Research on Trajectory Design Method for the Terminal Area Energy Management of Reusable Launch Vehicles

The nominal trajectory tracking is an effective guidance method for reusable launch vehicles (RLV) in the terminal area energy management (TAEM) phase. In order to ensure the safety of the flight, large uncertainties of initial states should be considered in the trajectory generation of TAEM phase for RLVs, as well as the process constraints like overload, dynamic pressure, and etcetera. In this paper, a parameterized design method based on the Hermite interpolation principle is proposed to generate a more adaptable nominal trajectory. The three degree-of-freedom (3DOF) dynamic model of RLV is established. The nominal control variables are derived based on the differential equation of motion, the formula of ground track and the altitude profile. The algorithm divides the trajectory of RLV into the lateral and longitudinal sub-planes. Based on the parameterized ground track and altitude profile, the nominal trajectory was generated using the inverse solutions of the control variables. Simulation results demonstrate that the algorithm can successfully generate the RLV trajectories in TAEM phase with multiple constraints and achieve complex flight missions.