Type 93 Torpedo
|Country of Origin||Japan|
|Machinery||Kerosene-Oxygen Wet-Heater steam engine|
|Explosive Charge||490kg Type 97 Explosive (60% TNT and 40% hexanitrodiphenylamine)|
Contributor: David Stubblebineww2dbaseThe Japanese Type 93 torpedo, by all accounts, was the finest torpedo of World War II and was the most advanced torpedo design in the world at the time. The Type 93 was given the name "Long Lance" by post-war American Naval historian Samuel Eliot Morison but the term did not exist during the war and was never used by the Japanese.
The Type 93 torpedo was intended to be fired from surface ships such as destroyers, cruisers, and battleships and was developed in parallel with the slightly smaller Type 95 torpedo for use from submarines. What set the Type 93 apart was its sheer size and its innovative engine design that gave the torpedo great speed and great range while taking up a compact space within the torpedo body. The speed, range, and compactness are all due to the use of pure oxygen as a fuel oxidizer instead of air.
In 1926, Japanese Naval attach├ę Lieutenant Oyagi Shizui returned to Japan from the United Kingdom reporting that the British had developed an oxygen-based torpedo for their Nelson-class battleships. The Royal Navy's 24.5-inch Mark I torpedo actually relied on oxygen-enriched air, but Shizui's report prompted Japan's development of a torpedo based on pure oxygen. Many nations had already tried to develop a pure oxygen torpedo but the tendency for the entire device to violently explode without warning caused most designers to return to the far more stable oxidizer of plain air. The Japanese development process suffered from a few explosions due to oxygen's increased volatility, but they found ways to make it work. Explosions were most likely when the oxygen encountered petroleum compounds such as lubricants or the torpedo's fuel, normally kerosene. All parts that would come into contact with oxygen were thoroughly degreased and the introduction of the oxygen to the fuel was done in a very clever way; this particular design feature is what made the entire concept practical. Like most torpedo motors, the Type 93 had a fuel flask and a separate oxidizer flask with the two substances being brought together in the combustion chamber. The Type 93, however, had a small third flask filled with plain air. When the torpedo was launched and the motor was started, the combustion began with a fuel-air mixture and the oxygen would only begin to flow after the pressure in the air flask was reduced. Even then, the oxygen did not flow directly to the combustion chamber but flowed into the air flask where it mixed with the remaining air to briefly create oxygen-enriched air until all of the air was displaced by the oxygen. In this way, the oxygen level in the combustion chamber was quickly but not suddenly increased and by the time the fuel was mixing with pure oxygen, the torpedo was well away from the firing vessel so any accidental explosions posed a smaller hazard.
An additional obstacle to using pure oxygen was leakage. While this was never fully resolved, much of the problem was mitigated by the development of a special 4,000-ton press that could form most of a seamless oxygen flask from a single piece of steel.
Once the concept was made practical, the advantages were many. The first advantage came from the near perfectly efficient combustion created in a pure oxygen and fuel ignition. This greatly increased the power output giving the Type 93 its speed advantage.
The second advantage was that the oxidizer flask could be much smaller because storing plain air also requires storing a large amount of inert nitrogen which makes up 78% of air's volume. Put another way, an oxygen flask with 21% of the volume of an air flask could contain the same amount of oxygen (actually, a little more because of oxygen's greater compressibility). Then, if the size of the oxygen and fuel flasks were sized to fit in the same space as a set of air and fuel flasks, the overall running time of the engine could be tremendously increased. This is precisely what the Japanese did and this, coupled with the high speed, is what gave the Type 93 its over-the-horizon range of twelve miles. Another use the Japanese found for the added space created by the smaller oxidizer flask was to increase the size of the warhead.
The next advantage came from the exhaust in this type of combustion. An air-fuel combustion produces water vapor, carbon dioxide, and all that inert nitrogen that came through with the air, which would emerge heated and expanded. An oxygen-fuel combustion still produces water vapor and carbon dioxide but no nitrogen. Once these products were vented to the outside seawater, the water vapor condensed and the carbon dioxide dissolved. The advantage here is that there was no tell-tale trail of white exhaust bubbles announcing the torpedo's approach and pointing directly to its point of origin. Instead, the torpedo's run was nearly invisible.
Once the intricacies of the torpedo motor were ironed out, there was still the rest of the torpedo to be considered. The Type 93 had a 490-kilogram warhead (1,080 pounds), the most powerful torpedo warhead of World War II. The Type 93 used a standard gyroscope guidance system and was fitted with a very simple but reliable contact exploder. The sensitivity of the exploder could be adjusted at any time right up to launch and the crews commonly set the sensitivity to the lowest setting hoping to ensure that any kind of hit would set off the charge. Unfortunately, this setting was so sensitive that certain external pressure changes could cause the torpedo to explode prematurely. There were some reports of temperature gradients in the water creating pressure differences sufficient to set off the exploders and there were several cases where the torpedoes exploded as they passed through ships' wakes. The same Lieutenant Oyagi Shizui who brought the concept to Japan, as Rear Admiral Shizui after the war, said he wished they had never given the crews the ability to adjust the exploder sensitivity.
Another major factor contributing to the Type 93 torpedo's success, and this point cannot be overstated, was the fact it was extensively and rigorously tested in live-fire trials during its development. Japan's larger strategy for enhancing its position in the western Pacific was heavily dependent on having a reliable long-range naval torpedo so the country's commitment to developing a torpedo like the Type 93 was quite expansive compared with other nations, especially the United States. Early tests were against the cliffs of Izu-Oshima south of Tokyo Bay but later, almost any aging hulk they could find became a test target for the Type 93.
As with any weapon development, the work on the Type 93 was done in completely secrecy. Even so, in 1940 the United States Office of Naval Intelligence received information about the torpedo design from an "impeccable source." Navy Commander Henri Smith-Hutton, a United States naval attach├ę in Tokyo, developed a Chinese-Japanese contact who was scheduled to visit a Japanese destroyer. The informant reported back that the ship's torpedoes had a larger diameter than previously believed and that a Japanese torpedoman boasted the torpedoes used pure oxygen. The information was passed along to the Office of Naval Intelligence who passed it on to the Navy's Bureau of Ordnance (BuOrd). In a colossal case of hubris and racial arrogance, BuOrd dismissed the report as an impossibility based on their belief the Japanese could not have built a torpedo more sophisticated than BuOrd's own designs and that oxygen torpedoes were so complex and dangerous that they were beyond Japanese comprehension (the grand irony being the American torpedoes were fraught with fatal flaws that this same arrogance prevented from being rectified until late 1943 while the Japanese torpedoes were wildly successful from the opening of hostilities).
The design of the Type 93 proved so effective that parts of it were borrowed for other projects. The Type 95 submarine torpedo was developed alongside the Type 93 and in late 1944, the Type 1 Kaiten one-man submarine design used the Type 93 torpedo motor for its propulsion, but substituted compressed air for pure oxygen.
The combat success of the Type 93 torpedo came from a blend of design and tactics. Japanese naval surface warfare tactics early in the war depended on torpedoes almost more than big guns and also tried to use the cover of darkness whenever possible. Specifically, their tactics called for several ships to launch a spread of many torpedoes at extreme range and do so before giving away their positions with gunfire. This resulted in Allied ships suddenly exploding without ever knowing they were under attack. Sometimes these were attributed to striking mines and sometimes they were blamed on undetected submarines at a closer range.
The United States did not begin to fully appreciate how formidable a weapon they were up against until early 1943 when a Type 93 beached itself on Point Cruz on Guadalcanal. Before even touching this torpedo, the Americans had to be impressed with the sheer enormity of the weapon. At 2 feet in diameter, 30 feet in length, and 3 tons in weight, the Type 93 was considerably more massive than anything in the United States Navy's torpedo arsenal.
Combat successes for the Type 93 torpedo were many, particularly in the engagements in and around the Solomon Islands in 1942 and 1943. Considering warships alone, the Type 93 is credited with sinking thirteen warships outright and another ten sunk by a combination of torpedo hits and aerial bombs and/or gunfire. These include one fleet carrier, USS Hornet (Yorktown-class), eleven cruisers, and eleven destroyers from the navies of the United States, United Kingdom, Australia, and the Netherlands. An even greater number of warships were damaged but did not sink. Successes against troop ships, merchant ships, and other auxiliaries were certainly much higher, although these were targets for submarines more often than for destroyers.
With the defeat of Japan, the Type 93 torpedo saw no service after 1945 and the total number produced is unknown.
United States Navy
Naval Weapons of the World (navweaps.com)
Imperial Japanese Navy History (combinedfleet.com)
Military History Online
Drachinifel Naval Historiographer YouTube Channel
The National Interest Magazine
The History Channel
The Pacific War Online Encyclopedia
United States National Bureau of Standards
Last Major Revision: Oct 2021
Type 93 Torpedo Interactive Map
Type 93 Timeline
|19 Feb 1942┬á||In the Battle of the Java Sea, Dutch destroyer HNLMS Piet Hein was sunk by Type 93 torpedoes launched from Japanese destroyer Asashio with a loss of 64 men including the captain.|
|27 Feb 1942┬á||American seaplane tender USS Langley with 32 P-40 fighters aboard, en route to Java, was sunk by Japanese Navy land-based aircraft. On the same day, at the Battle of the Java Sea, Japanese cruisers Haguro and Nachi sank Dutch cruisers HNLMS Java and De Ruyter along with destroyer HNLMS Kortenaer and two other Dutch destroyers with Type 93 torpedoes without any Japanese losses.|
|1 Mar 1942┬á||HMS Encounter, HMS Exeter, and USS Pope were sunk at the Second Battle of the Java Sea; the ships suffered 7, 54, and 1 killed, respectively. Meanwhile, at the Battle of Sunda Strait, Allied cruisers USS Houston and HMAS Perth intercepted a Japanese invasion force but were both sunk as they attacked; four Japanese transports and a minesweepers were sunk, but two of the transports were later refloated. Also on this date, Japanese troops landed on Java and immediately began marching for Batavia, with the Japanese 2nd Division capturing Serang and the 230th Infantry Regiment capturing Kalidjati airfield at Soebang en route. Finally, Japanese air raids at Surabaya damaged destroyer USS Stewart and Dutch destroyer Witte de With.|
|8 Aug 1942┬á||In the pre-dawn morning, 7 Japanese cruisers and 1 destroyer under Gunichi Mikawa departed Kavieng, New Ireland and Rabaul, New Britain, sailing south without being detected; after sundown, the force caught Allied warships by surprise off Guadalcanal in the Solomon Islands; in the Battle of Savo Island, Japanese cruisers Ch┼Źkai, Aoba, Kako, Kinugasa, and Furutaka used Type 93 torpedoes and gunfire to sink US cruisers USS Quincy, Vincennes, and Astoria and Australian cruiser HMAS Canberra; 1,077 US personnel were killed in this battle (Canberra was badly damaged and was ultimately scuttled by a US destroyer).|
|22 Aug 1942┬á||US and Japanese supplying destroyers made contact in the Savo Sound off Guadalcanal, Solomon Islands; Japanese destroyer Kawakaze disabled destroyer USS Blue with Type 93 torpedoes at 0359 hours (killing 9; she would be scuttled on the following day).|
|26 Oct 1942┬á||At the Battle of Santa Cruz Islands, US forces achieved victory but saw USS Enterprise, USS South Dakota, and USS San Juan damaged. Aircraft carrier USS Hornet (Yorktown-class) was badly damaged from aerial bombs and torpedoes and then finally hit by three Type 93 torpedoes launched from Japanese destroyers Akigumo and Makigumo which caused her to sink 30 minutes later. On the Japanese side, carriers Shokaku and Zuiho were damaged by dive bombers from USS Hornet and USS Enterprise, respectively.|
|13 Nov 1942┬á||Cruiser USS Atlanta was sunk by Type 93 torpedoes launched from Japanese destroyer Akatsuki; destroyer USS Barton was sunk by Type 93 torpedoes launched from Japanese destroyer Amatsukaze; and destroyer USS Laffey was sunk by Type 93 torpedoes launched from unidentified Japanese destroyers.|
|14 Nov 1942┬á||After dark, the Second Naval Battle of Guadalcanal began with Japanese ships severely crippling the American destroyer screen. Japanese destroyers launched Type 93 torpedoes that took the bows off destroyers USS Walke and Benham; Walke sank almost immediately and Benham was scuttled sixteen hours later by USS Gwinn, herself badly damaged in the action.|
|30 Nov 1942┬á||Near Guadalcanal, Solomon Islands, US cruisers ambushed a night time fast destroyer convoy led personally by Rear Admiral Raizo Tanaka. Tanaka's quick thinking led to a Japanese victory in the Battle of Tassafaronga. Cruisers USS Northampton, USS Pensacola, USS Minneapolis, and USS New Orleans (New Orleans-class) were badly damaged by torpedoes. Cruiser USS Northampton was sunk by Type 93 torpedoes launched by Japanese destroyer Oyashio.|
|6 Jul 1943┬á||During Battle of Kula Gulf northwest of New Georgia, USS Helena ambushed an incoming Japanese convoy at 0157 hours, but the many gun flashes in turn made her an attractive target for Japanese gunners. She was struck by a Japanese Type 93 torpedo launched by Japanese destroyers Suzukaze and Tanikaze at 0203 hours, followed by two more at 0205 hours. She would sink at 0225 hours. In Vella Gulf, destroyer USS Strong was also struck and sunk by a Type 93 torpedo launched from Japanese destroyer Niizuki.|
|12 Jul 1943┬á||Yugure, Yukikaze, Hamakaze, and Kiyonami departed Shortland Islands, Solomon Islands, escorting a troop transport mission involving light cruiser Jintsu to Kolombangara, New Georgia, Solomon Islands. En route, they encountered Allied warships, resulting in the Battle of Kolombangara that lasted into the next morning. Jintsu and USS Gwin were sunk (Gwinn by a Type 93 torpedo launched by a Japanese destroyer), and USS Honolulu and USS St. Louis were damaged. The Japanese were able to land 1,200 men.|
|6 Oct 1943┬á||During the Battle of Vella Lavella, destroyer USS Chevalier was sunk by Type 93 torpedoes launched from Japanese destroyer Yugumo.|
|3 Dec 1944┬á||With her Type 93 torpedoes, Japanese destroyer Take torpedoed and sank the Allen M. Sumner-class destroyer USS Cooper in Leyte Gulf, Philippine Islands.|
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