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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 379 records · Page 21
All sourcesNASA NTRSDOE OSTI
NASA NTRS1980

Downslope movement of material on Deimos

Viking Orbiter images have shown downslope movement of loose material to be an important surface process on Deimos. Loose surface material moves downslope from prominent ridges and accumulates in topographic lows. In some areas, up to 10 m of surface material have been removed; in others, craters up to 200 m in diameter have been filled completely by material moving downslope. Brighter material associated with, and probably derived from crater rims, also moves downslope and forms tapered streamers up to 3 km in length which appear as prominent features on the satellite. The mechanism for downslope movement is uncertain, but thermal creep, micrometeroroid bombardment and impact-related seismic shaking may be involved. Certain craters show conspicuous infilling even though their prominent rims should prevent material moving downslope from reaching their interiors. Such fill must have been emplaced ballistically - the amounts of sediment suggest that over half of all ejecta produced on Deimos are retained on the satellite. Phobos appears to retain little ejecta and shows little evidence of downslope movement of debris.

Thomas, P.↗
NASA NTRS1981

Analysis and simulation of a magnetic bearing suspension system for a laboratory model annular momentum control device

A linear analysis and the results of a nonlinear simulation of a magnetic bearing suspension system which uses permanent magnet flux biasing are presented. The magnetic bearing suspension is part of a 4068 N-m-s (3000 lb-ft-sec) laboratory model annular momentum control device (AMCD). The simulation includes rigid body rim dynamics, linear and nonlinear axial actuators, linear radial actuators, axial and radial rim warp, and power supply and power driver current limits.

Groom, N. J.↗
NASA NTRS1980

Method for horizontally growing ribbon crystal

A high speed method for forming ribbon crystal of desired width and thickness is characterized by drawing out the ribbon through a space whose distance is 5.7 times that of the thickness of the grown ribbon. The ribbon is drawn out between the molten body of the lower surface and the tip of the upper surface of the seed crystal and growing crystal. The ribbon growing at the tip of the seed crystal is drawn out horizontally and centrifugally by controlling the amount of cooling and heating. The temperature is maintained about equal to the upper surface of the outlets from which the molten substance is drawn, at least in certain portions of the crucible rim, the rim is elevated to prevent dropping of the molten raw material.

Kudo, B.↗
NASA NTRS1980

Some important geometrical features of conic-section-generated offset reflector antennas

Geometrical characteristics of conic-section-generated offset reflectors are studied in a unified fashion. Some unique geometrical features of the reflector rim constructed from the intersection of the reflector surface and a cone or cylinder are explored in detail. It is found that the intersection curve (rim) of the rotationally generated conic-section reflector surface and a circular cone with its tip at the focal point is always a planar curve and has a circular projection on the focal plane only for the offset parabolic reflector. Furthermore, in this case, the line going through the center of the circle, parallel to the focal axis, and the central axis of the cone do not intersect the reflector surface at the same point. Numerical results are presented to demonstrate some unique features of offset parabolic reflectors.

Jamnejad-Dailami, V.↗
NASA NTRS1981

Circular feature among dunes of the Great Sand Sea, Egypt

A circular crater, about 4 kilometers in diameter and located at 24.2 deg N, 26.4 deg E, was discovered in Landsat images among the linear dunes of the Great Sand Sea, Egypt. The crater has a sharp and crenulated rim crest, a terraced wall, a discontinuous inner structure (approximately 1.6 kilometers in diameter), and a few rim blocks. Its morphological and morphometric characteristics are similar to those of meteorite impact craters and other circular structures on the moon and the terrestrial planets. Because of its interaction with windblown sand, it is particularly comparable with craters on Mars.

El-Baz, F.↗
NASA NTRS1982

Dual-Alloy Disks are Formed by Powder Metallurgy

High-performance disks have widely varying properties from hub to rim. Dual property disk is fabricated using two nickel-base alloys, AF-115 for rim and Rene 95 for hub. Dual-alloy fabrication may find applications in automobiles, earth-moving equipment, and energy conversion systems as well as aircraft powerplants. There is potential for such applications as shafts, gears, and blades.

Harf, F. H.↗
NASA NTRS1982

Hot isostatically pressed manufacture of high strength MERL 76 disk and seal shapes

The feasibility of using MERL 76, an advanced high strength direct hot isostatic pressed powder metallurgy superalloy, as a full scale component in a high technology, long life, commercial turbine engine were demonstrated. The component was a JT9D first stage turbine disk. The JT9D disk rim temperature capability was increased by at least 22 C and the weight of JT9D high pressure turbine rotating components was reduced by at least 35 pounds by replacement of forged Superwaspaloy components with hot isostatic pressed (HIP) MERL 76 components. The process control plan and acceptance criteria for manufacture of MERL 76 HIP consolidated components were generated. Disk components were manufactured for spin/burst rig test, experimental engine tests, and design data generation, which established lower design properties including tensile, stress-rupture, 0.2% creep and notched (Kt = 2.5) low cycle fatigue properties, Sonntag, fatigue crack propagation, and low cycle fatigue crack threshold data. Direct HIP MERL 76, when compared to conventionally forged Superwaspaloy, is demonstrated to be superior in mechanical properties, increased rim temperature capability, reduced component weight, and reduced material cost by at least 30% based on 1980 costs.

Eng, R. D.↗
NASA NTRS1982

Instrument manual for the retarding ion mass spectrometer on Dynamics Explorer-1

The retarding ion mass spectrometer (RIMS) for Dynamics Explorer-1 is an instrument designed to measure the details of the thermal plasma distribution. It combines the ion temperature determining capability of the retarding potential analyzer with the compositional capabilities of the mass spectrometer and adds multiple sensor heads to sample all directions relative to the spacecraft ram direction. This manual provides a functional description of the RIMS, the instrument calibration, and a description of the commands which can be stored in the instrument logic to control its operation.

Fields, S. A.↗
NASA NTRS1981

The Retarding Ion Mass Spectrometer on Dynamics Explorer-A

The thermal component of the magnetospheric plasma plays a key role in magnetosphere-ionosphere coupling processes, acting as a strong influence on ionospheric structure at low altitudes and as a source and modifier of the hotter plasma population at high altitudes. The Retarding Ion Mass Spectrometer (RIMS) instrument on Dynamics Explorer-A is designed to measure this important thermal plasma component. Using a combination of retarding potential analysis and magnetic ion mass spectrometer techniques, the RIMS instrument will measure the bulk plasma parameters of ion density (0.1 to 1,000,000 ions/cu cm), temperature (0-45 eV), and bulk flow (greater than 0.5 km/sec) in the inner plasmasphere and ionosphere, and the specific ion pitch angle and energy spectral characteristics in the outer plasmasphere and plasma trough for a mass range of 1-32 amu. The energy and mass spectral step sequences, as well as the multiplexing of the resultant data, can be tailored to accomplish a variety of thermal ion measurements throughout the inner magnetosphere.

Chappell, C. R.↗
NASA NTRS1980

Variations in interior morphology of 15-20 km lunar craters - Implications for a major subsurface discontinuity

Craters vary in morphology as a function of crater diameter, age, and mode of origin. This study concentrates on the morphology of young lunar impact craters within a limited size range. Elimination of morphologic variations generally attributed to crater size or age leaves a small population which should nearly reflect the varying properties of the lunar substrate. The sample consists of 17 craters 15-20 km in diameter with both simple and complex morphologies. While depth/diameter ratios do not obviously differ between mare and highland subsets, apparent depth, rim height, and profile data do differ distinctly. Highland craters tend to be deep, simple, and bowl-shaped. Mare craters tend to be shallow and flat-floored. Rim heights of complex mare craters are typically greater than those of simple craters. Differences of highland and mare crater morphologies are attributed to variations in the thickness of the lunar megaregolith. Highland craters in this size range do not penetrate the megaregolith. The depth and morphology of complex craters are controlled by the discontinuity at the transition from highly brecciated megaregolith to more coherent crystalline material of the upper crust.

De Hon, R. A.↗
NASA NTRS1980

Cratering flow fields - Implications for the excavation and transient expansion stages of crater formation

Theoretical depths, volumes of excavation, hinge radii, ejection angles and transient structural rim uplifts are calculated, for comparison with experimental and field data from impact and explosion craters, by means of a Maxwell Z-model cratering flow field originating at non-zero depths-of-burst. It is found that the formation of a hinge, about which the coherent ejecta flap rotates at the rim of the transient crater, divides material in the flow field into ejected and downward and outward-driven portions. Ejected material originates from an excavation cavity whose geometry is distinct from that of the transient crater. The shallow depths of excavation both observed in impact and explosion craters and predicted by the Z-model flow fields imply that thickness estimates of such lunar geologic units as the maria basalts, which are determined by assuming that excavation depths are similar to (1) final or (2) transient crater depths, must be reduced by factors of two to three respectively. It is concluded that lunar basin excavation cavities exhibit proportional growth, and have maximum depths of excavation near 0.1 the diameter of the basin transient crater.

Croft, S. K.↗
NASA NTRS1982

The intercrater plains of Mercury and the Moon: Their nature, origin and role in terrestrial planet evolution. Crater statistical data

The total number of craters within a bin of mean diameter, and the number of craters of each degradational type within that bin are tabulated. Rim-to-rim diameters were measured at arbitrary azimuths for rectified photos or photos taken at vertical incidence (most lunar photos), and at azimuths paralleling a local tangent to the limb for oblique images.

Leake, M. A.↗
NASA NTRS1983

Analytical and experimental study of a standing torus with normal loads

Finite element analysis is applied to study the large deflection and stress of a thin-walled pressurized torus loaded by normal contact with a plane. Experimentally determined stresses are compared to those resulting from finite element analysis at various meridional and circumferential coordinates of the torus, including the footprint area. Circumferential strains compare favorably while meridional strains are higher in the finite element analysis, probably due to slippage of the boundary at the rim. The STAGS finite element computer program was used. The purpose of the study was to evaluate the various program options for structural loading, for material modeling, for stress analysis, and for grid refinement. The experimental model, a thin-walled rubber tube mounted on a steel cylindrical rim, provided measured results to compare with various analytical trade-offs. It was found that there was almost no difference in predicted deflections or stress distributions between linear and nonlinear material description. However, the difference between linear analysis and that of geometric nonlinearities utilizing incremental loading was marked.

Mack, M. J., Jr.↗
NASA NTRS1981

Data base management system analysis and performance testing with respect to NASA requirements

Several candidate Data Base Management Systems (DBM's) that could support the NASA End-to-End Data System's Integrated Data Base Management System (IDBMS) Project, later rescoped and renamed the Packet Management System (PMS) were evaluated. The candidate DBMS systems which had to run on the Digital Equipment Corporation VAX 11/780 computer system were ORACLE, SEED and RIM. Oracle and RIM are both based on the relational data base model while SEED employs a CODASYL network approach. A single data base application which managed stratospheric temperature profiles was studied. The primary reasons for using this application were an insufficient volume of available PMS-like data, a mandate to use actual rather than simulated data, and the abundance of available temperature profile data.

Martin, E. A.↗
NASA NTRS1982

Volumetric analysis of complex lunar craters - Implications for basin ring formation

The crater to basin transition in complex lunar craters is characterized by combining morphological and volumetric analyses of their central peaks with subsurface data from terrestrial complex impact structures which suggest that the amount of uplifted material, as judged from its depth of origin, continues to increase with increasing rim diameter. This latter phenomenon implies that a redistribution of uplifted material away from a centralized peak may occur in the larger craters. The morphological and volumetric changes described occur over a rim diameter range of 51-80 km, which is considerably lower than the previously proposed range for the crater to basin transition of 140-175 km. Evidence is given in support of a crater to basin transition which begins at 51-80 km, and is characterized by a relative reduction in central peak volume and a development of rings of floor roughening which may be precursors of peak ring development.

Hale, W. S.↗
NASA NTRS1983

Refractory inclusions in the Murchison meteorite

Although melilite-rich and feldspathoid-bearing inclusions have been revealed in the Murchison C2 chondrite by mineralogical and petrographic studies, none of these is identical to the inclusions found to date in Allende. Each type of inclusion is characterized by a different suite of alteration products and/or rim layers from all the other types, indicating modification of the inclusions in a wide range of different physicochemical environments after their primary crystallization. All of these inclusions contain some iron-free rim phases which could not have formed by reaction of the inclusions with fluids in the Murchison parent body, because the latter would presumably have been rich in oxidized iron.

Macpherson, G. J.↗
NASA NTRS1983

Characteristics of thermal and suprathermal ions associated with the dayside plasma trough as measured by the dynamics explorer retarding ion mass spectrometer

The thermal and suprathermal ion populations present in the refilling regions after a magnetic storm are examined using retarding ion mass spectrometer (RIMS) data from the Dynamics Explorer 1 spacecraft. The RIMS instrument is described, and data are presented and discussed in detail for the outer plasmasphere, plasmapause, depleted dayside magnetosphere, and dayside cusp. Three distinct populations were observed: thermal ions, warm anisotropic plasma, and the polar wind. The characteristics of these populations are considered, including the densities, temperatures, and density ratios. Aspects of the ionospheric plasma outflow are discussed, including the field-aligned flow speed, the ionospheric plasma escape flux, plasmaspheric refilling, and wave-particle phenomena.

Sojka, J. J.↗
NASA NTRS1984

Morphology of buried craters: Lava thickness estimates by simulated flooding

Partially and completely buried craters on planetary surfaces are used as probes to determine the thickness and extent of the overlying material as well as the composition of underlying terrain units. Rims of craters protruding through mare basalts on the Moon have been used extensively by DeHon (1977, 1979) to develop isopach maps of both the circular and irregular maria. Such estimates are possible because of Apollo topographic data and the extensive coverage by Lunar Orbiter photographs at various sun angles. On planetary surfaces without such data, however, shadow measurements can only be made by pixel listings with appropriate assumptions concerning support data. In addition, high resolution geochemical data is not available to determine whether the exposed crater rim is composed of material dissimilar from the lavas. Because of the need for lava thickness data, flooding of lunar mare and highland craters was simulated in order to determine empirical relationships between dimensions observed in orbital images and the thickness of the lava.

Maxwell, T. A.↗