Phalanx Mk 15 Close-In Weapons System

The Phalanx Mk 15 Close-In Weapons System (CIWS) provides shipboard automatic defense against anti-ship cruise missiles. Only 1 Mk 15 CIWS is installed per ship and consists of 1 or more Mk 16 Weapon Groups, the same number of Mk 339 local control panels, and 1 Mk 340 remote control panel.

The Mk 16 Weapon Group is composed of:

  1. a modified M61 Vulcan 6-barrel Gatling cannon assembly,
  2. fitted to a mount and train drive assembly,
  3. the search and J-band pulse-doppler fire control radars housed in a domed cylinder located above the gun and known as the fire control radar/servo assembly,
  4. barbette assembly containing the mount's digital computer,
  5. and the Weapon Group electronics enclosure. The basic mount does not require deck penetration and can be fitted to a wide range of ships.

The Mk 16's computer classifies threats detected by the search radar and lays the mount on the target azimuth. The J-band tracking radar follows both the target and the M61's bullet stream. The computer uses a closed-loop spotting technique to reduce the difference between the radar line-of-sight and the projectile trajectory to zero. The mount ceases fire when the target is out of range or destroyed.

The projectile is a Mk 149 sub-caliber (12.75-mm) Depleted Uranium (DU) penetrator that is 2 1/2 times as dense as steel. The "heavy" metal can inflict much greater damage on a missile's skin than a conventional projectile of the same weight. It is sheathed by a nylon sabot and spun initially by an aluminum "pusher." Procurement of the depleted uranium projectile ceased in 1990, and all Phalanx ammunition purchases since then have been of the tungsten penetrator. Using the tungsten penetrator will lower costs and simplify storage and handling. It was estimated that all Phalanxs will fire a mix of DU and tungsten penetrators until 1996, when the DU stocks were exhausted.

Phalanx can be used against surface targets by using conventional optical target designators. The US Navy discourages this practice, preferring to use other light guns against small surface combatants.

Lockheed Martin, USA.


 Weight, Mk 16
   Block 0, empty         12,000 lb (5,443 kg)
   Block 1, empty         12,756 lb (5,786 kg)
   Block 1, loaded        13,629 lb (6,182 kg)
      bore                20 mm/76 cal
        Block 0           -10/+70 deg
        Block 1           -25/+80 deg
      traverse (Block 1)  +155 deg
      slew rates (Block 1)
        elevation         92 deg/sec
        train             126 deg/sec
      maximum range       1,625 yd (1,486 m)
      rate of fire
        Block 0           3,000 rpm theoretical maximum
        Block 1           4,500 rpm theoretical maximum
      muzzle velocity
        Block 0           3,280 fps (1,000 mps)
        Block 1           3,600+ fps (1,097+ mps)
      reaction time       60 seconds from being switched on to
                            being operational
                          2 seconds from threat detection
      projectile          Mk 149 sub-caliber (12.75 mm) depleted
                            uranium penetrator
      magazine capacity
        Mod 0 Block 0     980 rounds
              Block 1     1,562 rounds
 Fire Control
      VPS-2 pulse-doppler, J-band search and track radar with
        closed-loop spotting which follows both target and its
        own 20-mm projectiles
      high-speed digital computer automatically engages incoming,
        high speed threat unless countermanded by the operator
 Crew   unmanned
      enclosed mount


Block 0
First production variant. In production from 1979 to 1987. Mod numbers indicate number of mounts on a particular ship. Mod 1 1 mount per ship. Mod 2 2 mounts per ship Mod 3 3 mounts per ship Mod 4 4 mounts per ship

Block I
Parabolic search radar is replaced by four-plate back-to-back search radar array for better high-elevation coverage. Mount has greater ammunition stowage, higher rate of fire, and enhanced reliability and maintainability. In full production by October 1987. First installed in summer 1988 in WISCONSIN (BB 64) and CORAL SEA (CV 43). Mod 11 1 mount per ship. Mod 12 2 mounts per ship Mod 13 3 mounts per ship Mod 14 4 mounts per ship

All US Navy Phalanxes were scheduled to be upgraded to Block I standards by 1997.

Block 2
A number of improvements are being considered for the CIWS to counter improvements in anti-ship missile performance. The Block 2 version must be capable of search- while-track operation, and have increased detection range, increased track accuracy, and greater computational power. Block 2 would also be operational immediately upon being switched on. Proposals include a General Electric twin 25-mm gun and a Tround quadruple breechless gun. Alternatives include adoption of a foreign CIWS, including an updated Goalkeeper mount. (Goalkeeper , which combines the US 30-mm GAU-8/A Gatling gun with Dutch fire control, is being fitted into British and Dutch ships; see separate database entry.) Budget cuts may force the Block 2 to be based on the current system. This would eliminate the Goalkeeper from consideration.

Issues and Notes

The installation of Phalanx CIWS came several years after the appearance of similar rapid-fire guns systems, of larger caliber, in Russian surface warships. Most foreign CIWS designs include 25-mm or 30-mm rapid-fire guns rather than the smaller 20-mm/12.75-mm of the Phalanx.

The CIWS on the USS STARK (FFG 31) did not engage the French-built Exocet AM-39 air-to-surface missiles launched against the ship by an Iraqi aircraft on 17 May 1987. The CIWS was not activated at the time. In the Senate Hearings before the Committee on Appropriations for FY1986, US Department of Defense officials were asked about the effectiveness of the CIWS against Exocet missiles, to which they replied, "In recent operational tests, PHALANX destroyed numerous EXOCETS in an impressive fashion."

The Canadian destroyer ATHABASKAN, frigate TERRA NOVA, and replenishment ship PROTECTEUR were hurriedly readied for their September 1990 Persian Gulf deployments. Among other refits, a Phalanx CIWS was mounted on a support platform built over the empty Limbo well on the ATHABASKAN and TERRA NOVA. 2 mounts were fitted in the PROTECTEUR. The ATHABASKAN had been scheduled to receive the PHALANX during her TRUMP overhaul; no plans had been made to add the system to the other 2 ships.