New Control Functionalities for Launcher Load Relief in Ascent and Descent Flight

The development of effective load relief strategies is key to the improvement of launcher flight performance as it enables a joint increase of wind resilience and decrease of mass. This is particularly relevant for reusable launchers, which are aimed at maximising their operational availability and payload capacity. Yet, despite various advances in aeronautics and wind energy load relief, classical feedback-only techniques remain the state-of-practice for launchers. In this article, an improved load relief functionality is proposed by augmenting a conventional control design with a disturbance observer for on-board wind anticipation. Without requiring any change in the feedback loop,this approach also paves the way for the use of forward looking wind estimation in the launcher domain. The disturbance observer is designed and analysed using robust control techniques for a lightweight, non-winged reusable launch vehicle, which relies on the use of planar fins for unpropelled descent attitude control. While the use of fins for launch is not a common practice, the article also exemplifies how their use can further improve launcher performance.