humans and the thermal hazard to insects and birds would be largely mitigated, and the possibility of thermal blooming would be reduced. Hole boring through thin clouds and fogs is still possible by adding the output of a repetitively pulsed laser to the continuous-wave power-transmission beam (21). The pulsed laser, having a peak power density ~ 10‘ W/cm2 but a low average power density, bores through aerosol formations by explosive heating of the droplets while the continuous-wave laser operates at a power density ~10 W/cm2. Clearly, the most pressing technical problem is development of advanced laser concepts which would result in a smaller satellite specific mass compared with photovoltaic/EDL systems. Cogent research is being conducted by the present author (21) and others (61), although the list of all potentially feasible candidates is far from exhausted. Results of the environmental impact assessment, however, are encouraging and can be summarized as follows: (1) global climatic change resulting from the proliferation of laser-SPS systems is highly improbable, (2) mesoscale weather modifications at receptor locations will be less significant than such phenomena associated with conventional or nuclear electric power plants of comparable power rating, (3) sensible heating of the lower troposphere by the laser beam will promote waste-heat dispersal by vertical mixing, but will also induce severe turbulence which could be hazardous to aircraft intruding into the restricted air zone, (4) the environmental impact on certain wildlife, especially birds and insects, is uncertain, (5) laser-plasma interactions in the ionosphere are insignificant, (6) laser-beam perturbation of the plasma chemistry in the mesosphere and thermosphere is believed to be of negligible magnitude and consequence; however, confirming research is needed to substantiate this claim, and (7) serious environmental modifications, such as depletion of the ozone concentration in the stratosphere, are not possible. Acknowledgements — The Editor wishes to thank Gordon Woodcock and Ross A. Henderson for their assistance in reviewing this paper. REFERENCES 1. J.F. Coneybear, in Radiation Energy Conversion in Space, K.W. Billman, ed., Progr. Astronaut. Aeronaut., 61, AIAA, New York, 279-310, 1978. 2. C.N. Bain, PRC Energy Analysis Company Report No. R-1861. 1978. 3. Lockheed Palo Alto Research Laboratory, Presentation to NASA Lewis Research Center on Contract No. NAS3-21132, 1978. 4. Rockwell International, Final Report No. SSD 79-0010 on Contract No. NAS8-32475, 1979. 5. D.J. Monson, in Radiation Energy Conversion in Space, K.W. Billman, ed., Progr. Astronaut. Aeronaut., 61, AIAA, New York, 333-345, 1978. 6. D.J. Monson, AIAA J., 14 (614), 1976. 7. R.K. Burns, NASA Lewis Research Center Report No. NASA TN D-7658, 1974. 8. G.E. Mevers et al., Rockwell International, Autonetics Division Report No. NASA CR-134952, 1977. 9. R.A. McClatchey, Air Force Geophysics Laboratory Report No. AFCRL-71-0370. 1971. 10. J.W. Daiber and H.M. Thompson, IEEE J. Quant. Electron., QE-13110), 1977. 11. D.K. Rice, Northrop Research and Technology Center Report No. NRTC-74-44R, 1974. 12. M.M. Mann, AIAA J., 14(549), 1976. 13. E.L. Klosterman, S.R. Byron and D.C. Quimby, Mathematical Sciences Northwest Report No. AFWL-TR-76-298, 1977. 14. D.J. Monson and G. Srinivasan, Appt. Phys. Lett., 31(828), 1977. 15. R.R. Berggren and G.E. Lenertz, itek Corporation Report No. NASA CR-134903, 1975. 16. R.R. Altenhof, Opt. Engr., 15(2650), 1975. 17. G.V. Rodkevich and V.l. Robachevskaya, Sot. J. Opt. TechnoL, 44(515), 1977. 18. T.T. Saito, Appl. Opt., 14, 1773, 1975. 19. T.T. Saito, Proc. SPIE, 65(118), 1975 and OCLI technical information sheets. 20. P.L. Kelley, R.A. McClatchey, R.A. Long and A. Snelson. Opt. Quant. Electron.. 8(117), 1976.
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