Warplanes of Japan: Mitsubishi J8M Shusui

Mitsubishi J8M Shusui

(I(JAAF Photo)

Mitsubishi J8M1 Navy Experimental 19-Shi Rocket-Powered Interceptor Fighter Shusui (Sharp Sword).

The Mitsubishi J8M Shūsui (Japanese: 三菱 J8M 秋水, literally "Autumn Water",used as a poetic term meaning "Sharp Sword" deriving from theswishing sound of a sword) is a Japanese World War II rocket-poweredinterceptor aircraft closely based on the German Messerschmitt Me 163 Komet.Built as a joint project for both the Navy and the Army Air Services, it wasdesignated J8M (Navy) and Ki-200 (Army).

The J8M1 was intended to be a licence-built copy of the Messerschmitt Me 163Komet. Difficulties in shipping an example to Japan meant that the aircrafteventually had to be reverse-engineered from a flight operations manual andother limited documentation. A single prototype was tested before the end ofWorld War II.

The Japanese were aware of the results of the strategic bombing of Germany, andknew that the B-29 Superfortress would be bombing Japan and the resultantproblems which would arise from trying to combat this. Japanese militaryattachés had become aware of the Komet during a visit to the Bad Zwischenahnairfield of Erprobungskommando 16, the Luftwaffe evaluation squadron chargedwith service test of the revolutionary rocket-propelled interceptor. Theynegotiated the rights to licence-produce the aircraft and its Walter HWK 509Arocket engine. The engine licence alone cost the Japanese 20 million Reichsmarks(equivalent to 81 million 2021 euros). The agreement was for Germany to provide the following by spring 1944:

Complete blueprints of the Me 163B Komet and the HWK 509A engine. One complete Komet; two sets of sub-assemblies and components. Three complete HWK 509A engines. Inform Japan of any improvements and developments of the Komet. Allow the Japanese to study the manufacturing processes for both the Komet andthe engine. Allow the Japanese to study Luftwaffe operational procedures for the Komet.

The broken-down aircraft and engine were sent to Kobe, Japan in early 1944. It is probable that the airframe was on the Japanese submarine RO-501 (ex-U-1224), 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 USS Bogue. 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 bythe submarine USS Sawfish on 26 July 1944, near the Philippines, after leaving Singapore.

The Japanese decided to attempt to copy the Me 163 using a basic instructional manual on the Komet 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 Imperial Japanese Army Air Service (IJAAF)/Imperial Japanese Navy Air Service (JNAF) venture. The IJAAF wanted a new design to be drawn up. The IJNAF, on the other hand, felt the design should mimic the German Komet because it had already proven to be a stable aerodynamic body. It was the IJNAF which won and issued the 19-shi specification in July 1944 for the design of the rocket-powered defence fighter. The contract went to Mitsubishi Jukogyo KK, which would produce both the IJNAF version, the J8M1 Shūsui and the IJAAF version Ki-200. The project was headed by Mijiro Takahashi. The JAAF, however decided toundertake their own design to meet the 19-shi specifications, working at their Rikugun Kokugijitsu Kenkyujo (JAAF Aerotechnical Institute) in secret.

At the 1st Naval Air Technical Arsenal in Yokosuka, in association with Mitsubishi and Yokosuka Arsenal, work began to adapt the Walter HWK 509A engineto Japanese manufacturing capabilities and techniques. This was also where efforts were underway to produce a glider version of the J8M to provide handling data. While working on this glider, the MXY8 Akigusa (秋草, "Autumn Grass"), Mitsubishi completed a mock-up of the J8M1 in September 1944.

Both the JAAF and JNAF approved its design and construction and a prototype wasbuilt. In December 1944, the MXY8 was completed and, on 8 December 1944, at the Hyakurigahara Airfield, Lieutenant-Commander Toyohiko Inuzuka took the controlsof the MXY8. Once in the air, Inuzuka found the MXY8 almost perfectly emulated the handling characteristics of the Komet. Two additional MXY8 gliders were constructed in the naval yard at Yokosuka, one being delivered to the Rikugun Kokugijitsu Kenkyujo (JAAF Aerotechnical Institute) at Tachikawa forevaluation. The JNAF initiated the construction of another prototype,production designation Ku-13. This was to use water ballast to simulate the weight of an operational J8M complete with engine and weapons. This variant wasto be built by Maeda Aircraft Institute, while the IJAAF version was to beconstructed by Yokoi Koku KK (Yoki Aircraft Co). The IJNAF also proposed a moreadvanced trainer, designated the MXY9 Shūka (秋火,"Autumn Fire") which would be powered by a 2 kN (450 lbf) thrust Tsu-11 ducted-fan engine. The war, however, ended before this model could bebuilt.

Mitsubishi and partners Nissan and Fuji proceeded with development of the airframe and Yokosuka Arsenal was adapting the engine for Japanese production, designated the Ro.2. The Japanese succeeded in producing prototypes thatoutwardly looked very much similar to the Komet. The J8M1 had a wet weight that was 400 kg (880 lb) lighter, the aircraft having a plywood main spar and wooden vertical tail. The designers had also dispensed with the armoured glass in thecockpit and the aircraft carried less ammunition and slightly less fuel.

The Ki-200 and the J8M1 differed only in minor items, but the most obvious difference was the IJAAF's Ki-200 was armed with two 30 mm (1.18 in) Type 5 cannon (with a rate of fire of 450 rounds per minute and a muzzle velocity of 920 m/s (3,000 ft/s)), while the J8M1 was armed with two 30 mm (1.18 in) Ho-105cannon (rate of fire 400 rounds per minute, muzzle velocity 750 m/s (2,500ft/s). The Ho-105 was the lighter of the two and both offered a higher velocity than the MK 108 cannon of the Me 163 (whose muzzle velocity was 520 m/s (1,700ft/s). The Toko Ro.2 (KR10) rocket motor did not offer the same thrust rating as the original, and Mitsubishi calculated that the lighter weight of the J8M1 would not offset this. Performance would not be as good as that of the Komet, but was still substantial.

The engine used the German propellants of T-Stoff oxidizer and C-Stoff fuel (hydrogen peroxide/methanol-hydrazine), known in Japan as Ko and Otsu respectively.

A total of 60 of the training version (Ku-13, Ki-13, MXY-8, MXY-9) were produced by Yokosuka, Yokoi and Maeda. Seven of the operational version (J8M1/Ki-200) were built by Mitsubishi.

On 8 January 1945, one of the two J8M1 prototypes was towed aloft, water ballast added in place of the fuel tank and rocket engine to test itsaerodynamics. The test flights confirmed the design. Training courses for JAAFand JNAF pilots began on the Ku-53 glider, which shared a similar configuration to the J8M1. The 312th Naval Air Group was selected to operate the first J8M1. Mitsubishi, Fuji Hikoki, and Nissan Jidosha all had tooling for mass production well into the advanced stages, ready to produce both the J8M1 and the J8M2 variant, which differed from the J8M1 in sacrificing one of the Type 5 cannon for a small increase in fuel capacity. The first J8M1 prototype to be equipped with the Toko Ro.2 (KR10) was ready in June 1945. They were then transferred from the Nagoya plant to Yokoku for final checks before powered flight testing, after final glide tests with the engine installed.

The J8M took to the air for its first powered flight on 7 July 1945, with Lieutenant Commander Toyohiko Inuzuka at the controls; after his "sharpstart" 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 400 m (1,300 ft), the engine stopped abruptly and theJ8M1 stalled. Inuzuka managed to glide the aircraft back, but clipped a smallbuilding 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 wereg rounded. The engine cutout had occurred because the angle of climb, coupled with the fuel tanks being half-filled for this first flight, caused a shifting of the fuel, which in turn caused an auto cutout device to activate because of an air lock in the fuel line. Requests to continue flight testing were denied pending the modification of the fuel pumps in the aircraft. The sixth and seventh prototypes were to be fitted with the modified Ro.2 engine.

Full-scale production readiness was almost at hand, and component construction was already underway. Flight testing was to resume, despite another explosion of the fuel mixture during a ground test days after the crash, in late August 1945 and the J8M2 design was finalized. But on 15 August 1945, the war ended for the Japanese and all work on the J8M ceased. The end of the war also spelled the end of the JAAF's Ki-202 Shūsui-Kai (Modified Shusui), 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 IJAAF in 1946, but no metal was cut before Japan's surrender.

Germany tried to send another Komet in U-864, but the submarine was sunk near Bergen by the British submarine HMS Venturer in February 1945.

As with many other Japanese fighter types combating air raids over Japan, the Ki-200 was considered for use in ramming attacks against B-29s. The envisioned mission profile was to make one or two firing passes and then, with the remaining energy, conduct a ramming attack. Any fuel left on board would most likely detonate, increasing the effectiveness of the attack, but also meaning the pilot had little chance of survival. Nevertheless, the cost was deemed to be worth it and plans were being drawn up to form a "Hagakure-Tai" (Special Attack Unit), similar to the German Sonderkommando Elbe, when the war ended.

Variants
Ki-200
An interceptor variant for the IJAAS, almost identical to the IJNAS J8M
J8M1
J8M2 Shūsui Model 21(?)
Long-range version for Navy, identical to J8M1, but armament reduced to asingle 30 mm (1.18 in) cannon.
J8M3 Shūsui Model 22 (Rikugun Ki-202 Shūsui-kai)
Long-range version for Army and Navy, with fuselage and wingspan lengthened to7.10 m (23 ft 3 in) and 9.75 m (32 ft 0 in) respectively. Powered by 19.6 kN(4,410 lbf) Tokuro-3, projected maximum speed 900 km/h (560 mph).
Yokosuka MXY8 "Akigusa" (Yokoi Ku-13)
Training glider using J8M airframe for Navy and Army.
Yokosuka MXY9 "Shuka"
Training version using J8M airframe, powered by Tsu-11 thermojet engine.
In November 1945, two aircraft were taken from Yokosuka to the United Statesfor evaluation aboard USS Barnes. FE-300/T2-300 (USA ident) (Japanese ident403) is now exhibited at the Planes of Fame Museum in Chino, California. 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 ina 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. (Wikipedia)

Mitsubishi J8M1 Navy Experimental 19-Shi Rocket-Powered Interceptor Fighter Shusui (Sharp Sword).  (IJAAF Photos)

(IJAAF Photos)

Mitsubishi J8M1 Navy Experimental 19-Shi Rocket-Powered Interceptor Fighter Shusui (Sharp Sword), Akikusa glider trainer.

(IJAAF Photos)

Mitsubishi J8M1 Navy Experimental 19-Shi Rocket-Powered Interceptor Fighter Shusui (Sharp Sword), (Serial No. 403), A25.  This aircraft was closely based on the German Messerschmitt Me 163 Komet.  This aircraft was shipped to the USA where it was designated USAAF FE-300.  It is now in the Planes of Fame Museum, Chino, California.  The Shusui was built as a joint project for both the Navy and the Army Air Services, it was designated J8M (Navy) and Ki-200 (Army).  Successful gliding tests were carried out, and one prototype was tested but crashed on take-off on 7 July 1945, and no further tests took place before the war ended.  A total of 60 of the training version (Ku-13, Ki-13, MXY-8, MXY-9) were produced by Yokosuka, Yokoi and Maeda.  Seven of the operational version (J8M1/Ki-200) were built by Mitsubishi.  

(Jeffrey G. Scism Photo)

(Alan Wilson Photo)

(Dustin May Photo)

(Sekinei Photo)

Mitsubishi J8M1 Shusui (Autumn Water) (Serial No. 403), USAAF FE-300, on display in the Planes of Fame Museum, Merrill Field, Chino, California.

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