Entry Trajectory Reconstruction for an Unpowered Reusable Launch Vehicle Under the Change of Landing Field

This paper presents an entry trajectory reconstruction method for an unpowered reusable launch vehicle (RLV), which can replan a feasible trajectory during the entry flight when the landing field is changed in an emergency. Using the quasi-equilibrium condition, the upper- and lower-bounds of the bank angle are obtained. In order to satisfy the path constraints, a weighted combination of the bounds is proposed to determine the magnitude of the bank angle. Then, the sign of the bank angle is determined based on a lateral planning algorithm. Thus, the trajectory reconstruction process can be simplified as a three-parameter search problem for satisfying the terminal constraints. A secant method provides an effective way to solve this root-finding problem. Finally, the performance of the trajectory reconstruction algorithm is assessed with different alternative landing fields.