Russia is currently developing nuclear powered cruise missiles. These presumably use nuclear ramjet propulsion in the same way that the US's Project Pluto would have. Is there enough similarity between nuclear ramjets and nuclear thermal rockets, that research into the first is likely to lead to breakthroughs for the second?
Are the two technologies similar enough that there is the possibility of a hybrid nuclear engine that operates as a nuclear ramjet in atmosphere and then switches to a NTR mode once in space? Similar to how SABRE uses air as the oxidiser in atmosphere and switches over to being a chemical rocket engine in space.