Onboard guidance for reusable rockets: Aerodynamic descent and powered landing

This paper describes a novel general on-board guidance strategy which can be applied to both the aerodynamically-controlled descent and the powered landing phase of reusable rockets. The proposed guidance method is based on sequential convex optimization applied to a Cartesian representation of the equations of motion. The contributions are an exploitation of convex and non-convex contributions, which are processed separately to maximize the computational efficiency of the approach, the inclusion of highly nonlinear terms represented by aerodynamic accelerations, a complete reformulation of the problem based on the use of Euler angle rates as control means, an improved transcription based on the use of a generalized hp pseudospectral method, and a dedicated formulation of the aerodynamic guidance problem for reusable rockets. The problem is solved for a 40 kN-class reusable rocket. Results show that the proposed technique is a very effective methodology able to satisfy all the constraints acting on the system, and can be potentially employed online to solve the entire descent phase of reusable rockets in real-time.