| Materials Processing at Mt. Malapert
By Dave Dietzler 2008 Mt. Malapert in yellow box. Image courtesy of Burt Sharpe. Mt. Malapert is surrounded by anorthositic (some geologists call it feldspathic) highland regolith the lacks titanium and has only about 3% iron compared to 12-14% iron for mare regolith. There might be iron rich material on the NE slope. Magma electrolysis requires feedstock with a high iron content like that of mare “soil.” What if we just magnetically separate out all the iron bearing pyroxenes (Fe2Si2O6) and olivines (FeSi2O4) and mix them with highland regolith then put that thru magma electrolysis to get oxygen, iron, silicon and ceramic blocks? Since hiland soil is 3% iron we’d need to mine three times as much as we would in the mare. Take the 3% out of three masses of regolith and mix it with raw unprocessed regolith with 3% iron and you get material with 12% iron, right??? What do we do with all that “de-ironed” regolith? We could roast it at 1800-2000 C. to drive out MgO and SiO2 to get a CaO and Al2O3 enriched cement mix. Then robots could take the mix into a pressurized inflatable work chamber, after mixing the cement with sand (actually sieved and sized regolith) and gravel, mix it with water, pour out slabs and let them dry. Condensors will capture the water vapor as the concrete slabs dry. Concrete will retain some water so we need a water supply and we are betting on ice from shadowed craters. Then take the dried slabs outside and use them for road slabs. Hopefully they won’t crack quickly due to temperature extremes. These roads won’t go very far but they’d be used for driving around between different parts of the robotic base without kicking up dust. There could be “entry ramps” made of concrete slabs to the base area. When the robots are returning with loads of regolith, iron fines, ice, and volatiles they could drive onto a road about 100 meters from the perimeter of the base area and enter the area without kicking up dust. We will have to find some level ground on the slopes of Mt. Malapert (slopes of 6 to 32 degrees) and string cables up to the solar panels mounted on the top of the mountain ridge. Perhaps the most level spot is at the top of the mountain. Another use for concrete would be pouring concrete floors in inflated robot work chambers so that spillage of hot, even molten, metals does not melt thru the kevlar floor and to give the balloon like chamber some stability. At first we could just cover the kevlar floor with regolith, but concrete will make a more solid floor to work on and mount machinery. The best shape for the inflatables will be sort of a saucer shape to maximize floor space. We don’t need upper floors like those pictured for manned inflatables. Though these chambers won’t need radiation protection ‘cause we are using robots we might need some thermal insulation in the form of a couple of feet of regolith covering the chambers because we don’t want water vapor freezing out of the air. It’s cold down near the south pole. Do robots need solar flare shelters? If so, the inflatables could serve that function if we have enough of them. But then the robots all have to file in and out thru the airlocks. Perhaps a garage consisting of kevlar with pressurized tubes in it for support and some regolith on top would make a sufficient solar flare shelter. But what parts of the robots would be damaged by high energy solar flare particles?? Probably just the electronics, so we put the electronics in shielded boxes. Satellites seem to endure solar flares well enough. The inflatables will need airlocks, probably pressurized tubes in the walls for support, and plastic doors or hatches and tight seals. How do the robots get into there? Walking robots would be very complex. Perhaps one robot throws down a ramp over the rim of the airlock and another robot drives over it into the lock, then the first robot removes the ramp and the motorized outer door closes. Compressors will be needed to pump down the lock before the robot exits. There will be some loss, but we hope to make plenty of oxygen. Since we are using robots instead of humans, perhaps we can get away with just one or two psi in the inflated chambers instead of 3 psi of oxygen. This might be just enough to keep things like water and molten metals from boiling away. That we need to know more about because 1 psi to 2 psi is like stratospheric pressure. Something I didn’t list in the “Attempting to Define a Lunar Industrial Seed” article was tool attachments for the robots. They will need drills, possibly hammers, grinding wheels, circular saws (got to cut up the landers), shovels possibly (got to load the furnaces). I did list welders, probably laser and/or electron beam welders. The robotic cranes could have electromagnet attachments, claws, and buckets for digging up regolith to load in magnetic separators and furnaces. So the robots will go to work and load up electric furnaces extract metals, make concrete and ceramics, and build larger robots and more materials extraction systems as well as machines of various sorts and pressurized metallic work chambers for casting molten steel, magnesium and aluminum that would boil away in the vacuum, water quenching of hot steel, and operating CNC machines in a dust free environment as the chambers would also have “air” filtration systems inside. Then the robot swarms will move out with loads of machines and other products made on the Moon to other locations where volcanic glass and ilmenite exist. They will need power and fuel cells or batteries won’t get them very far. The thing to do is to expand the solar power plant on top of Mt. Malapert, be it solar panels or a solar thermal power plant, and have the robots string cables out as they move along and tap the cable when they need to recharge. This means we need aluminum cable and/or calcium cable clad in aluminum. The cable will need insulation, probably glass fiber cloth. Do we really need to string the cable up on poles? That would be a lot of mass to make and haul. Submarine cables lay on the sea bed….and regolith is not a very good electrical conductor. The downside is that we probably won’t be able to get a good ground in regolith and will need at least two cables for single phase AC. One of the robot “trucks” will have a transformer and rectifier to step down the voltage for recharging the batteries in other robots. The cable will not be live at all times. Only when the robots need to recharge will we command the automated circuit breakers to activate the line by radio of course. So how do we make large qtys of aluminum and calcium? There are several processes. One I’ve read about involves melting, quenching and grinding of anorthosite-CaAl2Si2O8, leaching it in H2SO4, roasting the Al2(SO4)3 to Al2O3, carbochlorinating the Al2O3 to AlCl3 and electrolyzing it to aluminum metal. The carbon electrodes won’t burn up with this system unlike carbon electrodes in cryolite in the conventional Hall-Heroult process. Solar carbothermal reduction of alumina to get an aluminum-silicon alloy that must be purified to aluminum is another possibility, but not much work has been done on that. Highland regolith could be roasted in electric furnaces and FeO will boil out (not that there is FeO in the regolith but iron-silicon-oxygen minerals that will break down at high temp in the vacuum) at 1200 C. and at 1500 C. and higher MgO (which strangely enough doesn’t even melt until about 3000 C. in one atmosphere of pressure) and SiO2 boil out. If we keep the roast going until all the SiO2 boils out we get calcium aluminate-CaAl2O4. This would be placed in an electrolyte of lithium flouride sent up to the Moon and electrolyzed to aluminum and calcium metal. The electrodes would be strontium doped lanthanum manganite. See appendix E of The Moon: Resources, Future Development and Settlement by Schrunk, Sharpe, Cooper and Thangavelu. So this requires sending up a bunch of stuff to the Moon and there are problems with filtering the calcium and aluminum out of the hot electrolyte of LiF. We need simpler processes for getting aluminum and calcium that don’t rely on upported (to use a Peter Kokh term) chemicals. There is enough sulfur, hydrogen and oxygen on the Moon to make sulfuric acid. We could upport a vanadium pentoxide catalyst. That won’t amass too much, or we could just use regolith as the catalyst that allows the combination of 2SO2 with O2 to make 2SO3 that is then reacted with water to make H2SO4. We will need tubes and containers, valves, pumps and glass fiber filters. High silicon alloy iron (14% silicon) resists sulfuric acid and cast basalt resists 96% sulfuric acid so we have materials to make the tubes and containers. We don’t need stainless steel. If we leach CaAl2O4 in H2SO4 we could filter out the CaSO4 that forms because it is barely soluble in water and get a solution of Al2(SO4)3 that would be boiled down and the Al2(SO4)3 would be roasted to Al2O3. This melts at 2000 C. at 1 atm pressure. That’s the main reason it is dissolved in cryolite, to lower the melting point and electrolysis temperature and it still takes a lot of energy to make aluminum. If we could find a ceramic material that conducts at high temperature and a ceramic material to make the furnace lining out of, perhaps with cooling passages in it, perhaps we could directly electrolyze Al2O3 to aluminum metal. The electrode material would also have to resist oxygen at 2000 C. coming out of the cell. That’s about as simple as I can make it. The CaSO4 can be used as is. It’s plaster. We could also roast it at 1500 C. + to CaO and then reduce the CaO with aluminum to calcium metal. Al and Ca production will require huge amounts of energy, especially if we are doing it the brute force way of direct alumina electrolysis. If we are lucky, carbon nanotube technology will advance to the point in coming decades by the time we are really ready for the Moon so that we can use carbon nanofiber superconducting cable. This stuff would be worth sending to the Moon. Writers like Gerard K. O’Neill and others wanted massive qtys. of aluminum because that’s what they planned to make solar power satellites out of. They wanted massive qtys. of silicon too, although O’Neill designed a solar thermal power satellite that made 5 or 10 GW and amassed 80,000 tons. Unless we get carbon nanotube superconductors we need aluminum to wire the Moon, and aluminum only becomes a superconductor at about 3 degrees Kelvin. We will only be able to transmit power 600 to 1000 miles from Mt. Malapert then we need more solar powerplants. Life would be so much easier if we could just launch nuclear rockets with solid core motors and mere liquid water for propellant and launch nuclear reactors to the Moon, wouldn’t it? The future is thru a glass darkly. We might have carbon nanotube superconductors. We might also have space elevators to haul up cargo and lower it to the lunar surface in the future too. We have to wonder about plasma separation also. The problem with this is temps of about 7000 to 8000 C are needed but the material ionizes and can be contained in magnetic fields. The oxygen does not ionize until higher temps so the metallic ions can be deflected away from the oxygen so that they don’t just re-oxidize. Then the plasma comes zooming out at really high speeds so we’d need a tube miles long for the plasma to cool by radiation. If the plasma hits a metal plate that is cooled we could condense it. The plasma would be at super high temps, but like a white hot spark from a sparkler it would not contain a lot of heat energy because its mass and density would be so low. As the metals built up they would conduct heat into the cold plate. But how productive is this system? More research is needed here too. Since lasers are only about 10% efficient and silicon solar cells about 15% efficient we can forget about fiber optic power cables. We must also consider tall microwave power transmission towers on the Moon. Perhaps the towers could have some kind of wave guide on top that directs the microwave beam to the next tower, etc. If we capture the microwaves with rectennas, convert them to electricity, then energize another microwave beam, we are looking at about 85% efficiency and 85% of 85% of 85% etc. is not going to go that far. Then there is bioleaching. Many living organisms accumulate calcium. Perhaps we could extract calcium with microbes. Once again we need chemicals to make the calcium water soluble and bioavailable because CaO is not soluble and CaSO4 is barely soluble. Then we need lots of water, nutrients for the microbes, temperature and pressure controlled environments and control of salt content and pH. When everybody shits a brick over the idea of leaching anorthosite with H2SO4 I can’t seen why they wouldn’t balk even harder at bioleaching. Perhaps a day will come when we can meet the life support demands large vats of microbes to get trace elements out of regolith. If we really want to get crazy, what about steel pipelines that we force high pressure oxygen thru and at various points and at the end of the line we have air motor driven generators that transmit power short distances thru real thick steel cables?? The robot swarms would include a truck with an air motor and generator to tap the line as they lay it down. Probably to much hydraulic resistance for this to work over very long distances. Looks like we just have to find some super electrode materials and use a lot of energy to make aluminum and calcium. Mt. Malapert is surrounded by calcium and aluminum rich regolith. But why agonize? We don’t have to make that much aluminum. AWG 1000 cable 380 amps 1813 gr/m 1813 kg/km 1813 tons/1000 km Say we can produce merely 181.3 tons of aluminum per year, in ten years we have enough for two cables 500 km long. Then production grows and grows. Since the conventional process uses 13-16 kWhrs per kg. and we might need twice that much or about 30 kWhrs per kg. ( a wild guess) we’d need 5440 MWhrs. to make 181.3 tons Al per year or a one megwatt power source operating for about 62% of a year, or a 620 kWe power source operating for a year. It would be so much easier if we could just use nuclear powered robots, but where do we get the nuclear fuel on the Moon? KREEP is just 4ppm uranium and 10ppm thorium. It’s no good and we’d need reactors. Oh well, the nuclear fuel launched up to the Moon would last for many years. But the politicos would never let us do it. Looks like we need a miracle like C60 nanofiber superconductor or we just have to make aluminum and calcium on the Moon and insulate it with glass fiber cloth and let it lay on the dry poorly conducting regolith like a submarine cable. |
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| Development of lunar south polar region. Image courtesy of Burt Sharpe, co-author of The Moon: Resources, Future Development and Settlement Top and bottom page images from: MALAPERT MOUNTAIN: GATEWAY TO THE MOON Burton L. Sharpe1 and David G. Schrunk 2 1 Formerly Head, Lunar Surface Experiment Operations Section 2 Quality of Laws Institute, |
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