The modern torpedo (historically called an automotive, automobile, locomotive, or fish torpedo) is a self-propelled explosive projectile weapon, launched above or below the water surface, propelled underwater toward a target, and designed to detonate on contact with, or in proximity to, a target. The term torpedo was originally used for a variety of devices, most of which would today be called mines. However, from World War I onwards, "torpedo" only applied to an underwater self-propelled missile. Torpedoes are also colloquially called "fish" or, in the German Navy, "Aale" (eels).

While the battleship had evolved primarily around engagements between armoured ships with large guns, the torpedo allowed torpedo boats, other lighter surface ships, submersible and aircraft to destroy large armored ships without the use of large-caliber guns, though sometimes at the risk of being hit by longer-range shellfire.

Today's torpedoes can be divided into lightweight and heavyweight classes; and into straight running, autonomous homers and wire-guided ones. They can be launched from a variety of platforms.

Launch platforms

Torpedoes may be launched from submarines, surface ships, helicopters and fixed-wing aircraft, unmanned naval mines and naval fortresses. They are also used in conjunction with other weapons; for example the Mark 46 torpedo used by the United States becomes the warhead section of the ASROC (Anti-Submarine ROCket) and the CAPTOR mine (CAPsulated TORpedo) is a submerged sensor platform which releases a torpedo when a hostile contact is detected.

Etymology

The word torpedo comes from a genus of electric rays in the order Torpediniformes, which in turn comes from the Latin "torpere" (to be stiff or numb). In naval usage, the torpedo was so named by Robert Fulton, who used it to refer to a towed gunpowder charge used by his submarine Nautilus to demonstrate that it could sink warships.

History

Before the invention of the self-propelled torpedo the term was applied to any number of different types of explosive devices, generally having the property of being secret or hidden, including devices which today would include booby traps, land mines and naval mines.

Much like the invention of the helicopter, the earliest torpedo concepts existed many centuries before being developed as working devices. The earliest known description is found in the work of Syrian engineer Hassan al-Rammah in 1275. His works show illustrations of a rocket-propelled device that appears to have been designed to move on the surface of water.

Early naval "torpedoes"

Although the term "torpedo" was not coined until 1800, the early submarine Turtle attacked using an explosive very similar in intent and function. Turtle dived under a British vessel to attach a bomb by means of an auger. The bomb was to be detonated by a timed fuse, probably a type of clockwork mechanism. In its only recorded attack, Turtle failed to attach its charge to the hull of HMS Eagle.

The first usage of the term torpedo to refer to a naval explosive was by American inventor Robert Fulton. In 1800, Fulton launched his submarine, Nautilus, and demonstrated its method of attack using a floating explosive charge Fulton called a torpedo. The submarine would tow the torpedo, submerging beneath an enemy vessel and dragging the torpedo into contact with it. Fulton successfully destroyed demonstration targets in both France and Britain, but neither government was interested in purchasing the vessel and Fulton's experiments ceased in 1805.

During the American Civil War, the term torpedo was used for what is today called a contact mine, floating on or below the water surface using an air-filled demijohn or similar flotation device. (As self-propelled torpedoes were developed the tethered variety became known as stationary torpedoes and later mines.) Several types of naval "torpedo" were developed and deployed, most often by the Confederates, who faced a severe disadvantage in more traditional warfare methods.

In this period, "torpedoes" floated freely on the surface or were bottom-moored just below the surface. They were detonated when struck by a ship, or after a set time, but were unreliable. These could be as much a danger to Confederate as to Union shipping, and were sometimes marked with flags that could be removed if Union attack was deemed imminent. Rivers mined with Confederate torpedoes were often cleared by Unionists placing captured Confederate soldiers with knowledge of the torpedoes' location in small boats ahead of the main fleet.

"Torpedoes" (mines) could also be detonated electrically by an operator on shore (as demonstrated also by Fulton), so friendly vessels or low-value enemy vessels could be ignored while waiting for the capital ships to sail over them. However, the Confederacy was plagued by a chronic shortage of materials including platinum and copper wire and acid for batteries, and the wires had a tendency to break. Electricity was a new technology, and the limitations of direct current for effective distance was poorly understood, so failures were also possible because of the decrease in voltage when the torpedoes were too far from the batteries. Former United States Navy Commander Matthew Maury, who served as a commander in the Confederate Navy, worked on the development of an underwater electrical mine.

David Farragut encountered tethered and floating contact mines in 1864 at the American Civil War Battle of Mobile Bay. After his leading ironclad, USS Tecumseh, was sunk by a tethered contact mine (torpedo), his vessels halted, afraid of hitting additional torpedoes. Inspiring his men to push forward, Farragut famously ordered, "Damn the torpedoes, full speed ahead!"

The first torpedo designed to attack a specific target was the spar torpedo, an explosive device mounted at the end of a spar up to long projecting forward underwater from the bow of the attacking vessel. When driven up against the enemy and detonated, a hole would be caused below the water line. Spar torpedoes were employed by the Confederate submarine H. L. Hunley (and were successful in sinking the USS Housatonic), as well as by David-class torpedo boats, among others. However, these torpedoes were apt to cause as much harm to their users as to their targets.

Bombs and booby traps

During the US Civil War, the term "torpedo" was also used to refer to various types of bombs and boobytraps. Confederate General Gabriel J. Rains deployed "sub-terra shells" or "land torpedoes", artillery shells with pressure fuses buried in the road by retreating Confederate forces to delay their pursuers. These were the forerunners of modern land mines. Union generals publicly deplored this conduct.

Confederate secret agent John Maxwell used a clockwork mechanism to detonate a large "horological torpedo" (time bomb) on August 9, 1864. The bomb was hidden in a box marked "candles" and placed aboard a barge containing Union ammunition (20,000–30,000 artillery shells and 75,000 small arms rounds) moored at City Point, Virginia, on the James River. The explosion caused more than US$2 million in damage and killed at least 43 people.

The coal torpedo was a bomb shaped like a lump of coal, to be hidden in coal piles used for fueling Union naval vessels. The bomb would be shoveled into the firebox along with the real coal, causing an explosion. Although the North referred to the device as the coal torpedo in newspaper articles, the Confederates referred to it as a "coal shell".

Self-propelled torpedoes

From the 1870s onwards, the word torpedo was increasingly used only to describe self-propelled projectiles that traveled under or on water. By the turn of the century, the term no longer included mines and booby-traps as the navies of the world added submarines, torpedo boats and torpedo boat destroyers to their fleets.

The first working prototype of the modern self-propelled torpedo was created by a commission placed by Giovanni Luppis (Ivan Lupis), an Austrian naval officer from Fiume, a port city of the Austrian Empire, on Robert Whitehead, an English engineer who was the manager of a Fiume factory. In 1864, Luppis presented Whitehead with the plans of the salvacoste (coastsaver), a floating weapon driven by ropes from the land, and made a contract with him in order to perfect the invention.

Whitehead was unable to improve the machine substantially, since the clockwork motor, the attached ropes and the surface attack mode all contributed to a slow and cumbersome weapon. However, he kept considering the problem after the contract had finished, and eventually developed a tubular device, designed to run underwater on its own, and powered by compressed air. The result was a submarine weapon, the Minenschiff (mine ship), the first real self-propelled torpedo, officially presented to the Austrian Imperial Naval commission on December 21, 1866.

Maintaining proper depth was a major problem in the early days but Whitehead introduced his "secret" in 1868 which overcame this. It was a mechanism consisting of a hydrostatic valve and pendulum that caused the torpedo's hydroplanes to be adjusted so as to maintain a preset depth.

After the Austrian government decided to invest in the invention, Whitehead started the first torpedo factory in Fiume. In 1870, they improved the devices to travel up to approximately at a speed of up to , and by 1881 the factory was exporting torpedoes to ten other countries. The torpedo was powered by compressed air and had an explosive charge of gloxyline (gun-cotton). Whitehead went on to develop more efficient devices, demonstrating torpedoes capable of in 1876, in 1886, and, finally, in 1890.

Royal Navy representatives visited Fiume for a demonstration in late 1869, and in 1870 a batch of torpedoes was ordered. In 1871, the British Admiralty paid Whitehead £15,000 for certain of his developments and production started at the Royal Laboratories in Woolwich the following year. In 1893, RN torpedo production was transferred to the Royal Gun Factory. The British later established a Torpedo Experimental Establishment at HMS Vernon and a production facility at the Royal Naval Torpedo Factory, Greenock in 1910. These are now closed.

Whitehead opened a new factory near Portland harbour, England in 1890, which continued making torpedoes until the end of the Second World War. Because orders from the RN were not as large as expected, torpedoes were mostly exported. A series of devices was produced at Fiume, with diameters from upward. The largest Whitehead torpedo was in diameter and long, made of polished steel or phosphor-bronze, with a gun-cotton warhead. It was propelled by a three-cylinder Brotherhood engine, using compressed air at around and driving two propellers, and was designed to self-regulate its course and depth as far as possible. By 1881, nearly 1500 torpedoes had been produced. Whitehead also opened a factory at St Tropez in 1890 which exported torpedoes to Brazil, Holland, Turkey and Greece.

Whitehead faced competition from the American Lieutenant Commander John A. Howell, whose own design, driven by flywheel, was simpler and cheaper. It was produced from 1885 to 1895, and it ran straight, leaving no wake. A Torpedo Test Station had been set up on Rhode Island in 1870, and an automobile torpedo produced in 1871 was unsuccessful. The Lay torpedoes were also largely unsuccessful as were various privately invented ones. The Howell torpedo was the only USN one until Whitehead torpedoes produced by Bliss and Williams (later E W Bliss and Co) came into service in 1894. Five varieties were produced, all diameter. An improved version, the Bliss-Leavitt, with a turbine engine was later produced, some with a larger diameter. Various versions were used in both World War I and World War II.

Whitehead purchased rights to the gyroscope of Ludwig Obry in 1888 but it was not sufficiently accurate, so in 1890 he purchased a better design (ironically from Howell) to improve control of his designs, which came to be called the "Devil's Device". The firm of L. Schwartzkopf in Germany also produced torpedoes and exported them to Russia, Japan and Spain. In 1885, Britain ordered a batch of 50 as torpedo production at home and at Fiume could not meet demand.



On 16 January 1878, the Turkish steamer Intibah became the first vessel to be sunk by self-propelled torpedoes, launched from torpedo boats operating from the tender Velikiy Knyaz Konstantin under the command of Stepan Osipovich Makarov during the Russo-Turkish War of 1877-78. In another early use of the torpedo, Chilean frigate Blanco Encalada was sunk on April 23, 1891 by a torpedo from the gunboat Almirante Lynch, during the Chilean Civil War.

By this time the torpedo boat, the first of which had been built at the shipyards of Sir John Thornycroft in 1877, had gained recognition for its effectiveness, and the first torpedo boat destroyer (later simply destroyers) were built to counter it. Torpedoes were also used to equip gunboats of around 1,000 tons, these becoming torpedo gunboats.

Originally, torpedoes were designed to be straight running, though this was not always the case in practice. Around 1897, Nikola Tesla patented a remote controlled boat and later demonstrated the feasibility of radio-guided torpedoes to the United States military.

The idea of dropping lightweight torpedoes from aircraft was conceived in the early 1910s by Bradley A. Fiske, an officer in the United States Navy. Awarded a patent in 1912,

Fiske worked out the mechanics of carrying and releasing the aerial torpedo from a bomber, and defined tactics that included a night-time approach so that the target ship would be less able to defend itself. Fiske determined that the notional torpedo bomber should descend rapidly in a sharp spiral to evade enemy guns, then when about   above the water the aircraft would straighten its flight long enough to line up with the torpedo's intended path. The aircraft would release the torpedo at a distance of   from the target. Fiske reported in 1915 that, using this method, enemy fleets could be attacked within their own harbors if there were enough room for the torpedo track.

World War I

Torpedoes were widely used in the First World War, both against shipping and against submarines. Germany and its allies disrupted the supply lines to Britain largely by use of submarine torpedoes (though submarines also extensively used guns). Britain and its allies also used torpedoes throughout the war. U-boats themselves were often targeted, twenty being sunk by torpedo.

Initially the Japanese Navy purchased Whitehead or Schwartzkopf torpedoes but by 1917 they were conducting experiments with pure oxygen instead of compressed air. Because of explosions they abandoned the experiments but resumed them in 1926 and by 1933 had a working torpedo. They also used conventional wet-heater torpedoes.

World War II

In the inter-war years, tight budgets caused nearly all navies to skimp on testing their torpedoes. As a result, only the Japanese had fully-tested torpedoes (in particular the Type 93, nicknamed "Long Lance" postwar) at the start of World War II. The lack of reliability caused major problems for the American Submarine Force in the early years of the American involvement in World War II, primarily in the Pacific War.

All classes of ship, including submarines, and aircraft were armed with torpedoes. Naval strategy at the time was to use torpedoes, launched from submarines or warships, against enemy warships in a fleet action on the high seas. Targeting unarmed enemy merchant shipping was prohibited by rules of war. (In the event, merchantmen were armed and acted as de facto naval auxiliaries, rendering the distinction moot.) There was concern torpedoes would be ineffective against warships' heavy armor; an answer to this was to detonate torpedoes underneath a ship, badly damaging its keel and the other structural members in the hull, commonly called "breaking its back". This was demonstrated by magnetic influence mines in World War I. The torpedo would be set to run at a depth just beneath the ship, relying on a magnetic exploder to activate at the appropriate time. Germany, Britain and the U.S. independently devised ways to do this; German and American torpedoes, however, suffered problems with their depth-keeping mechanisms, coupled with faults in magnetic pistols shared by all designs.

Inadequate testing had failed to reveal the effect of the Earth's magnetic field on ships and exploder mechanisms, which resulted in premature detonation. The Kriegsmarine and Royal Navy promptly identified and eliminated the problems. In the United States Navy, there was an extended wrangle over the problems plaguing the Mark 14 torpedo (and its Mark 6 exploder). Cursory trials had allowed bad designs to enter service. Both the Navy Bureau of Ordnance and the United States Congress were too busy protecting their own interests to correct the errors, and fully-functioning torpedoes only became available to the USN twenty-one months into the Pacific War.

British submarines used torpedoes to interdict the Axis supply shipping to North Africa, while Fleet Air Arm Swordfish sank three Italian battleships at Taranto by torpedo and (after a mistaken, but abortive, attack on Sheffield) scored one crucial hit in the hunt for the German battleship Bismarck. Large tonnages of merchant shipping were sunk by submarines with torpedoes in both the Battle of the Atlantic and the Pacific War.

Torpedo boats such as the American PT boats enabled relatively small but fast boats to carry enough firepower, in theory, to destroy a larger ship, though this rarely occurred in practice. Destroyers of all navies were also usually armed with torpedoes to attack larger ships. In the Battle off Samar, destroyer-mounted torpedoes of the American task force "Taffy 3" showed effectiveness at defeating armor. Damage and confusion caused by torpedo attacks were instrumental in beating back a superior Japanese force of battleships and cruisers.

Postwar

In postwar times, only the navies of Pakistan and the United Kingdom have made torpedo hits against hostile navy ships. The sinkings of INS Khukri and ARA General Belgrano caused a combined death toll of approximately 500. Also, during the Korean War the United States Navy successfully attacked a dam with torpedoes launched from airplanes.

Guided torpedoes

Later in the Second World War, torpedoes were given acoustic (homing) guidance systems, originally by the Germans in the G7es torpedo. Pattern-following and wake homing torpedoes were also developed. Acoustic homing formed the basis for torpedo guidance after the Second World War. Though Lupis' original design had been rope guided, torpedoes were not wireguided until the 1960s. Because of improved submarine strength and speed, torpedoes had to be given improved warheads and better motors. During the Cold War, torpedoes were an important asset with the advent of nuclear powered submarines, which did not have to surface often, particularly those carrying strategic nuclear missiles.

Energy sources

Compressed air

This first successful self-propelled Whitehead torpedo of 1866 used compressed air as its energy source. The air was stored at pressures of up to and fed to a piston engine which turned a single propeller at about 100 rpm. It was able to travel about at an average speed of . The speed and range of later models was improved by increasing the pressure of the stored air. In 1906 Whitehead built torpedoes which could cover nearly at an average speed of .

At higher pressures the cooling experienced by the air as it expanded in the engine caused icing problems (see adiabatic cooling). This drawback was remedied by heating the air with seawater before it was fed to the engine, which increased engine performance further, because the air expanded even more after heating. This was the principle used by the Brotherhood engine.

Heated torpedoes

This led to the idea of injecting a liquid fuel, like kerosene, into the air and igniting it. In this manner the air is heated up more and expands even further, and the burned propellant adds more gas to drive the engine. Construction of such heated torpedoes started circa 1904 by Whitehead's company.

Wet-heater

A further improvement was the use of water to cool the combustion chamber. This not only solved heating problems so more fuel could be burnt but also allowed additional power to be generated by feeding the resulting steam into the engine together with the combustion products. Torpedoes with such a propulsion system became known as wet heaters, while heated torpedoes without steam generation were retrospectively called dry heaters. A simpler system was introduced by the British Royal Gun factory in 1908. Most torpedoes used in World War I and World War II were wet-heaters.

Compressed oxygen

The amount of fuel that can be burnt by a torpedo engine is limited by the amount of oxygen it can carry. Since compressed air contains only about 21% of oxygen, engineers in Japan developed the Type 93 (nicknamed Long Lance postwar by historian Samuel E. Morison) for destroyers in the 1930s. The Type 93 used pure oxygen instead of compressed air and had unmatched performance in World War II. During the war, Germany experimented with hydrogen peroxide for the same purpose.

Wire driven

The Brennan torpedo had two wires wound around drums inside it. Shore-based steam winches pulled the wires, which spun the drums and drove the propellers. An operator controlled the relative speeds of the winches, providing guidance. Such systems were used for coastal defence of the British homeland and colonies from 1887 to 1903 and were purchased by, and under the control of, the Army as opposed to the Navy. Speed was about for over 2,400 m.

Flywheel

The Howell torpedo used by the US Navy in the late 1800s featured a heavy flywheel which had to be spun up before launch. It was able to travel about at . The Howell had the advantage of not leaving a trail of bubbles behind it, unlike compressed air torpedoes. This gave the target vessel less chance to detect and evade the torpedo, and avoided giving away the attacker's position. Additionally, it ran at a constant depth, unlike Whitehead models.

Electric batteries

Electric propulsion systems also avoided tell-tale bubbles. John Ericsson invented an electrically propelled torpedo in 1873; it was powered by a cable from an external power source, as batteries of the time had insufficient capacity. The Sims-Edison torpedo was similarly powered. The Nordfelt torpedo was also electrically powered and was steered by impulses down a trailing wire.

Germany introduced its first battery-powered torpedo shortly before World War II, the G7e. It was slower and had shorter range than the conventional G7a, but was wakeless and much cheaper. Its lead-acid rechargeable battery was sensitive to shock, required frequent maintenance before use, and required preheating for best performance. The experimental G7ep, an enhancement of the G7e, used primary cells.

The United States had an electric design, the Mark 18, largely copied from the German torpedo (although with improved batteries), as well as FIDO, an air-dropped acoustic homing torpedo for anti-submarine use.

Modern electric torpedoes such as the Mark 24 Tigerfish or DM2 series commonly use silver oxide batteries which need no maintenance, allowing torpedoes to be stored for years without losing performance.

Rockets

A number of experimental rocket-propelled torpedoes were tried soon after Whitehead's invention but they were not successful. Rocket propulsion has recently been revived in Russian and German torpedoes (see below): it is especially suitable for supercavitating devices.

Modern drive systems

Modern torpedoes utilize a variety of drive mechanisms, including gas turbines (the British Spearfish), monopropellants, and sulphur hexafluoride gas sprayed over a block of solid lithium. Some torpedoes, such as the Russian VA-111 Shkval, the Iranian Hoot and the proposed German Unterwasserlaufkörper / Barracuda, use supercavitation to increase their speed to over . By contrast, the American Mark 48 torpedo, which does not use supercavitation, does about .

Propulsion

The first of Whitehead's torpedoes had a single propeller and needed a large vane to stop it turning in a circle. Not long afterwards the idea of contra-rotating propellers was introduced (at Woolwich), to avoid the need for the vane. The three-bladed propellor came in 1893 and the four-bladed one in 1897. To minimise noise, today's torpedoes often use pump-jets.

Guidance and tactics

The Victorian era Brennan could be steered onto its target by varying the relative speeds of its contra-rotating propellers. However, the Brennan required a substantial infrastructure and was not suitable for ship-board use. Therefore, for the first part of its history, the torpedo was guided only in the sense its course could be regulated so as to achieve an intended impact depth (because of the sine wave running path of the Whitehead, this was a hit or miss proposition, even when everything worked correctly) and, through gyroscopes, a straight course. With such torpedoes the method of attack in small torpedo boats, Torpedo bombers and small submarines was to set on a collision course abeam to the target and to release the torpedo at the last minute, before peeling away; all the time running a gauntlet of defensive fire.

In larger ships and submarines, fire control calculators gave a wider engagement envelope. Originally, plotting tables (in large ships), combined with specialised slide rules (known in U.S. service as the "banjo" and "Is/Was"), reconciled the speed, distance, and course of a target with the firing ship's speed and course, together with the performance of its torpedoes, to provide a firing solution. By the Second World War, all sides had developed automatic electro-mechanical calculators, exemplified by the U.S. Navy's Torpedo Data Computer. Submarine commanders were still expected to be able to calculate a firing solution by hand as a back up against mechanical failure, and because many submarines existing at the start of the war were not equipped with a TDC; most could keep the "picture" in their heads and do much of the math (which was simple trigonometry) without recourse to paper calculations, from extensive training.

Against high value targets and multiple targets, submarines would launch a spread of torpedoes, to increase the probability of success. Similarly, squadrons of torpedo boats and torpedo bombers would attack together creating a "fan" of torpedoes across the target's course. Faced with such an attack, the prudent thing for a target to do was to turn 90 degrees to its original course and steam away from the torpedoes and the firer, allowing the relatively short range torpedoes to use up their fuel. An alternative was to "comb the tracks", turning 90 degrees towards the torpedoes. The intention of such a tactic was still to minimise the size of target offered to the torpedoes, but at the same time be able to aggressively engage the firer. This was the tactic advocated by critics of Jellicoe's actions at Jutland, his caution at turning away from the torpedoes being seen as the reason the Germans escaped.

The use of multiple torpedoes to engage single targets greatly reduces a submarine's combat endurance and its ability to stay on patrol. This can be improved by ensuring a target can be effectively engaged by a single torpedo, which gave rise to the guided torpedo. Guided torpedoes can use passive or active guidance, or a mix of the two. Passive acoustic torpedoes home in on emissions from a target. Active acoustic torpedoes home in on the reflection of a signal, or "ping", from the torpedo or its parent vehicle; this has the disadvantage of giving away the presence of the torpedo. In semi-active mode, a torpedo can be fired to the last known position or calculated position of a target, which is then acoustically illuminated ("pinged") once the torpedo is in attack range.

Torpedoes can operate on a fire and forget principle or be controlled by its firing vessel. During the Second World War, the U.S. experimented with frequency hopping radio controlled torpedoes using matching pairs of punched card rolls based on those of player pianos. Modern torpedoes use an umbilical wire; the advantage of the umbilical is the vastly greater computer processing power of the submarine or ship can be used. Torpedoes such as the U.S. Mark 48 can operate in a variety of modes increasing tactical flexibility.

Homing

The homing systems for torpedoes are generally acoustic, though there have been other target sensor types used. A ship's acoustic signature is not the only emission a torpedo can home in on. To engage U.S. supercarriers, the Soviet Union developed the 53-65 wake-homing torpedo.

Warhead/fuzing

The warhead is generally some form of aluminised explosive, because the sustained explosive pulse produced by the powdered aluminium is particularly destructive against underwater targets. Torpex was popular until the 1950s, but has been superseded by PBX compositions. Nuclear warheads for torpedoes have also been developed, e.g. the Mark 45 torpedo. In lightweight antisubmarine torpedoes designed to penetrate submarine hulls, a shaped charge can be used. Detonation can be triggered by direct contact with the target or by a proximity fuze incorporating sonar and/or magnetic sensors.

Control surfaces and hydrodynamics

Control surfaces are essential for a torpedo to maintain its course and depth. A homing torpedo also needs to be able to out-manoeuvre a target. Good hydrodynamics are needed for it to attain high speed efficiently and also to give long range since the torpedo has limited stored energy.

Torpedo classes and diameters

Torpedoes are launched several ways:

• From a torpedo tube mounted either in a trainable deck mount (common in destroyers), or fixed above or below the waterline of a surface vessel (as in cruisers, battleships, and armed merchant cruiser) or submarine.
• Early submarines, and some torpedo boats (such as the U.S. World War II PT boats, which used the Mark 13 aircraft torpedo) used deck-mounted "drop collars", which simply relied on gravity.
• From shackles aboard low-flying aircraft or helicopters.
• As the final stage of a compound rocket or ramjet powered munition (sometimes called an assisted torpedo).

Many navies have two weights of torpedoes:

• A light torpedo used primarily as a close attack weapon, particularly by aircraft.
• A heavy torpedo used primarily as a standoff weapon, particularly by submerged submarines.

In the case of deck or tube launched torpedoes, the diameter of the torpedo is obviously a key factor in determining the suitability of a particular torpedo to a tube or launcher, similar to the caliber of the gun. The size is not quite as critical as for a gun, but diameter has become the most common way of classifying torpedoes.



Length, weight, and other factors also contribute to compatibility. In the case of aircraft launched torpedoes, the key factors are weight, provision of suitable attachment points, and launch speed. Assisted torpedoes are the most recent development in torpedo design, and are normally engineered as an integrated package. Versions for aircraft and assisted launching have sometimes been based on deck or tube launched versions, and there has been at least one case of a submarine torpedo tube being designed to fire an aircraft torpedo.

As in all munition design, there is a compromise between standardisation, which simplifies manufacture and logistics, and specialisation, which may make the weapon significantly more effective. Small improvements in either logistics or effectiveness can translate into enormous operational advantages.

Some common torpedo diameters (using the most common designation, metric or inch, and listed in increasing order of size):

• 12.75 inch (approximately 324 mm) is the most common size for light torpedoes.
• 406 mm (16 inch) was the size of the earliest specialised Soviet ASW torpedoes. torpedo tubes were fitted to Soviet Hotel, Echo and early Delta class submarines, often in addition to tubes.
• 450 mm (17.7 inch) was the standard size for light torpedoes of the Imperial Japanese Navy. It was also widely used by Italian Navy (Regia Marina) during World War II; it was the common size of the torpedo used by torpedo bomber. This size is sometimes referred to as .
• 483 mm (19 inch) was the size for the first U.S. homing torpedo, the Mark 24, also known as Fido.
• 533 mm (21 inch) is the most common size for heavy torpedoes, including:
  • Allied torpedoes of World War II
  • Imperial Japanese Navy submarines
  • Torpedoes of the Kriegsmarine
  • NATO torpedoes
  • Some Soviet and Russian torpedoes, including the current ASW models
• 550 mm (approximately 21.7 inches) was the standard size for French Navy torpedoes until France joined NATO and switched to 533 mm
• 610 mm (24 inch) torpedoes, most famously the Type 93 'Long Lance', were used by Imperial Japanese Navy destroyers and cruisers, and as the basis for some Kaiten.
• 650 mm (approximately 25.6 inches) is the largest torpedo diameter used by the Russian navy, such as the Type 65. Adaptors are used to fire 533 mm (21 inch) models from 650 mm tubes.

Even larger sizes of torpedo tube, including 660 mm (26 inches), 762 mm (30 inches), and 916 mm (about 36 inches), have been installed on some nuclear submarines. These tubes are designed to be capable of firing large diameter munitions such as cruise missiles, as well as the standard 21 inch heavy torpedo.

Torpedoes used by various navies

German Navy

Modern German Navy:

• DM2A4 heavyweight torpedo
• DM2A3 heavyweight torpedo
• MU 90 lightweight impact torpedo
• Mark 46 torpedo
• Barracuda (supercavitating torpedo)

The torpedoes used by the World War II Kriegsmarine included:

• G7a (T1)
• G7e (T2)
• G7e/T4 (Falke)
• G7es (Zaunkönig)
• T11

Imperial Japanese Navy

The torpedoes used by the Imperial Japanese Navy (World War II) included:

• Type 91 torpedo
• Type 92 torpedo
• Type 93 torpedo
• Type 95 torpedo
• Type 97 torpedo
• Kaiten

Indian Navy

• Advanced Experimental Torpedo (lightweight torpedo)
• Varunastra (heavyweight torpedo)
• Takshak (heavy weight torpedo)

Royal Navy

The torpedoes used by the Royal Navy include:

• Spearfish torpedo
• Stingray torpedo
• Tigerfish

Russian Navy

Torpedoes used by the Russian Navy include:

• Type 53 torpedo
• Type 65 torpedo
• APR-3E torpedo
• VA-111 Shkval torpedo

U.S. Navy

The four major torpedoes in the United States Navy inventory are:

• the Mark 46 lightweight;
• the Mark 48 heavyweight torpedo;
• the Mark 50 advanced lightweight; and
• the Mark 54 Lightweight Hybrid Torpedo.

Launchers

Ship

Originally, Whitehead torpedoes were intended for launch underwater and the firm was upset when they found out the British were launching them above water, as they considered their torpedoes too delicate for this. However, the torpedoes survived. The launch tubes could be fitted in a ship's bow, which weakened it for ramming, or on the broadside; this introduced problems because of water flow twisting the torpedo, so guide rails and sleeves were used to prevent it. The torpedoes were originally ejected from the tubes by compressed air but later slow burning gunpowder was used. Torpedo boats originally used a frame that dropped the torpedo into the sea. Royal Navy Coastal Motor Boats of World War I used a rear-facing trough and a cordite ram to push the torpedoes into the water tail-first.

Developed in the run up to Second World War, multiple-tube mounts (up to quintuple in some ships) for 21" to 24" torpedoes in rotating turntable mounts appeared. Destroyers could be found with two or three of these mounts with between five and twelve tubes in total. The Japanese went one better, covering their tube mounts with splinter protection and adding reloading gear (both unlike any other navy in the world), making them true turrets and increasing the broadside without adding tubes and top hamper (as the quadruple and quintuple mounts did). Considering their Type 93 possible war winners, the IJN equipped their cruisers with torpedoes. The Germans also equipped their capital ships with torpedoes.

Smaller vessels such as PT boats carried their torpedoes in fixed deck mounted tubes using compressed air. These were either aligned to fire forward or at an offset angle from the centerline.

Late in the war lightweight mounts for 12.75" homing torpedoes were developed for anti-submarine use consisting of triple launch tubes used on the decks of ships. These were the Mark 32 launcher in the USA and part of STWS (Shipborne Torpedo Weapon System) in the UK. Later a below-decks launcher was used by the RN. This basic launch system continues to be used today with improved torpedoes and fire control systems.

Submarines

Submarine launched weapons now use compressed air, or the torpedoes swim out, or are pushed out by hydraulic ram. Both bow and stern tubes are usually fitted. The first French and Russian submarines carried their torpedoes externally in Drzewiecki drop collars. These were cheaper than launch tubes but unreliable.

Late in World War II, the U.S. adopted a 16" (40 cm) homing torpedo for use against escorts.

Air launch

Aerial torpedoes may be carried by fixed-wing aircraft, helicopters or missiles. They are launched from the first two at prescribed speeds and altitudes, dropped from bomb-bays or underwing hardpoints.

Torpedo handling equipment

Although lightweight torpedoes are fairly easily handled, the transport and handling of heavyweight ones is difficult, especially in the small space of a submarine. After the Second World War, some Type XXI submarines were obtained from Germany by the United States and Britain. One of the main novel developments seen was a mechanical handling system for torpedoes. Such systems were widely adopted as a result of this discovery.

See also

• List of torpedoes
• Missile guidance
• Human torpedo
• Bangalore Torpedo
• Autonomous Underwater Vehicle

Notes

1. The City Point Explosion (MilitaryHistoryOnline.com)
2. Hopkins, Albert Allis. The Scientific American War Book: The Mechanism and Technique of War, Chapter XLV: Aerial Torpedoes and Torpedo Mines. Munn & Company, Incorporated, 1915
3. Hart, Albert Bushnell. Harper's pictorial library of the world war, Volume 4. Harper, 1920, p. 335.
4. The New York Times, July 23, 1915. "Torpedo Boat That Flies. Admiral Fiske Invents a Craft to Attack Fleets in Harbors" Retrieved on September 29, 2009.
5. The war's top ace used them exclusively, and stuck religiously to the "cruiser rules"
6. Blair, p.20
7. Battle Off Samar
8. Diehl BGT: Unterwasserlaufkörper
9. Fitzsimons, Bernard, ed. "Bliss-Leavitt", in The Illustrated Encyclopedia of 20th Century Weapons and Warfare (London: Phoebus, 1978), Volume 4, p.386.
10. Beach, Edward L., Jr., Captain, USN (rtd). Run Silent, Run Deep.
11. The British called theirs the "fruit machine".
12. Beach describes it well in Run Silent, Run Deep.
13. The Attack Submarine suggests shorter patrols actually improve effectiveness.
14. NSTL achievements
15. Fitzsimons, Bernard, ed. Illustrated Encyclopedia of Weapons and Warfare (London: Phoebus, 1978), Volume 10, p.1040, "Fubuki"; Preston, Antony. Destroyers.
16. Blair, Clay, Jr. Silent Victory (Lippencott, 1975); Lockwood, Charles A., Admiral. Hellcats of the Sea.

References

• Blair, Clay. Silent Victory. Philadelphia: Lippincott, 1975.
• The Columbia Encyclopedia, Sixth Edition, online.
• Crowley, R.O. "Confederate Torpedo Service". The Century, Volume 56, Issue 2, The Century Company, New York, June 1898.
• Milford, Frederick J. "U.S. Navy Torpedoes: Part One—Torpedoes through the Thirties". The Submarine Review, April 1996. (quarterly publication of the Naval Submarine League, P.O. Box 1146, Annandale, VA 22003)
• Milford, Frederick J. "U.S. Navy Torpedoes: Part Two—The Great Torpedo Scandal, 1941-43". The Submarine Review, October 1996.
• Milford, Frederick J. "U.S. Navy Torpedoes: Part Three—WW II development of conventional torpedoes 1940–1946". The Submarine Review, January 1997.
• O'Kane, Richard H. (1987). "Seventh Patrol", Wahoo: The Patrols of America's Most Famous World War II Submarine. Novato, California: Presidio Press.
• Perry, Milton F. Infernal Machines: The Story of Confederate Submarine and Mine Warfare. Baton Rouge: Louisiana State University Press, 1985. ISBN 0807112852.

External links

• "Modern Torpedoes And Countermeasures", by Austin Joseph, Bharat Rakshak Monitor, Volume 3(4) January–February 2001.
• Navy Fact File Torpedoes: Mark 46, Mark 48, Mark 50, the source of the US Navy torpedo data (via the Internet Archive
• The US Navy – Fact File: Torpedo - Mark 46
• The US Navy – Fact File: Heavyweight Torpedo - Mark 48
• The US Navy – Fact File: Torpedo - Mark 50
• The US Navy – Fact File: Torpedo - Mark 54
• "A History of the Torpedo The Early Days"
• Torpedo Display, US Naval Undersea Museum
• Torpedo Collection, US Naval Undersea Museum
• Super Cavitation Torpedo 'Barracuda'