Higher, faster - the development of aviation torpedoes during the Second World War
After the outbreak of World War II, the Type 91 modified Type 2 torpedo equipped with a "ballast" was a great success in the attack on Pearl Harbor, and since then, the Japanese Navy has made relatively limited improvements to the Type 91 torpedo, mainly to improve strength and power, and in 1944, the larger cruciform four-type "frame plate" was put into use.
On the American side, because the masters of the Naval Ordnance Bureau refused to criticize from the fleet, the poor reliability of the MK 13, and the same poor flight performance of TBD, directly led to the slaughter of three American torpedo squadrons in the Battle of Midway while failing to hit a mine, although the US Navy won the Battle of Midway, but the performance of MK 13 still made the Pacific Fleet angry, at this time the Ordnance Bureau began to solve the reliability problem of American aviation torpedoes, In mid-1943, The US Navy organized an assessment of the MK 13 Mod 1 torpedo, torpedo bombers dropped 150 torpedoes at a speed of 105 knots (about 278 km / h), as a result, only about 31% of torpedoes sailed normally, 20% of torpedoes directly sank to the bottom, 36% of torpedoes showed a "cold run" phenomenon, that is, the engine failed to start normally, the torpedo only sailed a short distance by the compressed air starter, 18% had the problem of wrong depth, 20% had a deviation in direction, and 2% flew out of the water - In fact, excluding the torpedoes of normal navigation and direct sinking of the bottom of the torpedo, 49% of the torpedoes remained, with an average of more than 1.5 fault phenomena, and the result of this experiment was a big mouth in the face of the bureaucratic masters of the Ordnance Bureau and the naval torpedo station.
TBD plus Mark 13mod1 torpedoes, a nightmare for US naval aviation
At the end of 1942, the Ordnance Bureau submitted to the Defense Technical Committee an application for the development of a new aviation torpedo and the improvement of the MK 13 torpedo, the development project of the new aviation torpedo was given to Columbia University, and the project to improve the MK 13 torpedo was given to the California Institute of Technology. After accepting the project, Caltech used scale models to conduct indoor tank experiments on the one hand, and on the other hand, set about to build a 300-foot (about 91 meters) long air ejection slide in the Morris Reservoir, which is known for its clear water, to eject a full-scale torpedo model into the water, simulate the state of torpedoes entering the water at different angles and speeds, and record relevant video data from different angles with high-speed cameras for analysis. Caltech's first achievement is to overturn the conclusion that "low-altitude and low-speed" throwing is conducive to improving the reliability of torpedoes, and the study found that low-altitude and low-speed projection can easily cause the angle between the torpedo and the water surface when entering the water is too small, which can easily cause the tail of the torpedo to "bang" the water surface, resulting in mechanical and instrument failure. Studies have shown that torpedoes have the most suitable range of entry angles between 22 and 32 degrees, and this result has led the U.S. Navy to design a series of torpedo projection altitude and velocity combinations to achieve the ideal entry angle—but this is actually what the Japanese Navy had done before the war.
Report on the experiment of the Mark 13 torpedo tank
In addition to the angle of entry problem, Caltech has developed a series of MK 13 modification kits, the torpedoes installed in these modification kits will be sent to the Rhode Island test site for live mine projection testing, the results of the test will be fed back to the Caltech research team for further improvement, a total of more than 4300 real test throughout the war. The earlier modification kit was a set of wooden additional devices, one of the components was similar to the Japanese Type 91 modified 2 torpedo "frame plate" box-type detachable wooden tail stabilizer, in fact, this box-type stabilizer was directly inspired by the Type 91 torpedo, in the Battle of the Coral Sea, when the "Lexington" was struck by lightning, some of the ship's crew found that the Japanese air-dropped torpedo tail had strange wooden box-shaped components, Caltech conducted experiments based on this discovery and developed a similar box-type stabilizer. In addition to the tail stabilizer, another component is a wooden reducer mounted on the head of the torpedo, this reducer is called the "drag ring", nicknamed "pickle barrel", initially, the researchers tried to use the parachute to achieve the purpose of deceleration, but because of the lack of a corresponding air attitude control system, the projection effect of using the parachute is not ideal. This unassuming "pickle barrel" is spliced into a cylinder by three curved plates, which can effectively reduce the speed of torpedoes entering the water, and this reducer will disintegrate when the torpedo enters the water, further absorbing energy and reducing the impact of entering the water. By the end of the war, Caltech R&D teams involved a fixed ring guard/shroud that could replace the detached stabilizer, known as the "ring tail", which not only stabilized the attitude in the air, but also played a role in stabilizing the torpedo attitude when entering the water. After a series of similar improvements, by the second half of 1944, the projection speed specified by the MK13 at the time of use had been relaxed to 560 km / h and the altitude reached 240 meters, and in early 1945, the US Navy conducted a near-extreme mine delivery test, and 6 MK 13 torpedoes were delivered from an altitude of 1500-2100 m, and only one failed. From the middle of 1944, the US Navy began to equip the improved MK 13 torpedo, in order to speed up the equipment, the Naval Ordnance Bureau directly packaged the modification kit and sent it to the front line, on the front line to modify the existing stock of torpedoes, by the fall of 1944, the US Navy front-line torpedo machine unit has basically completed the replacement and modification of the new torpedo Torpedo aircraft attacked Japanese naval mobile units with only a few torpedoes and only hit the Flying Eagle, but by the end of October, during the Battle of Leyte Gulf, the Avenger torpedo aircraft began to use the improved MK 13 torpedo in large quantities, and achieved great results in the Battle of Leyte Gulf, including the super battleship "Musashi".
Mark 13 torpedoes with wooden tail and drag rings, standard in the U.S. Navy after the fall of 1944, in the USS Alabama Park
Mark 13 with tail and drag ring
MK13 tail deflector ring test report
Mark 13 with deflector ring
Mark 13 with deflector ring
The British Royal Navy from the middle of the war, as the "Swordfish" this two-wing flight net pocket gradually withdrew from the first line, flying faster "Barracuda" torpedo bombers began to come to the forefront, at this time the performance of MK XII appeared out of place, in order to adapt to the development of torpedo machine performance, Britain in 1942 and 1944 has put into service two new aviation torpedoes, 18-inch MK XV and 18-inch MK XVII, these two torpedoes are equipped with MK IV type large stabilized tail, Unlike the U.S.-Japan technical route, this tail is not fixed, but can be controlled by a gyroscope to keep the torpedo in the air stable and fall off when the torpedo enters the water. The MK XV was the main aviation torpedo equipment of the British Air Forces in the late stages of World War II, while the MK XVII entered service late and was only in service in small quantities at the end of the war.
MKXV torpedo, visible detachment tail
MKXV torpedoes without tail wing, photographed by the author at the Museum of Fleet Aviation
Swordfish and MKXV torpedoes, in fact, when MKXV entered service, the Swordfish was already out of the first line, the author photographed at the Fleet Air Weapons Museum
British MKXVII torpedo
Germany in 1941 will develop its own F5b aviation torpedo into service, gradually replace the F5w aviation torpedo from Italy, F5b aviation torpedo installed a large K3 type detachable wooden tail, which may be related to the pre-war German-Japanese military technical exchanges, in August 1942, the Japanese submarine "I-30" sent the Germans a full set of drawings of the Type 91 modified Type 2 aviation torpedo, the German copy version was named Lt-850 Type, Type 91 aviation torpedo technology, It may also have been used to improve the F5b torpedo , and the 1944 F5b torpedo was replaced with an L2 tail with gyroscope-controlled ailerons , probably derived from the Type 91 torpedo technology.
German F5b torpedo
Torpedo bombardment Fw5 with F190b