6 Environmental and Safety Issues In this chapter we report the work that was done mainly in order to investigate the impacts on the Earth's environment caused by space solar power beaming. We begin by examining the effects directly caused by the power beam (e.g. microwave or laser beam). Next we discuss the impacts that the construction of a large artificial structure in orbit will have on the environment and on the safety of the workers. Our discussion would be incomplete without the treatment of the problems related to the existence and operation of a large receiving rectifying antenna. Furthermore in the security and maintenance section, we will state our overall assessment of the Space Solar Power Program. Finally we will address one section of our chapter to the planning and scheduling of the stages that have to be performed before the implementation of a large solar power satellite. In this chapter we mainly deal with a large solar power satellite in geostationary orbit as proposed by the study of National Aeronautics and Space Administration (NASA) I Department of Energy (DOE) in the late seventies, however specific research concerning the design examples that are treated in Chapter 10 was done and will be found in the corresponding chapter. It is important that planners of any size space solar power station, do a very careful environmental impact study. 6.1 Effects of Transmission of Energy 6.1.1 Propagation of the Beam through the Atmosphere In this section we will address the questions connected to the interactions that the power beam can cause within the atmosphere, including the ionosphere. For our work we refer to a solar power satellite in geostationary orbit that will beam power in the 5 GW range to the Earth's surface as was proposed by the NASAZDOE study of the late seventies. As the main attenuation of the power beam is caused by the atmosphere, we concentrate only on a few frequencies, given by a minimum in atmospheric attenuation according to Figure 6.1. [Koert et al., 1991]. As one can see in the figure below, there are several frequency-bands, where the attenuation is low (less than 1 dB/km). According to availability of technology, we choose the frequencies listed in Table 6.1 [Koert et al., 1991 and Firmain 1991] for further investigations. Table 6.1 Frequencies to be Investigated in More Detail ______________________ and Available Technologies_____________________ Upon transmission of electromagnetic radiation through the atmosphere and ionosphere the following effects may occur: • Ohmic heating, • Thermal self-focusing instabilities, • Molecular absorption losses, • Scattering.
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