Japan's Emergency Point Defense Interceptor

[Spinners 15,986]

Mitsubishi Ki-204 'Kōsoku Jōshō' (Fast Ascent) - Imperial Japanese Army Air Force, 1946

Facing similar air defence problems as Germany, Japan considered that only radical solutions could give them any hope of intercepting the B-29 Superfortress bombers that were beginning to roam far and wide over the Japanese mainland during the summer of 1944. Japan had already sent military attachés to Germany to evaluate the Me-163 rocket-powered interceptor at the Bad Zwischenahn airfield of Erprobungskommando 16 and they had also visited the Bachem-Werke GmbH to evaluate the Ba-239 project (also rocket-powered) still on the drawing board but of equal interest to the Japanese who liked the fact that it was designed to be built by unskilled labor with inexpensive materials. At considerable expense, Japan negotiated the rights to licence-produce both the Me-163 and Ba-239 aircraft and their Walter HWK 509A rocket engine and in August 1944 Japan's new Prime Minister, Kuniaki Koiso, entrusted this work to the Mitsubishi Aircraft Company. Whilst the Me-163 would be produced for the IJN and the IJAAF, Kuniaki Koiso insisted that the Ba-239 would only be produced for the IJAAF under the designation of Ki-204.

With the design already completed by Bachem and requiring very little modification to accept Japanese equipment the Ki-204 progressed quickly and essentially mirrored the German Ba-239 programme by using towed unmanned glider flights before moving on to manned glider flights and then successful unmanned vertical take-offs from the experimental launch tower at Mitsubishi's Nagoya factory. However, using lessons learned from the unfortunate death of the Bachem test pilot Lothar Sieber during the unsuccessful first vertical take-off flight of the Ba-239 in March 1945 the first vertical take-off flight of the Ki-204 prototype was successful but was cut short when the main rocket engine cut out caused by a fuel pump failure in the T-Stoff (oxidiser) fuel line. With similar problems affecting the Ki-200 (Me-163) programme, Mitsubishi engineers worked flat-out to resolve the issue eventually traced to heat expansion in the pump and fuel line requiring increased localised insulation to combat the rapid heat build up when both fuels reacted during combustion.

Whilst the Ki-200 was considered the more important programme the Ki-204 'Kōsoku Jōshō' (Fast Ascent) continued to make progress during the remainder of 1945 and launch sites for the Ki-204 began to spring up across several Japanese cities during late 1945 and early 1946 under the ambitious 'Operation Dagger' which called for the 10 largest Japanese cities to be ringed with a circle of eight Ki-204 launch sites with each site having three individual launch pads and towers arranged at the corners of an equilateral triangle. Operation Dagger also called for the eventful recruitment and training of 240 volunteer pilots per week with no restrictions on age or gender although a lower age limit of 17 years was later stipulated. Training for the Ki-204 was to be a simple affair with some basic familiarisation of the Ki-204's controls, studying the standard intercept profile which included a single attack with the nose-mounted rockets followed by a glide back down to an altitude of about 3,000m before the pilot left the aircraft to descend by parachute. Ki-204's began to be delivered to the Osaka Defense Circle in May 1946 with the first operational launch of a Ki-204 taking place on June 2nd, 1946 when two aircraft were launched without success against B-29's. On June 5th the Nagoya Defense Circle launched three Ki-204 aircraft against a small force of B-42C Mixmaster bombers claiming one B-42C destroyed and one damaged but one Ki-204 exploded shortly after leaving it's launch pad. Both Ki-204 pilots successfully parachuted near the outskirts of Nagoya. The Ki-204 programme continued to have sporadic successes but the supply of aircraft and pilots could not keep up with the losses and the programme was essentially over at the time of the Japan Armistice of July 1946.