Well, to be frank, we currently have such a ship, but we're doing quite a lot to disrupt its capability of sustaining human life.
Of course, even if we stopped doing that, we'd need to figure out how to visit another place if our ship is passing close by. That also seems to pose a problem: both Voyagers are barely out of the exhaust fumes of our ship's motor, and getting so far took ~40 years.
Of course, even if we stopped doing that, we'd need to figure out how to visit another place if our ship is passing close by. That also seems to pose a problem: both Voyagers are barely out of the exhaust fumes of our ship's motor, and getting so far took ~40 years.