Reusable Launchers: Development of a Coupled Flight Mechanics, Guidance, and Control Benchmark

Abstract

This paper studies the mechanics of reusable retropropelled flight of slender low lift-to-drag bodies via integrated guidance and control simulations. To do this, a simulation benchmark focused on the coupling between flight mechanics, guidance, and control must be developed, as opposed to mission-optimization-oriented ones that simplify (or directly ignore) these couplings. The developed simulator covers vertical takeoff and landing of a first-stage booster for return to launch site and downrange landing missions. To steer it toward a controlled entry, followed by descent and precision landing, the vehicle is configured with a deep throttling thrust vector control system, fins, and cold gas thrusters. Comparative performance results are derived in terms of aerodynamic loads and heat fluxes for both recovery scenarios, as well as through a detailed closed-loop controllability analysis. The latter demonstrates that the configuration has sufficient authority and resolution to perform stable flight and adequate wind gust rejection. The developed benchmark (because of the coupled flight mechanics, guidance, and control) allows to provide a first assessment of operational limits, as well as mission and GNC specifications. This in turn paves the way for the synthesis and assessment of more sophisticated reusable launcher guidance and control algorithms.