That's what I figured (read an article in Pop. Sci. on several different drives-that seemed best because of low and high drive gears). Check out B-Chan's post about atomic bullets. I always wondered if that was possible and now I have a source for it. Great!
One last thing before I go. Sometimes I have a couple of beers with friends and we discuss what groups could terra-form Mars. Well, the Clintonistas cames up as a group. Basically, it would be : " Bill Clinton: Porn King of Mars". Where he sells tapes of himself doing the Kama-Sutra with 480 of the top porn stars (mostly women) to raise money. They use Californium and call themselves the "Californicates". After that we decided to stop drinking so much.
Take it easy. And thanks for the links to the "gas-core" technology.