Research of Onboard 3-D Guidance Trajectory Propagation of Terminal Area Energy Management for RLVs

An onboard 3-D guidance trajectory algorithm of terminal area energy management(TAEM) for reusable launch vehicle(RLV) was researched.According to initial dynamic pressure,position and heading,an onboard 3-D trajectory can be propagated following the restrictions of dynamic pressure,normal overload,final dynamic pressure,final position and final heading.Based on onboard generated reference dynamic pressure profile and lateral reference trajectory,propagation of 3-D trajectory was fulfilled by means of dynamics functions of center of mass.Lateral reference trajectory planning includes 2 steps,that is,erasing lateral position error,in which longitudinal error is reduced simulataneously,and erasing longitudinal position error.According to size of longitudinal position error,3 modes of trajectories were used to erase it by a set of logical procedures.In 3-D trajectory propagation stage,if the final position of trajectory generated by 3-D propagation exceeds the allowable scope,the path angle was compensated and the 3-D trajectory was propagated once more to generate an eligible trajectory.The simulated results show that the trajectory algorithm can propagate a 3-D guidance trajectory fast,exactly and has strong robustness in the distributions of initial position and heading.