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Wednesday, January 24, 2018

Mizuno Jinryū and Shinryū - The Divine Dragon I and II

Every so often, I come across a bit of Japanese historical info from WWII, that makes me wonder just why I hadn't heard of it before.

There are actually two aircraft given the designation of the "Divine Dragon", the Mizuno Jinryū and the Mizuno Shinryū II.

In both instances, both Jinryū and Shinryū are translated to "Divine Dragon", with Mizuno being the manufacturer.

In case you are wondering, THIS Mizuno is the very same as the Mizuno that makes excellent sporting goods. They also made sporting goods before the war, including gliders, which was why, during WWII, it was subverted to try and construct warplanes.

Whether it’s dragons, Mount Fuji (Fuji-yama) or effing cherry blossoms, the Japanese have a fascination for it… or maybe they have a fascination for it because everyone tells them they should have a fascination for it. Tail wagging the dog.

So, should it come as any surprise that there was a WWII plane you’ve never heard of that uses the name Dragon?

I’ve already written about one with the cherry moniker - HERE.


With Allied forces bombing Japan starting in June of 1944 with the Boeing B-29 Superfortresses, it began to seek out ways to better protect itself.

The B-29’s were on bombing runs trying to target key Japanese cities to annihilate its infrastructure and industries.

Japan’s Dai-Nippon Teikoku Kaigun Koukuu Hombu (海軍航空本部, Imperial Japanese Navy Air Service) came up with the need for the Mizuno Shinryū II.

Wait… the second one? What about the Mizuno Jinryū?

Initially, in November of 1944, when things were already bleak for Japan during the war, the Navy began to consider suicide flights… one-way flights.

Feeling that perhaps “silent but deadly” could be the solution, the Navy considered using a glider as the aircraft.

Now… a glider still needs to be towed up into the air… but the Navy said nu-uh, and said it wanted strap on some rocket boosters!

Yeah, man… and we can fire the gliders from hidden caves, and then the aircraft, which would be carrying a 100 kilogram (220 pound) explosive bomb, could be flown by a pilot right into Allied boats. Yeah. That’ll show’em not to mess with Japan.

Rocket powered gliders. Fug me. It sounds childish, doesn’t it… and then when you add in the part where it’s only a one-way trip… and we know the Japanese did use kamikaze (神風, divine wind) attacks somewhat successfully.

It was the duty of the Dai Ichi Kaigun Koku Gijutsu-shū at Yokosuka-shi (横須賀市, Yokosuka City) a city in Kanagawa Prefecture, to turn this Wile E. Coyote plan into something… because to me… a rocket propelled glider is something even the Acme Corporation might not want to sell, and they sold the Acme Bat-Suit glider… even they didn’t have rocket’s propelling it… just flapping.


Sakakibara Shigeki (surname first) was pressed to lead the various teams who would each be responsible for one part of the glider, for example, one team was to design the wings, another the fuselage, etc.

By this time in the war, Japan was reeling financially, and for that reason, the design team was told to build the glider using as much wood as possible, rather than the tougher to get ahold of metal.

Akita Yoshio (surname first) designed most of the glider by May of 1945, and by this time the Mizuno Corporation, which had experience in the construction of gliders, had nearly finished the prototype.

The initial concept was sent to the Imperial Navy who rejected it saying changes were needed. Luckily the design changes weren’t too bad, and the design was approved.

As of mid-June 1945, work began on the airplane now called Jinryū.

Because time was definitely of the essence, the finalized blueprints and work plans for the Jinryū were drawn up even as the components for the first prototype were being built.

Mizuno built two prototypes, finishing it and performing the Jinryū’s first test flight even before wind tunnel results had been presented.

That first flight was performed by test pilot Narabayashi Tashiichi (surname first), taking off from an airfield in Ishioka-shi, Ibaraki-ken.

The Jinryū was towed into the air by a Tachikawa Ki-9 (known to the Allies as Spruce) that was piloted by Fujikura Saburo, who (despite being the towing pilot) had flown gliders before the war.

Test 1 was to assess the Jinryū's handling, which was deemed by Narabayashi as stable with good handling characteristics.

Test 2 assessed the glider’s diving ability. From an altitude of 2,300 meters (7,545 feet), Narabayashi tried to release the tow rope from the Ki-9 - but it was stuck, forcing him to cut the rope to continue with the test.

During the dive, the Jinryū hit 300 kilometers per hour (186 miles per hour), but the aircraft began to vibrate so violently that Narabayashi couldn’t read the other gauges, and so had to reduce speed (pulling up). The team later determined that the tail needed better reinforcing, and the vertical stabilizer was too small, and was rectified by adding a second stabilizer and strengthening to the tail.  

Test 3 - powered flight. The Jinryū was modified to accept a group of three Toku-Ro I Type I rocket engines that combined would produce 661pounds of thrust during a 10-second burn.

During the tests, the rockets were found wanting, with inconsistent burn times, or simply failing to ignite.

Narabayashi  felt that as constituted, the aircraft was a failure, and should be reconfigured, taking his concerns to Major Suganuma who was in charge of the Jinryū project

He suggested it use six engines capable of supplying a 30-second burn that could help the Jinryū reach a speed of 750 kilometers per hour (466 miles per hour).

He also thought that instead of the single 100 kilogram bomb, it could carry 10 explosive charges adapted from artillery shells, which would enable it to be used against tanks and ships, as well as its original design target, the B-29 bombers.

Major Suganuma took Narabayashi's ideas and had a new team redesign the Jinryū to be an actual interceptor aircraft, rather than as a rocket-propelled glider - all good considering Suganuma had access to rocket engines that promised 32 second burn times.

Two people from the Jinryū project were kept, with everyone else replaced: lead designer Sakakibara; and Tonsho Yoshio (surname first) to oversee construction of the prototype.

Murakami Yujiro (surname first) would work on testing the aerodynamics of the Shinryū II.

Sakakibara would use a canard design (that's what it's called when you have those extra sets of wings near the front of the aircraft), the second such Japanese airplane after the Kyushu J7W Shinden.

The main wings had what is known as cropped delta (not a perfect triangle), which combined with the canard design would provide more stability during flight, and provide easier handling for the pilot - even m,ore important since by this time in the war, the pilots remaining were hardly the most experienced. 

Since the average Japanese pilot had little experience with canard-equipped aircraft, the Shinryū II had spoilers fitted into the top of each main wing which could rotate and help control the aircraft if the mechanism for controlling the spoilers was damaged, automatically returning to the closed position.

The airplane's powerplant featured four Toku-Ro I Type 2 rocket engines located in the rear of the fuselage, each capable of providing a 30-second burn time and a combined 600 kilograms (1,322 pounds) of thrust.

Two of these rockets would be utilized to get the Shinryū II airborne, while the others woulkd be used during the attack.

Now when strapping rockets to one's butt, it's going to get hot, so the team came up with two options:

1) an air-cooled combustion chamber that would have required an air inlet using a bayonet mechanism in order to maintain air flow across the chamber. It needed specific positioning of the fuel injectors so as not to have the air flow disrupt the injection process.
2) use of injectors to spray a water and alcohol mixture onto the rocket nozzle to cool it.

The water/alcohol system was the simplest, and was chosen.

For take-off, skids were used - not wheels. Landing? Who cares? Skids were also good enough for the Wright Brothers. Besides, are we so sure that the pilot is coming back?

Well, just in case, a nose skid was provided with a basic spring suspension to absorb the landing forces.

Under each wing was a non-sprung skid arrangement supported by two struts.

For take-off the Shinryū II was to use two wheeled dolly similar to the one used by the Mitsubishi J8M Shūsui, which could be jettisoned when airborne.

Because the Shinryū II was still made to intercept B-29 bombers which could fly to 10,241 meters  (33,600 feet), the cockpit was going to be pressureized, or if that proved too expensive (or added too much weight), the pilot could wear a pressure suit.

The Shinryū II was to be armed with eight rockets: attached to the inside of the rear landing skid arrangement were four tubes, one on top of the other and angled downwards, which contained the rockets.

It is surmised that if all the rocket weapons were used, the pilot had the option of also utilizing the fused explosive warhead contained within the aircraft's nose, at which point the pilot should try and crash the Shinryū II into his target.

Shinryū II  Specifications
  • Crew: 1;
  • Length: 7.60 meters (24.9 feet);
  • Wingspan: 7 meters (22.9 feet);
  • Height: 1.80 meters (5.9 feet);
  • Wing area: 11 square meters (118.4 square feet);
  • Empty weight: n/a;
  • Loaded weight: n/a (n/a);
  • Powerplant: four Toku-Ro I Type II, solid-fuel rockets, 330 pounds of force each;
  • Maximum speed: 300 kilometers per hour (186.4 miles per hour);
  • Cruise speed: 110 kilometers per hour (68.4 miles per hour);
  • Range: four kilometers (1.25 miles);
  • Service ceiling: 400 meters (1,312.34 feet);
  • Rockets: 8 x unguided rockets;
  • Bombs: 1 × 100 kilogram (220.46 pounds) explosive warhead in the nose;
  • Charges: 10 × charges adapted from 100mm artillery gun shells;
  • Guns: 4 × 30 mm Type 5 cannon  - this is just a guess.
The Mizuno Shinryū II was never completed, thanks to the surrender by Japan.

While there were five Jinryū gliders built, none were utilized in battle.

Because neither the Jinryū nor the Shinryū II were given military designation codes, the final name of the aircraft is subjective.

Andrew Joseph

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