Abstract
The degradation of materials in extreme environments is a critical issue affecting the reliability of mechanical systems in space. A low earth orbit (LEO) environment in particular has various factors that strongly affect materials. A number of materials for space applications were exposed to an LEO space environment by the Japan Experimental Module / Space Environment Exposure Device (JEM/SEED) experiment aboard the International Space Station (ISS) to evaluate how they would be affected by a real space flight environment. A solid lubricant coating was one of the experimental materials evaluated in the JEM/SEED experiment. In addition to the orbital evaluation, the same type of coating was irradiated with atomic oxygen (AO), and ultraviolet rays (UV) on the ground. The fluences of AO and UV irradiation corresponded to the exposure in LEO environment around the ISS during the SEED experiment. Samples from LEO exposure, ground irradiation with AO and UV, and a reference (non-flight and non-irradiated) sample were then subjected to friction tests in a vacuum and surface analyses. The results were compared to elucidate the effects of the various factors on the characteristics of the solid lubricant film.
