XL engine

"There was a time when energy was used to throw stuff off the back of a ship in order to make it go forward. These days, energy is used to throw space itself off the back of the ship. Aside from the constant migranes and strange inertial reactions with other nearby ships the new system has none of the drawbacks of the old conventional engines."

The largest engine available the XL engine requires the 5 central spaces at its rear to be touching an edge in order to be placed.