Wireless Power Transmission (July, 1959)

Wireless power transmission seems about to become a reality after many years of dreams, science fantasy and experiments by, among others, famed Nikola Tesla. Raytheon has announced a new microwave tube, the Amplitron, which can convert raw ac into microwaves with extremely high efficiency — on the order of 80%. In addition, the company said it has learned how to cool the Amplitron so well that up to about 10 times as much heat can be dissipated as previously. The combination of high efficiency and greatly improved cooling seems to point the way to relatively efficient microwave power transmission.

One dramatic proposal which the Amplitron makes possible may be the amateurs' long-dreamed-of "sky-hook." This unmanned, permanently anchored-in-the-sky platform would be a radio-controlled helicopter receiving the power to keep it up with a big parabolic antenna, say 100 feet in diameter. Amplitron-produced microwave energy would be beamed at the parabola in the sky from a battery of many similar parabolas on the ground. This would be used to heat compressed air to drive the rotor blades keeping the platform aloft. Efficiency of such a system is estimated to be such that about 35% of the power beamed would actually be delivered to the heat turbines. In other words, 1,000 watts ac on the ground might become 800 watts of microwave energy, delivering perhaps 280 watts to the heat turbines.

Immediate use for sky-stations would be as communications centers using microwaves to cover hundreds of thousands of miles.