Minimum Radiative Heat and Propellant Aerocapture Guidance with Attitude Kinematics Constraints

Aerocapture leverages atmospheric drag to convert a spacecraft’s hyperbolic trajectory into a bound orbit. For some aerocapture missions, heating due to the radiation of high-temperature gases in the shock layer can be much larger than the heat due to convection. This paper provides analytical proof and numerical validation that radiative heat load is minimized by the same trajectory that minimizes the final ΔV: a single switch bang-bang trajectory, starting with lift-up. The proof is general and is valid for several formulations of radiative heat flux; further, the same proof can be used to conclude that convective heat load, computed according to many of the available formulations, is instead maximized by that trajectory. Further, a novel guidance that plans a bang-bang trajectory with constraints in the attitude kinematics is introduced. While achieving performance similar to that of the current state-of-the-art, the inclusion of constraints in attitude kinematics allows for much less tuning. Finally, a lateral guidance that makes use of information on the final inclination of the predicted trajectory is introduced. Such guidance allows for very high accuracy in the inclination requirements with only two reversals by requiring a single parameter to be tuned.