A new field is developing involving the possible global activity of mankind: Power from Space, or Solar Power Satellites (SPS), which could solve some very difficult problems (see, for example, Proceedings of the Second International Symposium, SPS91: Power from Space, Paris, August 1991). There are difficulties involving the realization and even foundation of this program. Some of the difficulties concern the techniques and technology. Others concern environmental issues. Putting into orbit large payloads for SPS realization could produce environmental after-effects in the atmosphere. In addition to problems of energy and economy, there is a new environmental problem - loss of ozone from the upper layer of the atmosphere. There are different ways of solving these problems. A significant number of these problems could be solved by systems based on high-powered lasers. Power from Space by Lasers The most important and the trickiest problem is to create a global laser solar power system as a more competitive version of a global power network. The choice of the best energy transmission method from space to the Earth’s surface is also limited. Microwave transmission is quite logical and well-developed, but from our point of view has at least two disadvantages: the physical limitation on the lower diameter of the antennae, and some undesirable biological effects. The enormous constructions for transmitting and receiving high-power microwave beams are not only too expensive, but also limit the utilization of this energy (mobile consumers and separate, localized consumers are excluded from the SPS power supply system by microwave radiation). The optical (laser) version is now more promising. There are two principal possibilities for laser-type energy generation: 1) Conversion of solar radiation energy into electricity, followed by electric laser pumping, or 2) Direct pumping of the laser by solar radiation. Here it is harder to make a definite choice. Direct solar pumping is very attractive. In this case the SFS-system is simpler in terms of the number of necessary stages and it looks refined. However, the efficiency of electrically pumped, solid-state lasers is relatively good (there are photovoltaic converters, and high-efficiency, diode pumped lasers). The overall energy efficiency of SPS with electric pumping and direct solar pumping is estimated to be the same. This fact defines approximately equal areas and masses of solar concentrators. But the feasibility of the system as a whole would depend on its cost and maintenance. The electric version needs an on board electric facility for conversion of solar energy and for the conditioning of electric energy for
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