The MXY-7 Navy Suicide Attacker
Ohka was a manned
flying bomb that was conceived by
Ensign Mitsuo Ohta of the 405th
Kōkūtai, who had witnessed the multiple air attacks by the
Allies and observed that the defensive efforts of the
Imperial Japanese Navy had been decreasing in effectiveness, thus resolving to design an expendable
kamikaze aircraft purpose-built for suicide attacks upon enemy warships. Ohta obtained design assistance from several figures at the Aeronautical Research Institute at the
University of Tokyo, which included the construction of a scale model and
wind tunnel tests. This involvement of civilian engineers by Ohta ahead of approaching his superiors was likely a violation of protocol, but this infraction was seemingly overlooked. Having integrating the data from the university's research, on 5 August 1944, Ohta submitted his proposal at the First Navy Aeronautical Technology Arsenal. Part of the reason for such secrecy was to avoid the spreading of awareness at Japan's military circumstances to be developing such an aircraft. This desire led to the early dismissal of interest in the
subcontracting of production work to the private sector; instead, production was initially exclusively confined to military facilities. The navy designation
Marudai was assigned to the project, which was partially based on the first ideograph in Ohta's name. It took less than one month to produce the first prototype, as well as ten production-standard aircraft by the end of September 1944, which were referred to as the
Yokosuka MXY-7 Model 11. Both due to the single-use nature of the aircraft, and the resource shortages present across Japan's wider economy towards the end of the conflict, there was considerable pressure to design the Ohka to be as affordable as possible. In October 1944,
glide testing started at
Sagami Bay, just south of
Tokyo; powered trials commenced one month later. Operationally, the
Ohka was usually carried underneath a
Mitsubishi G4M2e Model 24J "Betty"
bomber to within range of its target. On release, the pilot would first glide towards the target and when close enough he would fire the
Ohkas three Type 4 Model 1 Mark 20
solid-fuel rocket motors, one at a time or in unison, and fly the missile towards the ship that he intended to destroy. The final approach was difficult for a defender to stop because the aircraft gained high speed ( in level flight and or even in a dive. Later versions were designed to be launched from coastal air bases and caves, and even from
submarines equipped with
aircraft catapults, although none were actually used in this way. The was the first Allied ship to be sunk by
Ohka aircraft, near
Okinawa, on 12 April 1945. Over the course of the conflict,
Ohkas sank or damaged beyond repair three ships and significantly damaged three more ships, with a total of seven U.S. ships damaged or sunk by
Ohkas. The
Ohka pilots, members of the
Jinrai Butai (Thunder Gods Corps), are honored in Japan at
Ohka Park in Kashima City, the
Ohka Monument in Kanoya City, the Kamakura
Ohka Monument at
Kenchō-ji Zen temple in Kamakura, Kanagawa, and the
Yasukuni Shrine in Tokyo. , Okinawa, April 1945 The
Ohka K-1 was an unpowered
trainer version with water
ballast in place of a
warhead and engines, that was used to provide pilots with handling experience. Unlike the combat aircraft, it was furnished with
flaps and a
landing skid. The water ballast would be dumped proir to landing. The K-1 remained a challenging aircraft to fly, possessing a relatively high landing speed of . 45 K-1s were produced by Dai-Ichi Kaigun Koku Gijitsusho. The Model 22 was designed to overcome the short standoff distance problem by using a
Campini-type
motorjet engine, the
Ishikawajima Tsu-11, giving a level speed of only at but extending the range to . This engine was successfully tested, and 50 Model 22
Ohkas were built at Yokosuka to accept this engine. The Model 33 was a larger version of the Model 22 powered by an
Ishikawajima Ne-20 turbojet with an warhead. The launch aircraft was to be the
Nakajima G8N Renzan, but the Model 33 was cancelled due to the likelihood that the
Renzan would not be available. Other unbuilt planned variants were the Model 43A with
folding wings, to be launched from submarines, and the Model 43B, a catapult/rocket-assisted version, also with folding wings so that it could be hidden in caves. Finally, the Model 53 would also use the Ne-20 turbojet, but was to be towed like a glider and released near its target. ==Operational history==