Japanese Jet Engines of WWII
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QAZ
Interested in Japanese jet development during WWII
It looks like a 7 stage compressor. I would say BMW 003, but the character ネ can be seen below. But it resembles BMW 003 extremely.
I think that Ne-230 drawing has never been recovered.
Maybe just 2nd Ne-130 diagram with different angle and scale. It's strange.
It looks like a Ne-130 with some ducting and a “spinner” housing a starter motor. Perhaps QAZ could answer this question?
@QAZ
QAZ
Interested in Japanese jet development during WWII
It looks somewhat like a rough BMW 003 diagram. If the scale is correct it can't be Ne-130. The only option would be Ne-230, but it's strange because this drawing is related to the discovery of Ne-230 parts. In the articles, it was said that the drawing of Ne-230 could not be found for reference, only 130 and 330.
blackkite
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QAZ
Interested in Japanese jet development during WWII
It's 2 nozzles and 1 nozzle cover, so one nozzle can be covered while the other is missing. "Nozzle cover" is interesting though, whether it could be a rear nacelle part of the 'Karyuu', or just another part of the jet engine beneath the outer nacelle.
By the way, regarding the 'unknown engine', I tried doing measurements assuming it is Ne-230 by overlaying the side profile of the actual Ne-230 nozzle, and the dimensions were about the same. However, without being able to verify if it is really Ne-230, it is just speculation, and in my opinion, it's only a cruder drawing of Ne-130 in a different configuration. I believe Ne-230 drawings are currently lost.
The original poster said that the drawings are Ne-130.
Airborne2001
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Do we know when the submarines carrying information on the BMW 003 and the copy of the engine were sent? I know that we have info of when they arrived, but I am curious about their departure date.
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A quick internet search and browsing through some books, just brought up, that probably no actual
engine part ever reached Japan, and probably not even a full set of plans. Two attempts to bring examples
of new technology to Japan by Uboats still in 1945 failed. U 234 surrendered on the 15th of April 1945,
U 864 was torpedoed by HMS Venturer on the 7th of February 1945 (BTW, the only case in WWII, when
a submerged sub was sank by another submerged sub).
The only case, I found, where at least some data actually reached Japan, was I-29. It was torpedoed by
USS Sawfish on, but a surviving crew member (the only one ?) could save some documents. It had started
its journey on the 16th of April 1944.
engine part ever reached Japan, and probably not even a full set of plans. Two attempts to bring examples
of new technology to Japan by Uboats still in 1945 failed. U 234 surrendered on the 15th of April 1945,
U 864 was torpedoed by HMS Venturer on the 7th of February 1945 (BTW, the only case in WWII, when
a submerged sub was sank by another submerged sub).
The only case, I found, where at least some data actually reached Japan, was I-29. It was torpedoed by
USS Sawfish on, but a surviving crew member (the only one ?) could save some documents. It had started
its journey on the 16th of April 1944.
QAZ
Interested in Japanese jet development during WWII
None of the submarines ever arrived. The small BMW 003 cutaway was received when Eiichi Iwaya departed I-29 at Singapore and returned to Japan separately. The vast majority of data, and the examples were lost.
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Forgive me for the mistake in saying when they arrived since I know that they came under attack. So I-29 was the only one to successfully make it?
QAZ
Interested in Japanese jet development during WWII
I-29 was intercepted near the Philippines and sunk en route to Kure. Only some of the files on board survived with Eiichi Iwaya who departed at Singapore as previously mentioned.
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Kawanishi Baika
Would Japan have not surrendered after the atomic attacks over Hiroshima and Nagasaki in August 1945, the Allies would have been forced to land on the Japanese home islands. There were plans to carry out the invasion in two phases. The first step, known as ‘Operation Olympic’, aimed to occupy the south of Kyushu Island and should start on November 1st. The second one, ‘Operation Coronet’, would have consisted of landings on Honshu Island, to control the Tokyo plain, and it was planned for March 1946. The whole plan, ‘Operation Downfall’, required 5,000,000 men, 3,000 ships, 66 aircraft carriers, loaded with 2,649 aircraft, and all the airplanes in the 7th, 8th and 10th Army Air Forces. Casualties were expected to be extremely heavy. A study requested by U.S. Navy Secretary estimated that conquering Japan would cost between 1.7 and 4 million casualties including 400,000 to 800,000 fatalities and the destruction of 800 Allied ships.
The defensive plan of the Japanese High Command (Operation Ketsu-Go) included the use of the 12,725 airplanes available in one single and uninterrupted attack with the purpose of collapsing the defences of the Allied fleet. A force of 2,000 IJA and IJN Japanese fighters would battle to control the skies over Kyushu Island. While the Allied fleet would still be in open sea and approaching Japan, the warships of the Task Force would be attacked by 330 IJN suicide bombers, then a group of 825 IJA and IJN suicide airplanes would try to sink the troop transports. Once the invasion ships got close to their proposed anchorages, another 2,000 suicide aircrafts would be launched hour after hour in nonstop attacks which the Japanese hoped could be sustained for 10 days. Thirty five camouflaged airfields and nine seaplane bases had been built in Kyushu to that purpose. The Japanese also had 20 suicide take off strips with underground hangars, from where the Ki.115 Tsurugi and Baika Model 1 could operate.
The Ohka 43-Otsu would use some straight railway sections and rocket-propelled trolleys to operate. It was very effective but had the handicap of using the new Ne-20 turbojet of which just a few units were available. The Ki.115 could use several types of second hand conventional engines but it required 80 octane gasoline which was almost non-existent in Japan due to the naval blockade. On the other hand, the Ne-20 could work with a mixture of wood turpentine and charcoal, although the battered Japanese industry could not manufacture them in high numbers on time for Ketsu-Go.
The Japanese scientists found the solution to this situation with the mass production of pulsejet engines based on the Argus As 109-014 scale drawings that the I-8 submarine had brought from Germany in 1943. The Japanese version, known as Maru Ka-10 was designed by professors Ichiro Tami and Taichiro Ogawa of the Aeronautical Institute of Tokyo Imperial University in 1944. The Maru Ka-10 was 3,750 mm long, had 550 mm of diameter and weighted 153 kg, producing 360 kg of thrust at 740 kph. It used Benzol as fuel during the flying tests, although it could also work with low quality oil or heavy kerosene. It was expected that the operational version would burn 1,600 lt of crude pine root oil that the local chemical industry produced as ersatz fuel.
The Japanese did never receive the blueprints for the V-1 missile or for their manned variant Reichenberg as the German submarine carrying them was sunk. They were forced to design their own version based in a general description of the German model. The result was a small low wing monoplane made out of wood and steel, given the scarcity of aluminium. By the beginning of 1945 their mass production was ordered to the Kawanishi Kokuki K.K. firm, under the Baika denomination. The plan was to manufacture three different versions.
The first one was the Kawanishi Baika model 1 that took off from a conventional aerodrome reaching the ignition speed of the pulsejet (360 kph) thanks to the thrust of its three Toku-Ro.1 Type 2 rockets with 600 kg of thrust, located in the wing roots and in the fuselage centreline. Its main undercarriage (from a Ki.115) and the rockets (from an Ohka 43) were jettisoned after take-off. The high rate of fuel consumption of the pulsejet allowed a range of just 204 km at the cruise speed of 556 kph and sea level. The model 1 could only operate against troops transports located near the southern coast of Kyushu. To that purpose they planned to have a Type 97 warhead with 150 kg of Torpex H.E. (from a Type 91 mod.1 airborne torpedo) to impact under the ship waterline.
The Kawanishi Baika model 2 was the second version. During the WWII the Japanese used 46 submarines with capacity to carry different types of airplanes in deck watertight hangars. By August 1945 they still kept six of them: The I-14 (AM class) with a hangar of 4.2 x 21 m. able to house two Seiran bombers, the I-36 (B1 class) and the I-58 (B3 class) with a hangar of 1.4 m high, 2.4 m. wide and 8.5 m long where they could transport a Watanabe reconnaissance floatplane and the I-400, I-401 and I-402 of the Sen-Toku Class that had a hangar of 4.2 m. of diameter and 31 m long with capacity for two Saiun or three Seiran or four Ohka type 43-Ko.
These submarines were ideal to transport specialized suicide airplanes that could attack the enemy fleet in their bases of Ulithi, Pearl Harbour, the west coast of USA or even when they were crossing the Panama Canal. They could be refuelled during the trip by the I-402, specially modified as tanker to that purpose. The I-400 could even reach New York and Washington going round South America from the south in a four months journey. Would the Allies have used poison gas against Iwo Jima in February 1945, New York could have been attacked in June using Type 7 bacteriological bombs, launched from six Seiran airplanes carried by the Sen-Toku submarines.
To compete against the Ohka type 43-Ko, the Kawanishi firm designed a Baika model 2 version to be launched from submarines. To facilitate their storage it was considered convenient to reduce their length in 63 cm moving forward the support structure of the pulsejet. The clear cockpit opened sliding forward. The wings were built in such a way that could be folded backwards, like in the Seiran, and put back in flying position very quickly using a hydraulic mechanism connected to the submarine. The warhead was a general purpose 250 kg bomb with nose priming plug and rear impact fuse.
The Baika model 2 used the same launch system than the Ohka type 43-Ko. It was positioned over a launch cart of 700 kg at the end of a catapult (26 m length, 116 cm track and 3º30’ pitch) shot by a 90-150 kg/sq. cm compressed air device coming from the torpedo launch system of the submarine. A buffer cable was used for decelerating the launch cart that was quickly stored under the deck. The four airplanes of a Sen-Toku could be launched within 20 minutes. The time required was of 6 min 23 sec for each from the oldest submarines.
The last version of the Baika was the model 3. One of the main reasons of the operational failure of the Ohka model 11 was the excessive weight of their warhead which had been designed for the single shot destruction of major warships.
To cover this gap, the Kawanishi firm designed an air launched variant of the Baika. Instead of solving the problem of integration with the Ginga by reducing the wingspan, so that it could be housed between the main undercarriage legs, the manufactured airplane weighted half the weight of an Ohka 11 and could be installed in a more rearward position within the Ginga bomb bay. To allow the ignition of the pulsejet during flight, it should be exposed to the air stream outside the carrier airplane. Its original location was therefore moved to below the fuselage centreline of the Baika. Although the cruise speed of the model 3, when launched from 6,100 m, was of just 481 kph, it started a shallow dive at 556 kph until being intercepted by the fighters flying at 600 kph. It then increased the dive angle until reaching 740 kph passing under the fighters screen and going to the target at sea level, impacting under the waterline, or climbing at 450 m to go down over the ship deck in a 75º dive, depending on the type of warhead used.
At this point of time the Japanese were no more interested in sinking the big heavily armoured warships. The political circumstances were more favourable to the kind of war that caused a high number of casualties to the Allies. It was better to try and destroy the little protected troop transports with a warhead of just 250 kg.
Kugisho MXY7 Ohka
The Ohka 43-Ko carried the same warhead (version of 800 kg) than the Ohka Model 33 but without the nose priming plug. Its fuel tank capacity was of 400 litres and it was located between the warhead and the main spar. The oil tank of 16 litres was between the pilot seat and the turbojet. It could reach targets placed 278 km from the launch point.
The ‘Ko’ version did not use auxiliary dive rockets. It released the folding wingtips by means of electrically activated explosive bolts, during the terminal dive to increase its speed. It was expected that it could surpass the 900 kph when reducing its wingspan to just 2.6 m. At this stage control was obtained by using the tail surfaces that could move in differential mode to act as ailerons. In normal configuration, the Model 43 had 13 sqm of wing surface, 4º 30' of dihedral angle and 2º 30' of tail plane incidence.
The ‘Otsu’ version was designed to take off from a 110 m length straight railway section and hide in the railway tunnels with its wings folded. Developed to avoid the use of conventional aerodromes in a situation of complete aerial superiority of the enemy, it was inspired by the launch procedure of the Messerschmitt P.1079 (July 3, 1942). The idea was to use it in a long range coastal artillery role to counteract the invasion of southern Kyushu, or ‘Olympic Operation’, which was expected to happen on November 1, 1945.
The Model 43-Otsu used a launch cart for take off similar to one used by the naval version but propelled by two Toku-Ro.1 Type 2 rocket engines with 600 kg thrust each and 30 seconds of life and by the power of its own Ne-20 turbojet. At the end of its run the cart was detached and braked by a cable and a counterweight system. At that moment, a third Toku-Ro.1 Type 3 rocket with 600 kg peak thrust and 20 seconds endurance automatically ignited. This was fixed to the fuselage centreline and its nozzle had an 8º 45' slope to make the thrust axis and the gravity centres of the Ohka converge, thus providing maximum lift.
The land version used the same warhead than the naval one but it was armed with two Type 3 machine guns of 13 mm with a rate of fire of 800 rpm located between the warhead and the fuel tank, which capacity had been reduced to 300 lt, and a combat range to 200 km. The guns configuration was inspired by the German air to air rocket bomber Sombold So 344 project and its objective was that the Ohka could break its way towards the Allies Task Forces fighting against the defensive fighters to which it was equal in speed. The ‘Otsu’ kept the mechanism to detach the wingtips of the naval version but was not considered a requirement to equip it with accelerator rockets for the terminal dive. It was expected that it would be able to surpass the 900 kph in a 50º dive with the Ne-20 at full throttle.
Nakajima Ki.115-Ko Tsurugi
Following the great loss of suicide airplanes during the American invasion of the Philippines, the IJA requested Nakajima to design an expendable suicide bomber on January 20, 1945. The mass production programme was known as Kokoku Heiki Go.3 and focused on the aircraft being easy to build by semi-skilled labour, using non-strategic materials and propelled by any surplus radial engine, with a power in the range between 800 and 1,500 hp.
The flight tests of the prototype started only seven weeks later, detecting serious problems of stability, poor handling and take off performance. The droppable landing gear was modified to improve its elasticity and equipped with drum brakes. Auxiliary flaps were attached to the trailing edge of the wing and anchor points for two Toku-Ro.1, Type 3 RATO rockets had to be fixed under the wings.
The Nakajima plants of Ota and Iwate assembled 104 aircrafts from externally supplied components between March and August 1945. All these aircrafts were powered by a Nakajima Ha-115-II engine of 1,130 hp, from the Ki.43-II-Otsu fighters, with one 2.9 m diameter, three bladed, fixed pitch propeller. The wing structure and cladding was still of light alloy in this first series, but in Nakajima they were studying the steel manufacturing techniques inspired on the German missile V-1. To facilitate construction, the fuselage had circular section and was fully made of steel. The tail surfaces were made of wood with control surfaces clad by fabric. The engine cowling was made of tin. The Ha-115 engine was fastened to the fuselage using four bolts only.
Designed to counteract the foreseeable invasion of Okinawa, taking off from the airfields to the south of Kyushu, the Tsurugi had a range of 1,200 km, ensured by two fuel tanks of 240 litres each positioned between the engine and the cockpit. In theory, it could even return to base or use only one tank, with the valuable 80 octane fuel, and fill the other tank with some kind of inflammable substance to magnify the destructive effect after the impact.
Partially recessed within the belly, the Tsurugi could transport one fixed antiship bomb of 250, 500 or 800 kg. The ’Ko’ version had a 8.6 m wingspan, 8.55 m length, 3.3 m high and 12.39 sq. m wing area. The maximum take off weight was of 2,630 kg and the estimated maximum speed of 551 kph.
When flights tests ended in June, it was made apparent that the aircraft was not suited for its use in combat by poor trained pilots, even after the modifications, and could not be used in the Battle of Okinawa.
Nakajima Ki.115-Otsu Tsurugi
This new version was designed to correct the handling problems experienced with the Ki.115-Ko by increasing the wingspan up to 9.69 m and the wing surface to 14.49 sq. m. Only nine units were built before the end of the WWII. They were propelled by a Mitsubishi Ha-112 engine of 1,500 hp, used by Kawasaki Ki.100 fighters, providing a maximum speed of 620 kph.
The wings were of wood/plywood, with integrated flaps. The ailerons structure was of light alloy with cladding of fabric. The fuselage and tail surface were those of the Ki.115-Ko, rejected by the IJA. The range was reduced when one of the fuel tanks was removed, but this allowed advancing the position of the cockpit to improve pilot visibility during take off. Loaded with a Number 80, Model I, of 807.5 antiship bomb, the Otsu weighted 2,880 kg.
Nakajima Ki.115-Hei Tsurugi
The ’Hei’ version reached the project phase only. Specifically designed to counteract the expected invasion of Kyushu Island ‘Operation Olympic’ this aircraft would enter into action when the transports of Allied fleet would be at a distance of 290 km from the beaches.
The ‘Hei’ was basically a version of the ‘Otsu’, entirely built of wood/plywood. Considering the short range of the flight and the generalised shortness of petrol, the size of the fuel tank was reduced (possibly down to 120 litres) and the pilot seat moved further to the front.
As it was expected that some pilots could be recovered, to take part in further attacks, the ‘Hei’ was equipped with a bomb release system that possibly was the same used by the Zeros for the Number 50 Model 2 of 507 kg antiship bomb.
Showa Toka
It was the version of the Ki.115-Ko for the IJN, with some modifications acquired from the Ki.115-Otsu. The flaps were modified as dive brakes, it had a single 450 litres fuel tank and the front cockpit was moved forward, as well as some additional naval equipment: an RT radio set to communicate with the guiding aircrafts, two under wing Toku-Ro.1 Type 3 with 600 kp peak thrust RATO rockets and two under wing iron tube launchers for I.S.R. 12 cm barrage rockets.
The Toka was designed to use different surplus engines: Kotobuki 41 of 785 hp, from the A5M Claude fighters; Sakae 12 of 1,130 hp, from the A6M2 Zeros; Zuisei 12 of 875 hp, from the C5M Babs; Kinsei 41 of 1,075 hp, from the G3N bombers; Kinsei 53 of 1,300 hp, from the H6K flying boats.
It had the same wingspan than the Ki.115-Ko, but the wing area was increased up to 13.10 sqm. A study by Nakaijma stated that the Toka could not transport 800 kg bombs, due to the additional weight of the naval equipment. It was expected to manufacture 850 units during the second half of 1945, using construction systems that required only 10 percent of the man hours needed for the Zero. Its empty weight was 1,700 kg.
The IJN also considered the possibility of manufacturing a version of the Toka entirely made of wood and possibly inspired on the Ki.115-Hei.
Nakajima Ki.230
It appears to be a project based on the Ki.115-Otsu, made of wood, and able to carry a bomb of 250 or 500 kg. Underpowered by an engine Ha-115-I of 1,105 hp, from the Ki.43-I-Ko fighters, and with the same empty weight than the Toka, the Ki.230 required a wingspan increased up to 9.69 m and a wing area of 13.09 sqm to take off without the help of the RATO rockets. Its estimated maximum speed, with a bomb of 250 kg, was of 557 kph.
It was possibly intended to be used to mass attack the transports of troops during the ‘Operation Coronet’, at a time when the Ketsu-Go Japanese strategy consisted of causing the biggest number of casualties to the Allies. With this strategy, they hoped that social structure of democracies could not stand the waste of human resources.
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Thanks very much.
QAZ
Interested in Japanese jet development during WWII
Since making this post, I wrote the articles about Japanese jet engines in WWII:
karyu.org
karyu.org
On that site, there's also an index of jet engines with specifications for every jet made by Japan in WWII.
Tanegashima’s Group: Birth of the Japanese Jet Engine
By the 1930s, the practical speed limit of piston-engined aircraft was being approached for the first time. Before a propeller-driven airplane can approach the speed of sound, there is a period where…
karyu.org
Kōgiken-IST Ne-130: Driven to Destruction After the War
Note that the following history is constructed largely from the recollections of those involved, rather than historical documents, of which very few survive.) On July 26th, 1944…
karyu.org
On that site, there's also an index of jet engines with specifications for every jet made by Japan in WWII.
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Thank you. Sir.
QAZ
Interested in Japanese jet development during WWII
Identifying Japanese Jets Captured by the US in 1945
Following the surrender of Japan in August 1945, the American occupational authorities sought to gather whatever aircraft developments were of potential interest. Naturally, the most cutting edge…
karyu.org
Scott Kenny
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So heavy that the US still has not used up all the Purple Hearts made in advance for the invasion of Japan(!).
On a much happier note, all the food stockpiled as Army rations for the invasion kept the Japanese people alive during the famine years of the 1940s. MacArthur opened the warehouses and gave those rations out as relief food.
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