It's really hard making a ship with hallways where astronauts can walk around (to the front or back of a really large ship), and the solution would be a part called an "Accessway." What it does is, when you put it somewhere, it automatically makes a hallway/tunnel through whatever parts you put it through. It works like a normal fuselage, it's reshapable, except instead of taking up space like a fuselage, it takes away any space where it's put. BAM: hallways for astronauts.
