The J8M Shūsui can trace its origins back to the
German Messerschmitt Me 163 Komet, a
rocket-powered interceptor aircraft developed during
World War II. The Me 163 had demonstrated impressive capabilities; during late 1941, a prototype had established a new
world speed record of . Furthermore, by late 1943, Japanese officials had witnessed of the
strategic bombing of Germany, and there was a growing suspicion that the
Allies' increasingly capable bombers, such as
Boeing B-29 Superfortress, would soon be attempting to bomb the
Japanese home islands. Recognising that existing piston-engined
fighter aircraft, such as the
Mitsubishi A6M Zero and
Mitsubishi J2M Raiden, would not be sufficiently capable against the looming bomber threat, there was an identified need for a better counter to this upcoming threat and motivated Japan to look towards the latest innovations of the
Axis powers. Japanese military
attachés had become aware of the Me 163 following a visit to the
Bad Zwischenahn airfield of
Erprobungskommando 16, the
Luftwaffe evaluation squadron charged with service test of the rocket-propelled interceptor. Japan promptly entered into talks with German for technical assistance in the development of their own rocket interceptor. In late 1943, the two powers had negotiated terms to
licence-produce both the Me 163 and its
Walter HWK 509A rocket engine. The engine licence alone cost the Japanese 20 million
Reichsmarks (equivalent to million euros). Under the agreement reached, Germany was to provide, by spring 1944, the complete
blueprints of the Me 163B and the HWK 509A engine, along with a single complete Me 163, two sets of sub-assemblies and components, and three complete HWK 509A engines. Furthermore, Germany would inform Japan of any improvements and developments of the Me 163, permit the Japanese to study the manufacturing processes for both the Me 163 and its engine and also allow the Japanese to study
Luftwaffe operational procedures for the Me 163. Accordingly, in early 1944, the disassembled aircraft and its engine were dispatched via submarine, destined for
Kobe, Japan. It is probable that the airframe was onboard the Japanese submarine
RO-501 (ex-''
), which left Kiel, Germany on 30 March 1944 and was sunk in the mid-Atlantic on 13 May 1944 by the hunter-killer group based on the escort carrier . Plans and engines were on the Japanese submarine I-29, which left Lorient, France on 16 April 1944 and arrived in Singapore on 14 July 1944, later sunk by the submarine on 26 July 1944, near the Philippines, after leaving Singapore. Germany is believed to have attempted to send a second Me 163 to Japan onboard U-864'', but this submarine was sunk near
Bergen by British submarine in February 1945. In response to these losses, Japanese officials decided to initiate a
reverse engineering effort using a basic instructional manual on the Me 163 in the hands of naval mission member Commander Eiichi Iwaya, who had travelled to Singapore in the
I-29 and flown on to Japan when the submarine docked. From its inception, the project was a joint venture between the
Imperial Japanese Army Air Service (JAAF) and the
Imperial Japanese Navy Air Service (JNAF), in accordance with the Army-Navy Aeronautical Technology Committee accord of August 1943, which stipulated that the services would collaborate in the development of advanced aeronautical weapons. While the JAAF were responsible for the development of the liquid-fuelled rocket engine, the JNAF were to oversee the production of the airframe; the JNAF also initiated work on an alternative
turbojet powerplant. Early on, there were some disagreements between the services however; while the JAAF wanted a new design to be drawn up as it judged there to be little difference in workload for a clean-sheet design, the JNAF preferred the design to be an accurate reproduction of the German Me 163 because it had already proven to be a stable
aerodynamic body. It was the JNAF's position that emerged victorious, leading to the issuing of the
19-shi specification in July 1944 for the design of the rocket-powered defence fighter. Shortly thereafter, the contract was awarded to
Mitsubishi Jukogyo KK, upon which point the company became responsible for both design and production of the aircraft; the project was headed by the aeronautical engineer Mijiro Takahashi. The JAAF decided to undertake their own design to meet the
19-shi specifications, working at their
Rikugun Kokugijitsu Kenkyujo (JAAF Aerotechnical Institute) in secret. While working on this glider, the
MXY8 , Mitsubishi completed a
mock-up of the J8M1 in September 1944. Both the JAAF and JNAF approved its design and construction, and the construction of a
prototype immediately commenced. However, manufacturers allegedly struggled to keep pace with the expedited production schedules (the J8M was set to attain quantity production in a third of the time that Japanese aircraft projects of the era typically would have); production work was also negatively impacted by Allied air raids on
Nagoya. Both personnel and resources were in short supply, while efforts to relocate production away for Japan's major cities also impacted the project. Furthermore, the JNAF continuously added new design features and requested modifications that created additional difficulties at Mitsubishi. According to the aviation author Walter E. Grunden, moral amongst the company's design team was low, and that some engineers had spoken out that it would be more promising and productive to concentrate resources on producing a copy of another advanced German fighter, the
jet-powered Messerschmitt Me 262 instead. The Ki-200 and the J8M1 differed only in minor items, but the most obvious difference was the JAAF's Ki-200 was armed with a pair of 30 mm (1.18 in)
Type 5 cannon (with a rate of fire of 450 rounds per minute and a muzzle velocity of ), while the J8M1 was armed with two 30 mm (1.18 in) Ho-105 cannon (rate of fire 400 rounds per minute, muzzle velocity . The engine used the German propellants of
T-Stoff oxidizer and
C-Stoff fuel (hydrogen peroxide/methanol-hydrazine), known in Japan as "A" (
kō) and "B" (
otsu) respectively. Sixty training versions (Ku-13, Ki-13, MXY-8 & MXY-9) were produced by
Yokosuka, Yokoi and
Maeda. Seven of the operational version (J8M1/Ki-200) were completed by Mitsubishi. == Operational history ==