1.3 An Historical Perspective for Space Solar Power It is important to consider the development of any project in the context of what has gone before. Here is presented a brief introduction to the history of space power. A more complete list of concepts and references is given in Appendix H. The utilization of solar power for electrical production on Earth has been proposed by many people. [Brown, 1984] The first important step was to prove that power transmission without wires was possible. Heinrich Hertz first demonstrated the transfer of power between antennae and Nikola Tesla suggested and attempted to implement large scale experiments in 1899. In 1912 Konstantin Tsiolkovski, in “Exploration of the World Territories by Means of Reactive Devices”, proposed beaming power to Earth from satellites for the first time. Significant quantities of power were transferred without wires for the first time in the early 1930s, when H.V.Noble of Westinghouse Laboratory collected power with an antenna separation of 8m. Little more was said about power beaming for almost 30 years. In 1959 the Raytheon Airborne Microwave Platform (RAMP) was proposed, using microwaves to heat air which drove the rotors of a helicopter, for use as a high altitude surveillance vehicle. In Russia, Nikolai Varvarov talked of “heliostations providing ... electricity in unlimited amount” to Earth, suggesting the use of photovoltaics for the first time, while Kraft Ehrike proposed Earth to Earth power relaying using huge space-borne reflectors to reflect a microwave beam generated on one continent to receiving stations on another. Isaac Asimov in “Caves of Steel” had future thinkers considering the theoretical notion of beaming power to the Earth from satellites near the orbit of Mercury. [Asimov, 1953] Figure 1.1 Artist's Impression of the RAMP [Brown, 1984] These proposals were not much more than dreams, as the beaming of power by electro-magnetic radiation had yet to be tested. Practical experiments were successfully carried out for the first time in America. Between 1959 and the 1970's Raytheon demonstrated small-scale laboratory demonstrations of power beaming with DC to DC efficiencies of up to 54%. In 1964 a small tethered helicopter powered by microwaves was demonstrated, followed in 1967 by an untethered model, which flew for up to ten hours. [Brown, 1965, Brown, 1969] These innovations were largely the result of the work of William Brown, who also did a lot of work in developing and improving microwave transmission and reception technologies. Dr. Peter E. Glaser of ADL Inc. proposed Space Solar Power as a serious concept in 1968. The design involved a geostationary satellite system with photovoltaic arrays transmitting energy at 2.45 GHz to Earth. In the mid 1970's, when the energy crisis encouraged research into alternative energy sources. Raytheon, in association with JPL, demonstrated power beaming on a large scale in 1975, sending
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