Trajectory optimization for reducing unsteady heat input of aerospace craft

Heat input reduction by optimal trajectory control is considered for the return-to-base cruise of a winged two-stage space transportation system the carrier stage of which is propelled by a turbo/ram jet engines combination. A mathematical model is developed for describing the unsteady heat transfer through the thermal protection system. This model is coupled to the equations of motion of the vehicle. An efficient optimization technique is applied for constructing a solution for the return-to-base cruise problem. The results show that significant heat input reductions can be achieved with only small penalties in fuel consumption.