Application of Optimal Control Techniques to the Parafoil Flight of Space Rider

The Space Rider program falls within the framework of ESA activities for the design of affordable and sustainable reusable aerospace vehicles. Among the greatest challenges for this mission is the design of the Guidance, Navigation and Control (GNC) subsystem for the re-entry phase. The final stage of the latter consists of an autonomous flight under parafoil that must guarantee a smooth and precise landing. To ensure compliance with the requirements in terms of landing accuracy and ground speed constraints at touchdown, the GNC subsystem must be able to counterbalance the effect of the wind during the flight and guarantee an upwind landing. A key role in this regard is played by what is commonly referred to as the Terminal Guidance phase i.e., the final part of the descent under parafoil where the vehicle performs the final approach to the designated landing point. The study presented in this work has been developed at the AOCS/GNC department of SENER Aeroespacial and the objective is to design a complete solution for managing the Terminal Guidance phase of a Space Rider-type case. This includes a guidance algorithm based on a direct method to generate an optimal solution for the trajectory, a path-tracking procedure, and a guidance logic that allows for a correct implementation within the whole GNC software. The optimal terminal guidance algorithm has then been implemented within the six-degrees-of-freedom simulator developed by SENER Aeroespacial demonstrating an excellent functioning for the proposed problem.