Flight Mechanics and Control: Safety Improvement for Two-Stage-to-Orbit Vehicles by Appropriate Mission Abort Strategies

The improvement of the safety of two-stage-to-orbit vehicles is considered which consist of a carrier stage with airbreathing turbo/ram jet engines and a rocket propelled orbital stage. Formulating the nominal mission and the abort scenarios as an optimal control problem allows full exploitation of safety reserves. The shaping of the nominal mission significantly affects the prospective safety. Therefore, most relevant mission aborts are optimized together with the nominal mission treating them as a branched trajectory problem. With this method, the feasibility of the included mission aborts can be assured with minimum payload penalty. All other mission aborts can be separately treated, with the initial condition given by the state of the nominal trajectory at failure occurrence. A mission abort plan is set up for all emergency scenarios.