Abstract
This study evaluated effects of a low earth orbit (LEO) space environment on properties of a solid lubricant used for space applications. The tested lubricant was a bonded MoS2 film with organic binder. The film was exposed to a real LEO space environment aboard the International Space Station (ISS) by the Space Environment Exposure Device (SEED) experiment for about 1400 days. Additionally, it was irradiated individually with atomic oxygen (AO), ultraviolet rays (UV), and electron beam (EB) on the ground. Fluences of these factors corresponded to exposure to the LEO environment by the SEED experiment. Friction tests in vacuum and surface analyses were carried out for the samples. Tribological behavior of the different samples was measured using classical reciprocating pin-on-flat friction tests. Furthermore, XPS analysis was performed for the film surface and rubbing tracks of the samples. Results show that the friction coefficient decreased by AO irradiation at an early stage of the tests. It resembled the result of the film exposed to the real LEO environment.
