Draft:Japanese 45 cm torpedo

Numerous 45cm (17.7-inch or 18-inch) torpedoes have been used by the Imperial Japanese Navy and Imperial Japanese Navy Air Service. The size category has not been used by Japan since the end of the Second World War.

Torpedoes of 18-inch caliber were much more common during the early 20th century. Historically, this size category was often used by aircraft. Submarines and surface ships generally used 53 cm torpedoes, and surface ships additionally used 61 cm torpedoes. Japan also employs 32 cm torpedoes which conform to the NATO 12.75-inch (323.8mm) standard; these are dedicated ASW weapons, often delivered via aircraft. Due to their historical importance, this page also includes the smaller 14-inch (35.6cm) predecessors to the 45 cm torpedoes, and some of the miscellaneous developments during the Second World War.

Up to the beginning of the First World War, Japan had used more torpedoes against live targets than all the other navies of the world combined. During that time period, the torpedoes listed in this article were the primary ones employed.

Prior to 6 October 1917, imperial measurements were used. After this date, metric units were used. As such, the 18-inch torpedoes were designated as 45 cm torpedoes. Japanese torpedoes have usually conformed to the 45 cm (17.7-inch or 18-inch), the 53 cm (21-inch), and the 61 cm (24-inch) 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 (Showa Era year 55), a Type 40 (Imperial Year 2640), or a Type 80 (Gregorian year 1980).

Predecessors
Following the Boshin War, Japan rapidly modernized during the Meiji Restoration, and this included the adoption of new technologies for its navy. Prior to Japan developing its own torpedoes, specimens were purchased from Schwartzkopff and Whitehead during the 1880s. These would see use in the Sino-Japanese War and the Russo-Japanese War. The use of torpedoes during these two wars proved highly successful, and had a long-lasting effect on Japanese naval doctrine.

These early torpedoes, all with a 14-inch (35.6 cm) diameter, were sold on the global market with very little restriction. Early models from both firms varied in size as they were incrementally developed. Upon adoption for Japanese service, the torpedoes received type designations, as well as the label of either "Shu" (シュ) or "Ho" (ホ), which corresponded to the first syllable of the developer's name ("Schwartzkopff" was spelled as シュワルツコフ, and "Whitehead" was spelled as ホワイトヘッド). The early 14-inch torpedoes would see active use on Japanese ships, such as Matsushima and Yoshino.

Specifications:

Shu Type 84
 * Entered service: 1884
 * Propulsion: Compressed air
 * Weight: 275 kg
 * Length: 4.57 m
 * Explosive charge: 20 kg Guncotton
 * Range and speed: 400 m at 22 kn
 * Notes: Purchased from Schwartzkopff, model of 1883. Bronze body. A total of 200 units were purchased.



Shu Type 88
 * Entered service: 1888
 * Propulsion: Compressed air
 * Weight: 332 kg
 * Length: 4.62 m
 * Explosive charge: 57 kg Guncotton
 * Range and speed: 400 m at 26 kn, 600 m at 24 kn
 * Notes: Purchased from Schwartzkopff, model of 1885. Bronze body. A total of 307 units were purchased.

During the First Sino-Japanese War, Schwartzkopff torpedoes of various models were used by both of the belligerent sides. The novel weapon proved to be sensitive to deficient maintenance practices. At the Battle of the Yalu River, the Chinese launched multiple torpedo salvos at the ironclad Hiei as it executed a flanking maneuver. Torpedoes could be seen breaching the waves, indicative of a failure of the depth-keeping mechanism due to poor maintenance. This greatly reduced both the accuracy and propulsive endurance of the weapons, and none managed to hit the vessel. Later in the war, during the Battle of Weihaiwei, the Japanese attacked with Schwartzkopff torpedoes of their own, launched from torpedo boats, targeting Chinese vessels harbored in the naval base at the Shangdong peninsula. The torpedoes functioned reliably and proved to be decisive, sinking multiple vessels and sending the rest of the defending fleet into disarray.



Ho Type 26
 * Entered service: 1893
 * Propulsion: Compressed air
 * Weight: 332 kg
 * Length: 4.46 m
 * Explosive charge: 49 kg Guncotton or Lyddite equivalent
 * Range and speed: 660 m at 26 kn, 800 m at 22 kn
 * Notes: Purchased from Whitehead, Fiume Mark IV model of 1885, with incremental improvements. Steel body, phosphor bronze internals. A total of 100 units were purchased. The best torpedo of the Sino-Japanese War.

Ho Type 30
 * Entered service: 1897
 * Propulsion: Compressed air
 * Weight: 338 kg
 * Length: 4.56 m
 * Explosive charge: 52 kg Shimose
 * Range and speed: 600 m at 30 kn, 800 m at 22 kn, 2500 m at 12 kn
 * Notes: Purchased from Whitehead, Fiume Mark V model of 1893, upgraded after 1895. Featured gyroscopic guidance using the Obry gyroscope. A total of 50 units were purchased. Domestic production was set up at the Kure Naval Arsenal. A 45 cm version of this torpedo was also procured.

Ho Type 32
 * Entered service: 1899
 * Propulsion: Compressed air
 * Weight: 338 kg
 * Length: 4.56 m
 * Explosive charge: 50 kg Shimose
 * Range and speed: 600 m at 30 kn, 800 m at 24 kn, 2500 m at 15 kn
 * Notes: Purchased from Whitehead, Fiume Mark V model of 1895. Featured gyroscopic guidance using the Obry gyroscope. A total of 76 units were purchased. Domestic production was set up at the Kure Naval Arsenal. A 45 cm version of this torpedo was also procured.

Yokosuka Naval Arsenal Aerial Torpedo Prototype

The following is a description of a derivative of one of the aforementioned 14-inch torpedoes, which is historically significant in its own right as having been the first Japanese attempt at an aerial torpedo in 1916. Japan would soon thereafter, in 1922, develop the unsuccessful 1MT1N torpedo bomber, followed by the successful B1M in 1923. Both of these would be designed to carry dedicated 45 cm aerial torpedoes.


 * Prototype Date: 1916
 * Propulsion: Compressed air
 * Weight: Approximately 350 kg
 * Length: Unknown, less than 4.56 m
 * Explosive charge: 50 kg Dummy warhead
 * Range and speed: 500-600 m at 30 kn
 * Max airdrop speed: Approximately 60 kn
 * Notes: First ever attempt at a Japanese aerial torpedo. A modified Ho Type 32, which had been shortened and reinforced by the Yokosuka Naval Arsenal. Designed as part of a project for an experimental float plane torpedo bomber, the Yokosho Twin-Engine, created in 1916 by Chikuhei Nakajima. The design did not result in a torpedo bomber, though it did contribute to the Yokosho Ro-go Ko-gata reconnaissance float plane.

Kasumigaura Training Series Aerial Torpedo Prototype

The following is a description of Japan's first intensive aerial torpedo training program, which took place during 1921, at the newly-constructed Kasumigaura Air Field near Tokyo. Torpedo bombing tests were carried out under the supervision of 29 British instructors, using the Sopwith Cuckoo and Blackburn Swift aircraft, as well as the Supermarine Channel and Felixstowe F5 flying boats. Japan would subsequently purchase a group of 7 Blackburn Swift aircraft, designated the Swift Mark II. Also purchased were a group of 3 Supermarine Channels. The Felixstowe F5 would later be license-built in Japan. During this time period, Britain utilized the 18-inch Mark VII and Mark VIII torpedoes for aerial launch, though it is unknown if live examples were furnished for the training program. Dummy torpedoes may have been used, based on the Type 38 - the last of the cold-runner compressed air designs.


 * Prototype Date: 1921
 * Propulsion: Unknown, likely compressed air
 * Weight: Unknown, less than 1800 kg
 * Length: Unknown, less than 5.00 m
 * Explosive charge: Unknown, dummy warhead
 * Range and speed: Unknown
 * Max airdrop speed: Unknown
 * Notes: First ever successful test series of torpedo bombing runs by the Japanese.

Torpedo work at the Kasumigaura air field continued until January 1923, which is when a final torpedo design without an explosive payload was tested on the new Mitsubishi B1M bomber, and finally implemented with a warhead the same year. The torpedo thus used was a modification of the Type 44, which lasted until 1931, whereupon it was gradually replaced with prototypes of the Type 91 Mod 1, and retired from the aerial torpedo role after 1933.

Type 30
Main article: Whitehead Mark 1B torpedo

Whitehead Mark 1B torpedo of 1892, purchased and slightly modified by the Japanese. The original wet guncotton filler was replaced with stabilized picric acid, transitioning to the Shimose system in later units. Procured in 1896, and in service in 1897, immediately after the First Sino-Japanese War. This was the first 45cm torpedo in Japanese service. Used on surface ships.

Specifications:


 * Entered service: 1897
 * Propulsion: Compressed air
 * Weight: 532 kg
 * Length: 4.95 m
 * Explosive charge: 100 kg Lyddite equivalent or Shimose
 * Range and speed: 1000 m at 27 kn

Type 32
Main article: Whitehead Mark 2C torpedo

Whitehead Mark 2C torpedo of 1893, fitted with the Obry gyrocompass of the contemporary Whitehead Mark 3, purchased and slightly modified by the Japanese. The original wet guncotton filler was replaced with stabilized picric acid, transitioning to the Shimose system in later units. Procured in 1898, in service in 1899. The first Japanese torpedo to feature gyroscope guidance. Used on surface ships.

Specifications:


 * Entered service: 1899
 * Propulsion: Compressed air
 * Weight: 541 kg
 * Length: 4.95 m
 * Explosive charge: 90 kg Lyddite equivalent or Shimose
 * Range and speed: 1000 m at 28 kn, 3000 m at 15 kn

Type 34
Main article: Whitehead Mark 3 torpedo

Whitehead Mark 3 torpedo of 1893 with gyroscopic guidance, purchased in part and significantly modified by the Japanese. The torpedo body was extended to 6.5 meters, though this proved to be too fragile for the rough handling that torpedoes normally endured, and the length was not exceeded in subsequent developments of 45cm torpedoes. The warhead was the same as the one used on the Type 32, entirely using Shimose filler. In service in 1901. Used on surface ships and land emplacements for strait defense.

Specifications:


 * Entered service: 1901
 * Propulsion: Compressed air
 * Weight: 895 kg
 * Length: 6.50 m
 * Explosive charge: 90 kg Shimose
 * Range and speed: 2000 m at 27 kn, 3500 m at 20 kn

Type 37
Designed 1904, in service 1904. A close derivative of a Whitehead design, the Ho Type 32, with numerous modifications. The Type 37 was the first Japanese torpedo to be manufactured indigenously at the Kure Naval Arsenal. Used on surface ships.

Specifications:


 * Entered service: 1904
 * Propulsion: Compressed air
 * Weight: 541 kg
 * Length: 4.95 m
 * Explosive charge: 90 kg Shimose
 * Range and speed: 1000 m at 28 kn, 3000 m at 15 kn

Type 38
Designed 1904, in service 1905. Three variants existed - Type 38 No.1, Type 38 No.2 "A", and Type 38 No.2 "B". The Type 38 was a Japanese derivative of a Whitehead design, and the first Japanese torpedo to be both designed and manufactured indigenously. Variants 2A and 2B utilized a four-cylinder radial engine, and 2B was further advanced by switching it to dry heater propulsion, significantly increasing speed. Used on surface ships.

Specifications:

Type 38 No.1
 * Entered service: 1905
 * Propulsion: Compressed air
 * Weight: 617 kg
 * Length: 5.15 m
 * Explosive charge: 100 kg Shimose
 * Range and speed: 1000 m at 27 kn, 2000 m at 24 kn, 3000 m at 20 kn

Type 38 No.2A
 * Entered service: Unknown
 * Propulsion: Compressed air
 * Weight: 640 kg
 * Length: 5.09 m
 * Explosive charge: 95 kg Shimose
 * Range and speed: 1000 m at 31.5 kn, 2000 m at 26 kn, 3000 m at 20.3 kn

Type 38 No.2B
 * Entered service: Unknown
 * Propulsion: Dry heater
 * Weight: 663 kg
 * Length: 5.19 m
 * Explosive charge: 95 kg Shimose
 * Range and speed: 1000 m at 40 kn, 2000 m at 32 kn, 3000 m at 23 kn

Type 42
Designed 1908, in service 1909. The last Japanese torpedo to be purchased from Whitehead. Used on surface ships.

Specifications:


 * Entered service: 1909
 * Propulsion: Dry heater
 * Weight: 660 kg
 * Length: 5.15 m
 * Explosive charge: 95 kg Shimose
 * Range and speed: 1000 m at 40 kn, 5000 m at 22 kn

Type 43
Designed 1909, in service 1910. Manufactured wholly in Japan using plans furnished by Whitehead (Whitehead Mark 5). Used on surface ships, such as the Kawachi class battleship.

Specifications:


 * Entered service: 1910
 * Propulsion: Dry heater
 * Weight: 663 kg
 * Length: 5.19 m
 * Explosive charge: 95 kg Shimose
 * Range and speed: 5000 m at 26 kn

Type 44 18-inch
Based upon plans supplied by Whitehead (Whitehead Mark 5) and the Type 43. Designed 1910, in service 1911. 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. Originally designed as improved torpedoes for the Eight-Eight Fleet program. Used on surface ships and aircraft, such as the B1M, B2M, and B3Y biplane torpedo bombers. The first ever domestically-designed Japanese carrier-borne torpedo bomber, the 1MT, was also slated to carry a variant of the Type 44 torpedo, but in practice was unable to take off from the carrier deck while carrying one. 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.

Specifications:

Type 44 No.1 18-inch
 * Entered service: 1911
 * Propulsion: Wet heater
 * Weight: 719 kg
 * Length: 5.39 m
 * Explosive charge: 110 kg Shimose
 * Range and speed: 4000 m at 36 kn

Type 44 No.2 18-inch
 * Entered service: 1911
 * Propulsion: Wet heater
 * Weight: 750 kg
 * Length: 5.39 m
 * Explosive charge: 110 kg Shimose
 * Range and speed: 4000 m at 36 kn, 8000 m at 26 kn

Type 91
Main article: Type 91 torpedo (ja)

Enormously significant torpedo of the Second World War, capable of much higher drop speeds than American and British contemporaries. Predominantly used on aircraft; also saw use on surface ships.

Specifications:

Type 91 Mod 1 Type 91 Mod 2 Type 91 Mod 3 Type 91 Mod 3 Improved Type 91 Mod 3 Strong Type 91 Mod 4 Strong Type 91 Mod 7 Strong
 * Entered service: 1933
 * Weight: 784 kg
 * Length: 5.27 m
 * Explosive charge: 150 kg Type 97
 * Range and speed: 2000 m at 41-43 kn
 * Max airdrop speed: 260 kn
 * Entered service: 1941
 * Weight: 935 kg
 * Length: 5.48 m
 * Explosive charge: 205 kg Type 97
 * Range and speed: 2000 m at 41-43 kn
 * Max airdrop speed: 260 kn
 * Entered service: 1942
 * Weight: 849 kg
 * Length: 5.27 m
 * Explosive charge: 240 kg Type 97
 * Range and speed: 2000 m at 41-43 kn
 * Max airdrop speed: 260 kn
 * Entered service: 1943
 * Weight: 857 kg
 * Length: 5.27 m
 * Explosive charge: 240 kg Type 97
 * Range and speed: 2000 m at 41-43 kn
 * Max airdrop speed: 300 kn
 * Entered service: 1943
 * Weight: 857 kg
 * Length: 5.27 m
 * Explosive charge: 240 kg Type 97
 * Range and speed: 1500 m at 41-43 kn
 * Max airdrop speed: 350 kn
 * Entered service: 1944
 * Weight: 921 kg
 * Length: 5.27 m
 * Explosive charge: 308 kg Type 97
 * Range and speed: 1500 m at 41-43 kn
 * Max airdrop speed: 350 kn
 * Entered service: 1944
 * Weight: 1052 kg
 * Length: 5.71 m
 * Explosive charge: 420 kg Type 97
 * Range and speed: 1500 m at 40-42 kn
 * Max airdrop speed: 350 kn

Type 94 Mod 2
Designed 1934. Two variants existed, a Type 94 Mod 1 and a Type 94 Mod 2. The Type 94 Mod 2 was the 45cm variant. Experimental kerosene-oxygen torpedo for aircraft use; never deployed in service.

Specifications:


 * Entered service: Never
 * Weight: 848 kg
 * Length: 5.28 m
 * Explosive charge: 150 kg Type 97
 * Range and speed: 3000 m at 48 kn

Type 97
Main article: Type 97 torpedo

Designed 1937, in service 1939. Downscaled modification of the 61 cm Type 93 and 53 cm Type 95 torpedoes. Used on midget submarines, primarily the Ko-Hyoteki class. The Type 97 was prominently used during the Attack on Pearl Harbor. Approximately 100 units were produced; field testing revealed reliability problems with the compressed oxygen vessel. Further work resulted in the improved Type 98.

Specifications:


 * Entered service: 1939
 * Propulsion: Wet heater (kerosene-oxygen)
 * Weight: 980 kg
 * Length: 5.60 m
 * Explosive charge: 350 kg Type 97
 * Range and speed: 5500 m at 44-46 kn

Type 98
Main article: Type 97 torpedo

Design work commenced 1938, entered trials 1941, in service 1942. Redesigned version of the Type 97 torpedo, using 38% oxygen instead of pure oxygen, to reduce starting problems. Consequently also referred to as the Type 97 Special. Designated the Type 98 due to being a sequential development of the Type 97, just as the 53 cm Type 96 was developed from the Type 95. Used on midget submarines, primarily the Ko-Hyoteki class. Approximately 130 units were produced, beginning in 1942. Additionally, many of the remaining Type 97 torpedoes were reworked and modified into the Type 98.

Specifications:


 * Entered service: 1942
 * Propulsion: Wet heater (kerosene-air, oxygen-enriched)
 * Weight: 950 kg
 * Length: 5.60 m
 * Explosive charge: 350 kg Type 97
 * Range and speed: 3200 m at 40-42 kn

Type 2
Designed 1942, in service 1943. Modification of the Type 91 Mod 3 with a larger air vessel. Two variants existed, a Type 2 and a Type 2 Special; the latter used the smaller air vessel of the original Type 91. Used on midget submarines.

Specifications:

Type 2 Type 2 Special
 * Entered service: 1943
 * Weight: 1000 kg
 * Length: 5.60 m
 * Explosive charge: 350 kg Type 97
 * Range and speed: 3000 m at 39-41 kn
 * Entered service: 1944
 * Weight: 975 kg
 * Length: 5.60 m
 * Explosive charge: 350 kg Type 97
 * Range and speed: 2000 m at 38-40 kn

Type 4
Type 4 Mark 2: designed 1944, in service 1945. Modification of the Type 91 Mod 4. Used on aircraft.

Type 4 Mark 4: designed 1945, in service 1945. Variant with a larger warhead. Used on aircraft.