Entry Trajectory Options for High Ballistic Coefficient Vehicles at Mars

Abstract

Future large-scale Mars surface exploration missions require landed masses beyond the capability of current entry, descent, and landing technology. Hypersonic trajectory options for large ballistic coefficient vehicles are explored to assess the potential for improved landed mass capability in the absence of landed accuracy requirements. Hypersonic trajectories appropriate for use with supersonic parachute and supersonic retropropulsion descent systems are studied. Optimal control techniques are used to determine hypersonic bank-angle control profiles that achieve favorable conditions at terminal descent initiation. Terminal descent initiation altitude-maximizing bank strategies for parachute descent systems are explored across vehicle and mission design parameters of interest. A tradeoff between altitude and flight-path angle at terminal descent initiation is identified. Hypersonic trajectories that minimize required propellant for propulsive descent are identified and studied parametrically. A hypersonic ballistic coefficient and lift-to-drag ratio are shown to have the largest effects on required propellant mass fraction; changes to the vehicle state at entry interface have a smaller effect. The space of reachable supersonic retropropulsion ignition states is presented over a range of vehicle and trajectory parameters. Overall, results indicate execution of an appropriate hypersonic bank profile can significantly increase the parachute deploy altitude for parachute descent systems or reduce the amount of propellant required when compared to full lift-up entry for supersonic retropropulsion descent systems operating at Mars.