Naval weapon type for launching small depth charges against submarines
Anti-submarine mortars are artillery pieces deployed on ships for the purpose of sinking submarines by a direct hit with a small explosive charge. They are often larger versions of the mortar used by infantry and fire a projectile in relatively the same manner. They were created during World War II as a development of the depth charge and work on the same principle.
Anti-submarine warfare did not become an issue of great concern until World War I, when Germany used submarines in an attempt to strangle British shipping in the Atlantic Ocean and elsewhere. The earliest way to counter a submarine was in the form of depth charges, which were large canisters filled with explosives, rolled off the back of a ship and detonated by a hydrostatic fuse. Depth charges served well throughout World War I but were not without flaws. A ship had to pass directly over a submarine to score an effective hit, because of this depth charges were dropped in lines instead of more effective clusters and could only be carried in ships fast enough to avoid the concussion of the explosion. The depth charges were also not as effective as one might think at sinking a submarine - only a very close detonation would sink a submarine, and the problems of scoring a direct hit meant that a submarine was more often damaged then destroyed by depth charges.
After World War I depth charge throwers were developed, which could hurl depth charges some 100 feet (30m) off the side of a ship. These were a significant improvement over the old method, permitting the use of large 'patterns' of up to 10 depth charges from the throwers and stern depth charge rails used together. However they still required a ship to pass very close to a submarine, which entailed loss of sonar (ASDIC) contact during the final stages of the approach. Submarines could and did use this dead interval to take evasive action.
It was the British who developed the first anti-submarine mortars. Several versions appeared in 1917, most notably the BL 7.5 inch Naval Howitzer; however the anti-submarine mortar did not become a truly successful weapon until the advent of the multi-barrelled Hedgehog 25 years later.
WWII anti-submarine mortars
Hedgehog anti-submarine mortar on the forecastle of HMS Westcott, 28 November 1945
During World War II submarines once again posed a major threat to Allied shipping, which necessitated the development of more effective anti-submarine mortars. These all had the common characteristic of throwing multiple charges ahead of the attacking vessel, while it was still in sonar contact. The first was the famous Hedgehog, which consisted of 24 small mortar rounds, each one 7 inches (180mm) in diameter and weighing 65 pounds with a 35-pound warhead. Each projectile had a range of about 250 yards (230m) and was fired in a circular pattern in front of a ship. While the warhead on a Hedgehog was much smaller than that of a depth charge it scored three times as many kills than its predecessors. This was due to the use of a contact fuse on the projectile, which would only detonate on impact with a target. Since the projectile would only explode on a hit, the long periods of sonar "blackout" from the blast and turbulence of a conventional depth charge explosion were eliminated. In the later stages of World War II the Hedgehog was complemented in Britain by the Squid three-barrelled depth charge mortar, which fired 390-lb depth charges to a range of 250 metres, and in the US by the Mousetrap rockets.[1]
Modern uses
ORP Kaszub firing a RBU-6000 rocket depth charge.
The homing torpedo has largely replaced the anti-submarine mortar in naval combat, although several examples still exist. The British Limbo system, with three gyro-stabilized barrels, fires 350-pound projectiles to a range of 1,000 yards (910m). It remained in service with many British and Commonwealth navies until the 1980s. The Bofors anti-submarine rocket launcher was used until 1980 with the Swedish Navy. It had two or four barrels and fired a 550-pound projectile up to 3,800 yards (3,500m). Due to the poor sonar conditions of the Baltic Sea, mortars, rocket and missile launchers still retain a place next to torpedoes. The former Soviet Navy (and by extension, the Russian Navy) is the largest user of anti-submarine mortars. Keeping with the Soviet idea that weapons should be simple, cheap and reliable, several versions of rocket-propelled anti-submarine mortars were developed. Trials were also conducted on destroying oncoming torpedoes with anti-submarine mortars. The most common is the RBU-6000, which fires twelve 160-pound projectiles in a horseshoe pattern up to 6,500 yards (5,900m) away. There was also a more extreme version, the nuclear RPK-1 Vikhr, though this is more technically an anti-submarine rocket. It had anti-surface and land-attack uses as well.
The RUR-5 ASROC 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.
A modern torpedo is an underwater ranged weapon launched above or below the water surface, self-propelled towards a target, and with an explosive warhead designed to detonate either on contact with or in proximity to the target. Historically, such a device was called an automotive, automobile, locomotive, or fish torpedo; colloquially a fish. The term torpedo originally applied to a variety of devices, most of which would today be called mines. From about 1900, torpedo has been used strictly to designate a self-propelled underwater explosive device.
A depth charge is an anti-submarine warfare (ASW) weapon. It is intended to destroy a submarine by being dropped into the water nearby and detonating, subjecting the target to a powerful and destructive hydraulic shock. Most depth charges use high explosive charges and a fuze set to detonate the charge, typically at a specific depth. Depth charges can be dropped by ships, patrol aircraft, and helicopters.
A mortar is usually a simple, lightweight, man-portable, muzzle-loaded weapon, consisting of a smooth-bore metal tube fixed to a base plate with a lightweight bipod mount and a sight. Mortars launch explosive shells in high-arching ballistic trajectories. Mortars are typically used as indirect fire weapons for close fire support with a variety of ammunition.
The Hedgehog was a forward-throwing anti-submarine weapon that was used primarily during the Second World War. The device, which was developed by the Royal Navy, fired up to 24 spigot mortars ahead of a ship when attacking a U-boat. It was deployed on convoy escort warships such as destroyers and corvettes to supplement the depth charges.
HMCS Yukon was a Mackenzie-class destroyer that served in the Royal Canadian Navy (RCN) and later the Canadian Forces. She was the first Canadian naval unit to carry the name. She was named for the Yukon River that runs from British Columbia through Yukon and into Alaska in the United States.
Squid was a British World War II ship-mounted anti-submarine weapon. It consisted of a three-barrelled mortar which launched depth charges. It replaced the Hedgehog system, and was in turn replaced by the Limbo system.
An anti-submarine weapon (ASW) is any one of a number of devices that are intended to act against a submarine and its crew, to destroy (sink) the vessel or reduce its capability as a weapon of war. In its simplest sense, an anti-submarine weapon is usually a projectile, missile or bomb that is optimized to destroy submarines.
Limbo, or Anti Submarine Mortar Mark 10, was the final development of the forward-throwing anti-submarine weapon Squid, designed during the Second World War and was developed by the Admiralty Underwater Weapons Establishment in the 1950s.
An acoustic torpedo is a torpedo that aims itself by listening for characteristic sounds of its target or by searching for it using sonar. Acoustic torpedoes are usually designed for medium-range use, and often fired from a submarine.
Anti-submarine warfare is a branch of underwater warfare that uses surface warships, aircraft, submarines, or other platforms, to find, track, and deter, damage, or destroy enemy submarines. Such operations are typically carried out to protect friendly shipping and coastal facilities from submarine attacks and to overcome blockades.
The Claud Jones-class destroyer escorts were four destroyer escorts built for the United States Navy in the late 1950s. These ships were a diesel-powered version of the earlier Dealey class and were designed with the aim of producing a cheaper ship suitable for rapid production in wartime. These ships also had reduced armament and speed compared to their predecessors. They were not seen as effective anti-submarine warfare vessels by the United States Navy and were sold after only 15 years service to the Indonesian Navy.
An anti-submarine missile is a standoff anti-submarine weapon. Often a variant of anti-ship missile designs, an anti-submarine systems typically use a jet or rocket engine, to deliver an explosive warhead aimed directly at a submarine, a depth charge, or a homing torpedo that is carried from a launch ship, or other platform, to the vicinity of a target.
HMCS Qu'Appelle was a Mackenzie-class destroyer that served in the Royal Canadian Navy and later the Canadian Forces. The ship's insignia and logo was the head of a fox facing forward centered in a diagonal line double white with a red center sqiggley line from the top left to bottom right. The moniker of the ship was "Follow the Fox".
The Parchim-class corvette, Soviet designation Project 1331M, was developed for the East German Navy in the late 1970s, and built by the Wolgast Peene-Werft. The ships were designed for coastal anti-submarine warfare. In case of an all-out NATO-Warsaw Pact war in Europe their prime targets would have been the small U-206 coastal submarines of the West German navy. The first ship, Wismar, was launched on 9 April 1981 in Rostock, and subsequently another 15 ships were built until 1986. To make production more economical, the Soviet Union agreed to purchase another 12 ships from Wolgaster Peenewerft built between 1986 and 1990, thereby effectively subsidising the East German shipbuilding industry.
The Mackenzie-class destroyer was a class of warship used by the Royal Canadian Navy and Canadian Forces from the 1960s–1990s. Six such ships were envisioned, of which four were completed to this specification. The last two hulls were completed to the post DDH conversion St. Laurent-class design ; they were designated as the Annapolis class instead. The four Mackenzie-class destroyers spent most of their service in the Pacific Ocean, used primarily in a training role. Their only significant update was the DELEX program, which was completed between 1982 and 1985 and updated their navigational radar and their sonar.
HMCS Saskatchewan was a Mackenzie-class destroyer that served in the Royal Canadian Navy (RCN) and later the Canadian Forces. She was the second Canadian naval unit to bear the name HMCS Saskatchewan. The ship was named for the Saskatchewan River which runs from Saskatchewan to Manitoba in Canada.
The Annapolis-class destroyer escort was a two-ship class of destroyer escorts that saw service with the Royal Canadian Navy and Canadian Forces from the 1960s to the 1990s. The final version of the St. Laurent-class design, the class was used extensively for anti-submarine warfare purposes. Both ships were sunk as artificial reefs after being retired, one on each coast of Canada.
The Dealey-class destroyer escorts were the first post-World War II escort ships built for the United States Navy.
The Fairlie Mortar was an unsuccessful British anti-submarine mortar design of the early second World War. It projected small anti-submarine bombs simultaneously, ten from each side of the ship's forecastle, each containing 20 lb (9.1 kg) of explosive. The Fairlie Mortar was not a success and 'Hedgehog', a spigot mortar projecting 24 small bombs from a platform, eventually became the predominant British ship-borne anti-submarine weapon in the war.
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