seen if this process can be scaled up and whether the purity required for solar cell production can be met. Figure 9.13 Average Lunar Soil Composition An indigenous space resources utilization (ISRU) program has been envisaged which will be evolutionary, justify itself at each step, and demonstrate the necessary technologies for the next step. This can all be done with an eye towards developing technology to support an SPS construction project in the long term. This long-term vision will always be present, but should not be the sole purpose of the program. Of course, this approach only makes sense when a lunar base has been established. A program which aims to produce large amounts of materials in the long term needs to start out first demonstrating the basic technologies. We need to consider which products can reasonably be made at a lunar outpost, considering the constraints both in the near term and in the long range capabilities. Obviously, as in an Earth-based marketplace, some products will have higher value and some will be easier to produce than others. When considering the general operations that must be accomplished to produce materials from the regolith, several steps can be outlined. First, one must be able to obtain the soil by deconsolidating and hauling it from a mine site and placing it into the processing equipment. This is no minor task in the hostile environment encountered on the Moon. Next, there can be physical and/or chemical processing. This is often quite energy intensive and done in a pressure vessel. Both these requirements place a heavy burden on the infrastructure of the lunar outpost. The product must then be separated from any by-products, and both must be removed from the pressurized reactor. Finally, any processing aids, such as chemical reagents or consumable equipment, must be recycled as completed as possible to reduce any re-supply requirements from Earth. Many of the above tasks will involve the use of robotics or expert systems. By learning to accomplish these unit operations on the lunar surface, the experience should be applicable to many other products and processes, and will act as a knowledge base for future scale-up. Lunar Oxygen Lunar-derived liquid oxygen (LOX) is one of the products which is most likely to be worth producing at a lunar outpost. Its main use, from a mass viewpoint, will be as a propellant to power a lunar lander up to lunar orbit and back down to the lunar surface, or just for a direct return to Earth. The amount of oxygen required to make up for losses in the life support system is likely to be small, but represents another market - one that might be attainable before the larger production capacity is in place. Moderate amounts of oxygen might even make it practical to have less complex life support systems for habitats and extravehicular activities. The cost and maintenance of these systems may therefore be reduced.
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