Solar Effects on Tensile and Optical Properties of Hubble Space Telescope Silver-Teflon Insulation
- PDF / 3,813,165 Bytes
- 14 Pages / 612 x 792 pts (letter) Page_size
- 13 Downloads / 193 Views
0929-II05-08
Solar Effects on Tensile and Optical Properties of Hubble Space Telescope Silver-Teflon Insulation Kim K. de Groh1, Joyce A. Dever1, Aaron Snyder1, Sharon Kaminski2, Catherine E. McCarthy2, Allison L. Rapoport2, and Rochelle N. Rucker2 1 Electro-Physics Branch, NASA Glenn Research Center, 21000 Brookpark Rd., M.S. 309-2, Cleveland, OH, 44135 2 Hathaway Brown School, 19600 North Park Blvd., Shaker Heights, OH, 44122
ABSTRACT A section of the retrieved Hubble Space Telescope (HST) solar array drive arm (SADA) multilayer insulation (MLI), which experienced 8.25 years of space exposure, was analyzed for environmental durability of the top layer of silver-Teflon fluorinated ethylene propylene (AgFEP). Because the SADA MLI had solar and anti-solar facing surfaces and was exposed to the space environment for a long duration, it provided a unique opportunity to study solar effects on the environmental degradation of Ag-FEP, a commonly used spacecraft thermal control material. Data obtained included tensile properties, solar absorptance, surface morphology and chemistry. The solar facing surface was found to be extremely embrittled and contained numerous throughthickness cracks. Tensile testing indicated that the solar facing surface lost 60% of its mechanical strength and 90% of its elasticity while the anti-solar facing surface had ductility similar to pristine FEP. The solar absorptance of both the solar facing surface (0.155 ± 0.032) and the anti-solar facing surface (0.208 ± 0.012) were found to be greater than pristine Ag-FEP (0.074). Solar facing and anti-solar facing surfaces were microscopically textured, and locations of isolated contamination were present on the anti-solar surface resulting in increased localized texturing. Yet, the overall texture was significantly more pronounced on the solar facing surface indicating a synergistic effect of combined solar exposure and increased heating with atomic oxygen erosion. The results indicate a very strong dependence of degradation, particularly embrittlement, upon solar exposure with orbital thermal cycling having a significant effect. INTRODUCTION The Hubble Space Telescope was launched on April 25, 1990 into low Earth orbit as the first mission of NASA’s Great Observatories program. The HST was designed to be serviced on-orbit to upgrade scientific capabilities. In December 1993, during the first servicing mission (SM1) the original solar arrays (SA-I) were replaced with a second set of arrays (SA-II) containing bi-stem thermal shields to eliminate a thermal induced jitter problem. In March of 2002, after 8.25 years of space exposure, the SA-II was replaced with a third set of arrays (SAIII) during the fourth servicing mission (SM3B), and the SA-II was brought back to Earth. A section of the retrieved SA-II solar array drive arm (SADA) multilayer insulation (MLI) was provided to NASA Glenn Research Center so that environmental durability analyses of the top layer of silver-Teflon® fluorinated ethylene propylene (Ag-FEP) could be conducted.
The SADA M
Data Loading...
