Changes in Tribological Characteristics of MoS2 Bonded Film by Exposure to Low Earth Orbit Space Environment

Effects of a low earth orbit (LEO) space environment on tribological characteristics of a solid lubricant film were evaluated. The tested lubricant, which has been used for space applications, was a bonded molybdenum disulfide (MoS2) film with organic binder. Three sets of the specimen were exposed to a real LEO space environment for about 1, 2 and 3 years aboard the Service Module of the International Space Station (ISS) by the Space Environment Exposure Device (SEED) experiment. In this paper, results of friction tests in vacuum and surface analyses for the specimens exposed for 1 and 2 years are reported. The results are also compared to those of the specimens irradiated individually with atomic oxygen (AO), ultraviolet rays (UV) and electron beam (EB) on the ground.