Mark 13 torpedo | |
---|---|
Type | Aerial torpedo |
Place of origin | United States |
Service history | |
In service | 1936–1953 [1] |
Used by | United States Navy |
Wars | World War II, Korean War (Only on the Hwacheon Dam) |
Production history | |
Designer | Bureau of Ordnance [2] Bureau of Aeronautics |
Designed | 1925 [2] |
Manufacturer | Naval Torpedo Station [1] Pontiac Motor Division Amertorp Corporation International Harvester |
Produced | 1942–1945 [2] |
No. built | 16,600 [2] |
Variants | Mod 1 [3] Mod 2 [3] Mod 2A – Mod 13 [4] |
Specifications | |
Mass | 2,216 pounds (1,005 kg) [1] |
Length | 161 inches (4.1 m) [1] |
Diameter | 22.5 inches (57 cm) [1] |
Effective firing range | 6,300 yards (5.8 km) [1] |
Warhead | Torpex [1] |
Warhead weight | |
Detonation mechanism | |
Engine | Turbine [1] |
Maximum speed | 33.5 knots (62.0 km/h) [1] |
Guidance system | gyroscope [1] |
Launch platform | Douglas TBD Devastator [2] Grumman TBF Avenger Curtiss SB2C Helldiver Mark 1 Lightweight Rack [5] |
The Mark 13 torpedo was the U.S. Navy's most common aerial torpedo of World War II. It was the first American torpedo to be originally designed for launching from aircraft only. [3] They were also used on PT boats.
Originating in a 1925 design study, the Mark 13 was subject to changing USN requirements through its early years with resulting on-and-off development. Early models—even when dropped low to the water at slow speeds—were prone to running on the surface, or not running at all. By late 1944, the design had been modified to allow reliable drops from as high as 2,400 ft (730 m), at speeds up to 410 knots (760 km/h). The final Mark 13 weighed 2,216 lb (1,005 kg); 600 lb (270 kg) of the high explosive Torpex. [6]
The Mark 13 was designed with unusually squat dimensions for its type: diameter was 22.5 inches (570 mm) and length 13 feet 5 inches (4.09 m). In the water, the Mark 13 could reach a speed of 33.5 knots (62.0 km/h; 38.6 mph) for up to 6,300 yards (5,800 m). [7] [6] The Mark 13 ran 12.8 knots (23.7 km/h; 14.7 mph) slower than the Mark 14 torpedo, a characteristic which, along with a lesser mass, lesser negative buoyancy and the lack of a magnetic influence feature in its Mark IV exploder, meant that it did not suffer from some of the same problems as its larger siblings. [8] 17,000 were produced during the war. [9]
By 1942, poor combat performance had made it apparent that there were problems with the Mark 13:
Despite the complications that were attending the other phases of torpedo development, the Bureau of Ordnance considered the aircraft torpedo problem so important that it was assigned the highest priority at the Newport Station. The improvements and modifications of 1942 and 1943 still left the weapon unpopular, however, and production problems were as great as those stemming from incomplete development. In mid-1943 an analysis of 105 torpedoes dropped at speeds in excess of 150 knots (280 km/h) showed clearly why aviators distrusted the Mark 13: 36 percent ran cold, 20 percent sank, 20 percent had poor deflection performance, 18 percent gave unsatisfactory depth performance, 2 percent ran on the surface, and only 31 percent gave a satisfactory run. The total in excess of 100 percent proved that many torpedoes were subject to more than one of the defects, just as the bulk of the problems were still due to the effects of poor air stabilization on water behavior. Better performance at reduced aircraft speeds was small comfort since aviators could not be held down by paper restrictions that imposed serious and dangerous handicaps in combat. And even when they accepted the limitations, the water entry behavior of the torpedo produced frequent hooking and broaching. Time promised to complicate the problem still further. Unsatisfactory for existing planes, the torpedo would certainly fail to utilize the potentialities of aircraft then under development. Confronted with such a problem, the Bureau felt that it had two alternatives: it could accept the Mark 13 as an interim weapon with recognized tactical limitations and initiate the design of a new torpedo, or it could concentrate on eliminating the known defects in the existing weapon. To attempt both might spread effort too thin to assure success in either venture. The first alternative involved predictable delay, since the Bureau estimated that 2 years would be required to move a weapon from conception to production. On the other hand, 12 known defects seemed to preclude immediate success in converting the Mark 13 into an effective aircraft torpedo. Neither alternative was considered alone, so the Bureau decided to increase its resources and follow both at once. The National Defense Research Committee was appealed to for aid, and in late 1942 it accepted a double-barreled order from the Bureau. The Committee was given a blank check to produce a new aircraft torpedo, the Mark 25, for tactical use at 350 knots (650 km/h) launching speed, and it agreed to aid the Bureau in making immediate improvements to the Mark 13. [10]
The Committee assigned the California Institute of Technology to undertake the first systematic study of the dynamics of aerial launched torpedoes. Tank tests using scale models revealed that the "low and slow" approach that had been presumed necessary for a successful drop was actually counterproductive: striking the water at a flat angle frequently caused the after body of the torpedo to "slap", damaging the mechanism. Full scale testing simulated aerial torpedo drops under controlled conditions by pneumatically launching full size torpedoes down a 300 feet (91 m) slide on California's Morris Dam into a mountain lake known for its clarity, allowing all aspects of the water entry to be examined utilizing high-speed photography. Fragile or vulnerable components were improved, tested, refined, and tested again. Improved components were shipped to Newport Rhode Island for air drop testing – 4,300 drops in all. The Caltech study led to the development of "drag rings" that slowed and stabilized the torpedo in flight and cushioned its impact with the water and "shroud rings" (also known as the "ring tail") that reinforced the vulnerable tail fins. They also tested and developed a box-shaped wooden tail that stabilized the torpedo in flight and absorbed energy as it was stripped off as the torpedo entered the water, based on the Kyoban series of similar aerodynamic tails, first developed in 1936 by the Japanese for their Type 91 torpedo used at the attack on Pearl Harbor, but first observed at the Battle of the Coral Sea on 8 May 1942.
Experiment soon revealed that optimum water entry angles were approximately 22-32 degrees relative to the plane of the surface: the torpedo might plunge as deep as 50 feet (15 m) but it would return to its set depth and bearing if the mechanism was undamaged. This enabled the US Navy to develop a series of attack profiles that varied the combination of speed and altitude to produce the ideal 22-32 degree water entry angle. For the Grumman TBF Avenger torpedo bomber this meant drop altitudes as high as 800 feet (240 m) and drop speeds as high as 260 knots (480 km/h) which the Avenger could achieve by diving to the release point. Multiple attack profile options also allowed strike planners to de-conflict attack routes by assigning each torpedo squadron a different attack profile, greatly reducing the risk of mid-air collision over the target. Finally, there was the added benefit of increased range, as the torpedo traveled a significant distance in the air before entering the water (up to 1,000 yards (910 m) when released at 800 feet (240 m) and 300 mph (480 km/h)). Combined with radar that delivered the exact range to the target, the results proved to be remarkable: [11]
New planes outdated [the] Torpedo Mark 13, but drag rings and stabilizers renewed its usefulness. Throughout 1943 torpedo performance remained poor, but the following year witnessed a revolution in the behavior of the Mark 13. Minor changes to the propeller blades and a reduction in gyro damage helped, but the greatest improvement resulted from the stabilizing effects of two appendages--the drag ring and the shroud ring.
The first assembly, known familiarly as the pickle barrel, was readied for use by 1944. Early experiments with parachutes attached to aircraft torpedoes had demonstrated that a drag had a beneficial effect on the airflight characteristics of the weapon. While parachutes did not appear [to be] the solution to the problem, discovery of the principle involved led to the development of the drag ring. Constructed of plywood, the ring was attached to the head of a torpedo and served as a stabilizer for the period that the weapon was airborne. Oscillations were reduced and the ring effected a 40 percent deceleration in air speed, then acted as a shock absorber when the torpedo struck water. Better water entry, a byproduct of air stabilization, reduced damage so substantially that pilots were able to increase the heights and speeds at which torpedoes were released.
The drag ring went a long way toward making the Mark 13 a reliable torpedo, but underwater performance still called for improvement. By midsummer 1944, however, the shroud ring developed by the California Institute of Technology completed the torpedo revolution that had seemed so remote the year before. Almost an exact duplicate of an assembly developed by Newport in 1871, the shroud ring was made to fit over the tail blades of the torpedo. Known to pilots as the ring tail, it produced a steady water run by reducing hooks and broaches and eliminating much of the water roll which characterized the Mark 13. Speed and range were reduced but slightly. Early tests showed that ring-tailed torpedoes took too deep an initial dive, but readjustments of controls soon remedied that last obstacle. Hot, straight, and normal runs approached 100 percent, and the once critical battle reports soon became enthusiastic in praise of the Mark 13. Even psychologically, the appendages contributed to success, since the external design of the torpedo equipped with a pickle barrel and ring tail and the improved appearance of its underwater travel caught the fancy of the airmen.
To speed the availability of the modified torpedo the Bureau built tail assemblies with the shroud ring attached, then sent them to the fleet as substitutes for the equipment on hand. By the fall of 1944 the revamped weapon had a wide distribution. As a result of the new improvements, torpedo drops at altitudes up to 800 feet (240 m) and at speeds up to 300 knots (560 km/h) were authorized. Experience soon indicated that these limits could be extended even further. On one occasion in early 1945, 6 Mark 13 torpedoes were released from altitudes between 5,000 and 7,000 feet (1,500 and 2,100 m); 5 out of the 6 were observed to run hot, straight, and normal. Combat use increased rapidly and the new effectiveness seemed out of all proportion to the changes made. On one air strike on April 7, 1945, Mark 13's sent to the bottom the 45,000 ton (sic) battleship Yamato, a light cruiser, and several destroyers. Months before the end of the war the Mark 13 was universally accepted as the best aircraft torpedo owned by any nation. [10]
In 1942, US Navy Patrol Torpedo (PT) boats operating in the South Pacific were experiencing shortages of 21 inch (53 cm) Mark 8 and Mark 10 [ citation needed ] torpedoes and confronting large numbers of Japanese Daihatsu barges, which were generally too shallow to attack with torpedoes. Installing larger batteries of heavy machine guns and cannon on PT boats to deal with the barges was attempted. Such installations caused weight and stability problems, and torpedoes were still needed to counter larger Japanese vessels such as destroyers and cruisers.
One solution, implemented in 1943, was to replace each of the PT Boat's two to four Mark 8 torpedoes, and their Mark 18 torpedo tubes, with the significantly lighter Mark 13, carried in lightweight Mark 1 launching racks, at a total saving of more than 1,400 pounds (635 kg) each. The shorter Mark 13 also took up less deck space. The racks took advantage of the Mark 13's air-drop capability by simply allowing the torpedoes to roll over the side, eliminating the risks of a "hot run" within the tube and the flare of burning grease that sometimes gave away the PT boat's position upon firing. The Mark 13 also had the advantage of a significantly larger warhead (600-pound (270 kg) vs. 466-pound (211 kg)), containing the significantly more powerful explosive Torpex, which was approximately 1.5 times more powerful per unit of weight than TNT. [5] The Mark 13's shorter range and slower speed were considered acceptable tradeoffs for boats that usually operated at night and relied on stealth to reach firing position.
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 torpedo boat is a relatively small and fast naval ship designed to carry torpedoes into battle. The first designs were steam-powered craft dedicated to ramming enemy ships with explosive spar torpedoes. Later evolutions launched variants of self-propelled Whitehead torpedoes.
A PT boat was a motor torpedo boat used by the United States Navy in World War II. It was small, fast, and inexpensive to build, valued for its maneuverability and speed but hampered at the beginning of the war by ineffective torpedoes, limited armament, and comparatively fragile construction that limited some of the variants to coastal waters. In the US Navy they were organized in Motor Torpedo Boat Squadrons (MTBRONs).
Supercavitation is the use of a cavitation bubble to reduce skin friction drag on a submerged object and enable high speeds. Applications include torpedoes and propellers, but in theory, the technique could be extended to an entire underwater vessel.
A depth charge is an anti-submarine warfare (ASW) weapon designed to destroy submarines by detonating in the water near the target and subjecting it to a destructive hydraulic shock. Most depth charges use high explosives with a fuze set to detonate the charge, typically at a specific depth from the surface. Depth charges can be dropped by ships, patrol aircraft and helicopters.
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.
An Elektroboot was a submarine designed to operate entirely submerged, rather than as submersibles that could submerge as a temporary means to escape detection or launch an attack.
The Mark 44 torpedo is a now-obsolete air-launched and ship-launched lightweight torpedo manufactured in the United States, and under licence in Canada, France, Italy, Japan and the United Kingdom, with 10,500 being produced for U.S. service. It was superseded by the Mark 46 torpedo, beginning in the late 1960s. The Royal Australian Navy, however, continued to use it alongside its successor for a number of years, because the Mark 44 was thought to have superior performance in certain shallow-water conditions.
The motor gunboat (MGB) was a small, high-speed British military vessel of the Second World War, which was armed with a mix of guns, in contrast to the physically similar motor torpedo boat (MTB), whose main offensive weapon were torpedoes. The small size of the MGBs, and their high speed, made them difficult targets for German E-boats, though, like their opponents, they were limited by heavy weather, because they did not provide a stable-enough platform to aim the guns. The large number of guns meant the crew was relatively large, numbering as high as thirty men on the largest boats.
The AUM-N-2 Petrel, also known as Kingfisher C and AUM-2, was an air-to-surface missile produced as part of Project Kingfisher for the United States Navy. Intended for use against enemy surface ships and surfaced submarines, giving aircraft the ability to deliver aerial torpedoes from outside the range of defensive armament, it saw brief operational service in the late 1950s. The project was never considered a high priority by the Navy however, as it was useless against submerged submarines, which were considered the greatest potential threat.
The Mark 24 mine is an air-dropped anti-submarine (ASW) acoustic torpedo developed by the United States during World War II; it was called a mine to conceal its capabilities. The torpedo entered service with the Allies in March 1943; the United States Navy (USN) used it until 1948. Approximately 4,000 were produced. Of the 340 deployed during the war, 204 were fired, sinking 37 and damaging 18 Axis submarines.
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.
A bombsight is a device used by military aircraft to drop bombs accurately. Bombsights, a feature of combat aircraft since World War I, were first found on purpose-designed bomber aircraft and then moved to fighter-bombers and modern tactical aircraft as those aircraft took up the brunt of the bombing role.
The Hewitt-Sperry Automatic Airplane was a project undertaken during World War I to develop a flying bomb, or pilotless aircraft capable of carrying explosives to its target. It is considered by some to be a precursor of the cruise missile.
An aerial torpedo is a torpedo launched from a torpedo bomber aircraft into the water, after which the weapon propels itself to the target.
The Mark 14 torpedo was the United States Navy's standard submarine-launched anti-ship torpedo of World War II. This weapon was plagued with many problems which crippled its performance early in the war. It was supplemented by the Mark 18 electric torpedo in the last two years of the war. From December 1941 to November 1943 the Mark 14 and the destroyer-launched Mark 15 torpedo had numerous technical problems that took almost two years to fix. After the fixes, the Mark 14 played a major role in the devastating blow U.S. Navy submarines dealt to the Japanese naval and merchant marine forces during the Pacific War.
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.
There have been a number of 21-inch (53.3cm) torpedoes in service with the Royal Navy of the United Kingdom.
The Low Level Bombsight, Mark III, sometimes known as the Angular Velocity Sight, was a Royal Air Force (RAF) bombsight designed for attacks by aircraft flying below 1,000 feet (300 m) altitude. It combined components of the Mark XIV bomb sight with a new mechanical computer. It featured a unique solution for timing the drop, projecting a moving display onto a reflector sight that matched the apparent motion of the target at the right instant.
United States Navy submarines, surface ships, and aircraft launch torpedoes, missiles, and autonomous undersea vehicles as part of training exercises. Typically, these training munitions have no warhead and are recovered from the sea and reused. Similarly, new naval weapons under development are launched at sea in performance trials. These experimental units also need to be recovered, in their case to obtain evaluation data. At various points in history, newly manufactured torpedoes were fired as a quality control measure and these, too, had to be recovered before issuing them to the fleet. The U.S. Navy has used a variety of boats to accomplish the retrieval of these test and training munitions. As their missions evolved over the last century they have been variously known as torpedo retrievers, torpedo weapon retrievers, torpedo recovery boats, range support craft, and multi-purpose craft.
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