Emergency scenarios of a re-entry vehicle due to control degradation

A controls degradation scenario is investigated for a reentry vehicle. It is assumed that one of two body flaps is blocked. The reaction control system is used to generate control moments in combination with the aerodynamic surfaces still operative. Particular emphasis is placed on implementing a control allocation method which yields an optimum utilization of the aerodynamic control surfaces in terms of minimizing the propellant mass required for the reaction control system. Minimum-propellant trajectories for the blocked body flap scenarios are determined using an efficient optimization technique. Results are presented which address blocked body flap scenarios caused by off-normal situations already in the orbital phase. The results show that no additional landing sites are required if an adequate amount of propellant mass is available.