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Japan's Imperial Weapon Number 2: The Nakajima Kikka Jet-propelled Attack Aircraft


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Impressionistic illustration of the Nakajima Kikka in flight. Artist unknown but copyright Bob Hackett, 2018 (pic from combinedfleet.com)

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Picture showing the takeoff of the prototype Nakajima Kikka on its first test flight (pic from Heliosiah (2013) - see references below):

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In 1942, the Japanese military attaché in Germany witnessed flight trials of the Messerschmitt Me 262 jet-propelled fighter, and his enthusiastic reports eventually persuaded the naval staff in Japan to direct the Nakajima company (in September 1944) to develop a similar twin-engine jet aircraft to be used as a single-seat fast attack bomber. Note here that Luftwaffe chief Hermann Goering had, in July 1944, ordered that Japan be provided with necessary blueprints, and even a complete Me-262 aircraft. The specifications for the design of the new jet aircraft included the requirements that a largely unskilled labour force would be able to build it, and that the wings should be foldable. This latter requirement was for the purpose of hiding the planes in caves and tunnels around Japan as the Japanese navy prepared for the defence of the home islands. The project was placed in the hands of Nakajima designers Kazuo Ohno and Kenichi Matsamura, and the new aircraft emerged as an all-metal affair except for the control surfaces, superficially similar to the German Me-262. The plans included hinged outer wing panels that folded up so that ground personnel could more easily hide the aircraft, and the designers mounted the jet engines in pods slung beneath each wing to make it easier to install and test different engines. There has been some confusion over the official name and designation of the first Japanese jet aircraft and I have used the name most frequently associated with the type rather than the Japanese naval classification system (which was similar to the US system of aircraft classification at the time) or other names sometimes seen. In fact, the official Japanese name for the aircraft was “Kitsuka”, and the most commonly used name, “Kikka”, derives from the pronunciation of the Chinese kanji characters for the name, which mean in English, “Orange Blossom”. The Nakajima Kikka was also called Kokoku Nigo Heiki (dash above first and third 'o'), which translates in English as "Imperial Weapon No. 2".

The choice of engines for the Nakajima Kikka was to prove problematic. At the preliminary stage of the design, it was planned to use the Tsu-11, a rudimentary motor-jet style jet engine that was essentially a ducted fan with an afterburner. Subsequent designs were planned around the Ne-10 (TR-10) centrifugal-flow turbojet, and then the uprated Ne-12 which added a four-stage axial compressor to the front of the Ne-10. Tests of this power-plant soon revealed that there would still be nowhere near enough power to propel the aircraft and the Kikka project came to a temporary halt. Finally, it was decided to produce a new axial-flow turbojet, the Ne-20, which drew heavily on the German BMW 003 jet engine. In fact, the Japanese had been experimenting with jet power as early as the winter of 1941-42, and in 1943, a Japanese technical mission to Germany selected the BMW 003 axial-flow turbojet for development in Japan. A large cargo of engines, engineering plans, photographs and tooling was sent to Japan by submarine but vanished at sea. Fortunately, however, one of the technical mission engineers had left the ship and travelled to Japan in another submarine, and he arrived in Japan with his personal notes and several photographs of the BMW engine. From this material, by far the most important part of which was a single cutaway drawing of the BMW 003 engine, the Naval Technical Arsenal at Kugisho managed to develop the Ishikawajima Ne-20 turbojet engine, the first of which was successfully tested on 26 March 1945 in a cave set into a cliff in Yokusuka (see note at the end of this article for a slightly different version of the story of the technical mission from Germany) . This reawakened the dormant Kikka project and by mid-1945, matters were making progress once again.

 

 

 

Artist's imaginary impression of what the Nakajima Kikka would have looked like in combat - original illustration by Piotr Forkasiewicz (pic from cdna.artstation.com):

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At this point in my topic, and before going on with the narrative, it is important to discuss the relationship between the Kikka jet-propelled aircraft and aerial kamikaze missions which had begun in October 1944, as the war situation for the Japanese deteriorated.

It is notable that in keeping with kamikaze practice, the Kikka was generally referred to by its name rather than an alpha-numeric designation, and textual sources by and large support the notion that the Nakajima Kikka was, at least originally, designed with suicide missions in mind. Lee (2006) for example, quite confidently asserts a link between the design of the Kikka and kamikaze missions, stating that due to the shortage of high-strength metals, the turbine blades of the Kikka engines could only last a few hours, which meant that the Kikka was only suitable for short operational testing flights and one-way suicide attacks. Indeed, Lee states that “Several aircraft manufacturers turned to designing aircraft specifically for use during suicide missions, including the Nakajima Kikka.” Interestingly, against the common grain, Wikipedia throws doubt on the notion that the Japanese navy considered the new jet as a possible weapon for kamikaze attacks. The high cost and complexity associated with the manufacture of jet engines would have mitigated against the idea of using the new jet aircraft as a one-mission suicide weapon; there were other, more economical, projects in place designed specifically for suicide attacks, such as the Nakajima Toka [dash over the ‘o’] (intended to use up the stock of obsolete engines), the pulse-jet powered Kawanishi Baika, and the better-known Yokosuka Ohka. Finding the way through this debate to get to the truth is difficult. In Michael Peck’s article, it is claimed (by aviation historian Edwin Dyer) that the initial Kikka design had no landing gear and only a single bomb as armament in keeping with the idea of one-way suicide missions; the aircraft was apparently meant to be launched via a catapult with rocket assistance, and its proposed Ne-12 engines gave it a range of just 127 miles. According to Dyer, it was in March 1945 that the Kikka’s mission was changed, with the aircraft being designated as a tactical bomber or an interceptor armed with 30 m cannon and powered by the Ne-20 jet engine. My feeling is that initially, given the technological limitations at the time of the Kikka’s inception, the turbo-jet Kikka project was relegated to the idea of using the plane for suicide missions. However, with the development of the Ne-20 engine, the project gained new momentum and provided new horizons and ambitions for the Kikka beyond the kamikaze role.

 

 

 

Colour photograph showing the Nakajima Kikka in profile (pic from theaviationgeekclub.com) and, below, the Kikka viewed at an angle (pic from upload.wikimedia.org):

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Resuming our story of the first Japanese jet aircraft, the first prototype of the Nakajima Kikka commenced ground tests at the Nakajima factory on 30 June 1945. In July it was dismantled and delivered to Kisarazu Naval Airfield where it was reassembled and prepared for flight testing. The first flight, piloted by Lieutenant Commander Susumu Takaoka, took place on 7 August 1945, the day after the atomic bomb was dropped on Hiroshima. This flight lasted only twenty minutes, during which the plane performed well, with the only concern being the length of the take off run. Four days later, on 11 August 1945 - two days after Nagasaki and just four days before the Japanese declaration of surrender - the second test flight took place, again with Takaoka as pilot, but this time take off was to be assisted by two rocket units. Takaoka was concerned about the angle at which the two rocket assisted take off (RATO) tubes had been set, but there was no time to correct them; instead, it was decided to merely reduce the thrust of the rockets from 800 kg to 400 kg. Four seconds into take off, the RATO units were fired, with the result that the aircraft jolted back onto its tail leaving the pilot with no effective tail control. The rocket burn was for 9 seconds after which time the nose came down and the nose wheel touched the runway causing rapid deceleration. The jet engines were still operating normally but the pilot decided to abort the flight and now fought to bring the plane to a standstill. There was a danger that in an attempt to perform a ground loop, the aircraft would run into other installations, but eventually it ran over a drainage ditch which caught the tricycle landing gear and caused the aircraft to skid forward before stopping just short of the water’s edge. Although the technicians have been blamed for the crash through their incorrect mounting of the RATO rockets, Takaoka has also been criticized for perhaps mistaking the burnout of the rockets for turbojet engine trouble whereby he throttled back and executed a safe but unnecessary crash-landing.

The Kikka , not surprisingly, resembled the German Me-262, looking rather like a smaller version of the German aircraft; it was of all-metal monocoque construction apart from fabric covered control surfaces. The Kikka, though, was no copy or imitation of the Me-262, and the development of the plane itself was Japanese in character, even if the Ne-20 engine was heavily influenced by German technology. In fact, in terms of appearance, the Japanese Kikka had straight instead of swept back wings, putting its performance at a disadvantage when compared with the Me-262, and the performance goals of the Kikka were very different from those of the Messerschmitt, and would have caused the Allies initial but not lasting or significant concern. The Me-262 A-1a production fighter, armed with 4 MK 108 (30 mm) cannon and with 2 300-litre drop tanks, had a top speed of 540 miles per hour, whereas the Kikka, armed with a bomb load of 500 kg or 250 kg, had a maximum speed of just 432 mph; even the interceptor version only called for a top speed of 443 mph, which was little faster than the contemporary P-51D Mustang. The Messerschmitt also had a longer range, could land at a faster speed, and didn’t require the assistance of rockets in order to take off within a reasonable runway distance. It has to be said though that even with its superiority over the Kikka, the German Me-262 did not create a situation that compromised the outcome of the Second World War, partly because all the early jets of World War Two had engine reliability issues and were somewhat lacking in maneuverability. The Allies just had too many aircraft towards the end of the War, and were able to attack Me-262 aircraft on the ground during their vulnerable take off and landing runs; in addition, by this time, Nazi Germany was being overrun by Allied tanks. In a similar vein, the Nakajima Kikka was also too little too late. Had it been put into production earlier, the Kikka might have made some impact over battlefields, but its poor range essentially rendered it unsuitable for the long-distance flying that so characterized the Pacific War. It might also have been useful in the defence of the Japanese homelands, but here it was limited by its lack of radar, making it a daylight only interceptor. Ultimately, of course, Japan was faced with no choice but to surrender after the detonation of the Nagasaki and Hiroshima atom bombs.

 

 

 

A blueprint line drawing of the Nakajima Kikka with the Messerschmitt Me-262 shown in the shaded areas as a comparison (pic from Heliosiah ( 2013) - see references below):

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Two pictures showing the Nakajima Kikka prototype being prepared by groundcrew for flight testing at Kisarazu Naval Airfield (pics from combinedfleet.com):

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With the surrender of the Japanese four days after the second, aborted, test flight, development of the Kikka ended. At this point, there was a second prototype close to completion and the Americans discovered approximately 23 airframes under construction at the Nakajima main factory building in Koizumi (now called Oizumi, in Gunma Prefecture) and at a site on Kyushu Island. One of these was designated as a two-seat trainer, and there had been other follow-on versions of the Kikka proposed including a reconnaissance aircraft, and a fighter armed with two 30 mm Type 5 cannons with 50 rounds per gun. These follow-ons were expected to be powered by more advanced developments of the Ne-20 - the Ne-20-Kai 5.59 kN (570 kgf); the Ne-130 8.826 kN (900 kgf); the Ne-230 8.679 kN (885 kgf); or the Ne-330 13.043 kN (1330 kgf). These engines were planned to have approximately 15% to 140% better thrust than the Ne-20. The Nakajima Aircraft Company had apparently also designed a modified version of the Kikka, the “Nakajima Kikka-kai Prototype Turbojet Special Attacker” which was to be launched from a 200 m long catapult, had a projected total weight of 4080 kg and a maximum speed of 687 km/h at 6,000 m.

After the War, airframes 3, 4 and 5 (and possibly other partial airframes) were taken to the USA for study. There are currently two examples of the aircraft in the American National Air and Space Museum (NASM). The first is a very incomplete example that may have been completed using a number of semi-completed airframes. This plane was taken to the Patuxent River Naval Air Base, Maryland - US Naval records indicating its presence there on 18 February 1949 - from where it was shipped in 1960 to the Paul Garber Facility in Suitland-Silver Hill, MD. Museum staff accessioned the plane into the collection in March 1961 and it is still in storage at the Paul E. Garber Preservation, Restoration and Storage Facility in Suitland-Silver Hill. The second surviving Kikka is on display at the NASM Udvar-Hazy Centre in the Mary Baker Engen Restoration Hangar. A theory, put forward by Japanese propulsion specialist Kazuhiko Ishizawa in 2001, is that the Museum’s Kikka airframe was constructed by Nakajima for load testing rather than for flight tests, thus explaining why the engine nacelles on that aircraft are too small to enclose the Ne-20 engines.

 

 

 

A Nakajima Kikka stationed at the Patuxent River Naval Air Base, Maryland, 1946 (pic from upload.wikimedia.org):

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A photograph of a Nakajima Kikka in the restoration hangar at the Steven F. Udvar-Hazy Centre, in Chantilly, Virginia, close to Washington Dulles Airport, taken on 15 July 2012. Note that the wings have each been severed at the hinge point where they folded upwards to allow the aircraft to be stored safely in limited spaces (pic from theaviationgeekclub.com):

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Nakajima Kikka originally transferred from the US Navy to the collection of the National Air and Space Museum - Smithsonian Institution, Washington DC; currently housed in the Boeing Aviation Hangar, Steven F, Udvar-Hazy Centre, Chantilly, Virginia. (pic from airandspace.si.edu):

 NASM-NASM2016-00876.thumb.jpg.d13dbf547b6fba854d17ef86c1d772eb.jpg

 

 

 

The following basic list of Kikka specifications comes from Wikipedia, via Francillon (1995). However, I have found a far more complete (and interesting) set of specifications, given by Heliosiah on the War Thunder Forum (see references below):

 

General characteristics

· Crew: 1

· Length: 8.125 m (26 ft 8 in)

· Wingspan: 10 m (32 ft 10 in)

· Height: 2.95 m (9 ft 8 in)

· Wing area: 13.2 m2 (142 sq ft)

· Empty weight: 2,300 kg (5,071 lb)

· Gross weight: 3,500 kg (7,716 lb)

· Max takeoff weight: 4,080 kg (8,995 lb)

· Powerplant: 2 × Ishikawajima Ne-20 axial-flow turbojet engines, 4.66 kN (1,047 lbf) thrust each

 

Performance

· Maximum speed: 623 km/h (387 mph, 336 kn) at sea level

696 km/h (432 mph; 376 kn) at 10,000 m (32,808 ft)

 · Range: 943 km (586 mi, 509 nmi)

· Service ceiling: 12,000 m (39,000 ft)

· Rate of climb: 6.42 m/s (1,264 ft/min)

· Time to altitude: 10,000 m (32,808 ft) in 26 minutes

· Wing loading: 265 kg/m2 (54 lb/sq ft)

· Thrust/weight: 0.27

 

Armament

· Guns: 2 × 30 mm (1.181 in) Type 5 cannon

· Bombs: 1 × 500 kg (1,102 lb), or 1 × 800 kg (1,764 lb) bomb

 

 

A useful set of pictures of a Nakajima Kikka model-build by Chris Wauchop. The original 1/48 kit was by FineMolds and Chris Wauchop constructed the plane from the kit but worked to improve the detailing and accuracy to create a very lifelike representation of the aircraft as it was, including the tricycle undercarriage and RATO rockets, one beneath each wing (pics from chriswauchop.com):

fmkikkastbfrt2web.jpg.7a09fb44e6ca06ea53ed783df4ccc129.jpg

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Note

There is a slightly different version of this story; Hiromachi (2014), for example, states the following:

 

 “In May 1944 the Japanese negotiated manufacturing rights to the Messerschmitt Me 262 and examples of the Junkers 004 and BMW 003 turbojets. However, the Japanese submarine I-29 was sunk by US submarine after leaving Singapore, while carrying engines and one Me 262 example.

The only thing which survived with Commander Eichi Iwaya was a single copy of the cross-section of the BMW 003A. Based only on this and previous work with the Ne-12, Kugisho [dash over the ‘u’ and ‘o’] managed to continue the development until the end of January 1945. ...”

 

 

References and sources used for the text of this topic

 Francillon, René J, “Japanese Aircraft of the Pacific War”; Putnam & Company Ltd, 1995 (First edition 1970).

Heliosiah, “Kitsuka (Kikka) kanji characters for orange blossom Orange Blossom”; forum topic on War Thunder Forum 15 October 2013. Online at forum.warthunder.com/index.php?/topic/71503/kitsuka-kikka-kanji for orange blossom-orange-blossom/

Hiromachi, “[Historical] The First Flight of the Nakajima Kikka”; Topic on War Thunder Forums, Project News (Read Only), 6 August 2014. Online at forum.warthunder.com/index.php?/topic/166000-historical-the-first-flight-of-the-nakajima-kikka/

Lee, Russell, “The History of Japan’s First Jet Aircraft”; Aeronautics Department, Smithsonian National Air and Space Museum. Online at https://airandspace.si.edu/stories/editorial/history-japans-first-jet-aircraft

Peck, Michael, “Too Little, Too Late: Why the Nakajima Kikka Kamikaze Jet Couldn’t Save Japan”. The National Interest (The Reboot Blog), 31 August 2021. Online at https://nationalinterest.org/blog/reboot/too-little-too-late-why-nakajima-kikka-kamikaze-jet-couldnt-save-japan-192861

Wikipedia, “Nakajima Kikka”; online article, Wikipedia, last edited on 25 July 2021. Online at https://en.wikipedia.org/wiki/Nakajima_Kikka

Y_Sakuragi39 et al.; “I found mispelling! I’ts [sic] not “Kitsuka”, but “Kikka”. Thread on the War Thunder Forum. Online at forum.warthunder.com/index-php?/topic/192082-i-found-mispelling33-i39ts-not-34kitsuka34-but-34kikka34/

 

 

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