Below are all the cannon types for movecraft.
OrbitalRailgun (fires diamond block & nether star : 3x 30 diamond block, 1x 29 diamond block. 1x 28 emerald)
RailgunMk.1 (fires diamond block : 11 emerald long)
RailgunMk.2 (fires diamond block : 16 emerald long)
SpaceBattleship (fires emerald)
SpaceCruiser (fires emerald)
SpaceDestroyer (fires emerald)
SpaceYamato (fires emerald)
Here is what they look like and what each fires.
EDIT: Space cannons are now iron bars instead of end rods.