I think this is where CRISPR and extremophiles are going to enter the human genetic scene. Prolonged space flight for unmodified humans is a no go. We can’t replicate earth’s environment to satisfactory levels to not end up all kinds of dead and mutated. We’ll be self-mutating generations for survival. Increased radiation resistance and rapid gene repair is probably going to come in handy on earth as well if things keep going the way they’re going. Question is are robotics or genetic manipulation going to win the race for humankind’s survival? Or will we be some sort of blend of biotech and gene manipulation? … all ethical considerations aside, of course.