61 cm Type 90 torpedo
Encyclopedia
The 61 cm Type 90 torpedo was a surface-fired torpedo
Torpedo
The modern torpedo is a self-propelled missile weapon with an explosive warhead, launched above or below the water surface, propelled underwater towards a target, and designed to detonate either on contact with it or in proximity to it.The term torpedo was originally employed for...

 used by the Imperial Japanese Navy
Imperial Japanese Navy
The Imperial Japanese Navy was the navy of the Empire of Japan from 1869 until 1947, when it was dissolved following Japan's constitutional renunciation of the use of force as a means of settling international disputes...

 during World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...

. It was used in the s and in most cruisers, including the , , , and heavy cruisers after refits during the 1930s. It was superseded by the Type 93
Type 93 torpedo
The Type 93 was a -diameter torpedo of the Imperial Japanese Navy , launched from surface ships. It is commonly referred to as the Long Lance by most modern English-language naval historians, a nickname given it after the war by Samuel E. Morison, the chief historian of the U.S...

 oxygen-powered torpedo, commonly called the Long Lance, as oxygen generating equipment was installed aboard the cruisers.

Development

It was based on a newly developed British 46 knots (90.2 km/h) 21 inches (53.3 cm) Whitehead torpedo. This torpedo used a new double-action two-cylinder engine rather than the four-cylinder radial engine used by World War I
World War I
World War I , which was predominantly called the World War or the Great War from its occurrence until 1939, and the First World War or World War I thereafter, was a major war centred in Europe that began on 28 July 1914 and lasted until 11 November 1918...

-era British torpedoes. This was significantly faster (8–10 kn (15.7–19.6 km/h)), although it had much shorter range (only 10000 metres (10,936.1 yd)) than the Japanese 6th and 8th Year torpedoes. Twenty of these were bought with training warheads in 1926 for ¥30,000 each and the British allowed Japanese technicians to observe the manufacturing process and launch trials. Japan
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...

 bought a manufacturing license in 1928 for ¥150,000.

The Japanese didn't actually manufacture any of these torpedoes, but combined their technology with the results of independent Japanese research to produce the 61 cm Type 90. Testing of the prototypes was prolonged by the need to correct a number of design errors and manufacturing defects, but two prototypes were turned over to the Underwater School in 1931 for practical use. It was informally adopted for use in 1932, but not officially accepted until 15 November 1933. Production initially began at the Kure Naval Arsenal
Kure Naval Arsenal
was one of four principal naval shipyards owned and operated by the Imperial Japanese Navy. -History:The Kure Naval District was established at Kure, Hiroshima in 1889, as the second of the naval districts responsible for the defense of the Japanese home islands along with the establishment of the...

, but the Yokosuka
Yokosuka Naval Arsenal
was one of four principal naval shipyards owned and operated by the Imperial Japanese Navy, and was located at Yokosuka city, Kanagawa prefecture on Tokyo Bay, south of Yokohama...

 and Sasebo Naval Arsenal
Sasebo Naval Arsenal
was one of four principal naval shipyards owned and operated by the Imperial Japanese Navy. -History:The Sasebo Naval District was established at Sasebo, Nagasaki in 1886, as the third of the naval districts responsible for the defense of the Japanese home islands. After the establishment of the...

s began production later.

Description

The Type 90 had an actual diameter of 60.9 centimetres (24 in), weighed 2.54 tonne and was 8.55 metre long. It was very fast for the period and had an endurance of 7000 metres (7,655.3 yd) at 46 knots (90.2 km/h), 10000 metres (10,936.1 yd) at 42 knots (82.3 km/h), and 15000 metres (16,404.2 yd) at 35 knots (68.6 km/h). It was a wet-heater design and mixed kerosene with compressed air to further expand the air used to power the two-cylinder engine. The engine was cooled by saltwater and the resulting steam was recycled for use by the engine. Its warhead weighed 400 kg (881.8 lb) and its air chamber was pressurized at 220 bars (3,190.8 psi).
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