ABSTRACT
One of the limitations to using polymers and polymer matrix composites is their susceptibility to degradation in oxidizing and/or UV environments, so their use has been generally limited to environmentally mild service applications. The use of polymers and composites in space exemplifies this problem. To date, the widespread use of polymers and composites in space, on a prolonged basis, has been limited due to their low erosion resistance in the presence of active oxygen species, such as atomic oxygen (AO), that can be found in the residual atmosphere surrounding the Earth in low Earth orbit (LEO). AO is the predominant species in the LEO space environment at altitudes between 200 and 700 km. The atomic oxygen is formed through the dissociation of 0 2 by vacuum ultraviolet radiation (VUV). Although the AO concentration is low at the altitudes of most orbiting vehicles, such as satellites, space shuttle and International Space Station (ISS), the actual flux of atoms impinging on an orbiting vehicle is quite high (approx. 1014-1015 atom/cm2 -s) due to the high orbital velocity (approx. 7-8 km/s) of orbiting vehicles. In addition to the flux, at this high orbital velocity, AO impacts the surface of the space vehicles with considerable energy, about 4-5 eV, resulting in significant erosion and oxidation damage to exposed polymer-based materials [1, 2]. AO, having kinetic energy about 1 eV, and more typically in the range from about 2 eV to about 5 eV, is commonly referred to as "fast atomic oxygen" (FAO) or "hyperthermal atomic oxygen" (HAO).
