Onboard Autonomous Targeting for the Trans-Earth Phase of Orion

Abstract

The present investigation focuses on one aspect of the autonomous targeting process used onboard during the Orion trans-Earth injection phase, specifically, a fast and robust algorithm that identifies a feasible return trajectory, one that meets the entry constraints without exceeding the fuel available. Unlike earlier Apollo missions, Orion seeks to land near the polar regions of the moon. Thus, a substantial plane change maneuver is required before returning to Earth. To reduce the fuel expenditure associated with this plane change, a three-maneuver sequence is employed during the return phase. An autonomous onboard targeting process for precision entry (one that incorporates multiple coordinated trans-Earth maneuvers) is sought in the event of loss of communication with the ground. The latter scenario presents a very unique challenge: one never before required of any Apollo vehicle. The Apollo missions also benefited from flexible entry requirements in contrast to Orion. Precision targeting in multibody regimes has only been previously demonstrated in unmanned sample return missions such as Genesis. The formulation presented here ensures that the entry constraints are met without violating the available fuel budget.