Trajectory Optimization for a Free-Flying 500-kW Photovoltaic Array Vehicle using EP

TLDR: In this article, the authors investigated vehicle sizing and performance requirements for a free-flying 500-kW solar array in orbital formation with a power-consuming host vehicle, which required independent propulsion for two functions: formation keeping with the host and attitude control for sun-pointing maneuvers.

Abstract: This paper investigates vehicle sizing and performance requirements for a free-flying 500-kW solar array in orbital formation with a power-consuming host vehicle. To meet these requirements, the sail vehicle required independent propulsion for two functions: formation-keeping with the host and attitude control for sun-pointing maneuvers. The equations of motion were developed assuming a rigid vehicle subject to gravity, aerodynamic drag, and solar pressure. A numerical optimization tool was developed to select the optimum orbital trajectory for seven canonical electric propulsion technologies: Teflon pulsed plasma thruster, hydrazine resistojet, hydrazine arcjet, ammonia arcjet, xenon Hall thruster, and xenon ion thruster. Subject to orbital and formation-flying constraints, the thrust amplitudes, firing sequences where developed to minimize the total vehicle mass was minimized. The best performance (lowest vehicle total mass) was found using a xenon ion propulsion system resulting in a 1,693 kg vehicle. The worst performance, (highest vehicle mass) was found using the N2H4 Resistojet resulting in a 2,191 kg vehicle. In addition to providing electric propulsion mission feasibility information, it was found that the optimal orbits, invariant of the thruster technology, sacrificed sun-pointing time for external force reduction.