Talk-Polywell.org

Interesting piece on cities and moon colonies:

http://nextbigfuture.com/2010/12/settin ... -moon.html

More moon colony stuff:
http://nextbigfuture.com/2011/01/two-wo ... bling.html

Of course you could replace your nuclear cannon with a polywell powered Kantrowitz laser system:
http://en.wikipedia.org/wiki/Laser_propulsion
http://www.space.com/7067-laser-propuls ... shine.html
using free electron lasers:
http://www.jlab.org/fel/