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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 199 records · Page 11
All sourcesNASA NTRSDOE OSTI
NASA NTRS1978

Industrial ion source technology

An analytical model was developed to describe the development of a coned surface texture with ion bombardment and simultaneous deposition of an impurity. A mathematical model of sputter deposition rate from a beveled target was developed in conjuction with the texturing models to provide an important input to that model. The establishment of a general procedure that will allow the treatment of manay different sputtering configurations is outlined. Calculation of cross sections for energetic binary collisions was extened to Ar, Kr.. and Xe with total cross sections for viscosity and diffusion calculated for the interaction energy range from leV to 1000eV. Physical sputtering and reactive ion etching experiments provided experimental data on the operating limits of a broad beam ion source using CF4 as a working gas to produce reactive species in a sputtering beam. Magnetic clustering effects are observed when Al is seeded with Fe and sputtered with Ar(?) ions. Silicon was textured at a micron scale by using a substrate temperature of 600 C.

Kaufman, H. R.↗
NASA NTRS1978

The asteroids

The asteroids are small rocky bodies that orbit in modestly eccentric and inclined orbits, mainly between the orbits of Mars and Jupiter. With the comets, they are the only known population of residual planetesimals from the earliest epochs of solar system history. The observational characteristics of asteroids are discussed, taking into account aspects of photometry, rotations, masses and densities, spectrophotometry and surface compositions, surface textures and regoliths, size distribution, and erosion and fragmentation occurring as a result of interasteroidal collisions. Questions of dynamics and orbital evolution are investigated and ramifications for planetary evolution are explored. Attention is given to asteroids as planetesimals, aspects of early orbital evolution, the geochemical evolution of asteroids, commensurabilities and Kirkwood gaps, secular resonances, the material transport from the asteroid belt, Poisson's theorem, planetary masses, catalogs and selection effects, families, and Apollo, Amor, and Mars-crossing asteroids.

Chapman, C. R.↗
NASA NTRS1980

Modification of the electrical and optical properties of polymers

An electron bombardment argon ion source is used to form textured surfaces on polymide and fluorinated ethylene propylene polymers. This treatment improves the optical and electrical properties so that these polymers may be used in industrial and space applications.

Mirtich, M. J.↗
NASA NTRS1980

Tissue response to peritoneal implants

Peritoneal implants were fabricated from poly 2-OH, ethyl methacrylate (HEMA), polyetherurethane (polytetramethylene glycol 1000 MW, 1,4 methylene disocynate, and ethyl diamine), and untreated and sputter treated polytetrafluoroethylene (PTFE). The sputter treated PTFE implants were produced by an 8 cm diameter argon ion source. The treated samples consisted of ion beam sputter polished samples, sputter etched samples (to produce a microscopic surface cone texture) and surface pitted samples (produced by ion beam sputtering to result in 50 microns wide by 100 microns deep square pits). These materials were implanted in rats for periods ranging from 30 minutes to 14 days. The results were evaluated with regard to cell type and attachment kinetics onto the different materials. Scanning electron microscopy and histological sections were also evaluated. In general the smooth hydrophobic surfaces attracted less cells than the ion etched PTFE or the HEMA samples. The ion etching was observed to enhance cell attachment, multinucleated giant cell (MNGC) formation, cell to cell contact, and fibrous capsule formation. The cell responsed in the case of ion etched PTFE to an altered surface morphology. However, equally interesting was the similar attachment kinetics of HEMA verses the ion etched PTFE. However, HEMA resulted in a markedly different response with no MNGC's formation, minimal to no capsule formation, and sample coverage by a uniform cell layer.

Picha, G. J.↗
NASA NTRS1979

Einstein Observatory /HEAO-B/ mirror design and performance

The mirrors for the Einstein Observatory represent a substantial advance in the state of the art X-ray optics, and have been tested more thoroughly than previous telescopes. The image is characterized by a narrow, wavelength independent core, and broad energy dependent wings. The width of the core is about that expected from mechanical and visible light measurements taken during fabrication and assembly. The wings of the response function are caused by microscopic surface scattering, but only a qualitative understanding of this process exists. Improvement in surface texture to reduce the wide angle scatter is the most urgent task in the development of large X-ray optics. The mirrors have survived the experiment integration period and launch, and are performing in orbit as they performed upon the ground.

Van Speybroeck, L. P.↗
NASA NTRS1981

Recent Progress Towards Predicting Aircraft Ground Handling Performance

The significant progress which has been achieved in development of aircraft ground handling simulation capability is reviewed and additional improvements in software modeling identified. The problem associated with providing necessary simulator input data for adequate modeling of aircraft tire/runway friction behavior is discussed and efforts to improve this complex model, and hence simulator fidelity, are described. Aircraft braking performance data obtained on several wet runway surfaces is compared to ground vehicle friction measurements and, by use of empirically derived methods, good agreement between actual and estimated aircraft braking friction from ground vehilce data is shown. The performance of a relatively new friction measuring device, the friction tester, showed great promise in providing data applicable to aircraft friction performance. Additional research efforts to improve methods of predicting tire friction performance are discussed including use of an instrumented tire test vehicle to expand the tire friction data bank and a study of surface texture measurement techniques.

Yager, T. J.↗
NASA NTRS1981

Experiment K-314: Fetal and neonatal rat bone and joint development following in Utero spaceflight

Infant rat limb specimens from Soviet and U.S. ground-based studies were examined by radiography, macrophotography, histologic sectioning and staining and scanning electron microscopy. A comparison was conducted between vivarium and flight-type diets suggesting that nutritional obesity may adversely affect pregnancy. Data were obtained on maturation of ossification centers, orientation of collagen fibers in bone, tendon and ligaments, joint surface texture and spatial relationships of bones of the hind limb. Computer reconstructions of the knee and hip show promise as a means of investigating the etiology of congenital hip dislocation.

Sabelman, E. E.↗
NASA NTRS1982

A primer on sulfur for the planetary geologist

Sulfur has been proposed as the dominant composition for the volcanic material on Io. Sulfur is a complex element which forms many intramolecular and intermolecular allotropes exhibiting a variety of physical properties. Cyclo-S8 sulfur is the most abundant and stable molecular form. The important molecular species within liquid sulfur change in concentration with temperature. Concentrations of the allotropes control the physical properties of the melt. Discontinuities in density, viscosity, and thermal properties reflect the polymerization process within liquid sulfur. Variations in the melting point are related to autodissociation of the liquid. Many solids forms of sulfur have been identified but only orthorhombic alpha and monoclinic beta sulfur, both composed of cyclo-S8 sulfur, are stable under terrestrial conditions. Physical properties of solid sulfur are dependent on the allotrope and, in some cases, the thermal history. Three natural terrestrial sulfur flows are described: (1) Siretoko-Iosan, Japan; (2) Volcan Azufre, Galapagos Islands; and (3) Mauna Loa, Hawaii. All of the flows are associated with fumarolic areas and are considered to have formed by the melting and mobilization of sulfur deposits. Surface textures of the flows indicate a behavior of molten sulfur similar to that of silicate lava. Channels, rivulets, and lobate edges were described for the flows. The solidification of man-made sulfur flows formed as part of the Frasch mining process by which sulfur is removed from the subsurface in a liquid state is described.

Theilig, E.↗
NASA NTRS1981

Rock type discrimination techniques using Landsat and Seasat image data

Results of a sedimentary rock type discrimination project using Seasat radar and Landsat multispectral image data of the San Rafael Swell, in eastern Utah, are presented, which has the goal of determining the potential contribution of radar image data to Landsat image data for rock type discrimination, particularly when the images are coregistered. The procedure employs several images processing techniques using the Landsat and Seasat data independently, and then both data sets are coregistered. The images are evaluated according to the ease with which contacts can be located and rock units (not just stratigraphically adjacent ones) separated. Results show that of the Landsat images evaluated, the image using a supervised classification scheme is the best for sedimentary rock type discrimination. Of less value, in decreasing order, are color ratio composites, principal components, and the standard color composite. In addition, for rock type discrimination, the black and white Seasat image is less useful than any of the Landsat color images by itself. However, it is found that the incorporation of the surface textural measures made from the Seasat image provides a considerable and worthwhile improvement in rock type discrimination.

Blom, R.↗
NASA NTRS1983

Interpretation of integrated-disk photometry of Callisto and Ganymede

The Lumme-Bowell (1981) theory has been used to interpret the integrated phase curves of Callisto and Ganymede, and it is noted that while the theory explains the brightness angles of these satellites up to about 80 deg solar phase angle, the observed brightness drops off at larger angles more rapidly than predicted. It is suggested that this discrepancy is due to the fact that single regolith particles must have phase functions which are much more elongated in the forward or backward scattering directions than is allowed for by the Lumme-Bowell theory. The hemispheric asymmetry in Callisto's surface texture can be explained by invoking the formation of an ice film on the trailing side, consistent with Voyager detailed photometry and thermometry of Callisto.

Pang, K.↗
NASA NTRS1983

Influence of the microstructure on the corrosion behavior of magnetron sputter-quenched amorphous metallic alloys

The microstructure and corrosion behavior of magnetron sputter deposited amorphous metallic films of (Mo6ORu40)82B18 under varying sputtering atmospheres have been investigated. The microstructural details and topology of the films have been studied by scanning electron microscopy and correlated with the deposition conditions. By reducing the pressure of pure argon gas, the characteristic features of rough surface and columnar growth full of vertical voids can be converted into a mirror-smooth finish with very dense deposits. Films deposited in the presence of O2 or N2 exhibit columnar structure with vertical voids. Film deposited in pure argon at low pressure show remarkably high corrosion resistance due to the formation of a uniform passive surface layer. The influence of the microstructure and surface texture on the corrosion behavior is discussed.

Thakoor, A. P.↗
NASA NTRS1983

Application of image processing technology to problems in manuscript encapsulation

The long term effects of encapsulation individual sheets of the Codex Hammer were investigated. The manuscript was simulated with similar sheets of paper which were photographed under repeatable raking light conditions to enhance their surface texture, encapsulated in plexiglas, cycled in an environmental test chamber, and rephotographed at selected intervals. The film images were digitized, contrast enhanced, geometrically registered, and apodized. An FFT analysis of a control sheet and two experimental sheets indicates no micro-burnishing, but reveals that the ""mesoscale'' deformations with sizes 8mm are degrading monotonically, which is of no concern. Difference image analysis indicates that the sheets were increasingly stressed with time and that the plexiglas did not provide a sufficient environmental barrier under the simulation conditions. The relationship of these results to the Codex itself is to be determined.

Glackin, D. L.↗
NASA NTRS1984

Friction and wear behavior of aluminum and composite airplane skins

Friction and wear behavior was determined for small skin specimens under abrasive loading conditions typical of those occurring on the underside of a transport airplane during emergency belly landing. A test apparatus consisting of a standard belt sander provided the sliding surface. Small test specimens constructed of aluminum, standard graphite-epoxy composite, aramid-epoxy composite, and toughened-resin composites were tested undar a range of pressures, belt velocities, and belt-surface textures. The effects of these test variables on the wear rate and the coefficient of friction are discussed and comparisons are made between the composite materials and aluminum. The effect of fiber orientation in the composite materials on wear rate was also investigated. In addition, tests were performed in which thermocouples were imbedded into the various test specimens to obtain temperature-time histories during abrasion.

Jackson, K. E.↗
NASA NTRS1984

Experiments on water/melt explosions, nature of products, and models of dispersal

Experiments were carried out in a steel pressure device using controlled amounts of water and thermite melt to examine the mechanical energy released on explosive mixing following the initial contact of the two materials. An experimental design was used to allow the direct calculation of the mechanical energy by the dynamic lift of the device as recorded both optically and physically. A large number of experiments were run to accurately determine the optimum mixture of water and melt for the conversion of thermal to mechanical energy. The maximum efficiency observed was about 12% at a water/thermite mass ratio of 0.50. These experiments are the basis for the development of models of hydroexplosions and melt fragmentation. Particles collected from the experimental products are similar in size and shape to pyroclasts produced by much larger hydrovolcanic explosions. Melt rupture at optimum ratios produces very fine particles whereas rupture at high or low water/melt ratios produces large melt fragments. Grain surface textures in the experimental products are also related to the water/melt ratio and the mechanism of explosive mixing. It is thus possible to have qualitative information about the nature of the explosion from the sizes and shapes of the fragments produced.

Sheridan, M. F.↗
NASA NTRS1984

Age discrimination among basalt flows using digitally enhanced LANDSAT imagery

Digitally enhanced LANDSAT MSS data were used to discriminate among basalt flows of historical to Tertiary age, at a test site in Northwestern Saudi Arabia. Spectral signatures compared favorably with a field-defined classification that permits discrimination among five groups of basalt flows on the basis of geomorphic criteria. Characteristics that contributed to age definition include: surface texture, weathering, color, drainage evolution, and khabrah development. The inherent gradation in the evolution of geomorphic parameters, however, makes visual extrapolation between areas subjective. Therefore, incorporation of spectrally-derived volcanic units into the mapping process should produce more quantitatively consistent age groupings.

Blodget, H. W.↗
NASA NTRS1985

Io: Precise Comparison of Voyager Spectral Curves with Laboratory Measurements

In order to derive more accurate normal reflectances of regions on Io, the near-opposition (alpha 10 deg) photometry of a set of regions on the 20 W face of the satellite, the face with the most complete near-opposition Voyager imaging coverage was analyzed. Sixty-eight regions were chosen for study, each approximately 120 km on a side, and divided into three coherent color classes: white, orange, and polar brown regions. Derived Minneart parameters, while generally consistent with previous limb darkening determinations, show that: (1) for the white regions, k rises linearly with increasing B(0), which is the trend to be expected for normal materials; (2) the white regions are slightly limb brightened (k 0.5) at low wavelengths (low values of B(0)); and (3) k appears to drop with rising B(0) for the orange regions, contrary to the trend expected for most materials. Despite similar reflectances, there is one group of orange regions with large opposition surges and a second group showing significantly lower surges, possibly indicating differences in surface texture (porosity and/or particle size).

Simonelli, D. P.↗
NASA NTRS1985

Statistics of Aeolian Surface of Mars

Aeolian control of large scale surface texture is apparent in orbiter images from selected regions of Mars -- the polar areas, equatorial canyons, and some craters. At other locations on Mars there is evidence suggesting aeolian control on meter scales within a context provided by larger landforms.

Simpson, R. A.↗
NASA NTRS1985

Structure and properties of polyethylene films used in heavy lift balloons

The following features of five polyethylene films used by NASA in the construction of heavy lift balloons have been examined: molecular weight, molecular weight distribution, branching, melting behavior, density, surface texture, birefringence, orientation of crystalline regions, unlaxial deformation in the machine and transverse directions, and the effect of sample geometry and strain rate on deformation behavior. The goal of this exploratory study was to determine whether there are significant differences in any of the above mentioned features, or combination of features between the films. The acquisition of such information is a first step towards determining whether there are any specific correlations between film characteristics and the incidence of catastrophic failure of balloons during ascent through the troposphere. This exploratory study has resulted in the identification of similarities and differences between various features of the films.

Khoury, F.↗