Optimal abort trajectory control for a winged orbital stage

In recent years, two-stage winged flight systems for space transportation have been investigated in order to improve the space transportation capability and to reduce costs. These flight systems use the atmosphere to produce lift and thrust. The carrier stage is equipped with airbreathing turbo-ramjet engines, while the orbital stage uses rocket engines. An issue of primary concern is flight reliability and safety which may also be improved by the new space transportation concepts. An important safety aspect is the capability for safe aborts in case of emergency. A primary reason for a mission abort is a main engine failure shortly after separation. Optimization results are presented which show the maximum achievable range of the orbital stage in case of a mission abort. One particular detail of such mission terminations is the release of fuel for reducing weight prior landing. The computations show that there is a range increase when fuel is optimally released during the trajectory.