Well, you need something pressurized like a submarine. It's got to be resistant to cosmic and solar radiation, so you ought to make it out of lead.... but that's too heavy. Instead, build a micro-magnetosphere around your ship---like a force-field. Next, you're going to need a propulsion system. Ionic drives, powered by a nuclear reactor, will add enough speed over time, and heat your interior. You'll want rail guns with atomic cannon balls in case alien pirates come.