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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 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

Microscale fluctuations in the solar wind

Theoretical constraints on the interpretation of fluctuations (either propagating or stationary) in the interplanetary medium are reviewed, with emphasis on the important differences between the properties of hydromagnetic waves (and stationary structures) in collisionless and in collision-dominated plasmas, and on the possible roles of Landau damping and nonlinear effects in determining the interplanetary fluctuation spectrum. Hypotheses about the origins of the fluctuations and their influence on the large-scale properties of the solar wind are reviewed.

Barnes, A. A., Jr.↗
NASA NTRS1974

Evaluation of a new jet flap propulsive-lift system for turbofan-powered STOL transports

A large-scale STOL transport model with a new jet flap propulsive-lift system was subject to wind-tunnel testing. Aerodynamically, this IBF system combines the benefits of the jet flap and the mechanical flap with boundary layer control. Structurally, it creates its own spanwise air duct with the deflection of the mechanical flap. An additional short-chord control flap, located at the jet-flap exit, provides a powerful means for flight path and lateral controls. The results show that the overall effectiveness of this flap system compares well with other jet flap propulsive-lift systems. A preliminary study based on the wind-tunnel data was made on a medium-size IBF STOL jet transport configuration for a typical-military mission. This study showed that the IBF results in a configuration with a relatively low T/W ratio, making the system an attractive candidate for future designs.

Chin, Y. T.↗
NASA NTRS1974

Fine-scale structure of a cold hydrogen layer

Neutral-hydrogen absorption-line interferometer observations are reported for five continuum radio sources situated behind an extensive layer of cold interstellar H I gas. In contrast to low-spatial-resolution emission-line observations reported earlier which show the large-scale uniformity of the layer, the high-spatial-resolution absorption-line observations reveal variations in the velocity and density within the layer. The new results together with the old indicate the apparent coexistence of a large-scale mechanism for triggering the formation of cold hydrogen and an instability mechanism leading to small-scale irregularities.

Baker, P. L.↗
NASA NTRS1974

Stability region maximization by decomposition-aggregation method

This work is to improve the estimates of the stability regions by formulating and resolving a proper maximization problem. The solution of the problem provides the best estimate of the maximal value of the structural parameter and at the same time yields the optimum comparison system, which can be used to determine the degree of stability of the Skylab. The analysis procedure is completely computerized, resulting in a flexible and powerful tool for stability considerations of large-scale linear as well as nonlinear systems.

Siljak, D. D.↗
NASA NTRS1974

Kinematics of the Orion A molecular cloud

Examination of the velocity structure of J = 1 to J = 0 emission of CO in the Orion A molecular cloud, including a presentation of extended strip maps in both declination and right ascension intersecting at the position of peak intensity. The results in declination show evidence for large-scale rotation, while the right ascension maps show features which can be interpreted as gravitational condensations. The observed rotation is found to be sufficient to support a density equal to that estimated for the cloud (an H2 number density of about 2000 per cu cm).

Linke, R. A.↗
NASA NTRS1965

Lunar geothermal power - Some problems and potentials

Power from geothermal deposits on earth is an established fact, with plant capacities ranging from a few kilowatts to several hundred megawatts. The increasing evidence for contemporary volcanic and fumarolic activity on the moon lends strong support to the validity of the concepts of utilizing geothermal fluids as a source of lunar power. Geothermal energy, whatever the size of installation desired, will probably not be an energy source during early exploratory operations, because of the inherent uncertainty in developing natural resources. On the other hand, the attractiveness of geothermal concepts with their abundant potential for byproduct fuel and life-support production, plus the potential for large continuous power outputs, suggests chat the location and testing of areas of geothermal potential should be an early goa] for lunar exploration efforts. This paper briefly describes the chemical and structural properties of geothermal deposits and outlines the differences expected between lunar and terrestrial deposits and their surface expressions. The problems of finding geothermal deposits, and of then deciding upon the probable subsurface exploitive testing for initial production are suggested and the problems inherent in large-scale geothermal development and utilization are indicated.

ENERGY SOURCE↗
NASA NTRS1972

Analysis of large-scale Martian topography variations. I - Data preparation from earth-based radar, earth-based CO2 spectroscopy, and Mariners 6 and 7 CO2 spectroscopy.

Using direct radar ranging of surface heights on Mars and spectrophotometric observations of absorptions produced by carbon dioxide molecules in the Martian atmosphere, data have been obtained on Martian topographical variations at spatial resolutions ranging from about 100 to 1000 km. These data have been studied and analyzed. As a result, a surface height contour map has been produced which clearly reveals a structural complex of blocks and basins whose distribution enhances the magnitude of low-degree surface harmonics. It is emphasized that Mars possesses unexpectedly pronounced topography which can have important geophysical consequences.

Wells, R. A.↗
NASA NTRS1974

The differential rotation of the solar surface

The large-scale flow in the solar convection zone is discussed. The objective is to deduce from observation the principal physical balances in the governing equations. The simplest set of equations that seem potentially realistic are utilized. It is assumed that magnetic fields are negligible, that mixing-length theory gives an accurate representation of the mean structure, and that rigid-body rotation exists at the base. It is deduced that the zonal glow is geostrophic, the meridional flow is controlled by friction, and diffusive heating balances advective cooling due to vertical motion. Next, a detailed calculation of the latitude profile of surface angular velocity is performed, based on approximate equations containing only the principal balances, and agrees well with observation. Finally, it is demonstrated that the amplitude of the flow may be determined by the constraint that the net equatorward angular momentum flux vanish. The conclusions are consistent with the hypothesis that the flow is primarily a single large axisymmetric convection cell in each hemisphere.

Gierasch, P. J.↗
NASA NTRS1973

Applicability of ERTS-1 to Montana geology

The author has identified the following significant results. A detailed band 7 ERTS-1 lineament map covering western Montana and northern Idaho has been prepared and is being evaluated by direct comparison with geologic maps, by statistical plots of lineaments and known faults, and by field checking. Lineament patterns apparent in the Idaho and Boulder batholiths do not correspond to any known geologic structures. A band 5 mosaic of Montana and adjacent areas has been laid and a lineament annotation prepared for comparison with the band 7 map. All work to date indicates that ERTS-1 imagery is very useful for revealing patterns of high-angle faults, though much less useful for mapping rock units and patterns of low-angle faults. Large-scale mosaics of U-2 photographs of three test sites have been prepared for annotation and comparison with ERTS-1 maps. Mapping of Quaternary deposits in the Glacial Lake Missoula basin using U-2 color infrared transparencies has been successful resulting in the discovery of some deposits not previously mapped. Detailed work has been done for Test Site 354 D using ERTS-1 imagery; criteria for recognition of several rock types have been found. Photogeologic mapping for southeastern Montana suggest Wasatch deposits where none shown of geologic map.

Weidman, R. M.↗
NASA NTRS1974

The thermal state and internal structure of Mars

The evolution and state of the interior of Mars are studied through the use of theoretically calculated thermal history and density models. Invoking melting of an Fe-FeS mixture permits initial core formation within the first billion years. At the present time the core radius ranges from about 1300 to 1800 km, depending on composition, and the core is liquid even if the composition is varied from the eutectic. Large-scale differentiation of the silicates occurs in the last 2 b.y. When the mean density is 3.96 g/cu cm, the radius is 3389 km, and the moment of inertia factor is 0.377, the density models indicate high mantle densities near 3.74 g/cu cm. Thus an FeO content of about 29% is implied, consistent with the production of a low-viscosity magma. Chemical models of the Martian mantle indicate a composition primarily of olivine with about 56% forsterite.

Johnston, D. H.↗
NASA NTRS1974

Venus - Atmospheric motion and structure from Mariner 10 pictures

The Mariner 10 television cameras imaged the planet Venus in the visible and near ultraviolet for a period of 8 days at resolutions ranging from 100 meters to 130 kilometers. The general pattern of the atmospheric circulation in the upper tropospheric/lower stratospheric region is displayed in the pictures. Atmospheric flow is symmetrical between north and south hemispheres. The equatorial motions are zonal (east-west) at approximately 100 meters per second, consistent with the previously inferred 4-day retrograde rotation. Angular velocity increases with latitude. The subsolar region, and the region downwind from it, show evidence of large-scale convection that persists in spite of the main zonal motion. Dynamical interaction between the zonal motion and the relatively stationary region of convection is evidenced by bowlike waves.

Murray, B. C.↗
NASA NTRS1971

The earth and the moon /Harold Jeffreys Lecture/.

The internal structures of the earth and the moon are compared in the light of the latest extensive data on the earth structure, mobility of the earth outer layers, and the properties of lunar crust. The Monte Carlo method is applied to develop an earth model by a stepwise process beginning with a random distribution of two elastic velocities and the density as a function of de pth. Lunar seismic, magnetic, and rock analysis data are used to infer the properties of the moon. The marked planetological contrast between the earth and the moon is shown to consist in that the earth is highly differentiated and still undergoes a large-scale differentiation, while the moon has lost its volatiles in its early history and has a cold dynamically inactive shell which has been without basic changes for three billion years.

Press, F.↗
NASA NTRS1972

Review of sonic-boom simulation devices and techniques.

Research on aircraft-generated sonic booms has led to the development of special techniques to generate controlled sonic-boom-type disturbances without the complications and expense of supersonic flight operations. This paper contains brief descriptions of several of these techniques along with the significant hardware items involved and indicates the advantages and disadvantages of each in research applications. Included are wind tunnels, ballistic ranges, spark discharges, piston phones, shock tubes, high-speed valve systems, and shaped explosive charges. Specialized applications include sonic-boom generation and propagation studies and the responses of structures, terrain, people, and animals. Situations for which simulators are applicable are shown to include both small-scale and large-scale laboratory tests and full-scale field tests. Although no one approach to simulation is ideal, the various techniques available generally complement each other to provide desired capability for a broad range of sonic-boom studies.

Edge, P. M., Jr.↗
NASA NTRS1972

Physical structure of the moon.

The moon has a much thicker lithosphere than the earth, as predicted by thermal models and as evidenced by the support of mascons, lack of surface folding, etc. More in question is whether the moon has a core (more properly, asthenosphere) of high temperature, as suggested by the volcanism 1.0-1.3 b.y. after origin and by the large low-degree harmonics in the gravity field. The moon is like the earth in having a large offset of center-of-mass from center-of-volume, apparently the residue of an early convective overturn associated with large-scale differentiation. The moon differs significantly from the earth in its lower iron content, gross homogeneity, much slower rate-of-change, and closer approach to isostatic equilibrium in the sense of stress-difference magnitudes.

Kaula, W. M.↗
NASA NTRS1972

Large-scale negative polarity magnetic fields on the sun and particle-emitting flares

Some observational facts about the large-scale patterns formed by solar negative polarity magnetic fields during the 19th and 20th cycles of solar activity are presented. The close relation of the position of occurrence of very large flares accompanied by cosmic ray and PCA events as well as other phenomena of solar activity during the declining part of the 19th cycle of the regularities in the internal structure of large scale negative polarity features are demonstrated.

Bumba, V.↗
NASA NTRS1973

On the decentralized control of large-scale systems

The decentralized control of stochastic large scale systems was considered. Particular emphasis was given to control strategies which utilize decentralized information and can be computed in a decentralized manner. The deterministic constrained optimization problem is generalized to the stochastic case when each decision variable depends on different information and the constraint is only required to be satisfied on the average. For problems with a particular structure, a hierarchical decomposition is obtained. For the stochastic control of dynamic systems with different information sets, a new kind of optimality is proposed which exploits the coupled nature of the dynamic system. The subsystems are assumed to be uncoupled and then certain constraints are required to be satisfied, either in a off-line or on-line fashion. For off-line coordination, a hierarchical approach of solving the problem is obtained. The lower level problems are all uncoupled. For on-line coordination, distinction is made between open loop feedback optimal coordination and closed loop optimal coordination.

Chong, C.↗
NASA NTRS1973

Internal constitution and evolution of the moon.

The composition, structure and evolution of the moon's interior are narrowly constrained by a large assortment of physical and chemical data. Models of the thermal evolution of the moon that fit the chronology of igneous activity on the lunar surface, the stress history of the lunar lithosphere implied by the presence of mascons, and the surface concentrations of radioactive elements, involve extensive differentiation early in lunar history. This differentiation may be the result of rapid accretion and large-scale melting or of primary chemical layering during accretion; differences in present-day temperatures for these two possibilities are significant only in the inner 1000 km of the moon and may not be resolvable.

Solomon, S. C.↗