Abstract: Aiming at the problem that the windward side of very low orbit spacecraft is subjected to too much aerodynamic resistance，based on the theoretical solution to the aerodynamic drag of free molecular flow，the aerodynamic resistance of several typical windward side configurations with different length was calculated and the reasons for their changes were analyzed.After which an expression of the windward side was designed and an intelligent algorithm was introduced to iteratively optimize it.Given the constraints of the configuration，the penalty function was introduced to reduce the fitness of the infeasible solution.The results show that this method can obtain the approximate optimal solution of the windward side with minimum resistance.Under the constraints of existing materials，the maximum drag reduction of this method can be more than 5% compared with the conical structure，and the head volume of the spacecraft can be effectively increased.With the increase of windward height，the minimum resistance configuration gradually changes from near frustum to cone.The optimization method proposed in this paper can provide a reference for subsequent drag-reducing configuration design of very low orbit spacecraft.

Key words:  , very low orbit spacecraft；rarefied gas；Boltzmann equation；PSO algorithm；penalty function；drag reduction configuration