MoS2 dry lubricated contacts exposed to space environments

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Lubricating space mechanism is very challenging as lubrication must be sustained in several environments, over a wide temperature range while avoiding any risk of contamination of the spacecraft on-board equipment, especially optics, all along the mechanism life (up to 15 years once in space). Throughout the last 60 years, tribological studies have shown that coupling exists between physicochemistry and mechanics, influencing the tribological behaviour and efficiency of lubricants. Nonetheless, information is still lacking in order to formulate efficient predictive models of dry lubrication. Recommended for vacuum use since 1941, the mostly used dry lubricant for space application is the molybdenum disulphide MoS2. However, prediction of the MoS2 lubrication in real mechanism is still lacking. Recently, lubrication issues with MoS2 have still been encountered in the development of some equipment intended for the James Webb Space Telescope, which is a problem of great interest for COM DEV International. A former study on MoS2 gave strong insights and a complete qualitative explanation on the reason for the good or bad lubrication provided by MoS2 under different conditions. The key for low friction relies on the rheological properties of a thin layer, called the 3rd body, created between both moving parts and whose characteristics depends on the environment. The project aims to develop experimental tools to measure the mechanical properties of the 3rd body to characterize its rheology and inform a numerical model developed in parallel. The project will initiate a collaboration between COM DEV International and the NanoMechanics and Materials Laboratory (NanoM2), University of Toronto. Ultimately the project aims to develop a general model that can be used with different kind of materials for space applications.