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This article studies the mechanics of reusable retro-propelled flight of slender low liftto-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-optimisation 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. In order to steer it towards 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.

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 by DESCENDO operating in a closed-loop fashion over full recovery scenarios enable a computationally-efficient mission performance assessment.

Summary In this article, a complete modelling, synthesis, and analysis methodology of control compensators for descent and landing (D&L) on small planetary bodies is presented. These missions are scientifically very rewarding but technically extremely challenging due to the complex and poorly known environment around those bodies, which calls for the ability to manage competing robustness and performance requirements. While this issue is typically addressed via the redefinition of D&L guidance strategies, here, it is tackled through the augmentation with a simple yet robust control compensator. This compensator is designed using linear fractional transformation modelling to capture the interplay with uncertain gravity fields and the recently developed structured H∞ optimisation framework, which has been proved particularly suitable for industry‐oriented applications. The proposed approach is completely generic but uses the scenario of a landing on the Martian moon Phobos as an illustrative example. Different compensators are then verified and compared analytically via the structured singular value μ and through high‐fidelity Monte Carlo simulation.