I've seen them firing many times, but I've to confess that I've never seen one of these missiles systems getting loaded. It seems as easy as inserting a cartridge into a NES.
ATLANTIC OCEAN (May 20, 2014) Sailors assigned to the combat systems department of the aircraft carrier USS Theodore Roosevelt (CVN 71) prepare to load an Evolved Sea Sparrow missile system [ESSM]. Theodore Roosevelt is underway preparing for future deployments.(U.S. Navy photo by Mass Communication Specialist Seaman Apprentice Wyatt L. Anthony/Released) 140520-N-VH385-010
The ESSM is a missile designed to destroy supersonic anti-ship missiles, so they are crucial for aircraft carriers and any other ship. Here's a video of it being fired: