Guidance of Reusable Launchers: Improving Descent and Landing Performance

The sizing and capability definition of reusable launchers during high-speed recovery are very challenging problems. In this article, a convex optimisation guidance algorithm for this type of systems is proposed based on performance improvements arising from the study of the coupled flight mechanics, guidance and control problem. In order to appreciate the obtained improvements, trade-off analyses of powered descent and landing scenarios are presented first using traditional guidance techniques. Subsequently, these results are refined by using the proposed online successive convex optimisation-based guidance strategy. The DESCENDO (Descending over Extended Envelopes using Successive Convexification-based Optimisation) algorithm has been designed as a middle-ground between efficiency and optimality. This approach contrasts with previous convexification algorithms that either aimed at increasing computational efficiency (by typically disregarding aerodynamic deceleration) or reaching trajectory design optimality (by using exhaustive convex approximations). More critically, the algorithm is not confined to the mild coverage conditions assumed by previous approaches and can successfully handle the incorporation of the operational dynamics of reusable launchers. Insights provided byDESCENDOoperating in a closed-loop fashion over full recovery scenarios enable a computationally-efficient mission performance assessment.