Imagine pushing an enormous sphere of frozen deuterium in front of your spacecraft for 60 years while travelling to Alpha Centauri. In a nut shell, that was Project Enzmann - one of many fanciful, overambitious projects to come out of the '50s and '60s space race. I'm just putting this out there as an unusual (but relatively simple, one would think) idea for an Orbiter spacecraft.
Link (with pics) here: http://www.icarusinterstellar.org/project-enzmann/
Link (with pics) here: http://www.icarusinterstellar.org/project-enzmann/
