Aero-Gravity Assist Maneuvers: Coupled Trajectory and Vehicle Shape Optimization

The aero-gravity assist maneuver is proposed as a tool to improve the efficiency of the gravity assist as, due to the interaction with the planetary atmosphere, the angular deviation of the velocity vector can be definitely increased. Even though the drag reduces the spacecraft velocity, the overall Δv gain could be remarkable whenever a high lift-to-drag vehicle flies. A previous study addressed the 3D dynamic modeling and optimization of the maneuver including heliocentric plane change, heating rate, and structural load analysis. A multidisciplinary study of aero-gravity assist is proposed, focusing on coupled trajectory and vehicle shape optimization. A planar aero-gravity assist of Mars has been selected as a test case with the aim of maximizing the vehicle heliocentric velocity and limiting the heating rate experienced during the atmospheric path. A multiobjective approach has been adopted, and a particle swarm optimization algorithm has been chosen to detect the set of Pareto optimal solutions. The study includes a further refinement of the trajectory for three significant shapes belonging to the Pareto curve. The associated optimal control problem has been solved by selecting a direct method approach. The dynamics has been transcribed into a set of nonlinear constraints and the arising non linear programming problem has been solved through a sequential quadratic programming solver.