A growing interest in the commercial development of space and a recognized need for noncarbon energy sources are spurring a reexamination of the prospects for generating large amounts of electricity from space-based solar power systems. Technological advances over the past 20 years are casting a more favorable light on the technical and economic feasibility of large-scale space solar power, and continued progress is anticipated. But keeping the effort moving forward for the next several decades will require international public-private cooperation and investment by both the government and commercial sectors. Scientists and engineers have identified a variety of potential applications for solar power in space that could become interim markets for developing and deploying the technology on the way toward an ultimate realization of beaming solar electricity to Earth.
With little fanfare, an idea first proposed more than 30 years ago for supplying Earth with abundant, zero-carbon electricity from solar energy is being revisited--only this time the perceived need for such a source is greater, and the long-term outlook for its economic feasibility is more favorable. By the middle of this century, some physicists and research engineers contend, a large share of the world's demand for electricity could be met by a constellation of very large space-based solar photovoltaic (PV) arrays. Transmitters connected to these arrays would each beam as much as several billion watts of power to Earth at microwave radio frequencies for collection by wide-area rectifying ground antennas and conversion to electricity.
The physics and the fundamental technology for such a scheme are well known and largely in hand, advocates say although prodigious engineering development would be necessary to actually build a space power system. The greatest barrier to realizing the potential of power satellites in high Earth orbit is the same as it was three decades ago--the high cost of launching hundreds of thousands of tons of solar arrays and other equipment into space and assembling them. For several reasons, however, the challenge now appears somewhat less daunting than it did 30 years ago. (Another, arguably less significant, barrier remaining from the past is public concern about environmental, health, and safety risks of large-scale space-to-Earth microwave energy transmission. Exports say such risks are exceedingly small; see sidebar, p. 10.)
The most basic idea for space power stretches all the way back to one of the founders of the electric age and the discoverer of wireless radio, Nikola Tesla. "Throughout space there is energy" he told the American Institute of Electrical Engineers in 1881. "If [it is] static, our hopes are in vain; if kinetic--and this we know it is for certain--then it is a mere question of time when men will succeed in attaching their machinery to the very wheelwork of nature."
Teslas prophecy--and his attempts to demonstrate terrestrial wireless power transmission--inspired later visionaries of space solar power. As noted by R. Bryan Erb of the Canadian Space Agency the Russian Konstantin Tsiolkovsky suggested in 1912 that rocketry would enable the collection in space of solar energy in...
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