The 9-ft. bowl-shaped antenna pointed straight up. Above it floated an object that looked for all the world like a small, square bedspring with a tiny helicopter attached. The rotor blades whirled with a thin whine, and the helicopter strained at the guy wires that kept it from climbing more than 50 ft. There it hovered, its blades spinning sturdily, drawing their power out of invisible microwaves shooting up from below. This was Raytheon Co.'s first public demonstration of an aircraft powered solely by radio energy.
Dream of Power. The experimental flight at Burlington, Mass., last week was an impressive...
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