This page was inspired by work done at the University of Wisconsin. See: http://fti.neep.wisc.edu/pdf/fdm1304.pdf
During discussions with associates objections were raised about the fragility of heat pipes and the high power of over 10 MWt.
Perhaps more power is required. If six million tons of regolith is mined per year and 10% of the smallest fines extracted and heated to 600 C., then at 840 j/ kg. K and 151,000 kg. per hour of fines, 21.23 MWhrs of energy is needed, or the equivalent of burning two pounds of coal per second. That doesn't seem like too much. If the fines are heated to 600 C. and dumped, heat energy will be wasted. The University of Wisconsin researchers used waste heat from spent fines to preheat incoming fines. This isn't perpetual motion but simply transferring heat from one mass to another to reduce total heating requirments. Very little heat is conducted away by the evaporating volatiles as their mass is so small. Since significant amounts of heat can be recycled less than 20 MW of power might be used. However, I have not accounted for inefficiency of electrical systems and microwave heaters.
In addition, it is not necessary to heat the particles completely through, but only their surfaces that the volatiles adhere to, so much less energy is required than one would think based on simple calculations using mass throughput and specific heat cap. of basalt rock (1). U of Wisc researchers calculate 12.3 MW to heat 45% of the fines, about as much energy as is released by burning one pound of coal per second. Since the onboard furnace will reject most of that heat, there is no danger of it overheating. Still, given to low heat conductivity of regolith and the fragility of heat pipes, it's hard to imagine anything more practical than microwave heating. |
