A section of retrieved Hubble Space Telescope (HST) bi-stem thermal shields (BSTS), which experienced 8.25 years of space exposure, was analyzed for space environmental durability. The shields were comprised of 2 mil (0.051 mm) aluminized-Teflon fluorinated ethylene propylene (Al-FEP) rings fused together into a circular bellows shape. As the circular thermal shields had solar, anti-solar and solargrazing surfaces and were exposed to the space environment for a long duration, it provided a unique opportunity to study solar effects on the environmental degradation of Al-FEP, a commonly used spacecraft thermal control material. Therefore, the objective of this research was to characterize the degradation of retrieved HST BSTS Al-FEP with particular emphasis on solar effects. Data obtained included tensile properties, density (as-retrieved and after 200 deg C heating), solar absorptance, and surface morphology and chemistry. The solar-facing surfaces of the thermal shields were found to be extremely embrittled and contained numerous through-thickness cracks. Tensile testing verified that near solar-facing surfaces lost their mechanical strength and elasticity, whereas the anti-solar-facing surfaces maintained their ductility. The density of the as-retrieved BSTS insulation was similar to pristine FEP. Heating at 200 deg C resulted in significant increases in density for the solar-facing BSTS indicating chain scission damage, consistent with the loss of mechanical strength and elongation. The solar absorptance of the solar-grazing and the antisolar- facing surfaces were found to be similar to pristine BSTS, whereas the solar-facing surfaces were found to have significantly increased solar absorptance. Both solar- and anti-solar-facing surfaces were microscopically textured from sweeping atomic oxygen erosion with the solar-facing surface appearing to have a more pronounced texture in spite of being exposed to a lower atomic oxygen fluence indicating a possible solar/atomic oxygen synergistic effect. These results provide valuable information on space environmental degradation of Al-FEP, particularly with respect to solar radiation effects on embrittlement.


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    Title :

    Degradation of Hubble Space Telescope aluminized-Teflon bi-stem thermal shields


    Additional title:

    Der Abbau der aus aluminisiertem Teflon bestehenden, zweischäftigen Wärmeschutzschilde des Hubble-Weltraumteleskops


    Contributors:


    Publication date :

    2008


    Size :

    19 Seiten, 12 Bilder, 1 Tabelle, 15 Quellen




    Type of media :

    Conference paper


    Type of material :

    Print


    Language :

    English




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