Abstract: The engine thrust and aerodynamic forces are highly coupled in the landing of the vertical recovery rocket, and the feasibility and safety of the rocket not only depend on the trajectory terminal position, velocity and attitude deviation, but also on the initial attitude deviation and the control accuracy of the landing energy. In this paper, for the complex dynamic model trajectory planning problem with aerodynamic changes under the influence of the engine starting section and jet stream, the segmented trajectory online planning was carried out by adopting the polynomial guidance method in the starting section and the analytic initial value-sequence convex optimization method in the thrust throttling adjustment section. In order to eliminate the jumps of switching attitude angle caused by the difference of segmented solving models, a quintuple polynomial form was used to obtain the analytic initial value reference profile with the constraints of the initial attitude angle. Then, through the dynamic adjustment of the thrust angle and trajectory tilt angle constraints and the introduction of a deviation relaxation term, the terminal mass constraint was added to the optimization performance index function, and the optimization problem with constraints on the terminal position, velocity, attitude, and specified mass was completed by using the sequence-convex iterative method. The results show that compared with the traditional polynomial or convex optimization methods, the proposed method has advantages in accuracy index and number of constraints, and can achieve accurate terminal position, velocity and terminal mass constraints under the combination of deviation conditions, with the terminal attitude angle deviation of less than 1.5°, and the average time consumed for online planning is less than 1 s, which is of good engineering application prospect and can provide certain reference for the development of China's new generation of reusable manned launch vehicles.

Key words: Reusable Launch Vehicle, Vertical Landing, Energy Management, Analytical Initial Value, Sequential Convex Optimization