Direct Conversion for Space Solar Power

Abstract

Space Solar Power (SSP) is a powerful yet nearly untapped resource with revolutionary potential. SSP systems currently have several roadblocks to their implementation. With the technology in use today, converting solar power to useable energy is inefficient, the required converters have a large mass per unit power, and launching those converters is expensive. More fundamentally, in all current SSP systems, energy is generated in the form of a direct current before being converted again into whatever form is necessary. In addition to the large mass per unit energy of this conversion equipment, such conversion involves significant efficiency losses, further resulting in the prohibitive cost of launching these converters into space. If techniques could be discovered for converting broadband sunlight directly to a useable narrowband application dependent frequency, many fundamental breakthroughs in aerospace endeavors can be achieved. This project studied a large number of options that might lead to direct conversion. Those technology options were analyzed according to which would warrant further exploration from the point of view of aerospace systems applications and possible power per unit mass. Based on these technologies, several advanced concepts were considered. It is also important to make an estimate of the possible power per unit mass that could be achieved with each concept, so that architecture developers can proceed with the development of applications enabled by direct conversion technology. Accordingly, estimates of the possible power per unit mass of potential direct conversion systems were made, and future applications that would benefit from those direct conversion systems were identified. Three possible concepts were developed. These concepts include: a shocked photonic crystal system; a solar pumped maser based on naturally occurring astronomical masers; and an optical antenna array with central signal processing. The optical antenna array and the solar pumped maser were estimated to have a specific power approximately 15.0 and 10.8 times greater, respectively, than conventional photovoltaic systems. Additionally, several applications were identified that would benefit from direct conversion systems, including a SSP grid and electric propulsion.