The Yokosuka MXY7 Ohka (Cherry Blossom) 'Baka' was a manned suicide rocket that achieved limited success, but was dangerously vulnerable while being carried to its target.
The MXY7 had an unusual origin. The idea was suggested by Ensign Mitsuo Ohta of the 405th Kokutai, a transport pilot. He was given help by the Aeronautical Research Institute at the University of Tokyo, and together they drew up draft plans for a rocket powered suicide aircraft. In August 1944 these plans were submitted to the Naval Arsenal at Yokosuka, and the idea was accepted for further development. An engineering team was put together, and after that work on the design made rapid progress.
The MXY7 was designed for use against an Allied invasion fleet. It was to be carried into the air under a parent aircraft, and then released. It would glide towards its target and then fire its rockets for the final approach. It was designed to be simple to build and to use as few strategic resources as possible - it was mainly built from wood and alloys not used in other aircraft production. It had to be manoeuvrable and simple to fly.
The MXY7 was a simple looking aircraft. It had a cigar shaped fuselage, short stubby wings mounted towards the front of the fuselage and a single cockpit slightly more than half-way back along the aircraft. The tail was 'H' shaped, with two small vertical surfaces at the end of a long horizontal surface.
The MXY7 was accepted by the Japanese Navy Suicide Attacker Okha (Cherry Blossom) Model 11. This version was armed with a 2,646lb warhead and powered by three Type 4 Mark 1 Model 20 rockets, with a combined thrust of 1,764lbs. It was to be launched from a Mitsubishi Navy Type 1 Attack Bomber Model 24J (G4M2e) 'Betty'.
The first ten MXY7s were complete by the end of September. A careful test programme then began, starting with unpowered unmanned flights in October 1944. These were followed by unpowered manned flights and then in November by powered manned flights. By the time these tests were over the Navy had already ordered the MXY7 into production.
Between September 1944 and March 1945 755 MXY7 Ohka Model 11s were built. The Naval Arsenal at Yokosuka built 155, and the arsenal at Kasumigaura the remaining 600. Another 54 unpowered trainers were built at Yokosuka.
The Ohka made its combat debut on 21 March 1945. Sixteen were carried into action under a fleet of Mitsubishi G4M2es, but the mother ships were intercepted by Allied fighters and had to jettison the rocket aircraft too far from their targets.
The Ohka pilots didn't have to wait long for their first success. On 1 April they achieved four hits - one on the battleship USS West Virginia and the rest on transport ships. On 12 April they achieved their first victory, sinking the destroyer USS Mannert L. Abele off Okinawa.
Despite these successes the Ohka proved to be of limited value. Their mother ships were very vulnerable during the approach to their targets, making it very difficult to get close enough to launch the Ohka.
A number of attempts were made to solve this problem. The Ohka Model 22, of which 50 were built, used a Campini-type jet engine to increase its range. Versions were suggested for other aircraft, and for submarine launches, but none reached production.
Model KI (or K-1)
The Model KI (or K-1) was an unpowered trainer. It had water ballast in place of the warhead and the engines, and retractable landing skids. Forty five were built and they were designed to give the operational pilots a feel for the handling characteristics of the weapon.
The Model 11 was the main production version and the only version to be used in combat. 755 were built. It was powered by three Type 4 Mark 1 Model 20 rockets, with a combined thrust of 1,764lbs. It carried a 2,646lb warhead and was launched from a Mitsubishi Navy Type 1 Attack Bomber Model 24J (G4M2e) 'Betty'
The Model 22 was designed to be carried under the Yokosuka Navy Bomber Ginga (P1Y1). In an attempt to increase its range it was given a Tsu-11 jet engine, based on the Italian Campini jet engine. The wingspan had to be reduced to make it fit on the Ginga, and the warhead reduced in size to 1,323lb. Fifty were built at Yokosuka. Large scale production was originally given to Aichi, but they struggled to cope, and the decision was made to build dedicated underground factories instead. These were still under construction at the end of the war. One Model 22 did make a test flight, using auxiliary rockets under the wings. These fired too soon, and the aircraft stalled and crashed.
The Model 21 was to use the modified airframe of the Model 22, but retain the three Model 20 rockets of the Model 11.
The Model 33 was to be carried by the four-engined Nakajima G8N1 Renzan heavy bomber. It was larger than the Model 11, and was powered by a Ne-20 turbojet engine. It could carry a 1,764lb payload. None were built after progress on the G8N1 stalled.
The Model 43A was an enlarged version of the Model 33, for use from submarines. It had folding wings to allow it to be stored in a small deck hanger. It retained the Ne-20 turbojet, and was to be launched by catapult. None were built.
The Model 43B was similar to the 43A, but was designed to be catapulted out of caves on the Japanese home islands. It was designed for the defence of the Home Islands against the threatened invasion. None were built
Model 43 K-I Wakazakura (Young Cherry)
The Model 43 K-1 Kai Wakazakura (Young Cherry) was a training version of the Model 43B. A second cockpit replaced the warhead and it was given retractable landing skids. It was powered by a single Model 20 rocket and two were completed.
The Model 53 was to have been powered by a Ne-20 turbojet and towed to its target behind a G4M2. Again none were built.
Stats (Model 11)
Engine: Three solid-fuel Type 4 Mk 1 Model 20 rockets
Power: 1,764lb thrust in total
Span: 16ft 9in
Length: 19ft 10in
Height: 3ft 9in
Empty weight: 970lb
Loaded weight: 4,718lb
Max speed: 576mph in terminal dive, 403mph at 11,485ft in sustained flight
Service ceiling: not applicable
Endurance: 23 miles
Bomb load: 2,646lb warhead