Space Environment Test of Materials for Inflatable Structures

Abstract : Materials being considered for use in thin-film applications of inflatable structures were exposed to a simulated space environment representing a 5-year Low Earth Orbit (LEO) and also to a 5-year Geo- synchronous Orbit (GEO). Solar absorptance and tensile test measurements were performed, pre- and posttest. The materials consisted of various thin polymer foils, including 0.0005-in. bare and metallized Kapton E, LaRC-CPl, LaRC-CP2, FEP Teflon, Triton conductive COR, and slightly thicker (0.0008 to 0.0018-in.) films of Triton TOR, Triton TOR-LM, and Triton TOR-RC. A total of 34 samples were exposed plus control and contamination monitors. Measurements of solar absorptance and tensile properties were made on samples corresponding to both Low Earth and Geosynchronous Orbit exposures. Increases in solar absorptance were observed for many of the samples. Changes in mechanical properties are also indicated by the results, but there was scatter in the test data due to the limitation of the number of samples that allowed only two of each type to be exposed to each orbital condition, and some to only GEO exposure conditions. The property changes on thin polymer films due to space environmental exposure must be considered in the design of inflatable structures. The Kapton E samples and the fluorinated polyimides (CPl and CP2) showed the least degradation. The low-modulus version of TOR (TOR-LM) appeared to be the most stable of the other films.