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General Characteristics
Displacement:	46 tons submerged
Length:	23.9 m (78.5 ft)
Beam:	1.8 m (6 ft)
Height:	3 m (10.2 ft)
Ballast:	5899 lb (2,670 kg) in 534 times 11 lb (5 kg) lead bars
Designed Depth:	30 m (100 ft)
Propulsion:	one electric motor, 600 horsepower (450 kW) at 1800 rpm, two screws conter-rotating on single shaft, leading prop 1.35 m diameter, right-handed; trailing prop 1.25 m diameter, left-handed
Batteries:	192 trays of two two-volt cells each, 136 trays forward, 56 trays aft
Endurance:	100 nautical miles at 2 knots, 80 nautical miles at 6 knots, 18 nautical miles at 19 knots
Speed:	23 knots surfaced, 19 knots submerged
Complement:	one commander, one crewman
Armament:	two 18-inch torpedoes muzzle-loaded into tubes, one 300 lb (140 kg) scuttling charge

The ko-hyoteki (甲標的, "Type 'A' Target") class of Japanese midget submarines had hull numbers but no names. For simplicity, they are most often referred to by the hull number of the mother submarine. Thus, the midget carried by I-16 was known as the I-16 midget. The midget submarine hull numbers beginning with the character "HA", which can only be seen on a builder's plate inside the hull.

Fifty were built. The "A Target" name was assigned as a ruse -- if their design was prematurely discovered by Japan's foes, the Japanese Navy could insist that the vessels were battle practice targets. They were also called "tubes" and other slang names.

The first two, Ha-1 and Ha-2, were used only in testing. They did not have conning towers, which were added to the later boats for stability underwater.

Ha-19 was launched by the I-24 at Pearl Harbor. Most of the other fifty hull numbers are unaccounted for, although two were captured in Sydney (Australia), and others in Guam, Guadalcanal, and Kiska Island, accounting for some of the other hull numbers.

The submarines were each armed with two 17.7 inch torpedoes in muzzle-loading tubes one above the other on the port bow. In the Pearl Harbour attack the specially designed type 97 torpedo was used, but problems with the oxygen flasks meant that all later attacks used the type 91 torpedo designed for aircraft launching. There was also a demolition charge which it has been suggested was large enough to enable the submarine to be used as a suicide weapon, but there is no evidence that it was ever used as one.

Five of these boats participated in the Pearl Harbor attack, with one actually making into the harbor. Of the five used at Pearl Harbor, one was captured and the other four sunk or lost.

A photograph taken from a Japanese plane during the Pearl Harbor attack appeared to show a midget submarine inside Pearl Harbor firing torpedoes at Battleship Row, but subsequent research has completely disproven this theory.

Type A midget submarines were also used to attack Sydney, Australia, and Diego Suarez, Madagascar.

See also

• Midget submarine for more details of the Sydney attack.

References

• Ha-19 (Midget Submarine, 1938-1941): http://www.history.navy.mil/photos/sh-fornv/japan/japsh-h/ha19.htm

• Pearl Harbor Attacked website: http://www.pearlharborattacked.com

• Midget submarine attack on Sydney: http://www.awm.gov.au/atwar/remembering1942/midget_submarine/