What Is This?

I thought this was some kind of weapons system, an awesomely massive gun battery hidden in the ground, ready to take on enemy fighters. I read too many comic books. This thing doesn't fire bullets.

But it's awesome, anyway. They are catapult pistons on the deck of aircraft supercarrier USS Ronald Reagan, a huge mechanism designed to launch airplanes, helping them to quickly gain speed at take-off. [Flickr]