A naval mine is a self-contained explosive device placed in water to damage or destroy surface ships or submarines. Unlike depth charges, mines are deposited and left to wait until they are triggered by the approach of, or contact with, any vessel. Naval mines can be used offensively, to hamper enemy shipping movements or lock vessels into a harbour; or defensively, to protect friendly vessels and create "safe" zones.
Sonar is a technique that uses sound propagation to navigate, communicate with or detect objects on or under the surface of the water, such as other vessels. Two types of technology share the name "sonar": passive sonar is essentially listening for the sound made by vessels; active sonar is emitting pulses of sounds and listening for echoes. Sonar may be used as a means of acoustic location and of measurement of the echo characteristics of "targets" in the water. Acoustic location in air was used before the introduction of radar. Sonar may also be used in air for robot navigation, and SODAR is used for atmospheric investigations. The term sonar is also used for the equipment used to generate and receive the sound. The acoustic frequencies used in sonar systems vary from very low (infrasonic) to extremely high (ultrasonic). The study of underwater sound is known as underwater acoustics or hydroacoustics.
The Mark 46 torpedo is the backbone of the United States Navy's lightweight anti-submarine warfare torpedo inventory and is the NATO standard. These aerial torpedoes are designed to attack high-performance submarines. In 1989, an improvement program for the Mod 5 to the Mod 5A and Mod 5A(S) increased its shallow-water performance. The Mark 46 was initially developed as REsearch TORpedo Concept I, one of several weapons recommended for implementation by Project Nobska, a 1956 summer study on submarine warfare.
The G7e or more appropriately the G7e/T2, G7e/T3, and G7e/T4 Falke torpedoes were, with the exception of the T4 model, the standard torpedoes for Germany during World War II. All of the G7e models shared standardized dimensions for all German torpedoes designed for use by U-boats during World War II, they measured 53.3 cm (21 inches) in diameter, 7.16 m in length, and carried a Schießwolle 36 warhead of 280 kg. All were powered by 100 hp (75 kW) electric motors and lead-acid batteries which needed constant maintenance to maintain their reliability. Additionally, the batteries of these torpedoes needed to be preheated to a temperature of 30 °C (85 °F) to operate with maximum speed and range, though generally this was a non-issue as U-boats had the element of surprise and often had the advantage of firing the first shot.
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.
The Mark 24 mine is an air-dropped passive acoustic homing anti-submarine torpedo used by the United States during the Second World War. It entered service in March 1943 and remained in use with the US Navy until 1948. Approximately 4,000 torpedoes were produced, with 204 ultimately being deployed during the war. As a result of its use, 37 Axis submarines were sunk and a further 18 were damaged. The torpedo was also supplied to the British and Canadian forces. The deceptive name of "Mark 24 Mine" was deliberately chosen for security purposes, to conceal the true nature of the weapon.
The Mark 37 torpedo is a torpedo with electrical propulsion, developed for the US Navy after World War II. It entered service with the US Navy in the early 1950s, with over 3,300 produced. It was phased out of service with the US Navy during the 1970s, and the stockpiles were sold to foreign navies.
The People's Liberation Army Navy (PLAN) is the naval branch of the People's Liberation Army (PLA), the armed forces of the People's Republic of China. The PLAN force consists of approximately 250,000 men and over a hundred major combat vessels, organized into three fleets: the North Sea Fleet, the East Sea Fleet, and the South Sea Fleet.
The Mark 34 torpedo was a United States torpedo developed that entered service in 1948. It was an improved version of the Mark 24 FIDO passive acoustic homing torpedo developed during World War II for launch from fixed-wing aircraft. The principal differences from the Mark 24 were the use of two propulsion batteries, which could be used in parallel while the torpedo was searching for a target to provide greater endurance and in series to provide greater speed in attack mode.
The Yu-1 (鱼-1) torpedo was the first Chinese-built steam-powered torpedo; it was a development of the unguided straight-running Soviet ASuW Type 53 torpedo. It was type classified in September 1971. The Yu-1 was actually the second domestically produced torpedo to enter Chinese service; the first was the Yu-2 torpedo. During the 1980s a version was developed with passive acoustic homing designated the Yu-1A.
Yu-2 torpedo was a Chinese development of the unguided straight-running Soviet ASuW RAT-52 torpedo with passive acoustic homing capability added. The historical background of Yu–2 is identical to that of Yu-1 torpedo and Yu-4 torpedo. Contrary to the higher number assigned, Yu-2 torpedo was the first Chinese domestically produced torpedo entering service, ahead of the Yu-1 torpedo.
The Yu-3 (鱼-3) is a Chinese acoustic homing torpedo designed to be fired from submarines against surface targets. It entered service with the Chinese Navy in 1984. Several sources state that it may be a copy of the Soviet SET-65E, although this seems unlikely as development began in 1965 after the Sino-Soviet split. It is therefore probably the first indigenously developed torpedo in China.
Yu-4 (鱼-4) torpedo is the Chinese development of the Russian SAET-50 ASuW passive acoustic homing torpedo, and it is the Russian SAET-50 torpedo incorporating active acoustic homing guidance. Yu-4 torpedo is often erroneously claimed by many sources as the Chinese version of the SAET-60 acoustic homing torpedo, but Soviets had not completed the development of SAET-60 and only fielded the weapon in 1961, by then the relationship between former-Soviet Union and China had already worsened and China had not received any technical assistance on SAET-60 torpedo. The background of the development of Yu-4 torpedo is identical to that of Yu-1 torpedo and Yu-2 torpedo.
Yu-5 (鱼-5) torpedo is the first wire-guided torpedo developed by China. It is an ASW torpedo designed for conventional diesel-electric submarines. It is often erroneously referred as the Chinese copy of Soviet TEST-71 torpedo, which is incorrect as the Soviet torpedo was developed in 1971 and its successor TEST-71MKE was developed in 1977, at the worst time of Sino-Soviet split. With Yu-5 entering Chinese service in 1989, it was simply impossible to acquire any technologies of Soviet TEST-71 torpedo, which was not purchased by China until 1993, four years after the Yu-5 torpedo had already entered service. However, like all modern Chinese military hardware, the Yu-5 is not a product of indigenous development, and is instead based largely upon previous Soviet and American designs, with much of the propulsion system being derived from the American Mark 46 lightweight torpedo.
The Mark 27 torpedo was the first of the United States Navy 19-inch (48-cm) submarine-launched torpedoes. This electrically-propelled torpedo was 125 inches long and weighed 1174 pounds (534 kg). The torpedo employed a passive acoustic guidance system and was intended for both submarine and surface targets. Nicknamed "Cutie" by submarine crews, the Mark 27 entered service in 1943. The torpedo was classified as obsolete in the 1960s.
The Mark 21 torpedo, designated Mark 21 Mod 0 was a passive acoustic homing torpedo designed in 1943 by Westinghouse Electric Corporation. The Mark 21 successfully passed launching tests in 1943, however, due to difficulties encountered by Westinghouse, the project was abandoned after a few development models had been built.
The Mark 31 torpedo was a destroyer-launched acoustic torpedo developed by the Harvard and Pennsylvania State universities during World War II. A modification of the Mark 18 electric torpedo, it was conceived as an interim weapon to be used in the Pacific War until a new high-speed acoustic torpedo could be developed for the United States Navy.
The Mark 32 torpedo was the first active acoustic antisubmarine homing torpedo in United States Navy service. The Mark 32 was withdrawn from service use with the introduction of the Mark 43 torpedo.
The Mark 33 torpedo was the first passive acoustic antisurface ship/antisubmarine homing torpedo intended for the United States Navy to employ a cast aluminum shell. It featured two speeds – high and low, and was meant to be launched from submarines and aircraft.
