Oct 6 1975
From The Space Library
A massive new power source for earth-transmission of solar energy by microwave frequency-had been under study by the Jet Propulsion Laboratory at the Goldstone station near Barstow, Calif.
The dish antenna equipped with a 450-kw klystron tube for microwave transmission, represented a space station; the tower a mile away with an array of solar receivers to which the experimental power converted to microwave energy had been beamed represented aground station. This research had been designed to lead to a network of space stations that would collect solar energy 24 hr a day and beam it to ground stations; the Goldstone tests had been the first high-power field trials of the system. Tiny rectifying dipole antennas-called rectennas collect and convert the radio-frequency beam; the 17 panels in the tower receiver contain 4590 of the rectennas. The system had demonstrated a maximum output of 30.4 kw converting the microwave beam to usable electricity, an efficiency of 82.5%. A space-to-earth system would be 6 times more effective than a surface system, the Los Angeles Times commented, and could probably supply 15% to 20% of the earth's energy needs in the next century. Development of a utility operating system delivering 10 000 mw of power would cost about $60 billion, as much as NASA has spent to date on space programs. A single equatorial space station carrying a 1-kmdiameter antenna transmitting to a U.S. earth station 15 km long and 10 km wide could supply all the electrical needs of New York City or a third of the needs of the Los Angeles basin. (LA Times, 6 Sept 75, l NYT, 10 Sept 75, 2)
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