Optimal guidance for toss back concepts of Reusable Launch Vehicles

In the context of the development of future launchers, Toss Back concepts are being studied by CNES together with ONERA. Focusing on the recovery phase between end of ascent and start of the landing boost, a guidance algorithm using an indirect method of optimal control based on Pontryagin's Maximum Principle is presented. First, a reference trajectory is computed offline, then this trajectory is used to initialize the guidance algorithm which consists in recomputing the optimal control online. Promising results have shown their benefits. In particular, solutions are provided quickly, at a frequency that is compatible with embedded guidance components.