ASROC (for Anti-Submarine ROCket) is an all-weather, all sea-conditions anti-submarine missile system. Developed by the United States Navy in the 1950s, it was deployed in the 1960s, updated in the 1990s, and eventually installed on over 200 USN surface ships, specifically cruisers, destroyers, and frigates. The ASROC has been deployed on scores of warships of many other navies, including Canada, Germany, Italy, Japan, the Republic of China, Greece, Pakistan and others.

Description

After a surface ship, patrol plane or anti-submarine helicopter detects an enemy submarine by using sonar and/or other sensors, it could relay the sub's position to an ASROC-equipped ship for attack. The attacking ship would then fire an ASROC missile carrying an acoustic homing torpedo or a Nuclear Depth Bomb (NDB) onto an unguided ballistic trajectory toward the target. At a pre-determined point on the missile's trajectory, the payload separates from the missile and deploys a parachute to permit splashdown and water entry at a low speed and with minimum detectable noise. The water entry activates the torpedo, and guided by its own sonar system, it homes in on the target using either active sonar or passive sonar.

In cases where the ASROC missile carried an NDB, the unguided bomb would sink quickly to a predetermined depth where it would detonate. The nuclear-armed ASROC was never used beyond one or two tests in 1961-62. Eventually the Limited Nuclear Test Ban Treaty banning underwater nuclear tests went into effect. The nuclear weapon was never used in combat. An ASROC missile could hypothetically carry a 10 kiloton W44 nuclear warhead, although the W44-armed nuclear weapons were retired by 1989, and all types of nuclear depth bombs were removed from deployment.

Destroyer USS Agerholm fires an ASROC with a nuclear depth bomb in the "Swordfish" test in 1962

The first ASROC system (RUR-5), using the MK-112 "Matchbox" launcher, was developed in the 1950s and installed in the 1960s. This system was phased out in the 1990s and replaced with the RUM-139 Vertical Launch ASROC, or "VLA".

ASROC 'Matchbox' mounting installed just aft of the 76 mm gun turret on the Japanese Self Defense Force Asagiri class destroyer DD 158 Umigiri, photographed 28 July 2008 departing from Portsmouth Naval Base, UK.

ASROC 'Matchbox' reload doors can clearly be seen in this photograph of the Japanese Asagiri class destroyer Asagiri, formerly DD 156, renumbered TV 3516 after reclassification as a training vessel, seen here on 28 July 2008 departing from Portsmouth Naval Base, UK.

Spruance Class Installation

The 31-Spruance-class destroyers initially all had the Mk 112 ASROC reload system. They had one standard Mk 16 octuple launcher, but this was adjacent to a deckhouse which held 16 reload missiles. Thus, each Spruance-class originally carried a total of 24 ASROC.

Most other destroyers, destroyer escorts, and frigates only carried the one launcher with up to eight ASROC missiles, as some of those missiles could be replaced by the Boeing Harpoon anti-ship missile. The "matchbook" Mk 16 launchers were capable of carrying a mixture of the two types.
Most Spruance-class destroyers were later modified to include the MK-41 VLS, these launchers are capable of carrying a mixture of the VLS-ASROC, the Tomahawk TLAM, and other missiles. All of the Spruance destroyers carried two separate quad Harpoon launchers.

See also

• Ikara

• Hong Sang Eo (Red Shark) rocket-based torpedo (K-ASROC)

• Malafon

• MILAS

• RUM-139 VL-ASROC

• Sea Lance

• SUBROC