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  • 1
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    Thermocapillary flows and their stability (1980)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: Steady convective flows for geometries of varying complexity are described. This in general involves the solution of nonlinear free boundary problems. The stability of these flows were determined to more complicated (perhaps time dependent) modes of fluid motion. These include shear flow and free surface instability modes, with possible coupling between them. The effect of surface chemical species is described, including impurities which act as surfactants and insoluble oxide films, on the convective patterns and their stability.
    Keywords: ASTRONAUTICS (GENERAL)
    Type: NASA. Marshall Space Flight Center Float Zone Workshop; p 49-54
    Format: text
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  • 2
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    Creation and Distribution of CAIs in the Protoplanetary Nebula (2003)
    In:  CASI
    Details
    Publication Date: 2017-10-02
    Description: CaAl rich refractory mineral inclusions (CAIs) found at 1 - 10% mass fraction in primitive chondrites appear to be several million years older than the dominant (chondrule) components in the same parent bodies. A prevalent concern is that it is difficult to retain CAIs for this long against gas-drag-induced radial drift into the sun. We assess a hot inner (turbulent) nebula context for CAI formation, using analytical models of nebula evolution and particle diffusion. We show that outward radial diffusion in a weakly turbulent nebula can prevent significant numbers of CAI-size particles from being lost into the sun for times of 1 - 3 x 10(exp 6) years. To match the CAI abundances quantitatively, we advocate an enhancement of the inner hot nebula in silicate-forming material, due to rapid inward migration of very primitive, silicate and carbon rich, meter-sized objects. 'Combustion' of the carbon into CO would make the CAI formation environment more reduced than solar, as certain observations imply. Abundant CO might also play a role in mass-independent chemical fractionation of oxygen isotopes as seen in CAIs and associated primitive, high-temperature condensates.
    Keywords: Astrophysics
    Type: Lunar and Planetary Science XXXIV; LPI-Contrib-1156
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  • 3
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    Consistency of time dilation in temporal profiles and spectra of gamma-ray bursts (1995)
    In:  Other Sources
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    Publication Date: 2019-01-25
    Description: If gamma-ray bursters are at cosmological distances-a possibility suggested by their isotropic distribution and spatial inhomogeneity-then the temporal profiles and spectra of more distant sources will be time dilated compared to those of relatively nearby sources. Analyses of bright and dim Burst and Transient Source Experiment (BATSE) gamma-ray bursts yield a relative time-dilation factor of 2.3 on timescales of pulses and event durations. We redshift the spectra of time intervals near the intensity peaks of the bright sample on a trial grid and compare with spectra of the dim sample. A redshift factor of order two-with wide latitude permitted-brings the spectra of the two brightness groups into alignment. Thus there is coarse agreement with the time-dilation factor found in the temporal domain.
    Keywords: Astrophysics
    Type: Gamma ray astronomy; E2 Symposium of COSPAR Scientific Commission E, COSPAR Scientific Assembly, 30th, Hamburg, Germany, July 11-21, 1994 . (ISSN 0273-1177); 15; 5; p. (5)135-(5)138
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  • 4
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    Thermocapillary Flows and Their Stability: Effects of Surface Layers and Contamination (1985)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The objective is to study quantitatively thermocapillary flows in two-dimensional and axisymmetric geometries in order to learn the impact of such flows on float-zone refining configurations. The work begins with the analytical study of steady flows in slots and zones to obtain predictions of surface curvature, flow and heat transport. It then examines the instability of such flows. Three new instability mechanisms have been identified and the results show that thermocapillary flows of high Prandtl number fluid become convectively unstable while those of low Prandtl number fluid become hydrodynamically unstable. The work includes numerical simulations of steady, high Marangoni number flows in unit aspect ratio boxes and asymptotic solutions in large boxes. Furthermore, the effect of surface contamination on the steady thermocapillary flows was examined. This fundamental study focused on fluid dynamical systems used to understand events in the flow of melts in float-zone geometries both on Earth and in microgravity environments.
    Keywords: ASTRONAUTICS (GENERAL)
    Type: NASA, Washington Microgravity Sci. and Appl. Program Tasks; p 98-99
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  • 5
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    Catalog of double lunar swingby orbits for exploring the Earth's geomagnetic tail (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Forty three orbits, which are periodic in geocentric reference frames rotating at lunar and at solar rates were found using a patched conic technique. The different orbits provide coverage of different parts of the distant geomagnetic tail. The parameters for 43 sun synchronous double lunar swingby orbits and plots of the sun synchronous double lunar swingby orbits are included.
    Keywords: ASTRONAUTICS (GENERAL)
    Type: NASA-CR-160066 , CSC/TM-80/6322
    Format: application/pdf
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  • 6
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    Vorticity Transport and Wave Emission In A Protoplanetary Disk (2002)
    In:  Other Sources
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    Publication Date: 2019-07-18
    Description: Higher order numerical algorithms (4th order in time, 3rd order in space) are applied to the Euler equations and are used to examine vorticity transport and wave motion in a non-self gravitating, initially isentropic Keplerian disk. In this talk we will examine the response of the disk to an isolated vortex with a circulation about equal to the rotation rate of Jupiter. The vortex is located on the 4 AU circle and the nebula is simulated from 1 to 24 AU. We show that the vortex emits pressure-supported density and Rossby-type wave packets before it decays within a few orbits. The acoustic density waves evolve into weak (non entropy preserving) shock waves that propagate over the entire disk. The Rossby waves remain in the vicinity of the initial vortex disturbance, but are rapidly damped. Temporal frequencies and spatial wavenumbers are derived from the nonlinear simulation data and correlated with analytical dispersion relations from the linearized Euler and energy equations.
    Keywords: Astrophysics
    Type: AGU Meeting; May 28, 2002 - May 31, 2002; Washington, DC; United States
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  • 7
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    Vorticity Transport and Wave Emission in the Protoplanetary Nebula (2001)
    In:  Other Sources
    Details
    Publication Date: 2019-07-18
    Description: Higher order numerical algorithms (4th order in time, 3rd order in space) are applied to the Euler/Energy equations and are used to examine vorticity transport and wave motion in a non-self gravitating, initially isentropic Keplerian disk. In this talk we will examine the response of the nebula to an isolated vortex with a circulation about equal to the rotation rate of Jupiter. The vortex is located on the 4 AU circle and the nebula is simulated from 1 to 24 AU. We show that the vortex emits pressure-supported density and Rossby-type wave packets before it decays within a few orbits. The acoustic density waves evolve into weak (non entropy preserving) shock waves that propagate over the entire disk. The Rossby waves remain in the vicinity of the initial vortex disturbance, but are rapidly damped. Temporal frequencies and spatial wavenumbers are derived using the simulation data and compared with analytical dispersion relations from the linearized Euler/Energy equations.
    Keywords: Astrophysics
    Type: DPS; Nov 27, 2001 - Dec 01, 2001; New Orleans, LA; United States
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  • 8
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    Intelsat VI (F-3) reboost mission (1992)
    In:  Other Sources
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    Publication Date: 2019-08-28
    Description: As the result of a launch vehicle malfunction, the Intelsat VI(F-3) communications satellite failed to achieve geostationary orbit. The satellite is presently safe in a low-earth orbit pending a NASA Space Shuttle Program (SSP) mission to retrieve it and attach a solid rocket. This paper describes the recovery hardware design and the overall mission efforts undertaken to recover and reboost the satellite.
    Keywords: ASTRONAUTICS (GENERAL)
    Type: AIAA PAPER 92-1951
    Format: text
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