Fig. 7-4. Required Busbar Charges 7.3 ENVIRONMENTAL IMPACT 7.3.1 Exhaust Emissions All systems require the same land use for their rectennas, since a common microwave power transmission system was baselined. Also the effects of the microwave power system itself as regards ionospheric impact, heating, sidelobes, etc., will be the same. Effects of the launch vehicle exhaust will be in direct proportion to the mass of the system; refer back to Figure 7-2. Table 7-1 gives quantities of various exhaust products released into the atmosphere by the Table 7-1. Launch Vehicle Exhaust Emissions for Total Life Cycle of a Solar Brayton 10 GW SPS_______________ launches associated with a typical SPS installation (the Brayton type). The number of launches for each system is in the order of 1500, depending on system mass and includes launches for maintenance during a 30-year period. The emissions are for altitudes above 12 Km (40,000 ft.). Below this altitude, CO and CO2 emissions would be approximately the same as above 12 Km, but H2O would be very much less. The maximum H2O produced would be somewhat greater than a small thunderstorm, but considerably less than a tropical thunderstorm. The chart shows probable maximum masses of nitrides of oxygen which are too small to be drawn to scale. Also indicated are masses of HCL and AI2O3 produced by the space shuttle in associated crew rotation launches. 7.3.2 Energy Balance MSFC correspondence (1) directed that methods suggested in a recent article in Science (2) be considered. In (2), the author considers all energy necessary to perform functions (e.g., processing of ore to produce metal, transportation of parts, etc.) that are part of total plant construction as subsidy. Thus, the sum of all subsidies represents an energy investment and the useful energy output is the return. The ratio of the return to the subsidy is the performance index used in (2) and below. Subsidy density (defined as kWh/kg) data has been found in many sources. Wherever possible, those sources have been used that consider primary energy by using the "input-output method of analysis" (see (2)). Also in the case of fuel and plastics, feedstock energies are included in the subsidy. The approach used in (2) and here is somewhat new, and subsidies are not readily found for all materials or functions. All estimates for materials or functions for which no subsidy could be found were conservatively estimated. In these calculations energy subsidies are given in terms of kW thermal, as the majority of such quantities are related to hydrocarbon fossil fuels. However, system electrical output is, of course, in kW electric. Thus "energy grade" must be considered. In (2) the method used was to multiply electrical energy by a factor of 3.5, to compensate for the inefficiency of conversion of fossil to electrical energy in power plants. This method is used here, i.e., the 30 year electrical output is multiplied by the factor 3.5. Table 7-2 summarizes the various subsidy components, in terms of their masses and energy contents for each system. The liquid hydrogen is assumed to be produced by electrolysis, and its energy subsidy has, therefore,
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