I could reply all day on educated discussions such as this. I founf something intresting.
Nuclear salt water rocket fission space drive high specific impulse

(NSWR)nuclear salt water rocket ........WOW!

The basic difficulty with space propulsion comes down to the problem of energy. There simply is not enough energy stored in NASA's best chemical fuels to generate much push (or more precisely, specific impulse, a quantity measured in seconds and given by ISP=vex/g , i.e., exhaust velocity divided by gravitational acceleration). The laws of physics dictate that if the specific impulse is low, the fuel consumed per second must be correspondingly very large to provide enough thrust (upward force) to boost a reasonable payload.

Project Orion, a product of the swords-into-plowshares theme of the late 1950s, proposed to propel a space vehicle by using a series of nuclear bombs exploded behind a thick steel plate to drive the space vehicle forward. Orion was rendered illegal and canceled because of the Test Ban Treaty of 1963.

Zubrin's nuclear salt water rocket (NSWR), on the other hand, requires only minor extrapolations from the mature technology of existing nuclear power systems and could probably be implemented for prototype testing in a very short time. Writing the environmental impact statement for such tests, however, might present an interesting problem, because Zubrin's scheme vents highly radioactive nuclear fission products directly into space. It is therefore appropriate mainly for deep space missions. It is, in a sense, complementary to the laser-sustained propulsion scheme which requires a ground-bases laser within shooting distance of the space vehicle.

Source:This link laggs a little http://www.npl.washington.edu/AV/altvw56.html

http://www2.jpl.nasa.gov/galileo/mes...mess/RTGs.html

http://www.fas.org/nuke/space/index.html