An Assessment of Aerogravity-Assisted Trajectories for Aerocapture at the Ice Giants

Abstract

The Ice Giants, Neptune and Uranus, are two candidates for an aerocapture maneuver, in which a spacecraft is captured into a bound orbit through a single atmospheric pass. Another aeroassisted maneuver, the aerogravity-assist (AGA), uses an atmospheric pass to increase the turn angle about a planet, thus enabling large changes in a spacecraft's heliocentric velocity. Both maneuvers require high arrival velocities and thermal protection system technologies; thus, it may be beneficial to execute both maneuvers on a single mission. To investigate the possible benefit of an AGA trajectory for setting up an aerocapture maneuver at the Ice Giants, a two-layer optimization approach has been employed to investigate the trajectory space. As an AGA maneuver relies on minimal planetocentric velocity loss due to drag, previous studies have focused on AGAs with high lift-to-drag ratio (L/D) vehicles, despite all heritage interplanetary vehicles being low-L/D. Due to the technology barrier for high-L/D interplanetary vehicles, the present study uses lower L/D vehicles, from low-L/D heritage vehicles to mid-L/D optimally-shaped vehicles. Feasible trajectories are identified for both Uranus and Neptune that increase the number of feasible launches as compared to traditional gravity-assisted (GA) trajectories. In addition, the study identifies a new family of periodic high-altitude AGA trajectories to Uranus that are feasible using heritage vehicles. For Uranus, trajectories are identified that enable aerocapture within current heat shield technology constraints using a vehicle with L/D = 1.25.