Asteroid mining 2006
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Post on 11-May-2015
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DESCRIPTIONKind of funny - with all the news about Planetary Resources Inc and asteroid mining, here's some notes I made back in 2006 on the topic to talk with some of my colleagues on the subject.
<ul><li>1.Asteroid MiningOpportunitiesNotes1</li></ul><p>2. Early evidence suggests that there are trillions of dollars worth of minerals andmetals buried in asteroids that come close to the Earth. Asteroids are so close that many scientists think an asteroid miningmission is easily feasible. 3. Value3 4. Value of ANYMaterials per kg. Launch cost of material from earth: $10,000Note that the asteroidal materials we are talking about are, simply, water, nickel-iron metal, hydrocarbons, and silicate rock. Purified, and made available in low earth orbit, they will be worth something like $500,000 per ton, by virtue of having avoided terrestrial gravitys "launch cost levy."These values are up there with optical glass, doped semiconductors, specialty isotopes for research or medicine, diamonds, some pharmaceuticals, illicit drugs. On the mining scene, the only metal which has ever been so valuable was radium, which in the 1920s reached the fabulous value of $200,000 per gram!Platinum Group Metals (which are present in metallic and silicate asteroids, as proved by the "ground truth" of meteorite finds) have a value presently in the order of $1,000 per ounce or $30 per gram. Vastly expanded use in catalysts and for fuel cells will enhance their value, and PGM recovery from asteroid impact sites on the Moon is the basis of Dennis Wingos book, "Moonrush. 5. Value of MaterialsOne NASA report estimates that the mineral wealth of theasteroids in the asteroid belt might exceed $100 billion for each of the six billion people on Earth. John S. Lewis, author of the space mining book Mining the Sky, has said that an asteroid with a diameter of one kilometerwould have a mass of about two billion tons. There are perhaps one million asteroids of this size in the solarsystem. One of these asteroids, according to Lewis, would contain 30 million tons of nickel, 1.5 million tons of metal cobalt and 7,500 tons of platinum. The platinumalone would have a value of more than $150 billion! 6. Professor John Lewis has pointed out (in Mining the Sky) that the resources of the solar system (the most accessible of which being those in the NEAs) canpermanently support, in first-worldcomfort, some quadrillion people. 7. Resources7 8. Mineral Content Spectroscopic studies suggest, and ground-truth chemical assays of meteorites confirm,that a wide range of resources are present inasteroids and comets, including nickel-ironmetal, silicate minerals, semiconductor andplatinum group metals, water, bituminoushydrocarbons (Ralph: think OIL like materials),and trapped or frozen gases including carbondioxide and ammonia. 9. Mineral Content Even a relatively small asteroid with a diameter of one kilometercan contain billions of metric tons of raw materials. In 1989 the world production of iron ore reached a local peak of928,054 metric tons prior to the collapse of the Warsaw Pact. Incomparison, a comparatively small M-type asteroid with a meandiameter of 1 km could contain more than 3 billion metric tons ofiron-nickel ore, or 3,000 times the annual production for 1989. (Inother words, more iron ore than has ever been mined in humanhistory.) A small portion of the extracted material would also containprecious metals, although these would likely be more difficult toextract. 10. Platinum Elements As one startling pointer to the unexpectedriches in asteroids, many stony and stony-ironmeteorites contain Platinum Group Metals atgrades of up to 100 ppm (or 100 grams perton). Operating open pit platinum and goldmines in South Africa and elsewhere mine oresof grade 5 to 10 ppm, so grades of 10 to 20times higher would be regarded as spectacular ifavailable in quantity, on Earth. 11. Helium-3 Researchers see helium-3 as the perfect fuel source: extremelypotent, nonpolluting, with virtually no radioactive by-product.Proponents claim its the fuel of the 21st century. The trouble is,hardly any of it is found on Earth. But there is plenty of it on theextraterrestrial bodies (the moon and asteroids). "Helium 3 could be the cash crop for the moon (and asteroids),"said Kulcinski, a longtime advocate and leading pioneer in the field,who envisions the moon becoming "the Hudson Bay Store of Earth."Today helium 3 would have a cash value of $4 billion a ton in termsof its energy equivalent in oil, he estimates. 12. Water Water is an obvious first, and key, potentialproduct from asteroid mines, as it is a highlyprized resource in outer space. (ThinkMoon/Mars Colonies) Water could also be broken down into hydrogenand oxygen to form rocket engine propellant.(not only what we need to get stuff back home,but also a very valuable commodity to sell toother space faring companis) 13. Energy Solar Arrays think 24 hour a day sunlight Nuclear (cant build this kind of stuff on earth) 14. Extraction andProcessing 14 15. Mining There are two options for mining: Bring back raw asteroid material. Process it on-site to bring back only processed materials, andproduce fuel propellant for the return trip. Processing in situ for the purpose of extracting high-value minerals will reduce the energy requirements fortransporting the materials to the point of manufacture.However the processing facilities must then betransported to the mining site. Thus there is aneconomic trade-off. 16. Mining (contd) Mining and processing an asteroid is much less massive an operation than Earth orMoon mining. We do not need heavy mining and transport machinery, we dont needcomplex chemical processing as on the Moon in order to get valuable materials, andwaste disposal is achieved by just putting all waste into a big bag. However, the nearzero-gravity space environment has its unique challenges as well. A typical asteroid would probably be crumbly, consisting of silicate dirt embeddedwith nickel-iron granules and volatiles. We can make this assumption for thepurposes of this analysis, but should be aware that the consistency from asteroid toasteroid can vary from pure metal to pure powder, and could also entail a mix ofconsistencies. Many different methods have been discussed for mining the asteroid. Conventionalmethods include scraping away at the asteroids surface (i.e., strip mining), andtunneling into the asteroid. Most Earth mining depends upon gravity to hold thecutting edge against the ore. (However, for many Earth mining operations this is notenough, and other means are employed, e.g., cables and reels.) Scraping away atthe surface of the asteroid requires holding the cutting edge against the outer surfaceof the asteroid. This would require either local harpoons or anchors imbedded intothe surface of the asteroid, or cables or a net around the asteroid for the cutter tohold onto. 17. Mining (contd) Strip mining would result in a lot of dirt being thrown up. An unconventional space mining methodsees this not only as a problem but also as an opportunity. A canopy around the mining site can beused to collect ore purposely kicking up, the canopy shaped and rotating to use the centrifugal forceto channel the ore to the perimeter for collection, as this NASA artwork shows. If no canopy were putup, a lot of debris would cloud and cover the mining environment and probably interfere with miningoperations. (Mining without a canopy would certainly be unacceptable in Earth orbit. Companies willmost probably use a canopy also because the canopy would be quite profitable in terms of theamount of loose ore it would collect.) A variation on this is to have a stationary canopy. A dust kicker goes down to the asteroid and justkicks up the ore at low velocity. When theres enough ore in the canopy, its sealed off and moved tothe processing site (where the ore can be collected by rotation or other mechanical means). It issimple and highly reliable, presenting minimal risk of breakdown of mining machinery. Some studies adopted tunneling to mine an asteroid. The cutter holds itself steady by the walls ofthe tunnel -- pushing against the walls or cutting into them. Tunneling prevents consumption of theentire asteroid, but desirable ore veins or cracks can be followed. Another candidate process for extracting volatiles from within near Earth asteroids which aredormant comets (currently estimated to be around 40% of near Earth asteroids) is to drill into theasteroid, much like we do for oil and natural gas. Geological and Mining Consultant David L. Kuck ofOracle, Arizona, proposes in a long paper entitled "Exploitation of Space Oases" some highlyautomated methods of drilling and producing volatiles without the need for extraction of materialsand thus without dealing with the crushing, grinding and tailings disposal. 18. Mining Mechanisms One of the difficulties in mining an asteroid will be the rotation period of the body. It may benecessary to attach rockets to the asteroid in order to eliminate the spin before mining cancommence. Alternatively, the mining operation can be placed at the pole of the asteroid, or asteroidswith high rates of rotation can simply be avoided. The mining operation will require special equipment to handle the extraction and processing of ore inouter space. The machinery will need to be anchored to the body, but once emplaced the ore can bemoved about more readily due to the lack of gravity. Docking with an asteroid can be performedusing a harpoon-like process, where a projectile penetrates the surface to serve as an anchor thenan attached cable is used to winch the vehicle to the surface. There are several options for material extraction: Material is successively scraped off the surface in a process comparable to strip mining. The digging machine will need to be anchored against the asteroid using a series of attachments, then cut into the surface using a blade. The drawback to this approach is the large amount of loose material that will collect in the low-gravity environment about the asteroid. A mine can be dug into the asteroid, and the material extracted through the shaft. This eliminates the problem of producing loose material, but it would require a transportation system to carry the ore to the processing facility. Potentially the microgravity environment can be exploited to move the material to the surface. Ultrasonic/Laser Mining Due to the distance from Earth to an asteroid selected for mining, the round-trip time forcommunications is likely to be on the order of a minute or more. Thus any mining equipment willeither need to be highly automated, or a human presence will be needed nearby. Humans would alsobe useful for troubleshooting problems and for maintaining the equipment. So, at least untilautomated space mining technology improves sufficiently, the mining facilities would need to beaccompanied by a sealed-environment habitat. The operation is also likely to be of long duration, sothe health risks of weightlessness would need to be managed and the crew would require a shelteragainst radiation from solar flares. A habitat mounted on the asteroid and covered by surface 19. Mining Equipment Postulates The machinery will likely be solar powered, to reduce the need for fuel that would have to behauled to the asteroid by spacecraft. The equipment will also have to be lightweight to transport it to the asteroid. Some experts, including Lewis, have favored using robotic equipment to limit the personnelneeded to carry out the mining project. This would reduce the amount of supplies, like food,required for a manned mission. Miners on asteroids would use techniques similar to those used on Earth. The most likelymethod would be to scrape desired material off the asteroid, and tunnel into veins of specificsubstances. Scraping, or strip mining, will pull out valuable ore that will float off the asteroid. Because much of the ore will fly off, a large canopy might be used to collect it. Asteroids have nearly no gravity, so the mining equipment, and the astronaut-miners whooperate it, will have to use grapples to anchor themselves to the ground. However, the lack ofgravity is an advantage in moving mined material around without having to use much power. Once a load of material is ready to be sent to either Earth or a space colony, rocket fuel for aferrying spacecraft could be produced by breaking down water from the asteroid into hydrogenand oxygen. After an asteroids minerals and resources have been exhausted by the mining project, theequipment can then be transported to the next asteroid. 20. Processing Asteroidal material in general is exceptionally good ore requiring a minimum ofprocessing, since it has free metal already. Only basic ore processing need occur at the asteroid, producing free metal and volatiles(usually stored as ices), and perhaps selected minerals, glasses and ceramics. Therequired equipment is quite simple. The following is a sample ore processing system, but is not the only one proposed to date. At the input chute, the ore will be ground up and sieved into different sizes as the first stepof a basic ore processing system. Most asteroids probably offer far more crumbly materialthan we could consume in one mining expedition. Simple mechanical grinders, using a gentle rocking jaw arrangement for coarse crushingand a series of rollers for fine crushing, could be arranged in a slowly rotating housing toprovide centrigufal movement of the material. Vibrating screens are used to sift the grainsfor directing them to the proper sized grinders. The streams of material are put through magnetic fields to separate the nickel-iron metalgranules from the silicate grains. Alternatively, the streams can be dropped onto magneticdrums, whereby the silicates and weakly magnetic material deflect off the drum whereasthe magnetic granules and pebbles stick to the magnetic drum until the scrape off point.Repeated cycling through the magnetic field and perhaps additional grinders can givehighly pure bags of free nickel iron metal. An optional additional piece of equipment is an "impact grinder" or "centrifugal grinder"whereby a very rapidly spinning wheel accelerates the material down its spokes and flingsit against an impact block. Any silicate impurities still attached to the free metal areshattered off. Its feasible to have drum speeds sufficient to flatten the metal granules byimpact. A centrifugal grinder may be used after mechanical grinding and sieving, andbefore further magnetic separation. In fact, most of the shattered silicate will be smallparticles which could be sieved out. 21. Processing (contd) The nonmagnetic material is channelled into a solar oven where the volatiles are cooked out. In zero gravity andwindless space, the oven mirrors can be huge and made of aluminum foil. The gas stream is piped to tankslocated in a cold shadow of space. The tanks are put in series so that the furthest one away is coldest. This way,water condenses more in the first one, carbon dioxide and other vapors in the tanks downstream. Rocket fuel for the delivery trip to Earth orbit can be produced by separating oxygen and hydrogen gases...</p>
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