Power-Optimal Guidance for Planar Space Solar Power Satellites

This paper presents power-optimal guidance for a planar space solar power satellite (SSPS). Power-optimal guidance is the attitude trajectory that maximizes the solar power transmitted by the SSPS. Planarity is important because it couples the orientations of the SSPS's photovoltaic and antenna surfaces. Hence, the transmitted power depends on the relative geometry between the SSPS, the sun, and the receiving station. The orientation that maximizes power transfer changes as this relative geometry changes. Both single- and dual-sided SSPS architectures are considered. A single-sided SSPS has one photovoltaic surface and one antenna surface. A dual-sided SSPS is a single-sided SSPS with at least one additional photovoltaic or antenna surface. Geometric arguments show that a dual-sided SSPS has superior performance to a single-sided SSPS. Power-optimal guidance is then presented for the special cases of SSPSs in geostationary Earth orbit, medium Earth orbit, and low Earth orbit transmitting to an equatorial receiving station at the time of Earth's vernal equinox. These examples emphasize important solution properties, including the need for large slew maneuvers, and they show that, even though system efficiency decreases as orbit altitude decreases, reduced path losses actually increase the amount of received energy per unit aperture area. This has significant system implications for future space solar power missions.