过载约束下的探月飞船再入轨迹的在线设计

On Line Design of Reentry Trajectory under Aerodynamic Acceleration Load Constraint of a Lunar Vehicle

研究了以第二宇宙速度返回地球的载人探月飞船的再入制导律设计问题.针对基于落点分析的数值预测-校正算法不能有效满足再入过程的气动过载约束条件的问题,提出一种基于解析计算的常值气动过载算法与基于数值积分的预测-校正技术相结合的融合再入制导方案,在线生成了同时满足过载约束和落点精度要求的再入轨迹.数值仿真表明提出的制导算法不仅能满足达到高精度着陆的要求,还能满足气动过载约束要求.在一定的再入初始条件下,探月返回飞船可以不必采用逻辑复杂的阿波罗式跳跃再入方案.这一方案可为即将展开的载人探月活动制定月-地返回轨道和再入策略提供参考.

In this paper a guidance algorithm is presented to address the reentry problem of a lunar returning vehicle at the second cosmic velocity.The predictor-corrector method based on the accurate landing target location cannot meet the aerodynamic acceleration load constraint in general.For this technical problem,we combine the predictor-corrector method and a constant acceleration load method,and propose an integrated reentry guidance strategy.The improved scheme is based on real-time trajectory planning and generates a feasible trajectory during the reentry flight,thus satisfying both terminal path constraint and aerodynamic load constraint.Numerical simulation results are presented to demonstrate the effectiveness of the proposed scheme.It is shown from this presented study that if the initial reentry condition is selected appropriately,the skip trajectory entry guidance algorithm may not use the Apollo＇s scheme which has a very complicated logical technique.This work is of benefit to the design of moon to earth trajectory and the reentry strategy of our upcoming manned moon landing project.