マイクロサテライトにおけるトライボロジー技術と宇宙環境からの影響評価に関する研究

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This project deals with the effect on space environment of tribological properties of molybdenum disulfide(MoS2)lubricants. In the previous researches, tribological testing was always carried out in a post process, which means the start-up friction includes the force of forming a wear track. This phenomenon usually covers the effect of atomic oxygen in a friction force. In this research, in-situ tribological testing was conducted and effect of atomic oxygen was investigated by XPS, AES, RGA, AFM and friction test. The results clearly indicated that the friction force increases with atomic oxygen fluence and it reached more than 2.5 times larger than ordinary friction force. Not only the start-up friction, but also steady-state friction increased with atomic oxygen exposures. The atomic oxygen fluence dependence on a friction coefficient was clearly observed. XPS results were interpreted that sulfur atom was removed from the MoS_2 surface, and molybdenum was oxidized into MoO_3 by the atomic oxygen exposures. RGA measurements revealed that the volatile reactive products of atomic oxygen/MoS_2 system is So. From the results obtained in this study, we concluded that MoS_2 lubricant is severely influenced by the atomic oxygen exposures in low earth orbit. In the case of microsatellite system, which is a recent technological trends in satellite systems, applied load of a friction system will be reduced due to the reduced mass, i.e., low inertia, thus, the delaminating phenomenon at the frictional surface will not be expected very much in such a system. Conclusion is that the microsatellite will be influenced by the atomic oxygen more severely.