each case. Expected requirements of hydrogen-bearing reagents are listed in table 5.14. Although these calculations are highly sensitive to the assumptions employed, closure may be achieved if an allowance of 5% for spillage and other losses is adequate. Obviously a major leak could seriously jeopardize a hydrogen-based LMF system.
If hydrogen supply remains a critical problem it may become necessary to: (1) redesign the processing system for greater hydrogen frugality, (2) select a slightly higher extraction ratio R to permit recovery of a greater mass of H, (3) locate and "mine" particular lunar soils extra-rich in H, such as the suggested use of ilmenite as a hydrogen "ore" (Green, personal communication, 1980), (4) accept a replication time longer than 1 year, or (5) relax the 100% closure requirement and permit resupply of small amounts of hydrogen "vitamin" from Earth.
5E.4 Sector Mass and Power Estimates
The overall functional layout of the LMF chemical processing sector is illustrated in figure 5.16. The operations flowsheet shows that there are 13 components within the sector: (1) input hopper, (2) electrophoretic separators, (3) P/F/Cl extractors, (4) boron extractors, (5) sodium extractors, (6) volatiles extractors, (7) HF acid leach system, (8) freon producer, (9) ammonia producer, (10) silane producer, (11) nitric acid producer, (12) sulfuric acid producer,and (13) output hopper.
Mass and power consumption for LMF materials processing may be estimated by comparison with other automated chemical processing designs that have been considered, and which are summarized in table 5.15. For R = 40, a 100-ton/year (self-replicating) output demands a 4000-ton/year raw materials input, or 0.13 kg/sec. Taking the range of values given in table 5.15, sector mass should lie within 18,200 to 78,000 kg. Similarly, the estimated power requirements range from 455 kW up to 10.9 MW, although in this case the lower values seem more appropriate. Dry thermal chemical processing techniques are associated with very high energy requirements, whereas lower values are found in wet chemistry processes - of which the HF acid leach selected for the present design is an example.
| Source | kg plant kg/sec input |
kg chemicals kg/sec input |
kg chemicals kg plant |
Power, W kg plant |
|---|---|---|---|---|
| Johnson & Holbrow (1977) Al-processing plant | 3.1×105 | 2.6×104 | 8.5×10-2 | 25 |
| Phinney et al. (1977) carbo/silico-thermic plant | 3.3×105 | --- | --- | 140 |
| Waldron, Erstfeld, & Criswell (1979) HF acid-leach metal extraction plant | 3-6×105 | 3.5×105 | 4.1×10-1 | 37 |
| O'Neill, Driggers, & O'Leary (1980) reference design figure | 3.6×105 | --- | --- | --- |
| O'Neill (1976) carbothermic Space Manufacturing Center | 5.2×105 | --- | --- | 100 |
| Criswell (1980) | 3.6×105 | --- | --- | 100 |
| Vajk et al. (1979) Space Manufacturing support requirements | 1.4×105 | --- | --- | --- |
5E.5 Information and Control Estimates
Probably the most complex of the 13 sector components which appear in figure 5.41 is the HF acid leach system. From figure 5.41 this appears to consist of 34 component subsystems such as "precipitator," "dissolving tank," "fractional distillation tower," "centrifuge/filter," "Castner cell," etc. Each subsystem performs a single well defined task. In addition, there are 111 nodes (each denoting a point of connection of a pipe or supply line to another pipe or to a subsystem) each requiring at least one valve and valve control mechanism. At each valve there must be a number of sensors indicating valve position (open, closed, fractionally open), valve malfunction and cause (if simple), and volume or velocity of flow of material through the valves. Interface with actuators and reportage to the subsystem subcomputer are additional requirements.
Assuming each valve can be automated with a 1K computer allocation, and each subsystem can be automated with a 10K memory allocation, then the total computer capability required for continuous leach system operation is (1)(111) + (10)(34) = 451K which is 7.2×106 bits using 16-bit words. This should be sufficient to handle normal system operations and troubleshooting, although actual repair must be done by mobile repair robots. Also, any catastrophic malfunctions such as pipe ruptures, jammed fixtures, leaks, heating element burnouts or explosions must be diagnosed and corrected by the mobile repair robots.
The chemical processing sector looks not to be a place where complicated new automation techniques will be
