Mission safety improvement: A key factor for the success of next generation launchers

Two-stage winged space access vehicles consisting of a carrier stage with airbreathing turbo/ram jet engines and a rocket propelled orbital stage may significantly reduce future space transport costs. Beside other benefits, such a concept offers a great potential for mission safety improvements. Formulating the nominal mission and the abort scenario as an optimal control problem allows full exploitation of safety reserves. The shaping of the nominal mission significantly affects the prospective safety. For this purpose, most relevant mission aborts are optimized together with the nominal mission treating them as a branched trajectory problem. The applied method allows to assure the feasibility of the included mission aborts with minimum payload penalty. All other interesting mission aborts are separately treated, with the initial condition given by the state of the nominal trajectory at the time when a failure occurs. A mission abort plan is set up, covering all emergency scenarios.