Degradation of Spacesuit Fabrics Exposed to Low Earth Orbit

Two different outer spacesuit fabrics were exposed to the wake-side low Earth orbit (LEO) environment for two years in order to determine their long term durability in the space environment. One sample each of the Teflon fabrics that covered Apollo spacesuits and the Orthofabric that covers the Space Shuttle and ISS suits was flown on the ISS as part of the ORMatE-III experiment. Results were compared with previous experiment on MISSE-7 which had similar exposure conditions on the ISS for 18 months, as well as β-cloth exposures on the LDEF for 5.7 years and an ISS battery ORU that was exposed for 8 years. Both ORMatE-III samples darkened considerably, probably due to UV and high energy particle radiation. Spectral analysis showed increased absorption in the shorter than 500 nm portion of the spectrum, but became more reflective in the 500 to 1800 nm region, and as a result, there was little change in the absorptance of the fabrics. Measurement of the 2.5 to 25 μm spectra indicated that there was only a small change in the emittance of the fabrics in the 250 to 700 K. Thus, although on long exposure the spacesuits are expected to darken to the eye, their thermal properties will likely remain nearly constant for the Apollo FEP fabric, and will degrade only slowly for the Orthofabric. Although these sample were too small to characterize their mechanical properties, degradation of the MISSE-7 samples as well as metalized FEP films on the Hubble Space Telescope thermal shields suggest that long term exposure of these fabrics to the space radiation environments will cause them to embrittle.