Dreamy-eyed physicists have effused about the potential of stellar power, also known by the more prosaic name of space-based solar power, or SBSP, since the 1960s. They have sketched out preliminary designs that would bring that power from orbit to the grid — a giant engineering challenge, to be sure, but one that now has plausible solutions. What they haven’t been able to do is make it affordable.

Space scientists have roughed out designs for several different kinds of stellar power plants. Some look like an orbiting version of a terrestrial solar farm, with flat photovoltaic arrays stretching for miles. A design for NASA called SPS-Alpha, by former NASA physicist John Mankins, instead arranges thin-film mirrors into a bell shape that can redirect sunlight from almost any angle onto a smaller photovoltaic array.

The electrical current generated by an orbiting array can be sent to Earth in one of two forms. It could be converted into a broad infrared laser beam, or it could come down as a wider cone of microwaves, which, as Mankins notes, pass through clouds unimpeded. In either case, the satellite would focus its transmitter on a large receiving station on the ground. (See next page.) To ensure safety, the beam would be no more intense than the noonday sun, and a feedback signal would keep it from straying from its target.

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