Limbo (weapon)

Limbo, or Anti Submarine Mortar Mark 10 (A/S Mk.10), was the final British development of a forward-throwing anti-submarine weapon originally designed during the Second World War. Limbo, a three-barreled mortar similar to the earlier Hedgehog and Squid which it superseded, was developed by the Admiralty Underwater Weapons Establishment in the 1950s. Its mounting was stabilised in pitch and roll. Squid was loaded manually, which was difficult on a pitching deck in heavy seas with no protection from the elements; in contrast Limbo was loaded and fired automatically, with all the crew under cover. It was commonly installed on the quarterdeck of Royal Navy escort ships from 1955 to the mid-1980s. Australian–built versions of the Daring-class destroyer all carried Limbo as did the Australian River-class destroyer escort. Limbo was also widely employed by the Royal Canadian Navy, being incorporated into all destroyer designs from the late 1950s to the early 1970s, including the St. Laurent, Restigouche, Mackenzie, Annapolis and Iroquois classes. Limbo was carried on the Type 12 President Class Frigates built for the South African Navy in the 1960s.

A Limbo mortar on HMNZS Taranaki (F148)
TypeAnti-submarine mortar
Place of originUnited Kingdom
Service history
In service1955–1980s
Used byRoyal Navy
Royal Australian Navy
Royal Canadian Navy
Libyan Navy
South African Navy
WarsFalklands War
Production history
DesignerAdmiralty Underwater Weapons Establishment

Shell400lb depth charge
Calibre12 inches (30 cm)
Effective firing range400 yards (366 m) to 1,000 yards (914 m)
Warhead weight94 kilograms (207 lb)
Proximity and/or Time

Type 170 sonar

The firing distance of the mortars was controlled by opening gas vents; rounds could be fired from 400–1,000 yards (370–910 m). The weapon was linked to the sonar system of the ship, firing on command when the target was in range. The rounds were projected so that they fell in a triangular pattern around the target. Limbo could fire in any direction around the ship and is reported to have been very accurate. The weapon was used in the 1982 Falklands War, and remained in service in the Royal Navy and Commonwealth navies until the 1990s. A surviving system is preserved at Explosion! Museum of Naval Firepower in Gosport, Hampshire.

Sonar control of the A/S Mortar Mk 10

The firing of the Mortar Mk 10 was controlled by the Type 170 (and later the 502) attack sonar from the Sonar Control Room (SCR), which was generally located next to the operations room in the warship.

The 170 sonar had three operators who maintained sonar contact with the target and effectively aimed the weapon in bearing, range and depth. The operators were controlled by the SC (Sonar Controller) who was in charge of the SCR.

When a contact had been confirmed as a hostile submarine, the SC manually fired the Mortar Mk 10 from the SCR upon receiving the order from the captain in the operations room. The firing was done by means of a pistol grip and trigger mounted to the deckhead immediately behind the operators.

General characteristics

  • Total system weight: 35 tons including 51 projectiles (17 salvos).


  • Bogart, Charles H. (2010). "An Anti-submarine Weapon: The Limbo Mk NC 10 Mortar". Warship International. XLVII (4): 359–362. ISSN 0043-0374.
  • Naval Armament, Doug Richardson, 1981, Jane's Publishing, ISBN 0-531-03738-X
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