Numerical Analysis of the Effects of the Overboard Vent on Spacecraft

During the operation of manned spacecraft, the pressure relief of the cabin is inevitable when pressure imbalance, fire or atmospheric pollution occur. Process of venting through the nozzle will generate distinct counterforce if the design is unreasonable, which could significantly impact the orbit and attitude of spacecraft. A rapid numerical simulation method based on computational fluid dynamics (CFD) was built to evaluate the design of pressure relief system for the spacecraft cabin based on the analysis of the nozzle plume, where the simplified computational domain model was established according to typical structure design scheme and the boundary conditions were finally determined through sensitivity analysis. Steady-state analysis of cabin pressure relief venting process was carried out to consider the cabin pressure dropped from the 1atm to 0.2atm gradually while approaching vacuum outside. The general law of the pressure and density distribution outside the cabin as well as evaluation of counterforce and moment was obtained. Furthermore, the effects of structure parameters under multiple opening position and aperture was obtained from the perspective of force analysis. Three-dimensional analysis was then carried out on the basis of two-dimensional demonstration with analyzing the nozzle plume under the whole structure. In accordance with error analysis of the manufacture parameters based on typical optimized structure, the effects of one or more hole deviations consisted of size and axial or circumferential position were analyzed. Additionally, it was found that the effect of size deviation is much greater than axial and circumferential position deviations. This study developed a numerical simulation method which can be used to evaluate the structural design quickly and a method for estimating counterforce caused by nozzle plume, meanwhile, provided an available rapid analysis tool for designing pressure control and pressure relief system of spacecraft cabin.