TABLE 5 PHOTOREACTIONS INVOLVING CHARGED SPECIES FOUND IN THE D-REG1ON WHICH MAY BE INDUCED BY AN INTENSE IR-PHOTON FLUX The concentration of O3+ is so low that the consequences of increasing its photodissociation rate (which is already large because of the solar flux) by laser-power beaming are completely negligible. Furthermore, only shorter-wavelength laser photons have sufficient energy to induce this reaction. SUMMARY AND CONCLUSIONS A laser-SPS concept has been defined in order to address critical environmental impact questions related to laser transmission of power from space to earth. Using an existing microwave-based SPS point design (Rockwell International), we examined the system performance, safety, and environmental impact of replacing the microwave transmitters with laser transmitters using current or near-term state-of-the-art technology. No attempt was made to optimize the entire satellite design or to employ more advanced laser devices. Supersonic, closed-cycle flow CO EDLs were chosen in preference to CO2 systems because of their lower specific mass and larger electrical efficiency. Laser line selection was employed to maximize the transmission efficiency through the atmosphere. The present concept provides for 20 independently controllable laser systems and optical transmitters having a beam power of approximately 110 MW each. Each system is capable of sustained overloads of perhaps 20% to accommodate the routine or unscheduled maintenance of systems which must be off-line. Furthermore, with separate pointing capability, operation with either closely packed or geographically separated receptor devices is feasible. Adjustment of terrestrial load demand or bypass of sites temporarily subject to thick cloud cover can be accomplished by beam redirection to alternate locations. Guidelines for implementation of beam switching and receptor siting criteria are developed in Ref. (21). An adaptive, on-axis Cassegrain optical telescope transmits power to a heat-engine receptor (either an advanced Brayton cycle or binary cycle with energy exchanger). Because thermal energy conversion was selected, the Cassegrain transmitter must operate under best-focus conditions to maximize the receptor conversion efficiency. Note that if an efficient but non-thermal method of laser-energy conversion is perfected, then the power density of the incoming beam could be reduced. Consequently, the necessity for restricted airspace would be obviated, the ocular hazard to
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