There’s a petition on the White House website calling for the United States to rapidly develop a nuclear thermal rocket engine.
Technically, nuclear thermal rockets are a promising technology, but unless NASA develops a deep-space ship to put it on (like the Copernicus MTV, shown here, or the Nautilus X), a nuclear rocket engine would be wasted.
There is little chance of a commercial outfit working through all the red tape needed to launch a nuclear rocket engine into orbit. (It’s questionable whether the government could do that itself.)
We’ve discussed this problem with engineers at NASA’s Johnson Space Center, and all of us came to the same conclusion: the best hope for nuclear rocket engines is finding uranium or thorium on the Moon. That would solve the political/environmental problem by allowing nuclear reactors to be launched from Earth unfueled. It would also jump start the development of lunar industry.
Mining nuclear fuel on the Moon has an advantage over other lunar mining schemes, such as platinum group metal (PGM) mining. Those proposals work only if mining on the Moon is cheaper than mining on Earth. That is possible but not yet proven. The bar for mining nuclear material on the Moon is much lower, if environmental politics does not allow us to launch it from Earth.