Some aircraft carrier trivia. Someone correct me if I don't have the facts straight.
The jets are held back by a hold back bar while the engines are revved and waiting for the catapult. The pilot salutes the shooter when he/she is ready to go then the shooter has the catapult released. Some bars have a built in release, some are shearable and disposable. The shearable ones can hold the power of the jet engines but will break when the power of the catapult is added.
Also the landing catch cables have a maximum life number of catches, then they just throw them overboard.
Here's a photo of an S3 Viking shearable holdback release and a tail hook. It's the pinkish thing and as you can see, has been sheared. It's given to the pilot as a memento of their first carrier launch.
