The Survivors: Mitsubishi J8M Shusui – Imperial Japan’s Rocket Powered Interceptor

Just as the Allies were keen to gather as much information as they could on German rocket and jet technology during World War Two, the Japanese were likewise seeking this very same technology to aid their war effort. Their need was out of desperation, being constantly pounded by Allied bombing raids and rapidly losing territory they too looked towards any available Wunderwaffe (“wonder-weapon”) Germany could provide to try and stem the tide. Following a 1943 demonstration given to Japanese Army and Navy attaches in Germany, the diminutive, yet incredibly fast Messerschmitt Me-163 Komet rocket interceptor was one such weapon they wanted to pursue.

Mitsubishi J8M Shusui / Ki-200

The Mitsubishi J8M Shusui (“Autumn Water” which also relates poetically to “Sharp Sword” and the swishing sound a sword makes) was a joint Imperial Japanese Navy and Army project using the Messerschmitt Me-163 as a basis for the design (the army variant was designated Ki-200). The Japanese were meant to licence-build Me-163 variants but getting complete airframes and parts shipped by submarine proved problematic when the Japanese submarine RO-501 Satsuki (ex U-Boat U-1224) carrying a complete airframe and possibly the two sets of sub-assemblies was sunk by Allied ships en route in the Atlantic in May 1944. A second Japanese submarine I-29 Matsu with 3 rocket motors, blueprints and manufacturer manuals onboard made it to Singapore in July 1944 and the cargo was quickly flown to Japan (for redundancy purposes two submarines were used to split the airframe from the motors and manuals with RO-501 departing in March 1944 and I-29 in April 1944).

The Japanese then had to reverse engineer the aircraft using a flight operations manual and other documentation that had been provided under the deal with Germany (they paid Germany a 20 million Reichsmark licence fee for access to this technology! This was approximately $8 million USD). An impressive effort to develop such a radical piece of technology with few physical components to work from!

A captured Imperial Japanese Navy Mitsubishi J8M Shusui rocket interceptor in 1945
A captured Imperial Japanese Navy Mitsubishi J8M Shusui rocket interceptor in 1945 (USAF photo)
Toku-Ro.2 (KR10) bi-fuel rocket motor that powered the Mitsubishi J8M1
Toku-Ro.2 (KR10) bi-fuel rocket motor that powered the Mitsubishi J8M1

The Japanese developed their own variant of the German Walter HWK 109-509A rocket motor known as the Toku-Ro.2 (KR10). It was a bi-fuel rocket motor that produced 3,307 lb of thrust which was a little less powerful than the German motor (3,800 lb of thrust). The Toku-Ro.2 (KR10) enabled the J8M1 to reach a maximum speed of 900 km/h (559 mph) which was 59 km/h (37 mph) slower than the Me-163B production model. Regardless, it was still incredibly fast for the day!

The armament was also modified to include 2 x 30mm cannons of Japanese origin that had a higher muzzle velocity than the German Mk 108 30mm cannon (540 meters per second). The Imperial Japanese Army Ki-200 variant was fitted with Type 5 30mm cannons that had a rate of fire of 450 rounds per minute and a muzzle velocity of 720 metres per second. The Imperial Japanese Navy J8M1 was fitted with lighter Ho-105 30mm cannons that provided a rate of fire 400 rounds per minute with a muzzle velocity of 750 metres per second. Japanese radios and batteries were also fitted and although similar in appearance to the Me-163 the airframe of the J8M varied slightly to accommodate the different equipment fitted.

The slight variations in the German Messerschmitt Me-163B Komet (production variant) and the reverse engineered Mitsubishi J8M1 are quite evident, especially the cockpit canopy
The slight variations in the German Messerschmitt Me-163B Komet (production variant) and the reverse engineered Mitsubishi J8M1 are quite evident, especially the cockpit canopy (top – Luftwaffe Museum at Berlin-Gatow in 2010 and bottom – Planes of Fame, Chino 2015)

7 J8M production aircraft were manufactured by Mitsubishi before the end of World War Two. The first J8M1 was completed in December 1944 (quite fast considering the I-29 submarine only arrived in Singapore in July 1944) but a working rocket motor was not available until July 1945. The variants were the J8M1/Ki-200 for the IJN/IJA, the J8M2 for the IJN with a longer range and only 1 x 30mm cannon, and there was also the planned J8M3/Ki-202 for the IJN/IJA which had an extended fuselage, extended wings and a longer range.

Given the radical leap in performance and handling from traditional piston engine fighter aircraft to a tailless rocket powered interceptor, up to 50 – 60 Kugisho / Yokosuka MXY8 / Ku-13 Akikusa (“Autumn Grass”) wooden glider variants were produced for pilot training and unpowered flight testing. The first glider flew on December 8th, 1944.

Akikusa training variants of the Mitsubishi J8M
Akikusa glider training variants of the J8M
A damaged and seemingly abandoned MXY8 training glider circa 1945
A damaged and seemingly abandoned MXY8 training glider circa 1945

Despite the issues experienced in Germany the Japanese continued with the J8M program and used the same highly volatile German propellants of T-Stoff oxidizer (hydrogen peroxide) and C-Stoff (methanol-hydrazine) to create rocket fuel which was highly explosive, highly corrosive and deadly to touch. They were known as Ko and Otsu in Japanese.

Like the Me-163 the J8M1 had enough fuel for around 7.5 minutes of powered flight. As with the Me-163 it was designed to jettison the wheels after take-off and the plan once operational would have been for it to get there fast, hit the Allied bombers hard, then glide back to land on the skid and hopefully get home alive without any explosions (if the volatile fuel was onboard there was always a high risk of explosion, especially during landing)!

The first unpowered flight of an Imperial Japanese Navy J8M1 Shusui was completed on January 8th, 1945 (the aircraft used were known as “heavy gliders” to differentiate them from the Akikusa gliders). Then the first powered flight of a J8M1 was conducted on July 7th, 1945 but a fuel flow issue caused it to lose control and crash, bursting into flames (that fuel was volatile) and the aircraft was damaged beyond repair. 1 day later pilot Lieutenant Commander Toyohiko Inuzuka died from his injuries sustained in the crash. Shortly after the crash 2 more rocket motors exploded on ground testing, leaving only 1 rocket motor available which was owned by the Japanese Imperial Army.

Imperial Japanese Navy Mitsubishi J8M Shusui rocket interceptor possibly being prepared for its first powered flight on July 7th, 1945
Imperial Japanese Navy Mitsubishi J8M Shusui rocket interceptor possibly being prepared for its first powered flight on July 7th, 1945

These setbacks along with ongoing Allied bombing of the factory obviously delayed the production of airframes and the flight test program. One month later the atomic bombs were dropped on Hiroshima (August 6th, 1945) and Nagasaki (August 9th, 1945) and a few days later Japan agreed to surrender. Japanese representatives formally signed the unconditional surrender document aboard the USS Missouri on September 2nd, 1945 and with only 7 airframes completed, that was the end of the J8M program (unrealistically they had apparently planned to produce at least 3,600 J8M/Ki-200 variants by March 1946!).

Only 2 Mitsubishi J8M1 Shusui survive today. 1 is in the United States and the other in Japan. To date I have only seen the Chino example in person. It is interesting to see it in its orange livery (the IJN painted training and prototype aircraft in this highly visible scheme) and makes you think about the extreme efforts Germany and Japan had to take to implement such a dangerous and desperate project (I can only imagine what would have happened with such aircraft on Kamikaze missions)!

Planes of Fame Air Museum in Chino, California has a complete original captured Imperial Japanese Navy J8M1 on display. It was 1 of 2 bought back from Japan in 1945 for evaluation by the USAAF and US Navy respectively (neither were eventually flown). The other J8M1 was scrapped by the US Navy sometime after October 1946.

From the Land of the Rising Sun - the only surviving fully original Mitsubishi J8M1 Shusui rocket powered interceptor at the Planes of Fame Museum in Chino, California
From the Land of the Rising Sun – the only surviving fully original Mitsubishi J8M1 Shusui rocket powered interceptor at the Planes of Fame Museum in Chino, California (photo taken in 2015)
Mitsubishi J8M1 Shusui rocket powered interceptor at the Planes of Fame Museum in Chino, California (photo taken in 2015)
Mitsubishi J8M1 Shusui rocket powered interceptor at the Planes of Fame Museum in Chino, California (photo taken in 2015)
Mitsubishi J8M1 Shusui in the trainer/prototype orange livery of the Imperial Japanese Navy at the Planes of Fame Museum in 2015
Mitsubishi J8M1 Shusui in the trainer/prototype orange livery of the Imperial Japanese Navy at the Planes of Fame Museum in 2015
Mitsubishi J8M1 Shusui rocket powered interceptor at the Planes of Fame Museum in Chino, California (photo taken in 2015)
Mitsubishi J8M1 Shusui rocket powered interceptor at the Planes of Fame Museum in Chino, California (photo taken in 2015)
Mitsubishi J8M1 Shusui rocket powered interceptor at the Planes of Fame Museum in Chino, California (photo taken in 2015)
Shusui – the swishing of a sword through the air
Mitsubishi J8M1 Shusui rocket powered interceptor - the Japanese licence-built version of the Me-163 (Planes of Fame Museum in 2015)
Mitsubishi J8M1 Shusui rocket powered interceptor – the Japanese licence-built version of the Me-163 (Planes of Fame Museum in 2015)

The Mitsubishi Heavy Industry Museum at the Komaki Plant near Nagoya, Japan has an interesting J8M1 on display. In the 1960’s the incomplete, damaged J8M1 airframe was discovered in a cave in Japan (a bit different from the normal “barn find”). Until 1999 it was displayed as it was at a Japanese Air Self Defense Forces (JASDF) base near Gifu. Mitsubishi began a restoration project in 1999 and today it is on display at the Mitsubishi museum in a light green livery but only the fuselage is original, the remainder is made up of replica parts.

Mitsubishi J8M1 at the Mitsubishi Heavy Industry Museum (photo by FOREST-Chan)
Mitsubishi J8M1 at the Mitsubishi Heavy Industry Museum (photo by FOREST-Chan)

The Mitsubishi J8M1 Shusui provides another interesting yet flawed chapter in aviation history. Rocket powered aircraft were still experimented with in the early years of the Cold War but ultimately jet technology proved to be the way to go forward.

References:

Combined Fleet – Mitsubishi J8M

Military Factory – Mitsubishi J8M

Tails Through Time – Mitsubish J8M

The Aero Historian – February 2008

Wikipedia – Mistubishi J8M

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8 thoughts on “The Survivors: Mitsubishi J8M Shusui – Imperial Japan’s Rocket Powered Interceptor

  1. Another great post – thanks for sharing! I guess we have to be thankful on many levels that this technology wasn’t available to the Japanese earlier – to me the obvious solution to the problems they had with powered flight and landing was to adopt them as kamakaze weapons, with tragic outcomes for the pilot and his family, along with the losses caused – with their own grief and tragedy for victims and families – on their targets.

    As an aside, the U-boat traffic between Germany and Japan was slight but important – there is a story here in NZ of U-862, which ran the blockade from Norway in late 1944 and reached Singapore with a cargo of mercury and other materials the Japanese needed. Its return to German waters with an equivalent cargo of Nazi necessities was delayed by a venture into Australasian waters, including a night cruise, on the surface, past my home town of Napier. The crew could scarcely believe what they saw: a town in full peacetime rig, with what they thought were dancers in sea-front cafes (I think it was skating on a rink on the foreshore – I checked…). They attacked a ship that left Napier harbour, the torpedo missed, and were recalled to Singapore, where the boat was then drawn into the IJN. I later spoke to the daughter of one of the crew, who told me her Dad had been relieving himself off the side, saw the torpedo track and reported it – only to be rubbished, because no enemy could possibly be in New Zealand waters at this stage! Off-topic I know… but I wanted to share… There are many wonderful stories of this nature that haven’t been told… 🙂

    Liked by 1 person

    1. Thanks. It is quite fascinating how far they travelled in U Boats across all oceans. There are plenty of sunken ships along the US Atlantic coast that were nice backlit targets from lights on the coast!

      Liked by 1 person

    1. Thanks. Yes they experimented with a number of German aircraft but this was the main one that went into full development (they did also build a jet fighter that was similar in appearance to the Me 262 but it was not a licence built variant – Nakajima Kikka – it was smaller and had straight wings)

      Liked by 1 person

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