Phalanx CIWS: 75 Rounds a Second, No Friend-or-Foe and the USS Gravely Save

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The Phalanx Close-In Weapon System pairs a six-barrel 20mm M61 Vulcan cannon, firing 4,500 rounds a minute, or 75 a second, at over Mach 3, with two Ku-band radars under its white dome. It usually opens fire about one nautical mile out, leaving two to three seconds per engagement, and fires dense tungsten or depleted uranium APDS rounds, about $30 each, to shred a missile's airframe instead of blowing it into a cloud of fragments. The 12,000-pound mount carries 1,550 rounds and needs only 440-volt power and cooling water from the ship. It ignores identification friend or foe, engaging anything that is closing in range, on a collision course and within set speed limits, and its track radar follows its own bullets to walk the stream onto the target.

That logic has hit friendly targets. In 1991 the frigate USS Jarrett's Phalanx locked onto chaff fired by the battleship USS Missouri and struck the Missouri, injuring no one. In 1996 the Japanese destroyer Yugiri's system followed a tow cable up to a U.S. A-6 Intruder and shot it down; both crew ejected. Hesitation has cost more: in 1987 the USS Stark's Phalanx sat on standby when an Iraqi fighter's two Exocet missiles hit the frigate, killing 37 sailors. In January 2024, a Houthi anti-ship cruise missile got within a mile of the destroyer USS Gravely before its Phalanx destroyed it.

• The track radar locks on at about four and a half nautical miles after the search radar hands off a contact.
• The Block 1B upgrade added a forward-looking infrared sensor to engage small boats and drones.
• The Army's trailer-mounted Centurion C-RAM adapted the gun to stop rockets, artillery and mortars.
• C-RAM protected Baghdad's Green Zone and was the primary defense during the 2021 Kabul withdrawal.
• Its HEIT-SD rounds self-destruct after about four seconds, roughly 2,000 meters, if they miss.