Modeling of material outgassing and deposition phenomena

Based upon our previous study, the outgassing and deposition phenomena under thermal vacuum conditions can be expressed by empirically based mathematical models for each material. Herein, we compared several time-dependent outgassing models and temperature-dependent sticking models with the data obtained from ASTM E1559 tests. This study suggests that the Volatile Condensable Materials (VCMs) on a receiver at wide-range temperature can be simulated in consideration of re-evaporation effect of deposited species. On the other hand, we found that temperature-dependent outgassing models were necessary to predict actual molecular contamination environments considering the on-orbit thermal cycles. This paper describes evaluation results of temperature-dependent outgassing models and deposition models where deposited species are taken into consideration by using the test data of Outgassing Rate Measurement Apparatus in accordance with ASTM E1559. In these isothermal. tests, operating temperatures of four QCMs were set <90 K, 213 K, 263 K and 298 K. The effusion cell temperature was 323 K, 373 K and 423 K for each test. Furthermore, we discussed validity and issues of the mathematical models in order to predict on-orbit molecular contamination deposition.