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The Mitsubishi , naval-designation J8M, army-designation Ki-200, is a World War II rocket-powered interceptor aircraft designed and produced by the Japanese aircraft manufacturer Mitsubishi. It is closely based on the German Messerschmitt Me 163 Komet. The name Shūsui literally translates to "Autumn Water", but is used as a poetic term meaning "Sharp Sword" deriving from the swishing sound of a sword.

The J8M was developed as a joint project for both the Imperial Japanese Navy Air Service (JNAF) and the Imperial Japanese Army Air Service (JAAF), which sought to counter the growing threat of Allied strategic bombing of Japan. Originally, the J8M was intended to be a straightforward licence-built copy of the Me 163, however, difficulties in shipping an example and associated materials to Japan led to an effort to reverse engineer the aircraft from a flight operations manual and other limited documentation that had arrived. Starting in 1944, Mitsubishi's design team, headed by the aeronautical engineer Mijiro Takahashi, closely coordinated with the First Naval Air Technical Arsenal to design the airframe. Multiple companies, including Nissan and Fuji, were involved in the manufacturing effort.

During December 1944, an unpowered glider, the Yokosuka MXY8, flew to successfully validate the J8M's handling characteristics. Development was not straightforward, as the JNAF continuously requested design changes while the expedited production schedules overwhelmed some of the manufacturing partners, with readiness for full-scale production not being attained until the final weeks of the war. A single powered prototype was completed and made its maiden flight on 7 July 1945, only weeks prior to the Surrender of Japan that ended the conflict. No operational missions were ever flown. Two examples were transported to the US for evaluation, one of which was preserved and put on public display.

Design and development

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&nbsp;mm (1.18&nbsp;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&nbsp;mm (1.18&nbsp;in) Ho-105 cannon (rate of fire 400 rounds per minute, muzzle velocity . with Lieutenant Commander Toyohiko Inuzuka at the controls; after his "sharp start" rocket-powered takeoff, Inuzuka successfully jettisoned the dolly upon becoming airborne and began to gain speed, climbing skywards at a 45° angle. At an altitude of , the engine stopped abruptly, and the J8M1 stalled. Inuzuka managed to glide the aircraft back but clipped a small building at the edge of the airfield while trying to land, causing the aircraft to burst into flames. Inuzuka died the next day. While Mitsubishi and naval technicians sought to find the cause of the accident, all future flights were grounded. According to Grunden, the engine outage had occurred due to a design flaw in the fuel injection system. Despite another explosion of the fuel mixture during a ground test days after Inuzuka's crash, flight testing was to resume in late August 1945, and the J8M2 design was finalized. However, on 15 August 1945, Japan surrendered, after which all work on the J8M was abruptly terminated. The end of the conflict also spelled the end of the JAAF's Ki-202 Shūsui Kai (Shūsui modified), whose design had begun in secret months before. The Ki-202 was to offer improved flight endurance over the Ki-200 and was slated to be the priority fighter for the JAAF in 1946, but no metal was cut before Japan's surrender.

The other was at NAS Glenview in October 1946 (identity unknown), but was scrapped.

In the 1960s, a nearly complete (but badly damaged) fuselage was discovered in a cave in Japan. This was on display at a Japanese Air Self Defense Force base near Gifu until 1999, when it was restored and completed by Mitsubishi for display in the company's internal Komaki Plant Museum.

A Mitsubishi J8M1 Shūsui, at the Planes of Fame Museum, Chino, California, US:

<gallery widths="180" heights="150">

File:J8M1 Shu Sui.JPG

File:Mitsubishi-J8M1.jpg

File:Mitsubishi J8M1 Shūsui, Planes of Fame Museum, Chino, Californie.jpg

</gallery>

Comparative Specifications

{| class="wikitable left" style="text-align:center; width: 100%"

|- style="vertical-align:top; background-color:#ccc;"

| colspan="4" style="text-align:center;" | Specifications

|- style="vertical-align:top;"

! style="width:14%" |

! style="width:14%" | J8M1

! style="width:14%" | J8M2

! style="width:14%" | Ki-200

|- style="vertical-align:top;"

|-

| style="; text-align:left;" | Manufacturer: || colspan="3" | Mitsubishi Jukogyo K.K

|-

| style="; text-align:left;" | Type: || colspan="3" | Interceptor

|-

| style="; text-align:left;" | Crew: || colspan="3" | 1

|-

| style="; text-align:left;" | Span: || || ||

|-

| style="; text-align:left;" | Length: || || ||

|-

| style="; text-align:left;" | Height: || || ||

|-

| style="; text-align:left;" | Wing area: || || ||

|-

| style="; text-align:left;" | Wing loading: || 219.22&nbsp;kg/m<sup>2</sup> (44.9&nbsp;lb/ft<sup>2</sup>) || 219.70&nbsp;kg/m<sup>2</sup> (45&nbsp;lb/ft<sup>2</sup>) ||

|-

| style="; text-align:left;" | Empty weight: || || ||

|-

| style="; text-align:left;" | Loaded: || ||

|-

| style="; text-align:left;" | Maximum: || || ||

|-

| style="; text-align:left;" | Useful load: || || ||

|-

| style="; text-align:left;" | Fuel capacity: || colspan="3" align="center"| T-Stoff = <br> C-Stoff =

|-

|- style="vertical-align:top; text-align:center; background-color:#ccc;"

| colspan="4" | Armament

|-

| style="; text-align:left;" | Gun:

| 2 × Type 5 30 mm autocannon

| 1 × Type 5 30 mm autocannon

| 2 × Ho-155 30 mm autocannon or 2 × Ho-5 20 mm autocannon

|-

| style="; text-align:left;" | Capacity: || colspan="3" align="center"| 53 rounds per gun

|-

|- style="vertical-align:top; text-align:center; background-color:#ccc;"

| colspan="4" | Performance

|-

| style="; text-align:left;" | Powerplant: || colspan="3" align="center"| One Toku-Ro.2 (KR10) bipropellant rocket engine developing of thrust

|-

| style="; text-align:left;" | Liquid-propellant: || colspan="3" align="center"| T-Stoff = 80% hydrogen peroxide + 20% water with oxyquinoline and pyrophosphates <br> C-Stoff = 30% hydrazine hydrate + 70% methanol, water and potassium cyanocuprate catalyst

|-

| style="; text-align:left;" | Max speed: || colspan="3" align="center | at

|-

| style="; text-align:left;" | Cruise speed: || || ||

|-

| style="; text-align:left;" | Landing speed: || || ||

|-

| style="; text-align:left;" | Range: || three minutes and six seconds<br> of powered flight || || two minutes and 30 seconds<br> of powered flight

|-

| style="; text-align:left;" | Max range: || five minutes and 30 seconds<br> of powered flight || || seven minutes<br>of powered flight

|-

| style="; text-align:left;" | Climb: || <br>in 40 seconds <br><br>in two minutes and eight seconds <br><br>in three minutes and eight seconds <br><br>in three minutes and 50 seconds || || <br>in three minutes and 40 seconds

|-

| style="; text-align:left;" | Rate of climb: || || ||

|-

| style="; text-align:left;" | Ceiling: || colspan="3" |

|-

|}

See also

References

Citations

Bibliography

  • .

Further reading

  • JNAF pics.1
  • JNAF pics.2
  • U-boat forum