oxygen, silicon, calcium, iron, aluminum, magnesium and titanium, can be extracted from the lunar soil. Space power stations could be constructed of approximately 90% lunar derived material. 2. LUNAR ENVIRONMENT The principal distinguishing requirement for a successful lunar operation is that all materials unavailable from lunar sources must be shipped from earth and recycled with minimal loss. The following constraints apply to processing lunar ore: 1. Lack of virtually inexhaustible supplies of air and water. 2. Lack of fossil fuels. 3. Lack of inexhaustible oxidizing and reducing agents. Carbon is very scarce on the lunar surface. 4. Lack of expendable halogens, acids and bases. 5. Lack of air and water makes the management of process waste heat especially important. Rejected heat will ultimately have to be transferred to space through radiation. 6. Processing conditions must be adjusted for the lower lunar gravity. 3. LUNAR ORE The major lunar raw materials are ilmenite, plagioclase and anorthite. Anorthite (CaALSi2On) contains 19.4% aluminum, 20.2% silicon, 14.4% calcium, and 46% oxygen. A typical composition of lunar rock from Maria section would be silica 42%, titanium dioxide (TiO2) 7.5%, alumina 13.9%, iron oxide (FeO) 15.7%, magnesium oxide (MgO) 7.9%, calcium oxide (CaO) 12.1%. The composition of lunar rock from the highland area would be silica 45.4%, TiO2 0.5%, alumina 23.4%, FeO 7.4%, MgO 9.2%, CaO 13.4%, and traces of potassium oxide, sodium oxide, manganese oxide, phosphorus oxide, and chromium oxide (1). The majority of lunar soil is completely anhydrous and has an average grain size of 30-70 microns. Eighty-five percent to 95 wt.% of the lunar powder is less than 1 mm in diameter. 4. REVIEW OF LUNAR EXTRACTION PROCESSES Since carbon is very scarce on lunar surface, Rao and co-workers (2) decided quite early that carbothermic reduction of lunar soil would probably be impractical for space processing. They chose carbo-chlorination of lunar anorthite (CaAl2Si2OK) and lunar ilmenite (FeTiO:i). A major advantage of carbo-chlorination is that it would require little water. However, the recycling of chlorine and carbon would require facilities much larger than the basic processing plant. Of the nonelectrolytic processes studied to date, the hydrofluoric acid leach method appears to require the minimum operating mass to be transported to the moon. Waldron et al. (1) have described a low temperature hydrometallurgical step to remove the silicon from the other metallic oxides by conversion to fluorides and fluosilicates. This is followed by vaporization of the silica as SiF,, and separation of
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