Acoustic torpedo
An acoustic torpedo is a torpedo
The modern torpedo is a self-propelled missile weapon with an explosive warhead, launched above or below the water surface, propelled underwater towards a target, and designed to detonate either on contact with it or in proximity to it.The term torpedo was originally employed for...

 that aims itself by listening for characteristic sounds of its target or by searching for it using sonar
Sonar is a technique that uses sound propagation to navigate, communicate with or detect other vessels...

. Acoustic torpedoes are usually designed for medium-range use, and often fired from a submarine
A submarine is a watercraft capable of independent operation below the surface of the water. It differs from a submersible, which has more limited underwater capability...


The first passive acoustic torpedo was the G7es T-5 Zaunkönig torpedo
G7es torpedo
The G7es or Zaunkönig T-5 was a torpedo employed by German U-boats during World War II. It was known as the GNAT to the British.- Description :...

 deployed in late World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...

 by the German
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...

U-boat is the anglicized version of the German word U-Boot , itself an abbreviation of Unterseeboot , and refers to military submarines operated by Germany, particularly in World War I and World War II...

 fleet. This weapon was developed to attack escort vessels and merchant ships
Merchant vessel
A merchant vessel is a ship that transports cargo or passengers. The closely related term commercial vessel is defined by the United States Coast Guard as any vessel engaged in commercial trade or that carries passengers for hire...

 in convoys. In July 1944, Russian commando frogmen
Russian commando frogmen
# Scout diver is a Russian term for members of a special purpose unit of the Russian or Soviet Naval Spetsnaz - SpN VMF .# Сombat swimmer is a Russian term meaning members of special purpose anti-sabotage divers' units...

 discovered T-5 torpedoes aboard a sunken German submarine, U-250. Torpedoes were safely delivered to surface ships. Key components of the G7es T-5 Zaunkönig torpedo
G7es torpedo
The G7es or Zaunkönig T-5 was a torpedo employed by German U-boats during World War II. It was known as the GNAT to the British.- Description :...

 were later ordered by Joseph Stalin
Joseph Stalin
Joseph Vissarionovich Stalin was the Premier of the Soviet Union from 6 May 1941 to 5 March 1953. He was among the Bolshevik revolutionaries who brought about the October Revolution and had held the position of first General Secretary of the Communist Party of the Soviet Union's Central Committee...

 to be given to British naval specialists. However, after a protracted journey to Kronstadt
Kronstadt , also spelled Kronshtadt, Cronstadt |crown]]" and Stadt for "city"); is a municipal town in Kronshtadtsky District of the federal city of St. Petersburg, Russia, located on Kotlin Island, west of Saint Petersburg proper near the head of the Gulf of Finland. Population: It is also...

 the two Royal Navy
Royal Navy
The Royal Navy is the naval warfare service branch of the British Armed Forces. Founded in the 16th century, it is the oldest service branch and is known as the Senior Service...

 officers were not allowed access to the submarine and returned home empty handed . The capture of U-505 marked the second time that Allied forces gained access to this technology. The T-5 was countered by the introduction by the Allies of the Foxer
Foxer, was the codename for a British built acoustic decoy, used to confuse German acoustic homing torpedoes like the G7es torpedo during the Second World War. A US version codenamed FXR was deployed in 1943. A Canadian version was also built called the CAT...

 noise maker.

Since its introduction, the acoustic torpedo has proven to be an effective weapon against surface ships as well as serving as an anti-submarine weapon
Anti-submarine warfare
Anti-submarine warfare is a branch of naval warfare that uses surface warships, aircraft, or other submarines to find, track and deter, damage or destroy enemy submarines....

. Today, acoustic torpedoes are mostly used against submarines.

Before a torpedo is launched, the target must be 'boxed in'. A fire control system on the firing platform will set an initial search depth range which is passed to the weapon's microprocessor. The search parameters cover the expected depth of the target.

Acoustic homing torpedoes are equipped with a pattern of acoustic transducers on the nose of the weapon. By a process of phase delaying the signals from these transducers a series of "acoustic beams" (i.e. a variation of acoustic signal sensitivity dependent on the incident angle of the noise energy). In early homing torpedoes the "beam patterns" were fixed whereas in more modern weapons the patterns were modifiable under on-board computer control. These sensor systems are capable of either detecting sound originating from the target itself i.e. engine and machinery noise, propellor cavitation, etc., known as passive sonar or responding to noise energy reflections as a result of "illuminating" the target with sonar pulses,known as active sonar. Acoustic torpedoes can be compared to modern fire-and-forget
Fire-and-forget is a third-generation method of missile guidance. The military uses the term for a type of missile which does not require further guidance after launch such as illumination of the target or wire guidance , and can hit its target without the launcher being in line-of-sight of the...

 guided missiles. What this means is the enemy (most likely a submarine) will be detected by sonar in any direction it goes. The torpedo will start with passive sonar, simply trying to detect the submarine. Once the torpedo's passive sonar has detected something, it will switch over to an active sonar and will begin to track the target. At this point, the submarine has probably started evasive maneuvers and may have even deployed a noisemaker. The torpedo's logic circuitry, if not fooled by the noise maker, will home in on the noise signature of the target submarine.

Military examples

United States:
    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...

     Ship Launched anti submarine Missile
  • MK 48
    Mark 48 torpedo
    The Mark 48 and its improved ADCAP variant are heavyweight submarine-launched torpedoes. They were designed to sink fast, deep-diving nuclear-powered submarines and high-performance surface ships.-History:...

     ADCAP Submersion Launch Torpedo
  • MK 24 Passive Homing Surface / Submersible Fire Torpedo
  • MK 32 Active Homing Surface / Submersible / Air Fire Torpedo
  • MK 15 Surface to Surface Torpedo

External links

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