• John C Mankins

The concept of generating solar power in space for wireless transmission to receivers on the ground has been discussed at some length during the past three decades. During the first decades of the new century, global demand for electrical power is projected to grow dramatically - perhaps doubling from 12 terawatts to more than 24 terawatts. Achieving this power growth while managing environmental impacts effectively is a cruical international challenge. During 1995-1996, the National Aeronautics and Space Administration (NASA) conducted a far-reaching re-examination of the technologies, systems concepts and terrestrial markets that might be involved in future space solar power (SSP) systems. The principal objective of this "fresh look" study was to determine whether a solar power satellite (SPS) and associated systems could be defined that could deliver energy into terrestrial electrical power grids at prices equal to or below ground alternatives in a variety of markets, do so without major environmental drawbacks, and which could be developed at a fraction of the initial investment projected for the SPS Reference System of the late 1970s.

Working with a major focus on emerging nations - the study examined 5 different markets and about 30 different SPS concepts, ranging from the 1979 SPS Reference Concept defined by the US Department of Energy and NASA to very advanced concepts involving technologies that have not yet been validated in the laboratory. Following a preliminary assessment of technical and economic risks and projected costs, 7 SSP system architectures and 4 specific SPS concepts were chosen for employing in greater depth using a comprehensive, end-to-end systems analysis employing a desktop computer modeling tool that was developed for the study. Several innovative concepts were defined and a variety of new technology applications considered. A key ground rule to achieve initial cost goals was to avoid wherever possible the design, development, test and evaluation costs associated with SSP-unique infrastructure. Three architectures in particular were identified as promising: a sunsynchronous low Earth orbit (LEO) constellation, a middle Earth orbit (MEO) multiple-inclination constellation, and one or more stand-alone geostationary Earth orbit (GEO) SPS serving single, dedicated ground sites. This paper presents a summary of the results of the "Fresh Look" study, including architectures, systems concepts and technologies.