The spaceship you construct acts as your home base and the means of transportation between planets. Every ship is constructed of a variety of modules, allowing you to customize them and make them as large - or as compact - as you wish.
The ship does not move using thrust, but instead relies entirely on making "hyperjumps" using hyperdrive technology. These move the ship from one location to another, within a certain range, with no G's or inertia. This makes the shape of the ship irrelevant.