forces and internal stresses on the physical structure. The satellite will experience both particle drag forces and induction drag forces. Douglas et al. conclude that the environmental consequences of satellite induced processes could be minimal but that the drag forces on an SPS during construction in LEO and during orbit transfer may be important. 3.4.2 Troposphere - Microwave Related Effects The anticipated effects on the lower atmosphere are caused by waste heat released into the atmosphere by the rectifying antenna (rectenna) along with the heating of the atmosphere by absorption of the microwave beam. The possible consequences of this thermal energy release involve impacts on the weather and climate. The effects of heat dissipation from an approximately 100-sq-km rectenna would be analogous to the effect of heat islands, which create mesoscale circulation patterns in the atmosphere on a horizontal scale closely related to the size of the heat islands themselves. For example, increases in the frequencies of occurrence of convective cloud formation and thunderstorm activity, and hence creation of precipitation anomalies, have been observed in many urban areas and their surroundings, and are thought to be due in part to the release of heat from within such areas. The possible influence of microwave transmission through the troposphere is due to the absorption of microwave energy along the beam especially in clouds, causing local heating, enhanced turbulence, and possibly altering the dynamics of atmospheric circulation and contributing to microwave power beam spreading and wandering. A preliminary assessment of the possible meteorological effects due to SPS rectenna operation was conducted by the Lyndon Johnson Space Center in 1977 (Ref. 3.16). The studies, mainly based on scale comparison and simple analytic estimates, are primarily qualitative in nature. The assessment was based upon the maximum power density of about 23 mW/cm^ of microwave beam and an average of 0.75 mW/cm^ of waste heat release at a rectenna covering approximately 100 km^. The preliminary findings are that the effects of the SPS rectenna on weather and climate will be very small, and engineering considerations and the direct environmental consequences of construction will have much more significant impacts. A continuous release of 250 MW of waste heat from a 100 km^ rectenna would be equivalent to the heat release asso-
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