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  • 1
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    Combined Contamination and Space Environmental Effects on Solar Cells and Thermal Control Surfaces (1994)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: For spacecraft in low Earth orbit (LEO), contamination can occur from thruster fuel, sputter contamination products and from products of silicone degradation. This paper describes laboratory testing in which solar cell materials and thermal control surfaces were exposed to simulated spacecraft environmental effects including contamination, atomic oxygen, ultraviolet radiation and thermal cycling. The objective of these experiments was to determine how the interaction of the natural LEO environmental effects with contaminated spacecraft surfaces impacts the performance of these materials. Optical properties of samples were measured and solar cell performance data was obtained. In general, exposure to contamination by thruster fuel resulted in degradation of solar absorptance for fused silica and various thermal control surfaces and degradation of solar cell performance. Fused silica samples which were subsequently exposed to an atomic oxygen/vacuum ultraviolet radiation environment showed reversal of this degradation. These results imply that solar cells and thermal control surfaces which are susceptible to thruster fuel contamination and which also receive atomic oxygen exposure may not undergo significant performance degradation. Materials which were exposed to only vacuum ultraviolet radiation subsequent to contamination showed slight additional degradation in solar absorptance.
    Keywords: CHEMISTRY AND MATERIALS (GENERAL)
    Type: NASA-TM-106592 , E-8859 , NAS 1.15:106592 , AIAA PAPER 94-2627 , AIAA Aerospace Ground Testing Conference; Jun 20, 1994 - Jun 23, 1994; Colorado Springs, CO; United States
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 2
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    Atomic Oxygen Durability Evaluation of Protected Polymers Using Thermal Energy Plasma Systems (1995)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The durability evaluation of protected polymers intended for use in low Earth orbit (LEO) has necessitated the use of large-area, high-fluence, atomic oxygen exposure systems. Two thermal energy atomic oxygen exposure systems which are frequently used for such evaluations are radio frequency (RF) plasma ashers and electron cyclotron resonance plasma sources. Plasma source testing practices such as ample preparation, effective fluence prediction, atomic oxygen flux determination, erosion measurement, operational considerations, and erosion yield measurements are presented. Issues which influence the prediction of in-space durability based on ground laboratory thermal energy plasma system testing are also addressed.
    Keywords: CHEMISTRY AND MATERIALS (GENERAL)
    Type: NASA-TM-106855 , L-9452 , NAS 1.15:106855 , International Conference on Plasma Synthesis and Processing of Materials; Feb 21, 1993 - Feb 25, 1993; Denver, CO; United States
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 3
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    Low Earth orbital atomic oxygen environmental simulation facility for space materials evaluation (1993)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Simulation of low Earth orbit atomic oxygen for accelerated exposure in ground-based facilities is necessary for the durability evaluation of space power system component materials for Space Station Freedom (SSF) and future missions. A facility developed at the National Aeronautics and Space Administrations's (NASA) Lewis Research Center provides accelerated rates of exposure to a directed or scattered oxygen beam, vacuum ultraviolet (VUV) radiation, and offers in-situ optical characterization. The facility utilizes an electron-cyclotron resonance (ECR) plasma source to generate a low energy oxygen beam. Total hemispherical spectral reflectance of samples can be measured in situ over the wavelength range of 250 to 2500 nm. Deuterium lamps provide VUV radiation intensity levels in the 115 to 200 nm range of three to five equivalent suns. Retarding potential analyses show distributed ion energies below 30 electron volts (eV) for the operating conditions most suited for high flux, low energy testing. Peak ion energies are below the sputter threshold energy (approximately 30 eV) of the protective coatings on polymers that are evaluated in the facility, thus allowing long duration exposure without sputter erosion. Neutral species are expected to be at thermal energies of approximately .04 eV to .1 eV. The maximum effective flux level based on polyimide Kapton mass loss is 4.4 x 10 exp 6 atoms/((sq. cm)*s), thus providing a highly accelerated testing capability.
    Keywords: CHEMISTRY AND MATERIALS (GENERAL)
    Type: NASA-TM-106128 , E-7797 , NAS 1.15:106128 , International SAMPE Symposium and Exhibition; May 10, 1993 - May 13, 1993; Anaheim, CA; United States
    Format: application/pdf
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