Comparison of Properties of Solid Lubricant Between Two Exposure Experiments Aboard the ISS

摘要

To evaluate the degradation of materials in low Earth orbit space environment, the Space Environment Exposure Device (SEED) experiments were carried out on the International Space Station. As part of these experiments, changes in the tribological properties of a molybdenum disulfide bonded film that is used as a solid lubricant, were evaluated. The results of friction tests in a vacuum and surface analysis by XPS were compared between two exposure experiments aboard the Service Module (SM) and the Japan Experimental Module (JEM). The investigations revealed silicon and fluorine contaminations in the JEM/SEED flight sample, but with a lower amount of silicon contamination than the SM/SEED flight sample. The JEM/ SEED flight sample and ground-based tested samples showed lower friction coefficients than a reference sample at the beginning of the tests. The friction behavior of the JEM/SEED flight sample was similar to those of SM/SEED flight samples.