Жапондық теңіз күштерінің 93-типтік 24 дюймдік торпедасы

WW2 24 inch torpedo of the Imperial Japanese Navy

The Type 93 (酸素魚雷) was a diameter torpedo of the Imperial Japanese Navy (IJN), launched from surface ships. It is commonly referred to as the Long Lance by most modern English language naval historians, a nickname given to it after the war by Samuel Eliot Morison, the chief historian of the U. S. Navy, who spent much of the war in the Pacific Theater. In Japanese references, the term Sanso gyorai (酸素魚雷) is also used, in reference to its propulsion system. It was the most advanced naval torpedo in the world at the time.

The Type 93's development (in parallel with a submarine launched model, the Type 95) began in Japan in 1928, under the auspices of Rear Admiral Kaneji Kishimoto and Captain Toshihide Asakuma, as an evolution of the diameter Type 90 pneumatic torpedo. The torpedo design was inspired by the British oxygen enriched torpedoes used on the s, a naval officer believed them to be oxygen fuelled and it led to restarting research at Kure. At the time, the most powerful potential enemy of the Japanese Navy was the United States Navy's Pacific Fleet. The U. S. Navy's doctrine, presuming an invasion by Japan of the Philippines (an American commonwealth at that time), called for the battle line to fight its way across the Pacific Ocean, relieve or recapture the Philippines, and destroy the Japanese fleet. Since the IJN had fewer battleships than the U. S. Navy, it planned to use light forces (light cruisers, destroyers, and submarines) to whittle down the U. S. Navy's fleet in a succession of minor battles, mostly at night. After the number of American warships was sufficiently reduced, the IJN would commit its own presumably fresh and undamaged battleships to finish off the U. S. remnants in one huge climactic battle. (This was essentially what the U. S. Navy's "War Plan Orange" expected.) The Japanese Navy invested heavily in developing a large, heavy, and long range torpedo, the Type 93. Torpedoes were the only weapon that gave small warships, such as destroyers, the potential to cripple or sink battleships. The IJN's torpedo research and development focused on using highly compressed oxygen instead of compressed air as the fuel oxidizer in the torpedo's propulsion system. These torpedoes used an otherwise normal wet heater engine burning a fuel such as Kerosene. Since air is only 21% oxygen (and 78% nitrogen), pure oxygen provides nearly five times as much oxidizer in the same tank volume, thereby increasing torpedo range. In addition, the absence of the inert nitrogen resulted in the emission of significantly less exhaust gas, comprising only carbon dioxide, which is significantly soluble in water, and water vapor, thus greatly reducing tell tale bubble trails. Compressed oxygen is dangerous to handle and required lengthy research and development, not to mention additional training for the warship's torpedomen, for safe operational use. Eventually, the IJN's weapons development engineers found that by starting the torpedo's engine with compressed air, and then gradually switching to pure oxygen, they were able to overcome the problem of explosions that had hampered it before. To conceal the use of pure oxygen from the ship's crew and any potential enemy, the oxygen tank was named the secondary air tank. The pure oxygen torpedo was first deployed by the IJN in 1935.

The rotational speed of the gyrocompass was increased to 20,000 rpm for the Kaiten manned torpedo. The warhead of the Type 93 torpedo was (the same as the 1 ton gun of an Imperial Japanese battleship), increased to 1.6 tons for Kaiten. The Type 93 torpedo is long and weighs about three tons, while the Kaiten was long and weighed eight tons. The maximum speed of the Type 93 was and range The Kaiten had a range of at , and at The Kaiten had a stable slow cruising capability just beneath the surface.

The Type 93 had a maximum range of at with a high explosive warhead. Its long range, high speed, and heavy warheads provided a formidable punch in surface battles. In contrast, the U. S. Navy's standard surface launched torpedo of World War II, the Mark 15, had a maximum range of at , or at , with a significantly smaller warhead; torpedoes of other Allied nations did not have longer range. The Type 93 was launched from torpedo tubes mounted on the decks of IJN destroyers and cruisers; some Japanese destroyers, unlike ships of other navies, mounted their banks of torpedo tubes in turrets offering protection against splinters, and had tube loaders. The IJN armed nearly all of its cruisers with Type 93 torpedoes. In the early surface battles of 1942–43, Japanese destroyers and cruisers were able to launch their torpedoes from about at the unsuspecting Allied warships attempting to close to gun range. The Allied warships expected that, if torpedoes were used, they would be fired from not more than , their own typical torpedo range. The many torpedo hits suffered by Allied warships in such engagements led their officers to believe torpedoes had been fired by undetected Japanese submarines operating in concert with the surface warships. On rare occasions, stray Type 93s struck ships at a much longer range than their intended targets, leading the Allies on occasion to suspect their ships had been mined. The capabilities of the Type 93 went mostly unrecognized by the Allies until examples were captured intact in 1943. A version, the Type 97, was later developed for midget submarines, but was not a success, and was replaced operationally by Japan's standard aerial torpedo, the Type 91. A version for use by a few IJN submarines was designated the Type 95, and it was ultimately successful. A disadvantage of the Type 93 was that its Shimose explosive warhead was far more likely to detonate due to shock than a TNT loaded torpedo. The explosion from one Type 93, with its heavy warhead, was usually enough to sink the destroyer, or heavily damage the cruiser, carrying it. As American air strikes against IJN ships became more common, captains of destroyers and cruisers under air attack had to decide whether or not to jettison torpedoes to prevent them from being detonated during the attack. In one instance, the heavy cruiser Chikuma jettisoned her Type 93s just before being hit by bombs from several USN dive bombers at the Battle of the Santa Cruz Islands. It was initially believed that during the Battle off Samar (in the eastern Philippines) a shell from escort carrier USS White Plains struck the heavy cruiser Chōkai which detonated the cruiser's Type 93 torpedoes, causing damage that forced the ship to be scuttled; however the 2019 discovery by the RV Petrel of the wreck of the Chōkai with her torpedoes intact disproved this theory. The same Samar engagement saw the heavy cruiser Suzuya sunk by the detonation of her Type 93 torpedoes: a bomb near miss starboard amidships set off the torpedoes in the starboard tube mounts; the resultant fires propagated to other torpedoes nearby and beyond; the subsequent explosions damaged one of the boilers and the starboard engine rooms and eventually reached the main magazines.