There was something similar that's a lot more environmentally friendly (though this wouldn't be all that bad if it were just one or two flights a year) that was researched heavily during the run up to Apollo involves using nuclear fuel to super-heat a fluid for propulsion.
Imagine nuclear reactors; they use fuel rods to generate heat that turns water to steam that turns a turbine. These would have much more potent fuel rods and would run massive quantities of, say, water, through the engine. It gets vaporized instantly, and creates thrust similar to current rocket engines, with much better specific impulse.
Moon trips could be done round trip in two to three days, Mars trips could be done direct in as little as two to three *weeks* versus months or years for round trips. Some liquids would be better than water but fans always use water as its 'not bad' and infinite in supply.
Apollo was going to use it for the upper stage of the Saturn-V but had some slight engineering problems. By the time it was fixed for later projects, hippies were giving NASA huge, huge problems (several-thousand person protests at KSC for example) for just launching satellites with small amounts of nuclear fuel. Even though these engines would be safe, politically they were impossible..
Today with modern computers (versus whatever they used in the 50s & 60s -- abacus?) they'd be really simple to pull off, all the problems were basically fixed in the 60s before being put on ice.
See.. if I were made Imperial Emperor of the New American Empire, thats one of those things that'd be on the top of my list.. Hippies can protest all they want; I'd need the slave labor they'd provide on the Moon, Mars and in the Asteroid Belt...
There's a great wikipedia entry on it too, not making any of it up. They actually made these engines and test-fired them many, many times. Real stuff. It's not 100% accurate (nothing in wikipedia is), but it only misses some minor things that a friend of mine nitpicked (he's a nuclear engineer of some kind at nuclear power plants, has a sample of yellowcake on his desk, he knows of what he speaks), so it's a solid read.
http://en.wikipedia.org/wiki/Nuclear_thermal_rocket
It wouldn't shock me if some day a country that didn't give a crap about protestors (like Russia or China) used this technology.. they'd really leave the rest of the world behind, capability-wise.
Edit: One of those NTR designs on that wiki page doesn't mention it, but all of those could very easily do a one-way Alpha Centauri trip in about 120 years. Not exactly warp 9, but.. better than the 'never' current tech could handle.
