Lowie, in order to cross the vast distances in space to even realistically explore planets, how feasible do you think alternate propulsion systems are? I remember when fusion rockets were being examined, the benefits of fusion power being high thrust ability. "Project Daedalus" was one such study, which was the subject of A LOT of hard science fiction, but then it never really went anywhere. The other is the Hydrogen scoop ship. As I understand it, free hydrogen can be scooped up by using an electomagnetic net. The more hydrogen the ships captures, the faster it can go, which starts a near endless cycle. The drawbacks here are the size of the "net" which is needed. Of course there are the purely fantastical examples like warp drives and hyperspace, but the two above were supposed to be feasible with technology available even back in the 1980's. Now nothing to be heard from in this regard.