Orbit Options for Near-Term Space Solar Power

Studies of space solar power (SSP) for the commercial grid have usually considered transmitting power from geostationary orbit (GEO), via microwaves at frequencies below 10GHz, where the atmosphere is relatively transparent. Due to beam divergence from that distance at such frequencies, system sizes must be large, leading to power levels of 1000MW or more. However, the scale of the systems, and the need to develop low-cost routine access to space, make competing with traditional energy sources challenging in the near-term. More recently, studies by the US Naval Research Laboratory have considered SSP for nearer-term niche uses in remote locations. At such locations, providing power by conventional means can be challenging. Many remote locations are typically powered by generators, which depend on fuel delivered at great cost, often through hazardous environments. Power requirements for such users range from a few hundred kilowatts to several megawatts. Furthermore, some remote facilities are at high latitudes, which are inaccessible from geostationary orbit. This presentation will consider alternative orbits. Examples of such orbits are highly inclined orbits, which may be sun-synchronous, or have a repeating ground track, or both. In addition, elliptical orbits may be considered which have relatively long dwell times over ground sites that are beneath their apogee. Since non-GEO orbits do not remain over their intended groundsites, systems or constellations, of satellites must be designed, in which beam handoffs can provide a given ground site with power much of the time, while making maximum use of the satellites as multiple satellites serve multiple ground sites.