Three-Degree-of-Freedom Hypersonic Reentry Trajectory Optimization Using an Advanced Indirect Method

Abstract

This study investigates a complicated reentry trajectory optimization problem for a reusable launch vehicle (RLV) in the presence of two control constraints and three state path constraints. Upon using traditional indirect methods, the considered RLV reentry trajectory optimization problem is converted into a complicated 12-point boundary-value problem that requires a priori knowledge about the structure of control and state constraints. Instead, a recently developed indirect method, the uniform trigonometrization method (UTM) is used, which leads to a two-point boundary-value problem, making the solution procedure notably easier. New features are introduced into the UTM framework in order to incorporate mixed state-control path constraints. Two scenarios are considered in which the control and state path constraints are 1) inactive and 2) active, respectively. A numerical continuation strategy involving backward-in-time propagation of the dynamics from the final point to the initial point with sequential implementation of the path constraints is proposed. The results are validated with a direct pseudospectral method. This study is the first instance of applying the UTM to a three-degree-of-freedom RLV reentry trajectory optimization problem in the presence of multiple linear and polynomial-form control inputs and mixed state-control path constraints.