What Will Power the Spaceships of the Future?

Simply put: "Fusion"< br/> From Scientific American:

A fusion-powered spacecraft could reach Jupiter within four months, potentially opening up parts of the outer solar system to manned exploration, according to a 2010 NASA report. A number of hurdles would have to be overcome—particularly in the production and storage of antimatter—to make the technology feasible, but some experts imagine it could be ready to go in a half-centur