Britannia, Gigantic Spaceship Lost in Deep Space

Just imagine being in a tower block, with all the windows covered up in a society where everything is provided. All you need to do to maintain such a state of affairs is to prevent people from reading about the outside. That is the world that Lord One was born into. As a boy he thinks he sees his Father executed, for reading. Slowly he discovers that Britannia, a gigantic space ship, part of something much bigger, and they are somewhere in the universe. When they do discover where they are it leaves them with a dilemma. Carry on their automatic course for a possible new planet circling one of ours suns nearest neighbours. which is still six or seven thousand years journey time way with no guarantee it will be habitable, or return to Earth a similar journey time away. So how do you keep people happy and content?
In space there is no detectable force of gravity acting on our body. We just float around. What shape would we become? I wrote the book but and still I don’t have a picture in my mind what Lord One and Twenty24 look like.
All I know is after a few thousand years floating in space gravity would be a killer.