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  • 1
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    Low Earth orbital atomic oxygen micrometeoroid, and debris interactions with photovoltaic arrays (1991)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Polyimide Kapton solar array blankets can be protected from atomic oxygen in low earth orbit if SiO sub x thin film coatings are applied to their surfaces. The useful lifetime of a blanket protected in this manner strongly depends on the number and size of defects in the protective coatings. Atomic oxygen degradation is dominated by undercutting at defects in protective coatings caused by substrate roughness and processing rather than micrometeoroid or debris impacts. Recent findings from the Long Duration Exposure Facility (LDEF) and ground based studies show that interactions between atomic oxygen and silicones may cause grazing and contamination problems which may lead to solar array degradation.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: Space Photovoltaic Research and Technology Conference; 10 p
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 2
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    Blast wave in a nozzle for propulsive applications (1976)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: The reported investigation has been conducted in connection with studies concerning the development of a propulsion system based on the use of a detonating fluid propellant. Measurements have been made of the pressure and shock wave velocity in a conical nozzle at various ambient pressures and at an ambient temperature of 25 C. In the experiments a small amount of explosive was placed at the end wall of a conical aluminum nozzle and detonated by a microdetonator inside the nozzle. Differences regarding the characteristics of conventional chemical propulsion and detonation propulsion are illustrated with the aid of a graph. One- and two-dimensional numerical flow calculations were performed and compared with the experimental data.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Format: text
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    NASA TECHNICAL REPORTS
  • 3
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    Environmental Durability Issues for Solar Power Systems in Low Earth Orbit (1994)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Space solar power systems for use in the low Earth orbit (LEO) environment experience a variety of harsh environmental conditions. Materials used for solar power generation in LEO need to be durable to environmental threats such as atomic oxygen, ultraviolet (UV) radiation, thermal cycling, and micrometeoroid and debris impact. Another threat to LEO solar power performance is due to contamination from other spacecraft components. This paper gives an overview of these LEO environmental issues as they relate to space solar power system materials. Issues addressed include atomic oxygen erosion of organic materials, atomic oxygen undercutting of protective coatings, UV darkening of ceramics, UV embrittlement of Teflon, effects of thermal cycling on organic composites, and contamination due to silicone and organic materials. Specific examples of samples from the Long Duration Exposure Facility (LDEF) and materials returned from the first servicing mission of the Hubble Space Telescope (HST) are presented. Issues concerning ground laboratory facilities which simulate the LEO environment are discussed along with ground-to-space correlation issues.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: NASA-TM-106775 , E-9226 , NAS 1.15:106775 , 1995 International Solar Energy Conference; Mar 19, 1995 - Mar 24, 1995; Lahaina, HI; United States
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    NASA TECHNICAL REPORTS
  • 4
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    Low Earth orbit durability evaluation of protected silicone for advanced refractive photovoltaic concentrator arrays (1994)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The need for efficient, cost effective sources of electrical power in space has led to the development of photovoltaic power systems which make use of novel refractive solar concentrators. These concentrators have been conceived in both point-focus and linear-focus designs. Current concentrator lenses are fabricated from flexible silicones with Fresnel facets along their inside surface. To insure the efficient operation of these power systems, the concentrator lenses must be durable and the silicone material must remain specularly transmitting over a reasonable lifetime in low Earth orbit (LEO) and other space environments. Because of the vulnerability of silicones to atomic oxygen and ultraviolet radiation in LEO these lenses have been coated with a multi-layer metal oxide protective coating. The objective of this research was to evaluate the LEO durability of the multilayer coated silicone for advanced refractive photovoltaic concentrator arrays with respect to optical properties and microstructure. Flat metal oxide coated silicone samples were exposed to ground-laboratory and in-space atomic oxyqen for durability evaluation.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: NASA-TM-106543 , E-8687 , NAS 1.15:106543 , AIAA PAPER 94-0374 , AIAA Aerospace Sciences Meeting and Exhibit; Jan 10, 1994 - Jan 13, 1994; Reno, NV; United States
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  • 5
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    Performance and durability of high emittance heat receiver surfaces for solar dynamic power systems (1994)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Haynes 188, a cobalt-based superalloy, will be used to make thermal energy storage (TES) containment canisters for a 2 kW solar dynamic ground test demonstrator (SD GTD). Haynes 188 containment canisters with a high thermal emittance (epsilon) are desired for radiating heat away from local hot spots, improving the heating distribution, which will in turn improve canister service life. In addition to needing a high emittance, the surface needs to be durable in an elevated temperature, high vacuum environment for an extended time period. Thirty-five Haynes 188 samples were exposed to 14 different types of surface modification techniques for emittance and vacuum heat treatment (VHT) durability enhancement evaluation. Optical properties were obtained for the modified surfaces. Emittance enhanced samples were exposed to VHT for up to 2692 hours at 827 C and less than or equal to 10(exp -6) torr with integral thermal cycling. Optical properties were taken intermittently during exposure, and after final VHT exposure. The various surface modification treatments increased the emittance of pristine Haynes 188 from 0.11 up to 0.86. Seven different surface modification techniques were found to provide surfaces which met the SD GTD receiver VHT durability requirement. Of the 7 surface treatments, 2 were found to display excellent VHT durability: an alumina based (AB) coating and a zirconia based coating. The alumina based coating was chosen for the epsilon enhancement surface modification technique for the SD GTD receiver. Details of the performance and vacuum heat treatment durability of this coating and other Haynes 188 emittance surface modification techniques are discussed. Technology from this program will lead to successful demonstration of solar dynamic power for space applications, and has potential for application in other systems requiring high emittance surfaces.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: NASA-TM-106549 , E-8700 , NAS 1.15:106549 , 1994 ASME International Solar Energy Conference; Mar 27, 1994 - Mar 30, 1994; San Francisco, CA; United States
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    NASA TECHNICAL REPORTS
  • 6
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    Exit of a blast wave from a conical nozzle (1976)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The Eulerian computer code DORF was used in the analysis of a two-dimensional, unsteady flow field resulting from semi-confined explosions for propulsive applications. Initially, the ambient gas inside the conical shaped nozzle is set into motion due to the expansion of the explosion product gas, forming a shock wave. When this shock front exits the nozzle, it takes almost a spherical form while a complex interaction between the nozzle and compression and rarefaction waves takes place behind the shock. The results show an excellent agreement with experimental data.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: AIAA PAPER 76-401 , Fluid and Plasma Dynamics Conference; Jul 14, 1976 - Jul 16, 1976; San Diego, CA
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    NASA TECHNICAL REPORTS
  • 7
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    Measurements and calculations of detonation propulsion performance in helium (1974)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Previously obtained results are extended to helium ambient gas to help in the assessment of performance in the atmospheres of the major planets. Measurements confirm benefits derived form detonating propellant over conventional chemical rocket propulsion. Benefits however, are reduced at high pressures in low molecular weight gas. Numerical calculations by means of a monodimensional hydrodynamic code follow the different trends obtained experimentally for high and low molecular weight gas and also offer new insights on the time behavior of the process.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: AIAA PAPER 74-1206 , American Institute of Aeronautics and Astronautics and Society of Automotive Engineers, Propulsion Conference; Oct 21, 1974 - Oct 23, 1974; San Diego, CA
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    NASA TECHNICAL REPORTS
  • 8
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    Atomic oxygen durability of solar concentrator materials for Space Station Freedom (1990)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The findings are reviewed of atomic oxygen exposure testing of candidate solar concentrator materials containing SiO2 and Al2O3 protective coatings for use on Space Station Freedom solar dynamic power modules. Both continuous and iterative atomic oxygen exposure tests were conducted. Iterative air plasma ashing resulted in larger specular reflectance decreases and solar absorptance increases than continuous ashing to the same fluence, and appears to provide a more severe environment than the continuous atomic oxygen exposure that would occur in the low Earth orbit environment. First generation concentrator fabrication techniques produced surface defects including scratches, macroscopic bumps, dendritic regions, porosity, haziness, and pin hole defects. Several of these defects appear to be preferential sites for atomic oxygen attack leading to erosive undercutting. Extensive undercutting and flaking of reflective and protective coatings were found to be promoted through an undercutting tearing propagation process. Atomic oxygen erosion processes and effects on optical performance is presented.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: NASA-TM-105378 , E-6745 , NAS 1.15:105378 , Annual Air Force Workshop on Surface Reactions in the Space Environment; Sep 24, 1990 - Sep 25, 1990; Evanston, IL; United States
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  • 9
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    Transparent conducting thin films for spacecraft applications (1994)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Transparent conductive thin films are required for a variety of optoelectronic applications: automotive and aircraft windows, and solar cells for space applications. Transparent conductive coatings of indium-tin-oxide (ITO)-magnesium fluoride (MgF2) and aluminum doped zinc oxide (AZO) at several dopant levels are investigated for electrical resistivity (sheet resistance), carrier concentration, optical properties, and atomic oxygen durability. The sheet resistance values of ITO-MgF2 range from 10(exp 2) to 10(exp 11) ohms/square, with transmittance of 75 to 86 percent. The AZO films sheet resistances range from 10(exp 7) to 10(exp 11) ohms/square with transmittances from 84 to 91 percent. It was found that in general, with respect to the optical properties, the zinc oxide (ZnO), AZO, and the high MgF2 content ITO-MgF2 samples, were all durable to atomic oxygen plasma, while the low MgF2 content of ITO-MgF2 samples were not durable to atomic oxygen plasma exposure.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: NASA-TM-106466 , E-8332 , NAS 1.15:106466 , AIAA PAPER 94-0375 , Aerospace Sciences Meeting and Exhibit; Jan 10, 1994 - Jan 13, 1994; Reno, NV; United States
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    NASA TECHNICAL REPORTS
  • 10
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    LDEF spacecraft, ground laboratory, and computational modeling implications on Space Station Freedom's solar array materials and surfaces durability (1991)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The low earth orbital (LEO) durability of Space Station Freedom (SSF) solar array materials and surfaces is evaluated using results from the Long Duration Exposure Facility (LDEF), ground laboratory simulation tests, and Monte Carlo modeling. These results indicate that thin-film SiOx protective coatings are adequately durable to atomic oxygen, ultraviolet (UV) radiation, thermal cycling, and micrometeroid or debris impact.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: IEEE Photovoltaic Specialists Conference; Oct 07, 1991 - Oct 11, 1991; Las Vegas, NV; United States
    Format: text
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    NASA TECHNICAL REPORTS
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