Satellite Beams Solar Power Down To Earth, In First-of-a-Kind Demonstration

Researchers at the California Institute of Technology (Caltech) have successfully demonstrated the capability of steering power in a microwave beam from a satellite to targets in space, as well as transmitting some of that power to a detector on Earth. Science Magazine reports: The Caltech mission, funded by the Donald Bren Foundation and Northrop Grumman Corporation, aimed to go a step further with lightweight, inexpensive, and flexible components. The microwave transmitter was an array of 32 flat antennas packed onto a surface slightly larger than a dinner plate. By varying the timing of signals sent to the different antennas, the researchers could steer the array's beam. They pointed it at a pair of microwave receivers about a forearm's distance away and switched the beam from one receiver to the other at will, lighting up an LED on each.

The transmitted power was small, just 200 milliwatts, less than that of a cellphone camera light. But the team was still able to steer the beam toward Earth and detect it with a receiver at Caltech. 'It was a proof of concept,' says Caltech electrical engineer Ali Hajimiri. 'It indicates what an overall system can do.'

The Caltech spacecraft still has two more planned experiments. One is now testing 32 different varieties of solar cell to see which best survives the rigors of space. The second is a folded piece of ultralight composite material that will unfurl into a sail-like structure 2 meters across. Although the sail will not hold any solar cells, it is meant to test the kind of thin, flexible, and large deployments required for a future power station.

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