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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 613 records · Page 34
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NASA NTRS1982

The Blue Angel. I - The mineralogy and petrogenesis of a hibonite inclusion from the Murchison meteorite

Results are presented of a mineralogical and petrological examination of a relatively large hibonite-containing inclusion in the Murchison chondrite called the Blue Angel. Mechanisms of formation and modification of hibonite-rich inclusions are investigated. Evidence is found that modifying processes occurred before the inclusion was incorporated into its present location, which indicates a sequence of aqueous and metamorphic alteration followed by disruption and relithification of the protometeoritic material. The mineral chemistry and petrography of the Blue Angel is consistent with a three stage formation history, and extensive alteration of Ca-Al-rich inclusions may have occurred by aqueous alteration and thermal metamorphism followed by explosive mixing processes on a parent body.

Armstrong, J. T.↗
NASA NTRS1982

On the nature of particles in Saturn's spokes

It is noted that an observed deviation of the angular velocity of spoke features from the Keplerian value can yield the charge to mass (q/m) ratio of spoke particles. Observations in the literature of spoke motion are consistent with q/m in the neighborhood of -10 coul/kg. Since a lower limit on q is one electronic charge, this value yields a lower limit to the size of spoke particles of approximately 0.01 micron. The criteria for electrostatically ejecting small particles from larger parent bodies suggest an upper limit of approximately 1,000 m for the parent bodies. The stability of the grains to electrostatic disruption or field emission yields an upper limit of approximately 3 microns for the spoke particle size. It also leads to the conclusion that the spoke particles must consist of material that is stronger than loose dust balls.

Thomsen, M. F.↗
NASA NTRS1981

Nature and origin of basin-forming projectiles

The formation of the observed lunar multi-ring basins is discussed in the context of current theories of terrestrial planet formation, particularly those in which these planets formed by the accumulation of large planetesimals. The observed number, size, and timing of lunar basin-forming impacts is in the range expected for such theories. Tidal disruption during close encounters to earth and Venus can provide a single mechanism that explains a number of details concerning the number, size distribution, and stochastic nature of the timing of these impacts. A basin time scale is suggested in which Nectaris is associated with the 4.1 b.y. age of the Apollo 16 light matrix breccias. In accordance with the present consensus, Serenitatis is 3.86 b.y., Imbrium and Orientale 3.80-3.82 b.y. in age. Other nearside circular basins (e.g., Humorum and Crisium) are intermediate in age between 3.86 and 4.12 b.y. The large number of 3.8-3.9 b.y. ages is attributed primarily to the magnitude of the Imbrium and Serenitatis impacts, and sampling bias resulting from concentration of collection sites in proximity to these basins.

Wetherill, G. W.↗
NASA NTRS1982

Crystallographic texture in oxide-dispersion-strengthened alloys

Crystallographic and elastic moduli data are presented which document the degree of texture in several oxide dispersion-strengthened (ODS) nickel-base alloys. The existence of strong crystallographic textures in such multicrystalline alloys is considered important, since the small angle grain boundaries may be partially responsible for creep threshold stresses. Gleiter (1979) has shown that ideal, low energy boundaries will act as vacancy sources only when the applied stress is greater than a threshold stress, while large angle grain boundaries will emit vacancies at all stress levels. The continued operation of a net vacancy in an ODS alloy must be avoided, since it will lead to a localized disruption of the microstructure.

Whittenberger, J. D.↗
NASA NTRS1982

Embryonic development during chronic acceleration

Experiments carried out on chicken eggs indicate that the embryo is affected during very early development, especially over the first four days, and during hatching. In the first four days, the brain develops as well as the anlage for all other organs. In addition, the heart commences to function and the extraembryonic membranes that compartmentalize the egg contents form. The latter require an appreciable extension and folding of tissue which may be disrupted by the mechanical load. Observations of embryonic abnormalities that occur during chronic acceleration suggest an inhibition of development of the axial skeleton, which is rarely seen otherwise, a general retardation of embryonic growth, and circulatory problems. The final stages of development (after 18 days) involve the uptake of fluids, the transition to aerial respiration, and the reorientation of the embryo into a normal hatching position. At 4 G mortality is very high during this period, with a majority of embryos failing to reorient into the normal hatching position.

Smith, A. H.↗
NASA NTRS1982

Computer simulation of inner magnetospheric dynamics for the magnetic storm of July 29, 1977

The Rice University convection model is applied to the early main phase of the July 29, 1977 magnetic storm through a computer implementation that self-consistently calculates electric fields, currents, and plasma distributions and velocities in the inner magnetosphere/ionosphere system. On the basis of solar wind parameters and AL index as inputs, the model predicts the injection of plasma sheet plasma to form a substantial storm time ring current whose total predicted strength agrees with the observed Dst index. The possibility that the magnetic field may be sufficiently inflated to make 60 deg field lines extend to the outer magnetosphere is examined. In the model, distortion of the plasma sheet inner edge by magnetospheric compression associated with the sudden commencement temporarily disrupts the normal Birkeland current pattern. Normal Birkeland currents and shielding reassert themselves in about an hour.

Wolf, R. A.↗
NASA NTRS1982

Molecular shock waves in the BN-KL region of Orion

The H2, CO, and OH IR emission-line intensities in the BN-KL region of Orion are modeled by shock waves traveling at 36 km/s with respect to an ambient gas of density 200,000 per cu cm, ionization fraction of less than 3 x 10 to the -7th, CO abundance of approximately 0.0003, and transverse magnetic field of 0.45 milligauss. A global model is considered in which the shock waves are driven by strong winds emanating from KL. The mass-loss rate has been not less than 0.003 solar mass per year for approximately 1000 years. The total wind energy released from the star is not less than 5 x 10 to the 47th ergs. The total ejected momentum is approximately 10 to the 41st g cm/S, sufficient to disrupt the dense cloud surrounding BN-KL.

Chernoff, D. F.↗
NASA NTRS1981

The role of electrostatic charging of small and intermediate sized bodies in the solar system

The role of electrostatic charging of small and intermediate sized bodies in the solar system is reviewed. These bodies include planetary, interplanetary and cometary dust as well as cometary nuclei (at large heliocentric distances), asteroids and the larger bodies in the Saturnian ring system. While this charging has both physical and dynamical consequences for the small dust grains, it has only physical consequences for the larger bodies. The main physical consequences for the small grains are electrostatic erosion ('chipping') and disruption, whereas for the larger bodies they include electrostatic levitation and blow-off of fine loose dust from their surfaces.

Mendis, D. A.↗
NASA NTRS1982

Problems in the climatology of the 1980 Mount St. Helens eruptions

A brief review of the effects of climate and weather on the 1980 Mount St. Helens eruptions and the subsequent dispersion of ash and gases and the reciprocal influences of the eruptions on climate and climatology is presented. The effects of mesoscale destruction of snow fields and vegetation, a revised mountain profile, and ash deposits are addressed along with impacts on hemispheric climate and disruption of normal climatological observations, in the areas directly affected by the explosions and ashfall. Environmental and economic consequences are also considered.

Critchfield, H. J.↗
NASA NTRS1982

Conservation of strategic metals

A long-range program in support of the aerospace industry aimed at reducing the use of strategic materials in gas turbine engines is discussed. The program, which is called COSAM (Conservation of Strategic Aerospace Materials), has three general objectives. The first objective is to contribute basic scientific understanding to the turbine engine technology bank so that our national security is not jeopardized if our strategic material supply lines are disrupted. The second objective is to help reduce the dependence of United States military and civilian gas turbine engines on worldwide supply and price fluctuations in regard to strategic materials. The third objective is, through research, to contribute to the United States position of preeminence in the world gas turbine engine markets by minimizing the acquisition costs and optimizing the performance of gas turbine engines. Three major research thrusts are planned: strategic element substitution; advanced processing concepts; and alternate material identification. Results from research and any required supporting technology will give industry the materials technology options it needs to make tradeoffs in material properties for critical components against the cost and availability impacts related to their strategic metal content.

Joseph R. Stephens↗
NASA NTRS1981

Computation of inverse magnetic cascades

Inverse cascades of magnetic quantities for turbulent incompressible magnetohydrodynamics are reviewed, for two and three dimensions. The theory is extended to the Strauss equations, a description intermediate between two and three dimensions appropriate to Tokamak magnetofluids. Consideration of the absolute equilibrium Gibbs ensemble for the system leads to a prediction of an inverse cascade of magnetic helicity, which may manifest itself as a major disruption. An agenda for computational investigation of this conjecture is proposed.

Montgomery, D.↗
NASA NTRS1982

Simulation of plasma double-layer structures

Electrostatic plasma double layers are numerically simulated by means of a magnetized 2 1/2 dimensional particle in cell method. The investigation of planar double layers indicates that these one dimensional potential structures are susceptible to periodic disruption by instabilities in the low potential plasmas. Only a slight increase in the double layer thickness with an increase in its obliqueness to the magnetic field is observed. Weak magnetization results in the double layer electric field alignment of accelerated particles and strong magnetization results in their magnetic field alignment. The numerical simulations of spatially periodic two dimensional double layers also exhibit cyclical instability. A morphological invariance in two dimensional double layers with respect to the degree of magnetization implies that the potential structures scale with Debye lengths rather than with gyroradii. Electron beam excited electrostatic electron cyclotron waves and (ion beam driven) solitary waves are present in the plasmas adjacent to the double layers.

Borovsky, J. E.↗
NASA NTRS1983

Effects of aircraft noise on human activities

The effects of aircrft noise on human activities was investigated by developing a battery of tasks (1) representative of a range of human activities and (2) sensitive to the disruptive effects of noise. The noise used were recordings of jet aircraft and helicopter sounds at three lvels of loudness--60, 70, and 80 dB(A). Experiment 1 investigated 12 different cognitive tasks, along with two intelligibility tasks included to validate that the noises were being effective. Interference with intelligibility was essentially the same as found in the research literature, but only inconsistent effects were found on either accuracy or latency of performance on the cognitive tasks. When the tasks were grouped into four categories (Intelligibility, Matching, Verbal, and Arithmetic), reliable differences in rated annoyingness of the noises were related to the task category and to the type of noise (jet or helicopter).

Arnoult, M. D.↗
NASA NTRS1982

The passage of a star by a massive black hole

The gridless, smoothed particle hydrodynamic method of Lucy (1977) and Gingold and Monaghan (1977, 1980, a, b, 1981) is used to solve the three-dimensional problem posed by the effects on a 1.0 solar mass star of a 10,000 solar mass black hole's passage, in an initially parabolic orbit with a variety of pericenter distances. It is found that the tidal forces induce rotation and radial and nonradial pulsations in the star, and that the loss of orbital energy to these internal motions leads to the star's capture by the black hole. While the outer layers of the star are disrupted at small pericenter distances, the entire star is destroyed at even smaller distances. These results are applicable to X-ray sources, active galactic nuclei, and quasars

Nolthenius, R. A.↗
NASA NTRS1982

The geology of Europa

The map units and lineations of Europa are detailed, and the geologic processes, and history, and thick and thin ice models of the satellite are discussed. It is concluded that Europa lacks evidence of a horizontally stratified crust; the geology appears characterized by disruption of the crust and intrusions into an icy shell. The surface consists of plains and mottled terrain, the former being older. Numerous straight and curved lineations, streaks, stripes, and bands cross EuropA's surface on a global and surface scale. Most lineations appear related to fractures in the crust. Five fresh craters in the 10 to 30 km diameter range are visible. The dark spots, stripes, and bands that appear to have replaced sections of the crust suggest that material was transported to the surface from the subjacent silicate lithosphere. The apparent low density of craters superposed on Europa's surface suggests that the surface is about 100 million years old.

Lucchitta, B. K.↗
NASA NTRS1982

Internal stresses in Phobos and other triaxial bodies

The unusual dynamical behavior of Phobos, its strange appearance, and its mysterious network of grooves all make it an intriguing object. Geophysical studies, though, have been hampered by the lack of suitable theories applicable to nonspherical bodies. In this paper the Martian satellites are modeled as homogeneous, elastic triaxial ellipsoids subject to tidal, rotational, and self-gravitational stresses. A novel semianalytical treatment then gives the stress and strain fields throughout their interiors. Yield phenomena and their possible surface expressions are also investigated. The results indicate that Phobos and Deimos have always been stable with respect to tidal fracture or disruption, but that Phobos will probably break up before colliding with Mars. Applications of the new formulation to other nonspherical bodies in the solar system are also discussed.

Dobrovolskis, A. R.↗
NASA NTRS1982

Magma vesiculation and pyroclastic volcanism on Venus

Theoretical consideration of the magma vesiculation process under observed and inferred venusian surface conditions suggests that vesicles should form in basaltic melts, especially if CO2 is the primary magmatic volatile. However, the high surface atmospheric pressure (about 90 bars) and density on Venus retard bubble coalescence and disruption sufficiently to make explosive volcanism unlikely. The products of explosive volcanism (fire fountains, convecting eruption clouds, pyroclastic flows, and topography-mantling deposits of ash, spatter, and scoria) should be rare on Venus, and effusive eruptions should dominate. The volume fraction of vesicles in basaltic rocks on Venus are predicted to be less than in chemically similar rocks on earth. Detection of pyroclastic landforms or eruption products on Venus would indicate either abnormally high volatile contents of Venus magmas (2.5-4 wt%) or different environmental conditions (e.g., lower atmospheric pressure) in previous geologic history.

Garvin, J. B.↗
NASA NTRS1982

Sudden loss of mass from a binary gravitating system

Mitalas's (1980) study is generalized to treat sudden mass loss from a binary syste in an originally elliptical orbit. The orbits are characterized by angular momentum and energy, and it is shown that none of the changes in the relative orbit depends on which object it is that loses part of its mass. It is pointed out that, in principle, each could lose a different fraction. Time averages are introduced so that the orbital changes, which depend on where in orbit the mass loss takes place, can be suitably averaged over a statistical ensemble of initial systems. Even though many results that appear to be new are presented, it is noted that the main thrust is to choose and manipulate variables yielding the greatest economy of description and the greatest power of computation. Graphs are included showing the fraction of systems that on the average will be disrupted, the mean orbital changes for the survivors, and the extreme limits for the change in eccentricity.

Noerdlinger, P. D.↗