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  • ASTROPHYSICS  (27)
  • SPACECRAFT DESIGN, TESTING AND PERFORMANCE  (10)
  • 2015-2019
  • 1985-1989  (37)
  • 1
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    Axions, neutrinos and strings - The formation of structure in an SO(10) universe (1986)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: In a class of grand unified theories containing SO(10), cosmologically significant axion and neutrino energy densities are obtainable naturally. To obtain large scale structure, both components of dark matter are considered to exist with comparable energy densities. To obtain large scale structure, inflationary and non-inflationary scenarios are considered, as well as scenarios with and without vacuum strings. It is shown that inflation may be compatible with recent observations of the mass density within galaxy clusters and superclusters, especially if strings are present.
    Keywords: ASTROPHYSICS
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    NASA TECHNICAL REPORTS
  • 2
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    Anatomy of a cosmic-ray neutrino source and the Cygnus X-3 system (1985)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: The effects of an intense beam of ultra-high energy cosmic rays from a compact object in the Cygnus X-3 binary system hitting the companion star, and of the subsequent production of secondary neutrinos, are examined. A maximum allowable beam luminosity of about 10 to the 42nd erg/s is found for a system containing a 1-10 solar mass main sequence target star. The proton beam must heat a relatively small area of the target star to satisfy observational constraints on the resulting stellar wind. With such a model, the neutrino to gamma-ray flux ratio of about 1000 can result from a combination of gamma-ray absorption and a large neutrino to gamma-ray duty cycle ratio. It is found that the high density of the atmosphere resulting from compression by the beam leads to pion cascading and a neutrino spectrum peaking at 1-10 GeV energies.
    Keywords: ASTROPHYSICS
    Type: Nature (ISSN 0028-0836); 316; 418-420
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    NASA TECHNICAL REPORTS
  • 3
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    Spectra, fluxes, and observability of gamma rays from dark matter annihilation in the Galaxy (1989)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: Details of the physics of gamma-ray production by the annihilation of dark matter particles in the Galaxy are presented. Improved gamma-ray spectra and fluxes are calculated and compared with present observational data on cosmic gamma-ray fluxes at high Galactic latitudes. A comparison with the gamma-ray flux from cosmic-ray interactions is made. It is found that gamma-rays from dark matter annihilation are most potentially observable from patches of the sky at high Galactic latitudes in directions having an unusually low total column density of gas and from a dark matter core at the Galactic center.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 343; 169-176
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    NASA TECHNICAL REPORTS
  • 4
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    High energy neutrino absorption and its effects on stars in close X-ray binaries (1986)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The physics and astrophysics of high energy neutrino production and interactions in close X-ray binary systems are studied. These studies were stimulated by recent observations of ultrahigh energy gamma-rays and possibly other ultrahigh energy particles coming from the directions of Cygnus X-3 and other binary systems and possessing the periodicity characteristics of these systems. Systems in which a compact object, such as a neutron star, is a strong source of high energy particles which, in turn, produce photons, neutronos and other secondary particles by interactions in the atmosphere of the companion star were considered. The highest energy neutrinos are absorbed deep in the companion and the associated energy deposition may be large enough to effect its structure or lead to its ultimate disruption. This neutrino heating was evaluated, starting with a detailed numerical calculation of the hadronic cascade induced in the atmosphere of the companion star. For some theoretical models, the resulting energy deposition from neutrino absorption may be so great as to disrupt the companion star over an astronomically small timescale of the order of 10,000 years. Even if the energy deposition is smaller, it may still be high enough to alter the system substantially, perhaps leading to quenching of high energy signals from the source. Given the cosmic ray luminosities required to produce the observed gamma rays from cygnus X-3 and LMX X-4, such a situation may occur in these sources.
    Keywords: ASTROPHYSICS
    Type: NASA-TM-89269 , NAS 1.15:89269
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 5
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    Effect of G-jitters on the stability of rotating bubble under microgravity environment (1989)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The instability of liquid and gas interface can be induced by the pressure of longitudinal and lateral accelerations, vehicle vibration, and rotational fields of spacecraft in a microgravity environment. Characteristics of slosh waves excited by the restoring force field of gravity jitters have been investigated. Results show that lower frequency gravity jitters excite slosh waves with higher ratio of maximum amplitude to wave length than that of the slosh waves generated by the higher frequency gravity jitters.
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
    Type: IAF PAPER 89-409
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    NASA TECHNICAL REPORTS
  • 6
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    The solar dynamic radiator with a historical perspective (1988)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A historical perspective on pumped-fluid loop space radiators provides a basis for the design of the Space Station Solar Dynamic (SD) power module radiator. SD power modules, capable of generating 25 kW (electrical) each, are planned for growth in Station power requirements. The Brayton cycle SD module configuration incorporates a pumped-fluid loop radiator that must reject up to 99 kW (thermal). The thermal/hydraulic design conditions in combination with required radiator orientation and packaging envelope form a unique set of constraints as compared to previous pumped-fluid loop radiator systems. Nevertheless, past program successes have demonstrated a technology base that can be applied to the SD radiator development program to ensure a low risk, low cost system.
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
    Type: NASA-TM-100972 , E-4265 , NAS 1.15:100972 , Intersociety Energy Conversion Engineering Conference; Jul 31, 1988 - Aug 05, 1988; Denver, CO; United States
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 7
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    Effects of high-energy neutrino production and interactions on stars in close X-ray binaries (1986)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: Limits are discussed that may be placed on binary systems in which a compact partner is a strong source of high-energy particles that produce photons, neutrinos, and other secondary particles in the companion star. The highest energy neutrinos are absorbed deep in the companion and the associated energy deposition may be large enough to affect its structure or lead to its ultimate disruption. This neutrino heating is evaluated, starting with a detailed numerical calculation of the hadronic cascade induced in the atmosphere of the companion star. For some theoretical models, the resulting energy deposition from neutrino absorption may be so great as to disrupt the companion star over a time scale of 10,000-100,000 yr. Even if the energy deposition is smaller, it may still be high enough to alter the system substantially.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 309; 674-681
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    NASA TECHNICAL REPORTS
  • 8
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    Space Infrared Telescope Facility (SIRTF) observatory design (1986)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: The NASA Space IR Telescope Facility (SIRTF) is a 1-m aperture, cryogenically cooled IR observatory scheduled for launch into orbit in the mid-1990s. SIRTF will operate in the 2-700 micron range and yield a 1000-fold increase in sensitivity over NASA's IRAS observatory. A low inclination orbit compatible with Space Shuttle operations will be used. Results from comparisons of a system error budget allocation for the f/24 optical configuration with recent test data indicate that a figured fused silica mirror and a blade flexure mounting system can be cooled to cryogenic temperature while meeting required wavefront tolerances for substrate deformation. An all-He cooling system will be used in the low inclination orbit.
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
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    NASA TECHNICAL REPORTS
  • 9
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    Cometary comae (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The basis of our knowledge about the structure and composition of a comet nucleus is examined. Such knowledge is inferred from observations of the cometary atmosphere (coma). However, photodissociation, photoionization, and chemistry destroy the mother molecules evaporating from the nucleus. To extract the primary information, the chemical kinetics and the physics of the coma are modeled with a computer and the results are compared with coma observations. The physics and chemistry for a dust free coma are described taking into account energy balance, multi-fluid flow for fast atomic and molecular hydrogen and the bulk fluid, and the transition from a collision dominated inner region to the free molecular flow outer region. Special attention is paid to the molecular data requirements for the current modeld and for extended models which will include solar wind interaction and dust. Such models are an important tool in support of the Giotto mission to Halley's comet, in the analysis and interpretation of coma observations, and in the understanding of the earliest history of the solar system.
    Keywords: ASTROPHYSICS
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    NASA TECHNICAL REPORTS
  • 10
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    Polyoxymethylene in Comet Halley (1987)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: It is shown that polyoxymethylene (POM) with n about four or five explains the mass spectrum obtained with the PICCA instrument during the Giotto encounter with Comet Halley. A sequence of processes is presented showing the likelihood that POM will form under interstellar conditions. A preliminary comet coma model that includes POM is presented which predicts a qualitatively correct spectral intensity behavior when compared with observations.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters to the Editor (ISSN 0004-637X); 320; L149-L15
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