Tungsten alloy ball is small in volume but very dense. It is used as ammunition for Phalanx CIWS.
A land based variant known as C-RAM has recently been deployed in a short range missile defense role, to counter incoming rockets and artillery fire.
Because of their distinctive barrel-shaped radome and their automated nature of operation, Phalanx CIWS units are sometimes nicknamed "R2-D2" after the famous droid from Star Wars, and in the Royal Navy as Daleks, after the aliens from Doctor Who.
The basis of the system is the 20 mm M61 Vulcan Gatling gun autocannon, used since the 1960s by the United States military in nearly all fighter aircraft (and one land mounting, the M163 VADS), linked to a Ku-band radar system for acquiring and tracking targets. This proven system was combined with a purpose-made mounting, capable of fast elevation and traverse speeds, to track incoming targets. An entirely self-contained unit, the mounting houses the gun, an automated fire control system and all other major components, enabling it to automatically search for, detect, track, engage and confirm kills using its computer-controlled radar system. Due to this self-contained nature, Phalanx is ideal for support ships which lack integrated targeting systems and generally have limited sensors. The entire unit has a mass between 5,500 and 6,100 kg (12,400 to 13,500 lb).
Due to the continuing evolution of both threats and computer technology, the Phalanx system has, like most military systems, been developed through a number of different configurations. The basic (original) style is the Block 0, equipped with first generation solid state electronics and with marginal capability against surface targets. The Block 1 (1988) upgrade offered various improvements in radar, ammunition, rate of fire, increasing engagement elevation to +70 degrees, and computing. These improvements were intended to increase the system's capability against emerging Russian supersonic anti-ship missiles. Block 1A introduced a new computer system to counter more maneuverable targets. The Block 1B PSuM (Phalanx Surface Mode, 1999) adds a forward looking infrared (FLIR) sensor to allow the weapon to be used against surface targets. This addition was developed to provide ship defense against small vessel threats and other "floaters" in littoral waters and to improve the weapon's performance against slower low-flying aircraft. The FLIR's capability is also of use against low-observability missiles and can be linked with the RIM-116 Rolling Airframe Missile (RAM) system to increase RAM engagement range and accuracy. The Block 1B also allows for an operator to visually identify and target threats.
The U.S. is in the process of upgrading all their Phalanx systems to the Block 1B configuration. The Block 1B is also used by other navies such as Canada, Portugal, Japan, Egypt, Bahrain and the UK.
In May 2009, the US Navy awarded a $260 million contract to Raytheon Missile Systems to perform upgrades and other work on the Phalanx. The work is to be completed by September 2012.