profit and to tap an inexhaustible source of energy, it could be carried out as a joint venture of several or many nations. The worldwide food shortages that have been forecast for the next decades could be alleviated substantially by the provision to developing nations of low-cost energy for the manufacture of agricultural chemicals (22). In the SMF approach, subsidies of that kind to the Third World could be given out of new, nonterrestrial wealth, not requiring sacrifice by donor nations. The data in this article should be considered not as definitive, but as requiring substantiation or correction by additional research. So far, during a year of exposure of the SMF concept to technical review, no major changes in the basic concept have been necessary, but it is almost certain that further work will uncover both unsuspected problems and new technical possibilities. A modest amount of research on the key questions of productivity, life support needs, SMF and SSPS construction methods, and lunar materials transport could substantially improve our knowledge of the cost and time required for the achievement of the first beachhead in space, and of the speed with which the initial investment could be returned. 5 DECEMBER 1975 Summary The feasibility of establishing manufacturing facilities in a high orbit is under discussion. They could be used for the construction of satellite solar power stations from lunar materials. Estimates indicate that this may be considerably more economical than constructing power stations on the earth and lifting them into orbit. References and Notes I. G. K. O'Neill, Nature (London) 250, 636 (1974). 2. ~Phys. Today 27, 32 (September 1974). 3. P. E. Glaser, in Space Shuttle Payloads. Hearing Before the Commillee on Aeronautical and Space Sciences. U.S. Senate. 93rd Congress, Ist Session. on Candidate Missions for the Space Shu11le, 31 October 1973 (Government Printing Office, Washington, D.C., 1973), part 2, pp. 11-62. 4. G. D. Friedlander, IEEE Spectrum 12, 32 (May 1975). 5. Edison Electrical Institute, Statistical Yearbook of the Electricity Utility Industry for 1973 (Edison Electrical Institute, New York, 1973), p. 5, table 1-S. 6. Associated Universities, Inc., Reference Energy Systems and Resource Data for Use in the Assessment of Energy Technologies (AET-8, Associated Universities, Inc., Brookhaven National Laboratory, Upton, N.Y., 1972). 7. W. R. Cherry, Astronaut. Aeronaut. II, 30 (August 1973). 8. P. E. Glaser, NASA Contract. Rep. CR-2357 (1974). 9. W. C. Brown, Proc. IEEE 62, 11 (January 1974). 10. News release, Office of Public Information, Jet Propulsion Laboratory, California Institute of Technology, Pasadena, I May 1975. 11. R. E. Austin and R. Brantley, presentation at NASA Headquarters, Washington, D.C., 17 April 1975 (unpublished). 12. R. E. Austin, personal communication. 13. G. R. Woodcock and D. L. Gregory, AIAA paper 75-640, presented at the AIAA/ AAS (American Institute of Aeronautics and Astronautics/ American Astronomical Society) Conference on Solar Energy for Earth, 24 April 1975. 14. K. Bammert and G. Deuster, paper presented at the ASME (American Society of Mechanical Engineers) Gas Turbine Conference, Zurich, April 1974. 15. "Launch vehicle estimating factors for advance mission planning," NASA Handb. NHB-7100.58 (1973). 16. R. Wilson, in Proceedings of the Conference on Space Colonization, Princeton University, JO May 1974, G. K. O'Neill and R. W. Miles, Eds., m press. 17. H. P. Davis, in Proceedings of the 1975 Princeton University Conference on Space Manufacturing Facilities, G. K. O'Neill, R. W. Miles, R. H. Miles, Eds., in press. Typical values are: nonrecurring, $10 billion; recurring, $220/ kgsy. 18. NASA-Ames/ ASEE (American Society for Engineering Education/Stanford University Summer Study Report, System Design for Space Colonization (NASA-Ames Research Laboratory, Mountain View, Calif., in press). 19. B. Mason and W. G. Melson, The Lunar Rocks (Wiley-lnterscience, New York, 1970), p. 117. 20. G. K. O'Neill, in Future Space Programs 1975, Hearing Before the Subcommillee on Space Science and Applications, Committee on Science and Technology. U.S. House of Representatives. 94th Congress, /st Session. 23 July 1975 (Government Printing Office, Washington, D.C., 1975), p. 111. 21. Exxon Corporation, advertisement in Smithson. Mag. 6, 117 (April 1975). 22. D.R. Safrany, Sci. Am. 231, 64 (October 1974). 23. It is a pleasure to thank P. Glaser, M. Hopkins, D. Morgan, and G. Woodcock for providing useful information not yet published. The latter part of this study was carried out with support from the National Aeronautics and Space Administration. 8 January 1975; revised I October 1975 947
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