Starr and Searl, 1990, stated in an Electric Power Research Institute study that although both nuclear and solar electric power are capital intensive they both share the ability to expand without being natural resource limited. They go on to state the rather obvious fact that terrestrial solar is limited by its diurnal dependence and its need for a storage system if it is to break the chains of this limitation. In addition, they point out that competitive use of land and water for food production may be a major constraint on the use of biomass as fuel as the world’s population grows. This analysis does not address the already well known problems of deforestation and desertification which are caused by the excessive use of biomass for fuel in the developing nations. Starr and Searl advocate nuclear power as the ultimate solution to global energy problems. As a counterpoint to this, Markovic (1990) points out the impossibility of finding a political and socially acceptable solution to the problem of nuclear waste disposal. This single factor might be a sufficient reason to give up on nuclear energy altogether. What then are our options? I propose that energy from space is a viable solution to the environmental problems posed by power generation. It is not an end all solution and given both the historical time constant of a half-century for substantial changes in the mix of large scale energy systems reported by Starr and Searl (1991), and the need for testing and evaluation, it should not be a threatening technological alternative to vested interests. Rather it is the dark horse or technological long shot. Nevertheless, the almost studied way that the satellite power solution is ignored by energy planners is curious. In order to be an environmentally viable solution, the impact of SPS must be mild when compared to the alternatives and the benefits must be large, since SPS is "the new kid on the block." Environmental Impact of Building SPS There are at least two major environmental concerns about energy from space. They are the effect of the exhaust from the vehicles launching construction materials to LEO and the effect of microwaves on the atmosphere. The former is highly dependent upon the acceleration of the launch vehicle, transit times through atmosphere and the type of propellant used. The first concern can be subdivided into three phases. The three phases are: technology validation and demonstration; acceptance of the technology as a viable alternative and competitor to other forms of power generation; and establishment of SPS as a mature source of environmentally benign energy. Currently there is no foreseeable way to avoid environmental impact during the first two phases. The questions to be answered here are: what is the magnitude of that impact, and is the long term benefit to the environment worth the short term cost. A design constraint which should be considered for future launch systems is the type of propellant that will be used at different altitudes.
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