Abstract: China has developed a set of combined cushioning airbags for the test ship of its new human spacecraft. The return cabin of the new spacecraft was taken as research object, and a dynamic model of the cushioning process of combined airbags with inner airbags was established based on the theories of fluid mechanics and thermodynamics. Then, the validity of this model was verified by MSCDytran.Through simulation calculation, the influence of two inherent gas parameters that affect the airbag cushioning characteristics, gas freedom and molar mass, was analyzed. The research results show that, compared with the degree of gas freedom, molar mass has a greater impact on the cushioning characteristics, i.e. the smaller the molar mass of the gas, the faster the exhaust speed of the airbag and the smaller the required vent area. But by adjusting the vent area of airbags, several common gases can be used as airbag cushioning medium to achieve similar cuadjusting shioning effects. The maximum deviations of buffer  and rebound speed do not exceed 02g and 012m/s respectively. Research results of the article can provide references for the selection of gas medium in engineering applications of cushion airbags.

Key words: gas, airbag, dynamics, cushion characteristics, vent area