An alternative concept for aeroassisted orbit transfers

The primary results of this study are identification of possible new applications of aeroassisted orbital transfers to LightSat/TacSats and the feasibility evaluation of an on-line neural network implementation of an atmospheric trajectory/guidance scheme. AOT scenarios involve 2 distinct categories: on-orbit multiple-pass 'soft maneuvers' and the single-pass deep penetration into the atmosphere 'hard maneuver'. Due to propellant limitations, the soft maneuver is very conducive to address LightSac/TacSat orbital transfer requirements. Possible soft-maneuvers include inclination and perigee location stationkeeping. Hard maneuvers are more conducive to situations requiring a greater amount of maneuverability, e.g., emergency relocation of a satellite. Associated with each class of AOTs are a set of relevant vehicle and mission requirement parameters, which help define the overall feasibility of AOTs. Chief among these parameters is perigee altitude. Perigee altitude determines the amount of atmospheric density available to perform on-orbit maneuvers. Since density decreases exponentially with altitude, AOTs are not feasible beyond a perigee altitude of 200 km. Lower perigee altitudes come with detrimental effects of shorter orbital lifetimes. This can be ameliorated via more eccentric orbits. Among the relevant vehicle parameters are satellite mass, reference area, and aerodynamic efficiency. Trade-off studies were performed for two specific soft maneuvers: plane change and rotation of line of apsides.