Many of the concepts relating to asteroid mining were first seriously studied during the 1970s as part the Princeton/NASA—Ames investigations of space habitation and manufacturing. Any asteroid-mining venture will actually be a three-step process.
The initial mission phase concerns the transfer of equipment and personnel to the celestial object to be exploited. Then, the equipment must be installed upon the surface of the asteroid and the asteroid's rotation must be stopped. Finally, as much of the asteroid material as possible must be returned to a space manufacturing facility, most likely in Earth-Moon space.
The basic tool to be used in asteroid mining is most likely be the mass driver. Described by a number of authors, including Gerard K. O'Neill and Brian O'Leary, the mass driver is essentially a solar-powered electromagnetic catapult. It can be mounted on the lunar surface and used to fling payloads of mined material into space to be grappled by a mass catcher—a space equivalent of a catcher's mitt. Alternatively, it could be operated as an in-space propulsion system expelling any convenient material, such as ground-up, spent rocket stages or it could be mounted on an asteroid and utilized to propel the asteroid through space by throwing away packets of asteroid rock.
The exhaust velocity of a mass driver used as an in-space propulsion system would be as high as 8-10 kilometers per second; it could accelerate as much as a million kilograms per year. Its mass would be in the vicinity of 100,000 kilograms and its length would be in the multi-kilometer range. For use on a celestial body's surface, the mass driver could be optimized for higher mass throughput and lower exit velocity. Much of the technology of these devices has been tested and is shared with terrestrial devices including magnetically levitated (maglev) trains.
A mining expedition to an Aten object might look something like this:
Possibly under its own power, the robot mass driver departs Earth orbit first, possibly utilizing a low-energy trajectory (such as those discussed in Chapter 4) and lunar gravity assist, to effect rendezvous with the NEO. The human crew follows on a higher energy, chemical-rocket-propelled trajectory to minimize exposure to solar and galactic radiation.
Arriving at the destination, astronauts first set up camp on the surface of the NEO, using NEO material as cosmic-radiation shielding. The mass driver is then utilized to cancel the rotation of the NEO—a necessary, but not very major task since most asteroids rotate with periods of many hours.
The mass driver is then used as a rocket, the exhaust being parcels ofasteroid material flung into space. The NEO's trajectory is gradually altered so that it is captured as a distant satellite of the Earth, where workers from an orbital space manufacturing facility can disassemble it. As the entire process may take years, the astronauts on the NEO might be rotated back to Earth and replaced by fresh crews several times.
A tremendous amount of material could be returned to earth orbit for use in constructing solar-power satellites, radiation shields, and for other applications that we can only imagine. If only one-third of the estimated mass of Asteroid 2001 CQ36 could be returned in this manner, about one-billion kilograms of material would be available for space manufacturing.
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