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"Projected deaths" are only part of the health effects estimated, but they are proportionate to some of the others such as "person days lost." Deaths, from accident or disease, were calculated from past experience with power plants in various stages such as construction, fuel harvesting, conversion to electricity, and final wastes. Since no experience exists for large-scale plants in orbit, the death projection for power sats is

unknown.

On the strength of the strictly economic portion of the cost analysis, coal gasification, light-water nuclear reactors, and combined solarthermal/coal plants on the ground appear warranted, whereas orbital power stations do not. Indeed ERDA now is headed in this direction.

Have we arrived at the end of the story? Or is there a danger in isolating the "cost" of any of these mammoth systems from the environmental, world-political, and other factors that the systems themselves influence? I submit there is very much a danger. My argument is not that cost is an improper tool for assessing which technology to choose. It is an excellent tool. But all likely costs to society must be taken into

account.

A simple thought experiment may be useful in pointing out the fallacy in any line of reasoning that attempts to insulate the cost of a future power system from the cost of conditions it helps bring about. "Thought experiments," besides being cheaper than real experiments, were devised by scientists to reveal how events affect each other. The idea is to invent an imaginary situation in which chains of events lead to logical conclusions, pointing up contradictions or absurdities in some theory or plan. My thought experiment traces the financial and social condition of the world through two extreme scenarios, both of which "solve" the U.S.

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energy shortage:

power is ruled out

A Input: A few years from now, orbital solar after various studies show it to be "uneconomical." The NASA budget erodes further from its present level of $3.8-billion this year (from a high of $5.3-billion in 1965). NASA's scientific and engineering capability decreases much more than proportionately since a certain minimum is required simply to keep facilities operating, and research and development is the only place to cut. ERDA places major emphasis on nuclear power. At first, light-water reactors are built that use enriched uranium oxide as fuel. The light-water reactor is chosen because it kills fewer people than coal gasification, costs only slightly more, and among all nuclear alternatives it lessens the danger that fissionable wastes will proliferate for weapons. Soon, however, by 1990, we begin to deplete our uranium-235 resource. It is now too late to consider power sats because NASA's level of effort is reduced to $2-billion and the agency primarily serves the Departments of Transportation, Housing & Urban Development, and others in addition to conducting space science and aeronautics studies. Since a commitment had been made to nuclear power as the major supplement of fossil fuels, since no detrimental health effects or serious accidents have occurred, and since the swelling of energy demand continues unabated, another move--this time toward hard-core nuclear energy--is "forced," as chess players say. A commitment now is made to the liquid metal fast breeder reactor that converts the more plentiful U-238 to plutonium and is completely independent of depleted U-235 resources. Liquid metals carry the heat from the reactor core to a steam plant where it is converted to electricity with a thirty-nine per cent efficiency.

Result: At the year 2000, we finally approach energy independence

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in the United States, with the majority of our electric power derived from nuclear reactors, of which many of the new ones are breeders. The other less energy-rich nations become more and more restive. The first atomic bomb homemade from stolen plutonium is exploded as an outgrowth of a riot in Panama over the fate of the second hundred years of the Canal. The next fifteen bombs determine the survivor of the first (and last) IsraelArab War of the Twenty-First Century, a one-day war. The Pentagon wonders whether massive nuclear retaliation ever can be a deterrent when there is doubt as to the origin of enemy missiles.

B In the second scenario of my thought experiment, we opt for "best over cheapest" and "global over national." Input: Since we cannot afford

the enormous expense of building power satellites alone, and since it would not gain us much if we releived our own energy shortage while our trading partners remained shackled to oil (and to the oil cartel), we internationalize the program. After a decade of satellite prototypes and

of progress in reducing the weight and multiplying the efficiency of solar cells, we begin to launch very large satellites from Cape Canaveral. These are assembled in space using space shuttles and paid for one-third by the U.S. and two thrìds by a dozen or so of our allies in Europe, the Americas, and Asia. In the beginning each satellite weighs two hundred and twenty million pounds, contains twenty square miles of photovoltaic "blankets," and produces five gigawatts of electricity by the time it reaches the utility grids of earth. (A gigawatt is one billion watts or one million kilowats. For comparison purposes five gigawatts is just under the six-point-eight-gigawatt capacity of the entire Greater Houston area; all of the Tennessee Valley Authority generates about fifteen gigawatts of electricity.)

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The satellites are injected into two low orbital belts, providing power to all nations on earth that subscribe. By 1990, the international consortium of nations has thirty-five satellites in each of two belts and sells three hundred and fifty gigawatts of power to its own members and others. Over the next decade, more satellites are launched--and more efficient solar cells are developed and installed on the old satellites by second- or third-generation heavy space shuttles. Total capacity enlarges to fifteen hundred gigawatts. The United States as the major space power in the consortium derives income from the launches to offset part of its considerable outlay; U.S. corporations profit by manufacturing many of the components.

Result: By the year 2000 (the less optimistic may substitute the year 2030), power sats are sufficient to supply the total fifteen hundred gigawatt U.S. electrical need, which is some eighteen per cent of total U.S. energy demand--up from about eleven per cent in 1977. One-third of the powersat output is so deployed. The other two-thirds is consumed by

the other consortium nations and other subscribers, which now vie to participate. Electric cars begin to be built on a massive scale as electric storage technology is spurred by the new age of ample electricity. The percentage of energy delivered as electricity begins to multiply dramatically and the barbaric burning of fossil fuels declines. Each barrel of oil now replaced by powersat electricity is two barrels of oil saved for the ten thousand petrochemical uses petroleum so uniquely possesses. (The making of electricity from fossil fuel is a wasteful conversion, let alone a smoky one. In 1977 a quarter of all raw fuel consumed in the U.S. resulted in less than half that fraction of energy delivered to customers.)

Our trading partners expand their national

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Underdeveloped nations that

productive capacities along with the U.S. subscribe to the global powersat system become more developed as plentiful energy spearheads a rise in the world standard of living. And now, on the foundation of powersat space stations in place, capacity can be augmented at the rate of a hundred gigawatts a year in the Twenty-First Century. An eventual "all-electric world" appears attainable as energy growth contributes to higher living standards that contribute to population stabilization.

Scenario "B" obviously promotes peace (and plenty) over scenario "A." Admittedly it is an optimistic outcome, and of course there are many other possible futures between these two extremes. The point of the exercise is to illustrate that cost of a new technology cannot be isolated but is interdependent upon many other economic, biological, political, and social phenomena. Cost is not total cost, and cheapest rarely means least expensive.

Another cost

I have not included ground-based solar photovoltaic energy as a viable alternative, although it certainly may plan a role in prototypescale and regional power in many locations. Its projected direct cost is about the same as orbital energy without the economic and social advantages of becoming an international force toward peace. consideration deserves mention when comparing power satellites with any ground-based system. Orbiting solar plants have a tremendous advantage in being capital-expensive and maintenance-cheap: that is, in the hard vacuum of even low-orbit space where wind and weather are totally absent and the only degredation of materials possible is that caused by solar radiation itself, power sats will last much longer than ground-based plants. If a ground plant may be expected to last thirty years, then an

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