They're working away on earthly Nuke propulsion, but those are thermal transference and the like...
www.fas.org...
What you're talking about I think is a nuclear Pulse Engine, and as a concept has been around for decades and I have seen some design proposals for a
nuclear propulsion space craft, but they are pretty much frozen in limbo due to the international ban of nuclear testing in space. Ironic eh? You can
test them all you like here in the biosphere though, as long as you're one of the good guys that is.
Source
Pulsed Fission - Project Orion
The third idea for harnessing nuclear fission for space travel is by detonating nuclear bombs to provide propulsion. This idea is more commonly
referred to as a nuclear pulse rocket and was conceived in 1955 under the title Project Orion, which ran through the 1950's and into the 1960's. The
objective of the project was to send a manned mission to Mars.
