I would like to clarify that this post does not refer to radioisotope thermoelectric generators (RTG) that have been used in space since the ’60s. These are still used and will be used in future missions. What I am talking about here is a primary propulsion system that uses nuclear fission or fusion to generate thrust.
When Will the First Atomic Rocket Lift Off Earth?
Most likely never. The main reason for this is quite simple; even the smallest propulsion engine will likely qualify as a potential weapon of mass destruction. Even a few kilograms of radioactive material could cause a huge loss of life if it were to burn up on reentry and that would be the best case scenario of an accident involving such a craft. It would be so easy to weaponize such an engine that there would be massive international opposition to its development. Those that think that countries like the U.S.A. and China would not be effected by such opposition how simple huge boycotts could cripple the economies of any country and how universal the opposition would be.
Will We Ever Have Atomic Rockets?
Yes, atomic propulsion in space will be an important part of our expansion into space. The catch here is that the radioactive element used will not likely come from the Earth’s surface and will likely never approach it closer than Geosynchronous orbit. The main reason for this is that even intentional nuclear weapon will not be that much more destructive than more conventional weapons in space. A large mass traveling as a significant speed has the potential energy and destructive power of even our largest nuclear weapons and the radiation produced is not that much greater than is ‘natural’ in the local environment. As the Moon is made up of the same material as the Earth’s crust there will likely be enough heavy metal isotope there to use in the engine. Mining it will also not have the issue of contaminating the local environment that exists on Earth.
Atomic propulsion will be used but it most likely will be uncommon. There will be cheaper and cleaner ways to get from point A to B but there will be situation where the high fuel density and power output provided by an ‘atomic rocket’ will be the right tool for the job.