstellar disks and their evolutionary timescales are reviewed. It is concluded that disks appear to be a natural outcome of the star-formation process. The disks surrounding young stars initially are massive, with optically thick structures comprised of gas and micron-sized grains. Disk masses are found to range from 0.01 to 0.2 solar masses for solar-type PMS stars, and from 0.01 to 6 solar masses for young, intermediate mass stars. Massive, optically thick accretion disks have accretion rates between 10 exp -8 and 10 exp -6 solar masses/yr for solar type PMS stars and between 10 exp -6 and 10 exp -4 solar masses/yr for intermediate stars. The results suggest that a significant fraction of the mass comprising the star may have passed through a circumstellar accretion disk.

Strom, Stephen E.↗
NASA NTRS1993

Dimethylsulfide/cloud condensation nuclei/climate system - Relevant size-resolved measurements of the chemical and physical properties of atmospheric aerosol particles

The mass and number relationships occurring within the atmospheric dimethylsulfide/cloud condensation nuclei (CCN)/climate system, using simultaneous measurements of particulate phase mass size distributions of nss SO4(2-), methanesulfonic acid (MSA), and NH4(+); number size distributions of particles having diameters between 0.02 and 9.6 microns; CCN concentrations at a supersaturation of 0.3 percent; relative humidity; and temperature, obtained for the northeastern Pacific Ocean in April and May 1991. Based on these measurements, particulate nss SO4(2-), MSA, and NH4(+) mass appeared to be correlated with both particle effective surface area and number in the accumulation mode size range (0.16 to 0.5 micron). No correlations were found in the size range below 0.16 micron. A correlation was also found between nss SO4(2-) mass and the CCN number concentration, such that a doubling of the SO4(2-) mass corresponded to a 40 percent increase in the CCN number concentration. However, no correlation was found between MSA mass and CCN concentration.

Quinn, P. K.↗