A Fundamental Study on the Development of Lubrication Performance in Space Mechanisms under the Model Atmosphere on the Mars Surface

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Space mechanisms for mars investigation suffer from several conditions, such as high vacuum, low temperature, carbon dioxide atmosphere, and so on. A new vacuum tribometer was developed to investigate the lubrication performance of various lubricants including liquid lubricants considering the atmosphere on the mars surface. A vacuum of 10^<-7> Pa was attained using liquid N_2 trap. Residua gas could be analyzed using mass spectrometer. The lower friction specimen holder could be cooled down to around -100℃ by circulating liquid nitrogen in the base plate.In this work, commercially available 4 liquid lubricants for space applications, including 3 PFPEs (Type B, Type D and Type FZ) and 1 synthetic hydrocarbon (Malti-alkylated cyclopentan) were used. All the lubricants showed similar good lubricating performance under the room temperature in vacuum but when the temperature was gradually decreased during friction, all the lubricants showed sudden friction increase at the certain low temperatures. The order of the temperature where the sudden friction increase was observed is as follows. PFPE-B>PFPE-F>PFPE-D>MAC MAC maintain low and stable friction down to around - 70℃, but the friction surface lubricated with MAC was rougher and was much damaged compare to those lubricated with PFPEs.