Japanese 53 cm torpedo


Numerous 53 cm torpedoes have been used by the Imperial Japanese Navy and its successor, the Japan Maritime Self-Defense Force, since their first development just before the First World War.
Torpedoes of 21-inch caliber are the primary size category used worldwide. In Japan, they are used by surface ships and submarines, and comprise the predominant majority of submarine torpedoes; historically, aircraft and midget submarines used smaller 45 cm torpedoes, and surface ships additionally used 61 cm torpedoes. Japan also employs 32 cm torpedoes which conform to the NATO 12.75-inch standard; these are dedicated ASW weapons, often delivered via aircraft. The 12.75 inch standard for light ASW torpedoes was originally defined by the dimensions of the Mark 46 torpedo.
Prior to 6 October 1917, imperial measurements were used. After this date, metric units were used. As such, the 21-inch torpedoes were designated as 53 cm torpedoes. Japanese torpedoes have usually conformed to the 45 cm, the 53 cm, and the 61 cm calibers.
The Japanese type designation scheme has mostly used three different approaches. Units designed prior to the end of the Second World War were designated by either the regnal era year or the imperial year. In 1873, the Gregorian calendar was introduced in Japan; during the latter half of the 20th century, Japan increasingly switched to using this system, and as such, more recent torpedoes have type designations denoting Gregorian years. As an example of all three systems, a torpedo designed or accepted for service in 1980 could potentially be called either a Type 55, a Type 40, or a Type 80.
During the Second World War, Japanese torpedoes were superb. Rigorous live-fire testing in real-world conditions resulted in highly reliable designs. The Japanese were more willing to conduct dangerous experiments, an attitude that was also reflected in their highly realistic fleet exercises. Japan also possessed the fastest torpedoes in the world, having persevered in their pursuit of using pure oxygen as the oxidizer instead of air, whereas other navies abandoned the idea.
After the Second World War, Japan imported American torpedoes. These included the Mark 14, Mark 23, Mark 32, Mark 34, Mark 37, Mark 44, and Mark 46. This page presently only lists torpedoes which were indigenously produced in Japan.
After a brief period of postwar stagnation in the field, the Japanese experienced a revival of torpedo development. During the 1970s, indigenous designs became globally competitive.

Type 43 21-inch

Upscaled version of the Type 43 18-inch torpedo. The Type 43 was based upon plans supplied by Whitehead. Generally similar to the Type 38 No.2B and the Type 42, utilizing four-cylinder radial engines. The Type 43 was the only foreign torpedo design adopted for use with 21-inch torpedo tubes during the first half of the 20th century. Designed 1909, in service 1910. Used on surface ships.
Specifications:
  • Entered service: 1910
  • Propulsion: Dry heater
  • Weight:
  • Length:
  • Explosive charge: Shimose
  • Range and speed: at
During the 1910s, the Japanese experimented with designs for 21-inch torpedoes. In July 1910, the first of such projects reached the prototype phase; the torpedo was propelled by a 50-horsepower Antoinette 8-cylinder engine with 105 mm cylinder bores. Interest was also expressed in the turbine-propelled Bliss–Leavitt Mark 8, with a prototype based on the Mark 8 being constructed. Ultimately, the first entirely indigenous 21-inch torpedo would be the Type 6, adopted in 1917.

Type 44 21-inch

Based upon plans supplied by Whitehead and the Type 43. Designed 1910, in service 1911. Used on surface ships and submarines. This torpedo was the first type deployed on Japanese submarines, initially the F, L, and Kaichū types. The Type 44 torpedo series existed in both 18-inch and 21-inch calibers, each having a No.1 and a No.2 variant developed. The Type 44 was the first Japanese design to fully transition to steam for its wet heater cycle.
Concurrent with Type 44 development in 1910, internal combustion propulsion was also being tested for 21-inch torpedo propulsion. A prototype was constructed using a 50-horsepower, eight-cylinder Antoinette gasoline engine. Ultimately this effort was abandoned. Internal combustion propulsion would be tried again, a decade later, with the Type 12 project.
During the Second World War, the Type 44 was mostly relegated to old ships, coastal defense craft, and torpedo boats. The older Shimose filler was replaced with Type 97 or Type 98 explosive in any remaining units of the older versions.
Specifications:
Type 44 No.1 21-inch
  • Entered service: 1911
  • Propulsion: Wet heater
  • Weight:
  • Length:
  • Explosive charge: Shimose
  • Range and speed: at, at
Type 44 No.2 21-inch
  • Entered service: 1911
  • Propulsion: Wet heater
  • Weight:
  • Length:
  • Explosive charge: Shimose
  • Range and speed: at, at
Type 44 Late
  • Entered service: Unknown, likely 1939~1942
  • Propulsion: Wet heater
  • Weight:
  • Length:
  • Explosive charge: Type 97 or Type 98
  • Range and speed: at, at
  • Note: Retrofitted older torpedoes, refurbished for use by auxiliary surface vessels during WWII

    Type 6

The first type classified using metric measurements. Also referred to as the 6th Year Type in literature, referring to Taisho Era year 6. The weapon was designed by the then-recently established Imperial Japanese Navy Technical Department, which favored the regnal era naming scheme. Design work commenced in 1914 and was completed in 1917; in service 1918. Used on surface ships and submarines.
In the aftermath of the Russo-Japanese War, Japan pursued a tentative Eight-Eight Program, which stipulated the necessity for eight modern battleships of at least 20,000 tons displacement and eight modern battlecruisers of at least 18,000 tons displacement. These ships would be armed with new, increasingly powerful armaments, including torpedoes of 21-inch caliber, as opposed to the 18-inch standard common during the war. The torpedoes designed for this program were the Type 6, soon to be followed by the 61 cm Type 8. Alongside the new design, the decision was made to switch to metric units for all present and future torpedo programs. In 1922, the Washington Naval Treaty was signed, and the large new torpedoes were reassigned to new designs of cruisers and destroyers. In this way, the 53 cm torpedo caliber became increasingly significant.
Specifications:
  • Entered service: 1918
  • Propulsion: Wet heater
  • Weight:
  • Length:
  • Explosive charge: Shimose
  • Range and speed: at, at, at

    Type 89

Designed 1929, in service 1931. Initially used on submarines. The Type 89 replaced the Type 6 in the Junsen and Kaidai-type submarines after its adoption, and remained in service until being retired in 1942. Propulsion was with a two-cylinder, double-acting engine. Common during the Second World War as an older and less expensive alternative to the Type 95, especially during the first half of the war. Later during the war, the weapon was additionally assigned to various surface warships such as destroyers, torpedo boats, and training vessels, with the warheads fitted to the Type 89 being of a non-standard type. Alternative fillers for such units included of Shimose and of either Type 94 or Type 97. For this torpedo, the type designation refers to Imperial Year 2589. The type designation 89 was reused in 1989, referring to the Gregorian year.
Specifications:
Type 89
  • Entered service: 1931
  • Propulsion: Wet heater
  • Weight:
  • Length:
  • Explosive charge: Type 91
  • Range and speed: at, at, at
Type 89 Mod 1
  • Entered service: 1931
  • Propulsion: Wet heater
  • Weight:
  • Length:
  • Explosive charge: Type 91
  • Range and speed: at, at, at
Type 89 Mod 2
  • Entered service: 1939
  • Propulsion: Wet heater
  • Weight:
  • Length:
  • Explosive charge: Type 97
  • Range and speed: at, at, at

    Type 92

Design work commenced 1921, completed 1925. Mod 1 was ready for production in 1934. Electric propulsion. The Type 92 was the first of a series of sequentially-designated torpedo projects, classified as project A. The 1925 version submitted for trials had an endurance of at. Deemed unnecessary at the time due to peacetime considerations, and consequently not put into series production. Production of the Mod 1 began in 1941, in preparation for the onset of hostilities in the Pacific. Re-engineered in 1942 using elements of the German G7e torpedo design after ten samples of the G7e were delivered to Japan that year. This resulted in the Mod 2, production of which was started that year to supplement the high demand for the Type 95. The Type 92 was cheaper to produce than the Type 95. Used on submarines. In 1945, Mod 1 was selected to produce the Type 10 Kaiten, a piloted suicide weapon, following the American invasion of Okinawa and anticipated landings in Kyushu. The weapon was chosen for conversion due to a surplus existing in storage, as well as advantages like the absence of a surface bubble trail.
The Type 92 Mod 1 was also used to investigate the possibility of an acoustic homing system, the first of its kind in Japan. In his memoir, Captain Tameichi Hara mentions receiving homing torpedoes and training in their use in December 1944. There were two different types of homing Type 92 torpedoes, with only the first one, designated Mod 3 seeing field deployment against live targets. The torpedo was fitted with two hydrophones at 30 degree angles to port and starboard, in carefully engineered metal cavities with seamless ebonite covers, in the warhead casing. These would be wired through amplifiers to a differential relay which governed a transducer module mated with the torpedo's rudder. The other design, project designation "NR", used a phase differential circuit, with carbon granule hydrophones likewise set flush with the torpedo body behind ebonite covers. A smaller warhead from the Type 91 was used, with the hydrophones mounted in a tapering module behind the warhead. The system was designed to be capable of seeking targets in three dimensions, usable for ASW, which may have been the first of its kind in the world. In practice, the system was too sensitive to self-noise, resulting in a lower acquisition range than the Mod 3 ; also, the seeker head was confounded by boundary layer reflection noise from the surface of the water above, which greatly complicated control in the vertical plane. Project "NR" may have been preceded by the abortive project "R", which attempted to replicate a German passive acoustic homing torpedo obtained through a technology exchange with Germany.
Specifications:
Type 92 Mod 1
  • Entered service: 1934
  • Propulsion: Battery
  • Weight:
  • Length:
  • Explosive charge: Type 97
  • Range and speed: at , at
Type 92 Mod 2
  • Entered service: 1942
  • Propulsion: Battery
  • Weight:
  • Length:
  • Explosive charge: Type 1 Otsuyaku
  • Range and speed: at , at
  • Notes: Hybrid design closely resembling a G7e, including a reverse-engineered German warhead. Lowest cost of production. Manufactured in small numbers due to a shortage of manpower.
Type 92 Mod 3
  • Entered service: 1944
  • Propulsion: Battery
  • Weight:
  • Length:
  • Explosive charge: Type 97
  • Range and speed: at
  • Notes: Passive acoustic homing in the horizontal plane. Speed deliberately limited to 20 knots to reduce self-noise. In 1945, experimental versions with extensive rubber sound insulation and switching to a two-bladed mono screw as opposed to a standard contra-rotating pair of screws increased surface vessel acquisition range to anywhere from 500 to 2000 meters.
Type 92 NR Prototype
  • Prototype date: 1944
  • Propulsion: Battery
  • Weight:
  • Length:
  • Explosive charge: Type 97
  • Range and speed: at
  • Notes: Passive acoustic homing in three dimensions. Speed deliberately limited to 20 knots to reduce self-noise.