The HUB ship is a titan that the Arkelion's use as a mobile assault platform.
HUB(Huge Unreal Battlecruiser) as it is called by humanity as it's Arkelion title is extremely hard to pronounce
Though the ship is more like a moveable space station. It allows smaller ships like the scout cruiser, the frigate and the destroyer to dock and resupply. It also acts as fire support as it is on of the only Arkelion vessels able to combat one-man strike craft, and is equipped with enough weaponry to take on the entire Lunar defence fleet.
However due to it's size the HUB ship lacks the power generation abilities to activate it's engines and shield simultaneously therefore cannot be used as an assault craft because by the time the shields where raised the ship would be disabled or destroyed.