Trajectory Planning For A Reentry Vehicle Under Failure Conditions

In this paper, we discuss the trajectory planning problem for the unpowered approach and landing phase for a reusable launch vehicle. A method for modifying the aerodynamic database so that trim effects are taken into account is presented. This results in a method to take into account 6 degree-of-freedom effects in a reduced order model, that can then be used in trajectory planning problems. We set up the trajectory planning problem as a state-input constrained, fixed end-point, optimal control problem, and apply Pontryagin´s minimum principle to obtain first-order necessary conditions. We then present a variation of the modified simple shooting method to solve the resulting two-point boundary value problem. We present results from two numerical examples: (1) a nominal case with no effector failures, and (2) a case where the right ruddervator is failed upward at 3.5deg.