On another thread, Billy Brown wrote:
> To do this you nead to move each comet a long way - about 0.1 LY, if I
> remember right. Ion drives at .01 G will take around 20 years, which is
> long enough to make the whole scheme irrelevant. To do it fast enough to
> matter you need to apply a velocity change of several thousand KPS in a
> space of a year or less.
An interesting aspect of solar-system engineering is that there is this tradeoff between power and time. You can do a lot with little power if you are willing to take a long time at it.
Moving asteroids and comets around, taking them apart, providing resources to planetary bodies, can largely be done using solar power and in situ fusion reactions. Low-thrust ion rockets or mass drivers take time to build up delta V but are very efficient.
It should also be possible to exploit the chaotic dynamics of some parts of the solar system, where very tiny changes can produce big outcomes. Comets which pass close to the sun or Jupiter are good candidates for this.