CFD Simulation and Experimental Study on Outgassing and Damage Characteristics of Multilayer Insulation During Ascent

Multilayer insulation (MLI) is widely used on the outer surface of spacecrafts. In the ascent stage, the air pressure outside the spacecraft decreases rapidly from 1 atmosphere to 100 Pa within approximate 120 seconds. Hence, the inert gas of the spacecraft expands and then releases rapidly through the MLI, which may result in the damage of MLI. In this paper, a simplified geometrical model of MLI is established, and computational fluid dynamics (CFD) method is applied to simulate the outgassing process, the pressure contour and aerodynamic force of each MLI layer during ascent are calculated. The results show the pressure decreases gradually from the inside to outside layers, and the flow induced force generally rises from the inside to outside layers. The maximum aerodynamic force and stress occur at approximately the intermediate moment of the depressurization process. In addition, a test rig is designed to simulate the rapid depressurization process during ascent. MLI damage phenomena are observed in some geometric and fixation conditions. It is interesting that all the damage occurs at the outer layers of MLI firstly, and the maximum differential pressure between the upstream and downstream of MLI occurs at intermediate moment of the rapid depressurization process. These findings agree with the CFD results. Besides, the influence of layer number, fashion of outgassing holes and fixation on damage characteristics are discussed.

Keywords: Multilayer insulation, Ascent stage, CFD, Outgassing, Damage characteristics.

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