Engineers at NASA's Glenn Research Center, inspired by the spacecraft in the movie 2001, looked at the real prospects or a piloted craft capable of trips to the outer planets. The abstract of their 51-page study begins:
"A conceptual vehicle design enabling fast, piloted outer solar system travel was created predicated on a small aspect ratio spherical torus nuclear fusion reactor. The initial requirements were satisfied by the vehicle concept, which could deliver a 172 mt crew payload from Earth to Jupiter rendezvous in 118 days, with an initial mass in low Earth orbit of 1,690 mt."
The finding: there are real ways do do this. It's a long way off and may never be more than a study, but what matters is that people are looking seriously at these types of long-range questions.
The title link will take you to a page where you can download the entire study.