| Lunar Manufacturing Processes 2 by David Dietzler 2008 |
| From: http://www.islandone.org/MMSG/aasm/AASM5F.html We read that, "The team concluded that four basic processes - plaster casting, vapor deposition, extrusion, and laser machining are probably sufficiently versatile to permit self-replication and growth. These four techniques can be used to fabricate most parts to very high accuracy. Plaster casting was selected because it is the simplest casting technique for producing convoluted parts as well as flat-surface parts, to an acceptable level of accuracy. (A number of alternatives have already been reviewed in app. 4B.) The laser machining tool can then cut, weld, smooth, and polish cast parts to finer finishes as required. Vapor deposition is the least complicated, most versatile method of producing metal film sheets to be used as the manufacturing substrate for microelectronics components, mirrors or solar cells, or to be sliced into narrow strips by the laser for use as wire. The extruder is used to produce thread fibers of insulating material, presumably spun basalt drawn from a lunar soil melt as described in section 4.2.2. In addition to plaster casting, vapor deposition, extrusion and laser machining I would add 3D laser of electron beam sintering of titanium to make a wide variety of small complex parts. I would also add forging with non-hydraulic "gravity operated" mechanical drop forges. Also, sand casting. Plaster Casting Plaster can be obtained by sulfuric acid leaching of anorthostic highland regolith. The acid will break the minerals down into silica, calcium sulpate (plaster), other sulphate salts and water will form. Sulphate salts are all soluble except for lead, barium, silver, strontium and radium. CaSO4 is barely soluable, about 2 gr/liter. Thus, the CaSO4 and silica can be filtered out of the solution of aluminum, magnesium, iron, chromium, manganese, sodium and potassium sulfates. Sulfuric acid can be made from lunar sulfur present as solar wind implanted volatiles and FeS, troilite, of meteoric origin. A volatiles harvester with a furnace lined with cast basalt could tolerate the formation of H2SO4 during roasting of regolith onboard at temps. higher than 700 C. Sulfur dioxide will form and so will water due to reaction of hydrogen and sulfur with oxygen in the minerals and since regolith has catalytic qualities acid that will be hard on equipment will form. Fortunately, cast basalt resists 96% sulfuric acid, so it should be possible to build a mining robot that can also harvest sulfur. Calcium sulfate and silica could be separated by electrostatic separation. It will also be possible to roast anorthositic regolith at 1500 to 2000 C. to drive off FeO, SiO2, MgO, Na and K to get calcium aluminate- CaAl2O4. This could be leached in H2SO4 to get a solution of aluminum sulfate while the calcium sulfate is simply filtered out thru a silica wool filter without the use of electrostatic separation. Plaster casting of aluminum and magnesium can be done, but iron and steel cannot be cast in plaster because the iron or steel will absorb sulfur from the plaster and the temps. of molten steel and iron are about the same as the m.p. of plaster. Sand Casting Steel is usually sand casted in green sand, a mixture of sand, clay and binders. Regolith is not green sand. Perhaps it will be possible to sieve and size the regolith to get a useable sand and add binders made of sodium silicate or resin from hemp or some other plant. Polyurethane might be removed from ETs for binder. it might also be possible to syntheize epoxy and polyurethane binders from scavenged carbon, hydrogen, oxygen and nitrogen on the Moon in labs. We will also need vacuum grease for machines operating out-vac and conventional grease for machines indoors. Livestock scrap and manure can be converted to oil with heat and pressure. The oil could then be processed to lubricants and sand casting binders in labs on the Moon. See; http://news.nationalgeographic.com/news/2003/11/1125_031125_turkeyoil.html Vapor Deposition Iron can be reacted with CO gas to form gaseous carbonyls that can be deposited on hot metal forms that decompose the carbonyl and leave a thin layer of iron behind. The carbonyl releases CO gas that can be recycled and reused. Much work has been done on this at: http://www.space-mining.com/ In the vacuum it should be possible to boil aluminum and magnesium and make thin sheets by depositing the metallic vapors on cold forms. Extrusion Extruders can make rails, rods, bars, pipes and beams with various cross-sectional shapes from hot iron and steel or cold aluminum and magnesium. Wires and fibers of hot aluminum, calcium, basalt or glass can also be extruded. One extruder with different dies can make many different products. See: Lunar Manufacturing Processes 1 Laser Machining As stated above. lasers can cut, weld, smooth and polish. One important use for lasers would be to drill cooling passages in metallic molds and furnace crucibles. See: Molds and Mold Materials and Blister Steel 2 Lasers could cut thick flat plates of steel made by slab mold casting and rolling into various shapes. For instance, frames for rolling mills, drum magnet separators and electrostatic separators could be made on the Moon. The rollers would be made by casting steel in cylindrical metallic molds. Lasers could do all kinds of drilling operations without wearing out bits. Lasers could also cut cast basalt blocks into male and female blocks. See: Moon bricks Lasers could mill rough uneven metal surfaces to thousandths of an inch. They could bore and hone cylinders on the inner or outer surfaces. They can weld without large qtys. of welding gas. They could do jobs that are usually done with grinders. They could deburr and remove flashing from castings. This will save us the trouble of using so many cutting and grinding tools that will wear down fast with heavy usage. |
| 3D Sintering This technology can make very complex parts of modest sizes. Besides parts this can be used to make casting molds. See: http://lasersintering.com/ This method of manufacturing is well suited for making parts of titanium, especially in a vacuum since titanium tends fo abosrb nitrogen, oxygen and hydrogen, because titanium is a high melting point metal and casting is difficult. I have pseronally seen a chess piece- a rook with a little spiral staircase inside of it made by this process. So I can attest to the fact that very complex titanium parts can be made by 3D sintering with lasers or electron beams. Electron beam sintering has the advantage that energy is not reflected as is the case with a laser; however, radiation is given off by the e-beam so the sintering machine must be surrounded by shielding. On the Moon we would use regolith between retaining walls of cast or sintered basalt blocs. This process is also suited to automation. A 3D CAD file can be inputed to a computer that guides the sintering process and produces finished parts. |
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| Forging Many strong parts, large and small, can be made by forging white hot iron or steel. Iron or steel will be heated to 1000-1100 C. in solar or electric induction furnaces and placed by robots with titanium grippers (titanium mp. 1800 C softens at 1600 C.) into the drop forges. Various shapes can be made by switching dies. |
| This drop forge can make long L-shaped or curved pieces of steel. Long narrow plates of white hot pliable steel are inserted and banged into shape. |
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| Outer reinforcements for 10' x 10' x100' module with inner webs |
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| Power hammer forge: This machine is more complex than motor-pulley-weight forge, but it is more efficient and suited for repetitive operations. |
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