Abstract: To improve the landing stability of the Mengzhou manned spacecraft during the airbag buffering process, thereby enhancing the reliability and safety of the mission, relevant research on the underlying mechanisms and improvement methods is conducted. A finite element model (FEM) of the combined buffer airbag and the spacecraft reentry module is established based on LS-DYNA. The control volume method (CVM) is adopted to simulate the process of internal gas compression and work done during airbag buffering. Furthermore, a dynamic mechanism analysis of the airbag buffering process is conducted; combined with simulation results, the main factors affecting landing stability are further clarified. A novel overloadpressure combined control method based on differentiated active control is proposed: on the basis of the traditional overload control scheme, pressure data are incorporated, and the overturning moment generated during the buffering process is reduced through differentiated active control. Finally, the effectiveness of the proposed method is verified by the combination of multi-condition simulation comparison and full-scale model tests. The finite element simulation model of the reentry module-airbag assembly is obtained. The main factors affecting the landing stability of the reentry module during the buffering process are clarified, namely the pressure difference between the front and rear airbags and the tensile force of the airbags on the module. This is macroscopically manifested as: with other conditions fixed, the larger the noseup angle, the worse the landing stability. Three new control schemes are designed, and multi-condition comparative analysis is conducted between the traditional overload control scheme and the three new ones, followed by the selection of the optimal scheme. This scheme achieves a reduction in the maximum tilt angle of the module by 10.4%-18.2% respectively under the nose-up conditions, and the effectiveness of the new control scheme is verified through tests. An in-depth analysis is conducted on the main influencing factors and their tendencies regarding landing stability during the airbag buffering process. Based on the mechanism of the airbag buffering process, the traditional overload control scheme is optimized, which significantly improves the landing stability under various conditions. This research can provide reference for the design and optimization of landing stability in the airbag buffering system of subsequent large-scale crewed spacecraft.

Key words: Mengzhou manned spacecraft, buffering airbag, landing stability, differentiated active control, overload-pressure combined control, full-scale model test