RLV亚轨道再入段制导技术

重复使用运载器亚轨道再入段一般采用航天飞机应急返回发射场的飞行方案，分三个阶段：迎角恢复段、过载保持段和过渡段。该方案的难点是抑制动压，缺点是只有开环制导。分析了动压变化的影响因素，制订了抑制下沉率的制导策略，并给出迎角和过载指令的设计方法。其次分析初始状态偏差和气动升力/阻力系数偏差对动压的影响，提出了根据初始高度调整制导指令和根据下沉率进行过载指令补偿的闭环制导方案。仿真表明设计的轨迹能够满足飞行约束，闭环制导能有效减小最大动压偏差。

Guidance design of suborbital reentry for RLV

The guidance technique of suborbital reentry for reusable launch vehicle (RLV) is based on shuttle's gliding return to launch site (GRTLS).The flight uses open-loop guidance and includes three sequential phases:Alpha Recovery,Nz Hold and Alpha Transition.The main point is to reduce dynamic pressure.The factors contributed to dynamic pressure rate are analyzed,and the guidance strategy is designed to arrest the sink rate.The methods of both alpha and Nz commands design are also given.A close-loop guidance method is proposed to adjust the alpha and Nz commands based on keeping the maximum dynamic pressure near that of the nominal when initial altitude and aerodynamic are uncertain.The simulation results show that the flight constraints are well satisfied.