required (Ayres, 1952; Foster, 1963; Kallen, 1961; Luke, 1972). Component processes are all state-of-the-art. There is no need for visual processing during normal operations, and procedures are standardized so no expert systems or judgmental algorithms are required beyond the simple integration of well defined sensor data. All operations will probably be hard-automated, and materials will be moved about almost entirely in sealed vessels. If there is need for additional transport within the system a materials transit network may be erected using metal or basalt tracks, electric motors and small carrier vehicles.
If each of the 13 sector components is as complex as the HF acid leach system (certainly a gross overestimate), then the total computer control capability required is about 6 megabytes or 9.4×107 bits using 16-bit words. The information needed to describe the sector sufficiently for purposes of self-replication must also be estimated. Assuming that each HF leach subsystem requires 2×106 bits for complete description (about a 200-page printed book, or 80,000 English words), and that each valve requires about half as much (say, 100 book pages), then the total for the HF leach system is 1.8×108 bits. Again conservatively multiplying by 13, the total information to describe the sector components is 2.3×109 bits. If sector equipment is distributed across a floor space of 5000 m2, then to store a map with 1-cm placement resolution requires a memory capacity of 8×108 bits assuming one 16-bit word to describe the nominal status of each 1 cm2 of platform space. Note that large empty areas convey useful information and must be mapped, since they may be used for traffic routes, repair routes, temporary warehousing, etc. The total information for sector replication is thus about 3.1×109 bits. The information control budget is 9.4×107 bits.
5E.6 References
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Arnold, J. R.; Criswell, D. R.; and Waldron, R. D.: Progress Report on Experimental Program to Develop HF Acid Leach Process for Refining Lunar Soils. Paper presented at the 5th Princeton/AIAA/SSI Conference on Space Manufacturing, 18-21 May 1981, Princeton, NJ.
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