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What is needed is a true energy solution, as described in Table I. The primary objective of this solution is reestablishment of a sound national economy. Required characteristics of such a solution are also given. Hydroelectric power might be such a solution since it is nondepletable, is available within the United States, etc., but it fails on the third point, sufficiency. Much of the elevated water available for hydropower within the United States is currently in use. So let's consider some other source or sources with the required characteristics.

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What is that source to be? Several alternatives have been under study and development within the United States. Table 2 lists some of these and critical characteristics of each. This paper concerns itself with the last of these energy sources-space solar power.

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Figure 3 illustrates the principle of space power satellites. The satellites would be located in geosynchronous orbit some 22,000 miles above the Earth. In this orbit they remain in one position over the equator and provide direct line-of-sight transmission of energy by radio beam to receivers on the Earth. In this orbit the satellites are nearly constantly illuminated (over 99% of the time). The source of this energy is solar rays converted to electricity by an array of solar cells. The satellites are rather large, with areas of approximately 35 sq mi. Their output is, however, proportionate to the size in that approximately 10 million kilowatts of power are provided by each. The satellite shown is equipped with two transmitters and serves two Earth receiving sites (5 million kilowatts per site). Satellite sizes down to approximately 2.5 million kilowatts per receiver appear economically practical. The constancy of output of the ground receivers, without the effects of night and weather, provides baseload electrical power.

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As shown in Figure 4, a number of organizations, under the lead of the Department of Energy and the National Aeronautics and Space Administration, have studied the subject of solar power satellites for approximately 8 years. This activity has been scattered across the United States and has involved corporations of various types. Until approximately 1973 these studies were performed at a relatively low level and considered solar power satellite concepts appropriate for use in the 21st century; very high technology levels were to be utilized. Such satellites would also have a very high performance and showed the promise of producing very low cost electrical energy, perhaps only 2 cents per kilowatt hour. Recent studies indicated, however, that advanced technology is not required. Solar power satellite design concepts drawing on near term technology have the promise of producing electrical energy at approximately 4 cents per kilowatt hour by the early 1990's, a very attractive and competitive price.


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Because of the utilization of this near term technology it appears that SPS (Solar Power Satellites) will not require new science; instead SPS is a large engineering job and technological breakthroughs are not required.

Table 3 summarizes the characteristics of solar power satellites that would allow them to serve as a national energy solution. These seven characteristics will be addressed one by one.

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Figure 5 symbolizes ways in which solar power satellites would promote national economic stability. Today, we send our dollars overseas to oil owners who return to us oil which we burn to obtain only energy. With solar power satellites these dollars would stay in the United States, providing jobs for our people in addition to providing energy and creating lasting material wealth.

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In this respect solar power satellites are similar to hydroelectric dams. That is, once constructed they remain available and represent real wealth which has been added to our economy. As with our previous space programs, e.g., Apollo, the development and utilization of solar power satellites would produce many technological spin-offs, enhancing our overall technological stature and thereby improving our position in the world. Solar power satellites are also a potential item for export; not only could entire satellites and ground receivers be produced and exported, but also with our satellites operational on orbit it might be possible to divert energy beams to receivers in other countries at times when our own energy demand is low (such as at local midnight below a solar power satellite station). It must be emphasized here that dollars spent on solar power satellites, or for that matter any space program, are not thrown into space. They are used by our people and remain in circulation within our country.

The energy output form of solar power satellites has direct applicability to our national needs. As indicated on the left of Figure 6, we now use far more fossil fuel for heating than we do for transportation. This heating is accomplished by combustion of coal, natural gas, and oil in our homes, industries, shopping centers, etc. This heating could be effectively accomplished by electricity. If this were done with electricity from solar power satellites, fossil fuel now burned for heating could be made available for transportation. With technological advances, such as electric cars, fossil fuel consumption for transportation could be further reduced. As a side benefit, conversion of these localized heaters to electricity eliminates numerous polution sources.

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Figure 6. Solar Power Satellites Have APPLICABILITY to the Need (Produce a Usable Energy Form) Figure 7 shows how we can install as many solar power satellites as may be necessary to satisfy our forseeable energy needs. In orbit over the equator, satellites serving the United States would fall between roughly 90° and 150° of longitude. Note that in this location they are located entirely over the Pacific Ocean and not above any land mass. The arc in space in which the satellites would be placed is sufficiently long for hundreds of satellites.

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