The A-10 Thunderbolt is arguably the best close-air support plane in history thanks, primarily, to its GAU-8 cannon. The seven-barreled, 30mm Gatling gun holds 1,129 rounds and can chew up a modern tank. Despite its massive success in the air, the GAU-8 has proven to be far more versatile. Believe it or not, the GAU-8 is also at the heart of a last-ditch, anti-missile system used by a number of navies. That system is called the Goalkeeper.
The Goalkeeper uses a combination of sophisticated radars to detect incoming threats, typically missiles, and fires rounds from its cannon to obliterate the target before it can harm the ship. In function, this defense system is very similar to the U.S.’s Phalanx — the albino-R2D2 looking thing found on virtually every American ship built since the 1980s. The Phalanx, by comparison, uses the M61, a 20mm Gatling gun. It’s been upgraded over the years and has an effective range of roughly one mile.