Research On Reentry Trajectory Design Method For Reusable Launch Vehicle

Reusable launch vehicle(RLV)has been paid much attention by many countries because of its low cost and many times of use.The research on reentry trajectory design of reusable launch vehicle(RLV)can lay a good foundation for the design of guidance and control system of subsequent RLV.At the same time,excellent trajectory design can also reduce the research pressure of guidance and control system design.This paper studies the trajectory design scheme of the reentry flight phase of RLV.The reentry flight phase is divided into three stages: initial reentry,energy management and approach landing.The trajectory design and simulation analysis are given respectively.Firstly,the coordinate system and its transformation relationship used in this paper are explained,the earth model and aerodynamic model are introduced,and the motion model equations of each section are established according to the actual working conditions,which lays the foundation for the follow-up work.The traditional predictor corrector algorithm fixes the angle of attack profile in advance,plans the longitudinal trajectory by updating the pitch angle profile,and determines the pitch angle symbol through the heading angle error corridor,so as to plan the RLV flight trajectory online and in real time.Because the traditional algorithm needs to overturn the final pitch angle for many times,which affects the final accuracy,lateral guidance is introduced to avoid invalid overturning.The design principle of energy management section is introduced.The trajectory is designed to track the dynamic pressure height profile longitudinally and two tangent EDC circles and HAC circles laterally.The online trajectory planning is realized by updating the dynamic pressure value of the pitch angle and the midpoint of the dynamic pressure profile in real timeIn the approach landing phase,the lateral maneuver is not considered,and the quintic polynomial altitude profile is designed longitudinally.Compared with the traditional three segment landing method,the single segment trajectory profile in this paper has higher planning efficiency.