10-2. Status of Beamed Power Transmission Technology and Applications at 2.45 Gigahertz WILLIAM C. BROWN Summary A beamed power transmission system consists of the conversion of ordinary electric power into microwave or laser power, the illumination of a transmitting aperture with the power, transmission of the power through space, and its capture and reconversion into ordinary electric power at the receiving end. Beamed power transmission at 2.45 GHz has been under development for 25 years and has reached a high level of performance and application against which other beamed power approaches can be compared. Summary: Status of 2.45 GHz Technology The status of 2.45 GHz technology includes the following demonstrations and unique components: (1) a certified overall DC to DC efficiency of 54% in the laboratory, (2) the transmission of power over a distance of one mile with 32 kilowatts of continuous DC power output at the receiving end, (3) a low-mass, low-cost, ‘non-directive' receiving device called the ‘rectenna' that collects and converts microwave power into DC power with an overall efficiency of 85% and with a ratio of DC power output to mass of 1 kW/kg, (4) a low-cost transmitting module composed of slotted waveguide and the ordinary microwave oven magnetron that has been converted with external circuitry into a phase-locked, high-gain amplifier, and (5) a conceptual electronically steerable transmitting array composed of these modules and that will lock onto the rectenna at the receiving site. Its application includes demonstrations of a microwave-powered helicopter and recently (1987) of a free-flying microwave-powered airplane as the initial phase of the Canadian government sponsored SHARP system that involves a microwave-powered airplane flying at an altitude of 20 kilometers for communication and surveillance purposes. Its space applications include definitive studies for its use in (1) the Solar Power Satellite System where it efficiently transmits power from geosynchronous orbit to Earth, (2) a revolutionary LEO to GEO transportation system involving the use of high specific impulse ion thrusters that are powered by a space-borne rectenna capturing power beamed from the Earth, and (3) a system of‘industrial park satellites' orbiting in LEO and likewise powered by microwaves beamed from the Earth. These William C. Brown, Microwave Power Transmission Systems, 6 Perry Lane, Weston MA 02193, USA. Paper number IAF-ICOSP89-10-2.
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