Japanese KAITEN

Class: Type 4 “Human Torpedo”

Length: 54 feet

Diameter: 4 feet, 5 inches

Weight: 18.37 tons

Warhead: 1.98 tons of TNT

Crew: 1 man


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The design for the Japanese Kaiten was originally based on the highly successful Type 93 “Long Lance” torpedo. Nearly 400 Type 1’s were built and were the only type used operationally. The Type 4 oxygen-kerosene engine produced 1,500 horsepower, and had one shaft. Top speed was 40 knots. Range for Type 4 is listed as 38.5 miles at 20 knots, 23.6 miles at 30 knots, or 16.8 miles at 40 knots. Top speed could be maintained for about one hour. The warhead contained 3,960 pounds of TNT. Approximately 45-50 Type 4’s were built in 1945, but were never used operationally. (Carpenter Polmar, Submarines of the Imperial Japanese Navy, p. 49). Many Type 4s were found at Kure Naval Base after the war.

Kaitens were carried piggyback aboard mother submarines. At least three could be carried at a time on one mother sub and some I-boats carried as many as six Kaitens. Maximum depth was 264 feet, which placed that limit on the mother boat.

The only confirmed successfull sinkings by Kaitens (Type 1) where of the fleet tanker Mississinewa in Ulithi anchorage on 20 November 1944, and the destroyer escort Underhill on 24 July 1945. A few other ships are thought to have been damaged by Kaitens as well. In the IJN human torpedo program, eight mother submarines and almost 900 lives were lost .

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