(A) study on landing guidance for point-to-point rocket transportation systems

Abstract

This dissertation deals with the landing guidance for point-to-point rocket transportation systems. Reusable orbital rockets employed in point-to-point rocket transportation systems demonstrate distinct maneuvering characteristics during the landing phase. To account for these characteristics, the landing guidance methods are designed based on optimization problems utilizing the 6-DOF dynamic equations, involving both translational and rotational motions. The proposed landing guidance methods are composed of the trajectory planning problem that generates a reference trajectory and the trajectory tracking problem that produces tracking commands. The trajectory planning problem is formulated as a 6-DOF fuel-optimal landing trajectory optimization problem. This problem is structured as a multi-phase optimization problem to incorporate the specific constraints associated with each landing phase. The trajectory tracking problem is formulated based on 6-DOF dynamic equations and a linear quadratic tracking objective function. The model predictive control (MPC) framework is employed to iteratively compute trajectory tracking commands. Building on this guidance structure, two landing guidance methods are designed depending on the form of the trajectory tracking commands. The sequential convex programming (SCP) algorithm transforms the original nonconvex problems into convex subproblems, enhancing convergence performance by incorporating the virtual state and trust region. Furthermore, numerical simulations are conducted to validate the performance and robustness of the proposed methods. A sensitivity analysis is performed to examine the impact of various parameters, leveraging insights derived from the Monte Carlo simulation results.