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| Courtesy Kordite at flickr |
The mining of asteroids will begin in earnest within the next 10 to 100 years. The asteroids chosen for retrieval and processing will almost certainly contain water because water will be one of the most valuable commodities in space, if not the most valuable. Not only does water contain hydrogen and oxygen for rocket fuel, humans need it for survival; and it is very efficient at stopping many types of radiation.
If a current or future corporation is going to make a decision on which asteroid to go after, the metal content of the asteroid may not be the deciding factor. Asteroids with little or no water will be passed up for mining at least in the early phase of the industry. If our civilization remains technically and economically viable into the 22nd century, the asteroid mining industry should be hitting its stride and keeping economic growth positive for several hundred years. Even after this maturation, the industry will favor those space rocks containing water simply out of habit and tradition unless some special material is needed that can’t be found in combination with water. Another outlier would be a leap in engine technology, such as a compact fusion drive, that would mediate the reliance on water as stored rocket fuel.
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Let’s say some future company is evaluating two different asteroids for mining. One, 1999 JM8, is a nickel, cobalt, and iron asteroid worth $45 trillion dollars. It is fairly large at 4.35 miles in diameter, but only .024 Astronomical Units away at its closest approach to Earth, approximately 2.2 million miles or about ten times the distance from the Earth to the Moon.
Another asteroid, 1950 KA, is worth only $33.4 trillion dollars and is .097 AU at its closest pass to Earth, nearly four times that of 1999 JM8. It has a couple of things going for it, though. It is only 2.17 miles in diameter and has a composition of nickel, iron, cobalt, water, nitrogen, hydrogen, and ammonia.
This company will pick 1950 KA because of the water, hands down. Once the robotic retrieval craft gets to 1950 KA, it can mine water; and, with the abundant solar energy available in space, split it into hydrogen and oxygen for rocket fuel to move that mass back to Earth.
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| Courtesy NASA |
After 1950 KA is parked in orbit near Earth in one of the Lagrange points L4 or L5, the real fun begins. Using many specially designed, semi-autonomous robots, the asteroid is scraped, tunneled, bored, melted, smelted, hammered, drilled and crushed to extract its treasures. In the early going of asteroid mining, however, it will not be done without humans. We will be there to direct the overall strategy and change tactics when necessary, not to mention repairs and hands-on inspections. This is only because artificial intelligence will not yet be up to the autonomous decision making required of mining asteroids.
Human workers need a safe, even comfortable place to stay while performing these chores. Safe by logical necessity and comfortable to attract the type of person needed for this work given how long they will have to be in space. Money can only go so far as an incentive. Intelligent, athletic, engineering and scientific types only need apply, similar to astronauts in education and ability.
Here is where the water comes in. These people will be shielded from radiation by a wall of water, actually ice. As I mentioned above, water is very efficient at shielding many types of radiation, including that from solar flares, gamma radiation, and cosmic radiation. Although NASA has been working on a lightweight polyethylene plastic called RFX1, it has some serious problems in competing with water. One, you can’t drink it. Two, it has to be hauled up the gravity well of Earth.
Exactly how will water be used as a radiation shield? Three feet of water or ice will intercept and diffuse almost any radiation, including gamma rays and cosmic rays. Since there is plenty of water available from the asteroid, it makes sense to protect the entire facility instead of providing a vault or other safe area that people have to go to. At some point, an unexpected sleet of radiation is bound to sweep through the area. This way everyone will be protected all the time unless they are doing something outside of the habitat and not working inside the asteroid.
The geometry of the habitat will resemble a thick hockey puck. This will rotate to provide simulated gravity to the inhabitants. On the unit shown in the drawings, eight rotations per minuted will provide nearly one g at the outer wall or "lower" level. The second level will provide three quarter g, and the "upper" level one half g. The center on one side will have a docking facility. The center of the other side will sprout a boom about as long as twice the diameter of the pancake. At the end of this boom will be thrusters that can point in almost any direction. These thrusters will be powered by, you guessed it, electrolysed water in the form of hydrogen and oxygen burning to form, once again, water.
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Not only is it a habitat, but it can move around as required to view different parts of the asteroid or move equipment that is not self-motile. It will pick up and drop off people at the orbital end of the Lunar Space Elevator. It will be a habitat, taxi, and tug. Some may call it the "Ice Palace", but it’s a given the majority will nickname it the "Igloo."
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This three foot barrier of water will remain frozen because space is cold. Solar energy hitting the outside envelope of the vessel may have some effect, but as that surface rotates into shadow, it will become frozen again. The inside surface of the ice barrier will be in a constant state of melting. The human habitation will necessarily give off heat. No matter how thick the insulation, it will eventually melt this inner surface. This water, through centripetal forces will be routed to the outer surface where it will be refrozen. This ice barrier is a good buffer between the 70-75 degrees Fahrenheit in the habitat and the minus 450 degrees F. of outer space and will probably vary in temperature, getting colder from the inner to outer surfaces.
The lure of infinite wealth and energy will be too strong for capital to resist. A lot of money will be spent on this endeavor. Hopefully, it will be spent wisely, and progress will be swift and beneficial not only for those companies involved but for the rest of us as well. The bottleneck is the gravity well barrier that is currently so expensive to vault. Space is kind of like Vegas; what happens there stays there. However, companies like Obayashi Corporation are working on building an elevator to space. This would drastically reduce the cost of sending stuff into orbit and bringing it back. Their plan is to have it built by 2050, waiting only for the successful mass production of carbon nanotube fibers long enough to use. Hopefully, their prediction will not become similar to the refrain of nuclear fusion developers of having a practical fusion generator within thirty years … every year. While the industry can have some success with rockets, it will grow by leaps and bounds with a working space elevator.
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