Perhaps people are waiting for a space elevator or settlements in space that could build nuclear rockets. Project Daedalus ( https://en.wikipedia.org/wiki/Proj

Perhaps people are waiting for a space elevator or settlements in space that could build nuclear rockets. Project Daedalus ( https://en.wikipedia.org/wiki/Project_Daedalus https://en.wikipedia.org/wiki/Project_Daedalus) in the 1970s was the last time people looked seriously at theoretical proposals for nuclear powered interstellar flight.