Say the new Stirling radioisotope generators prove reliable and need limited maintenance. Now also say that they could generate enough juice to power a life support system and an engine, also you could use solar energy to charge gel battery's built into the walls, which would provide juice for navigation, communications, aux. life support, lighting..etc. Now granted it wouldn't be a small ship or even a fast ship, but it would be enough to land someone on one of Saturns moons and start the terraform process. For the crew, you could start with a group of infants, given up by their parents, to be trained for the sole purpose of flying to another planet or moon. As screwed up as that sounds, it would actually work out quit nicely. Anyone still fallowing me?
(also you would most likely have to assemble/build the ship in space or on the moon.)