THE NEW SPACE RACE: DARPA and NASA plan orbital nuclear rocket test. “By using a nuclear thermal engine to heat a propellant to extremely high temperatures to generate thrust, a rocket could have over three times the efficiency of a conventional chemical-fueled one, which would reduce transit times and increase payload potential. For a crewed Mars mission, this would mean less radiation exposure, fewer detrimental effects from weightlessness, and less of a need for supplies or overly robust flight systems.”

Seventy years late is still better than never.