0191-9067/81/030249-10$02.00/0 Copyright ® 1981 SUNSAT Energy Council USE OF LUNAR MATERIALS IN SPACE CONSTRUCTION EDWIN ROEDDER U.S. Geological Survey National Center, Stop 959 Reston, Virginia 22092 INTRODUCTION Large construction projects in Earth-Moon space, such as solar power satellites (SPS), will certainly be undertaken in the future; the only question is when? Such projects will consist of hundreds of thousands of tons of a variety of materials. What materials will be needed, where will we get them, and how and where will they be processed into the desired form? At a workshop on Glass and Ceramic Industries in Space held at NASA-Houston in April 1979, people from a very wide range of disciplines and interests were brought together to explore some of the many options and constraints. Of the three possible sources for such materials, Earth, Moon, and Earth-orbit-crossing asteroids, only the first two are of immediate concern, although the last may eventually become the optimum source. The choice between a source on Earth and one on the Moon, for a material available from both, is easy. Several studies (e.g., 1) have proven that for two reasons, the Moon presents a tremendous physical and hence financial advantage over the Earth as a source for materials available from both. The “gravity well” we live in on Earth requires a huge expenditure of energy to overcome. Although the Moon’s gravity is one-sixth that of the Earth, the energy needed for a given mass to escape from the Moon is only —5% of that needed for it to escape from the Earth; the resistance of the Earth’s atmosphere increases this difference. This lunar advantage is multiplied, however, by still another major factor. To take a payload off the Earth by currently available technology (e.g., chemical rocket) requires a vehicle whose payload normally consists of— 1.5% of the original lift-off mass. On the Moon, however, as a result of the lack of an atmosphere, essentially pure payloads, without a vehicle, could be accelerated to escape velocity on the surface, by using solar-derived electrical energy in a linear electric motor or “mass driver” (2). Thus, the energy requirements alone make it obvious that for any given space application, lunar materials should be used if at all possible. Certainly not all materials needed for space construction can be obtained most economically from the Moon, and much additional research and development is needed to optimize the system. The possible ramifications of such a new and developing technology are so numerous that input from individuals having widely differing experiences and backgrounds might well be useful. The following comments, adapted from those I presented at the workshop, are made in that context.
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