Sonar is a technique that uses sound propagation to navigate, measure distances (ranging), communicate with or detect objects on or under the surface of the water, such as other vessels.
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.
A sonobuoy is a small expendable sonar buoy dropped from aircraft or ships for anti-submarine warfare or underwater acoustic research. Sonobuoys are typically around 13 cm (5 in) in diameter and 91 cm (3 ft) long. When floating on the water, sonobuoys have both a radio transmitter above the surface and hydrophone sensors underwater.
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.
Anechoic tiles are rubber or synthetic polymer tiles containing thousands of tiny voids, applied to the outer hulls of military ships and submarines, as well as anechoic chambers. Their function is twofold:
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 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.
Bold was a German sonar decoy, used by U-boats during the Second World War from 1942 onwards. It consisted of a metal canister about 10 cm (3.9 in) in diameter filled with calcium hydride. It was launched by an ejector system colloquially referred to as Pillenwerfer. When mixed with seawater, the calcium hydride produced large quantities of hydrogen which bubbled out of the container, creating a false sonar target. A valve opened and closed, holding the device at a depth of about 30 m (98 ft). The device lasted 20 to 25 minutes. It replicated the echo of an Asdic-sonar submarine contact.
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.
HMS Swale (K217) was a River-class frigate of the Royal Navy (RN) from 1942 to 1955, loaned to the South African Navy for six months at the end of the Second World War.
The Fairmile B motor launch was a very numerous class of motor launch produced in kit form by British boatbuilder Fairmile Marine, and then assembled and fitted out by numerous boatyards during the Second World War to meet the Royal Navy's coastal operation requirements.
Robert William Boyle was a physicist and one of the most important early pioneers in the development of sonar.
The creeping attack was an anti submarine measure developed during the Battle of the Atlantic in World War II.
German submarine U-480 was an experimental Kriegsmarine Type VIIC U-boat of World War II.
A sonar decoy is a device for decoying sonar. Most are released from submarines to act as a false target.
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.
HMS Torrid was an R-class destroyer which served with the Royal Navy during World War I. The ship was launched on 10 February 1917 and served as part of the Harwich Force. Subsequently, Torrid was used in the 1930s as a trials ship for new anti-submarine warfare weapons, particularly playing a role in the development of ASDIC. During this time, the destroyer was commanded by Charles Pizey, later the first Chief of the Naval Staff of the Indian Navy. The vessel was wrecked off the Falmouth coast en route to being broken up on 16 March 1937.
The AN/SQS-504 Diver was an early naval medium-frequency active variable depth sonar (VDS) developed in Canada.
The Western Approaches Tactical Unit (WATU) was a unit of the British Royal Navy created in January 1942 to develop and disseminate new tactics to counter German submarine attacks on trans-Atlantic shipping convoys. It was led by Captain Gilbert Roberts and was principally staffed by officers and ratings from the Women's Royal Naval Service (Wrens). Their primary tool for studying U-boat attacks and developing countermeasures was wargames. After the U-boat threat to merchant shipping was defeated, WATU continued to develop anti-submarine tactics for later stages of the war, including Operation Overlord and the Pacific War. WATU trained naval officers in its tactics by hosting week-long training courses in which the students played wargames. WATU formally ceased operations at the end of July 1945.
The Canadian Fairmile B was a motor launch built during the Second World War for the Royal Canadian Navy. They were adaptations of the British Fairmile B motor launch design incorporating slight modifications for Canadian climatic and operational conditions. Eighty-eight were built in Canada for service with the Coastal Forces of the Royal Canadian Navy in home waters, of which eight were supplied to the United States Navy.