Quote from Robert Dyck (MIT discussion group)
"The first profit must make money for investors here on Earth. Short term profit from space will come from asteroids. I talked before about triangle trade for asteroid mining. Here's how it works: There are a lot of main belt asteroids, but they're far away. Near Earth asteroids are fewer, but they're a lot closer so easier to get to. Initial asteroid mining will be on near Earth asteroids. There are over 4,000 NEAs greater than 1km diameter, all closer than Mars or Venus and since their gravity is so low it takes less fuel to land on than the Moon. In fact, it takes so much less fuel to land and take off again that the total fuel to go from Earth orbit to the surface of an asteroid and back takes less fuel than the Moon. These are our near-by ore deposits. C-type asteroid: Carbonaceous chondrite asteroids are composed of chondrules (pebbles of rock) embedded in carbonaceous guck. That guck is a combination of clay, tar, salts, hydrated minerals like gypsum and epsom salts, and small crystals of ice. Yup, I said ice. Kuiper belt asteroids are out beyond Saturn, they're so far out that the Sun's heat doesn't reach them so still have all their ice. NEAs will have all of ice near the surface boiled off millions of years ago. But also remember that direct sunlight in space is hot, but shade is very cold. A spacesuit in Earth orbit experiences +150?C in sun, -120?C in shade. The core of a spinning big asteroid will be the average. Beneath a crust of fractured, baked, freeze dried, vacuum desiccated debris, the asteroid will still have it's ice. That ice can be drilled for the same way oil rigs on Earth drill for oil. On Earth, oil deposits are soaked within pours of sandstone; sometimes under pressure (tons of soil and rock sitting on it) but sometimes has to be pushed out with steam. An asteroid will have tiny ice crystals mixed in guck and pebbles. Drill down, melt ice with an electric heater. In vacuum ice will sublimate directly to steam, it takes pressure to make water. If the drill hole is plugged by the drill pipe, steam pressure will build up quickly, pressure to push dirty water up the pipe. Asteroids aren't held together very well, too much pressure could fracture the asteroid blowing out a chunk. Liquid water forms above 6.12 millibars pressure, Earth at sea level is 1013.25 millibars; just 10 millibars is well above the triple point of water (where gas, liquid and solid meet) but still only 1% the pressure on Earth. Deep within an asteroid that should hold together. Dirty water can be filtered to remove sand and mud, further filtered to make clean water, and filtered again with a reverse osmosis. The result is pure enough for electrolysis to make hydrogen and oxygen, rocket fuel. A proton transport membrane electrolysis unit is the most energy efficient and separates oxygen from hydrogen with that membrane. In the microgravity of an asteroid, keeping them separate is important. A refrigeration pump can liquefy oxygen and hydrogen for storage, and any boil-off directed back into the refrigeration pump. Filtered wet mud can be baked to get moisture out, moisture sent through electrolysis. Dry mud with tar can be burned with oxygen produced, resulting in carbon dioxide and water. A catalyst similar to a catalytic converter in a car can ensure complete combustion, professional chemists can tell you the optimum catalyst. Filters and refrigerators can separate water from CO2, in Earth pressure water freezes at 0?C but dry ice freezes at -78.5?C. The resultant baked, burned mud bricks can be dumped on the asteroid, that's your tailings. CO2 is most easily transported as dry ice. There are uses for CO2. M-type asteroid: Metal asteroids are also known as iron or iron-nickel because they're roughly 70% iron, 30% nickel, with traces of other metals. It isn't an oxide ore like any ore deposit on Earth, this is pure metal. That makes it very easy to purify. Asteroids are a mixture of metal and rock, but by definition an M-type asteroid has less than 30% rock pieces stuck in the metal. A commercial asteroid mine would look for very low rock content, some have less than 10% mineral inclusions. The exact mixture of metals vary from asteroid to asteroid, but the traces are very interesting. Gold and silver are always associated with iron deposits, either on asteroids or on Earth. Platinum group metals are always associated with nickel. The platinum group consists of 6 metals; one is platinum, the other five are palladium, iridium, rhodium, ruthenium, osmium. These are the 8 precious metals. If you want gold and silver, look for high iron content. If you want platinum group metals, look for high nickel content. Precious metals are a very valuable and obvious export for Earth. Many chemical reactions require platinum, others require palladium, some are best catalyzed by rhodium. Industrial chemical plants including oil refineries have a strong need for platinum group. In fact, proton transport membrane electrolysis units and fuel cells require a thin platinum layer. Since worldwide oil production peak is expected this year, but third world countries like China and India are growing rapidly, making full use of all petroleum available will be necessary. Coal can be converted into natural gas and burned, a process called Integrated Gasification Combustion Cycle (IGCC), but it also requires a catalyst. Sale of precious metals as catalysts will quickly outstrip supply. Here's a near-term market need. In fact, the Sudbury Basin is one of the worlds major nickel deposits, the 3rd largest platinum producing region, and it's a 2 billion year old 100km wide impact crater caused by a 10km wide asteroid. The asteroid ore is thinly mixed with Earth rock, going to an asteroid gives you pure asteroid material. Mining an M-type asteroid has a few steps: dig out rock, crush, then separate mineral inclusions by spinning in a centrifuge and pick out metal with a magnet. Mineral rock will be left behind; tailings. That rock can be melted with sunlight from a curved mirror to fuse into big pieces that can be anchored to the asteroid; tailings pile. You don't want a cloud of loose rock bits floating around the mine site, it wouldn't be safe for a cargo ship to arrive to pickup our product. Then the metal can be separated using the Mond process. This is already used by the nickel mining industry. It works by combining ferrous metal (iron or nickel) with carbon monoxide gas to form metal carbonyl. That vapour is drawn off and further heated to break it back down into metal and carbon monoxide. This works at roughly 200?C, a fairly low working temperature. The exact temperature is different for iron and nickel, permitting easy and cheap separation into 99.999% pure iron or nickel. Platinum group metals require much higher pressure to form carbonyl, permitting easy separation. All this requires carbon monoxide gas; reacting carbon dioxide with hydrogen forms water and carbon monoxide. Working fluids are then hydrogen and CO2, imported from the C-type asteroid. There are industrial mining chemical reactions to separate gold, such as dissolving it in mercury or reacting with sodium cyanide. Gold reacts to form a chemical that dissolves in water, silver and other metals don't dissolve. The reaction is: 4 Au + 8(NaCN) + O2 + 2 H2O = 4 NaAu(CN)2 + 4 NaOH Gold is precipitated by zinc: 2Au(CN) + Zn = 2Au + Zn(CN)4 Zinc cyanide and sodium hydroxide have to be recycled back into sodium cyanide and zinc metal. This is the most cost effective process on Earth, but it requires a lot of materials not readily available on asteroids. Gold will also combine with halogens chlorine bromine or iodine, or with sulphates, all of which can be harvested from the salts of a C-type asteroid, but it may be easiest initially to not bother with gold and silver. Transporting precious metals to Earth is a cost issue. You can't send up a rocket to go get it, the rocket would cost more than the precious metal cargo. You can make a aeroshell capsule from asteroid material and drop it on Earth. The metallic heat shield developed by NASA is a nickel alloy called Inconel. Inconel 718 is an alloy used for some Apollo and Space Shuttle parts, Inconel 617 handles higher temperatures and is used for new metallic heat shield materials. Inconel 617 consists of: 0.05-0.15% carbon 10-15% cobalt 20-24% chromium 8-10% molybdenum 0.8-1.5% aluminum some impurities they try to minimize the rest nickel Carbon can come from CO2, the other metals are found in an M-type asteroid. We can make an inconel aeroshell from left-over material after mining platinum group bullion. When NASA's probe called Genesis returned to Earth, it was supposed to deploy a parachute that would be caught in mid-air by a helicopter. The accelerometer was installed up-side-down so the parachute never deployed; the aeroshell crashed into the desert floor. Although the aeroshell cracked open and silicon wafer collection plates shattered, gold plates survived intact. I don't consider the Genesis crash a failure, it was a successful demonstration of asteroid mining technology. Commercial mines smelt bars to 98% then send them to a refinery for further purification. Asteroid mines can do the same, at the same refinery. Since bars returned to Earth will be melted anyway, it doesn't matter if they get bent, dented, twisted, etc. on impact with the ground. All we need is a 2 part moulded inconel clam shell, heat shield and back shell. Easy enough to fabricate in space. A reusable cargo ship will have a 3 point trade route: Earth, C-type asteroid, M-type asteroid. Pick-up equipment from Earth orbit for both asteroids, fill the ship's fuel tank at the C-type asteroid, transport CO2 & hydrogen to the M-type asteroid, and carry inconel aeroshells with precious metal bullion to Earth. Drop the aeroshell in a direct entry for Earth, but aerocapture the ship into Earth orbit. Note, Beagle 2 was released by Mars Express in a Direct Entry trajectory; Beagle 2 itself did not have any manoeuvring thrusters. Fuel can also be delivered to a depot in Earth orbit. Spy satellites need a lot of fuel for orbit changes, the space station needs fuel to maintain its orbit, and any mission beyond Earth orbit can be fueled from that depot."Back to spacetrader:
The end result cities in the asteroid belt , built like hornets nests. Each habitat maintains its own thistledown drive. The entire outer shell of the city can be used for mining and defense.