Predictor-Corrector Reentry Guidance Algorithm with Path Constraints for Atmospheric Entry Vehicles

The problem of reentry guidance for an atmospheric entry vehicle is taken up for the study with focus on the evolution of a guidance strategy, which satisfies both terminal and path constraints. For this purpose, the numerical predictor-corrector approach is adopted, and an algorithm, based on real-time trajectory planning, is presented. The proposed guidance algorithm generates a feasible trajectory at each guidance cycle during the reentry flight, which is a function of the reference trajectory generated at the previous cycle and the measured parameter dispersions. The predictor steering program includes the bank reversal philosophy, and the corrector algorithm is formulated based on two control parameters and two terminal constraints. The path constraints on heat rate, aerodynamic load, and dynamic pressure are implemented as part of the predictor-corrector algorithm, by designing a control law for following the allowable drag and drag rate profiles. This control law is implemented through steering corrections in each predictor step, which ensures that each predicted trajectory satisfies the path constraints. The performance results for nominal and dispersed cases show that the algorithm steers a typical entry vehicle along a feasible 3-11 trajectory, which satisfies both terminal and path constraints.