Small strike craft from the start: Raider, Interceptor, Corvette, Bomber and Frigate.
Medium warships as the Hadron Hangar grows: Destroyer (Lv 6), Drone Carrier (Lv 7, carries 24 robots) and Battlecruiser (Lv 8).
The Dreadnought, a mega warship, at Hangar Lv 10 — slow, and worth a whole fleet.
Bigger hulls take more hangar space but hit harder for the space they use. Raids send your biggest ships first; expeditions send the fastest.
The Arks: your Colony Ark (from the Colony Ark Drive) carries the colony to a new star, and the one Last Ark, docked at the Rift Engine, is the biggest ship in the universe.