Another scenario where laser power transmission could make significant reductions in system mass is the establishment of a lunar base. Such a base would require electrical power on the order of 1 MW for such operations as a human habitat, mining activities, an oxygen extraction and liquification plant, and a large astronomical observatory. The near-term primary power source would be solar-photovoltaic at low power evolving into a nuclear-reactor-driven Stirling engine to produce the 1 MW needed. Reactors are permanently fixed in location and may require robotic technology for maintenance. Alternately, a lunar orbiting solar- or nuclear-powered laser could beam its energy to the lunar surface where a lightweight simple photovoltaic laser-to- electric converter would satisfy the lunar base power requirements. Substantial mass savings result in the process of not taking the primary power source to the lunar surface. For example, a solar-powered laser diode array laser beaming 2.2 MW of laser energy to an AlGaAs converter at 46% efficiency, would produce 1 MW. The diode array laser and converter would have a LEO mass of less than 100 metric tons, whereas an equivalent nuclear reactor system would be over 100 metric tons. Such a comparison is shown in Fig. 6 where the low Earth orbit (LEO) masses of the reactor and laser power system are compared. The laser-to-electric converter by itself is extremely light and easily portable, allowing greater power generation flexibility for diverse missions and mission locations. Also, a laser could be used for other power missions when not in use by the lunar base. Thus, a very flexible power infrastructure is developed for a variety of lunar missions. 4. Summary The technologies of generating laser power for in-space transmission and of efficient conversion to electric power are being developed for future space missions. Both simple solar-pumped lasers and more advanced electrically powered diode laser arrays can form the basis for long-life space power stations. Both laser oscillator and laser amplifier configurations are being studied currently. Two examples of potential applications illustrate some of the advantages which beamed power offers over conventional on-board power generation. ACKNOWLEDGEMENT The authors wish to acknowledge the work of Gregory Schuster, Donald Humes, and Willard Weaver, who collaborated on the preliminary application studies of laser power beaming. REFERENCES [1] Ershov, L.S., Zalesskii, V. Yu, & Sokolov, V.N. (1988) Soviet Journal of Quantum Electronics, 8, 494, April. [2] Brederlow, G., Fill, E. & Witte, K.J. (1983) The High-Power Iodine Laser, (Springer-Verlag, New York), p. 24. [3] Zapata, L.E. (1987) Journal of Applied Physics, 62, 3110, 15 October. [4] Yariv, A. (1989) Quantum Electronics, 3rd ed. (John Wiley & Sons, New York). [5] Private Communication from Richard R. Craig, Hughes Research Lab, Malibu, CA 90265. [6] Price, Robert O. (1988) Aerospace Engineering, October, p. 21.
RkJQdWJsaXNoZXIy MTU5NjU0Mg==