How to Colonize an Asteroid
A linear induction engine, also know as a "mass driver", is basically an electric motor which has been unwound in a straight line. The device is essentially a row of electromagnets which are switched on and off in sequence to accelerate a ferrous object.
If the ferrous object is allowed to continue accelerating and is shot out of the end of the engine, thrust is produced. We can take advantage of this in a couple of different ways;
1. The object could be a type of ferrous bucket which is filled with non-ferrous material, such as regolith or debris from inside the asteroid. The linear induction engine, in this case, would have to include deceleration coils which would stop the bucket, but allow its non-ferrous contents to continue. This method could be used to change the trajectory of an asteroid, or two could be used on opposite sides to create the spin needed for artificial gravity.
2. The accelerated object could be a small probe or spacecraft with a ferrous shell. In this case, the induction engine would be used to shoot the spacecraft out into space from the asteroid colony. This technique could be used to boost a craft to a safe distance before it ignites a more dangerous chemical rocket engine, or could be the sole propulsion system of a small probe. One drawback to continually launching craft from the asteroid in this manner is that it will eventually change our orbit, as the spacecraft themselves become the reaction mass.
Experiments by graduate students at a university [ If you know whom, please e-mail me at obwan@cyberjunkie.com ] using superconducting coils have produced accelerations of over 8g's, which is twice that of the space shuttle. While it is not practical for most of us to experiment with superconducting coils, we can build a working model of a linear induction engine from commonly available electronic parts.