The J8M Shūsui was a Japanese World War II rocket-powered interceptor and stands as a testament to the desperate innovation that defined the era. The resemblance was more than coincidental, and the J8M was indeed a collaborative effort for both the Imperial Japanese Navy (IJN) and the Imperial Japanese Army (IJA), though it was styled J8M for the Navy and Ki-200 for the Army.
Military reasons, however, lie behind the advent of licensed production. Japan was an ardent enemy of licensing at that time because they did not want to suffer the same strategic bombing devastation as Germany. Japanese military attachés had noted the threats that American B-29 Superfortresses posed to their territory during a visit to the Bad Zwischenahn airfield, home to most of the remaining non-flown Komets. The Komet’s design, and its Walter HWK 509A rocket engine, were negotiated for licensing and production. Unfortunately, difficulty with shipping the aircraft meant that reverse-engineering from a flight operations manual and limited documentation had to suffice.
There were many hitches in the project being led by Mijiro Takahashi. The deal with Germany provided for the blueprints of a complete Komet, sub-assemblies, and engines to be supplied. The only submarine destined for delivery into Japan, RO-501, sank in mid-Atlantic. Another submarine carrying the planes and engines to Japan, I-29, was managed to deliver them in Singapore, thereafter sunk near the Philippines. The Japanese pressed on anyway, using a basic instructional manual to guide their efforts.
The first powered flight took place on July 7, 1945, with Lieutenant Commander Toyohiko Inuzuka at the helm of the J8M1 prototype. At a height of 1,300 feet, the engine failed and the aircraft stalled out before crashing. The flier’s fatal injuries killed him the next day. That accident was due to an air lock forming in the fuel line, and therefore a new layout of the fuel pumps was necessary.
Undeterred by this one crash, Mitsubishi and allies including Nissan and Fuji pressed on. The J8M1 featured a plywood main spar and wooden vertical tail; these differences combined for a 900-pound weight reduction under the original Komet. The airplane was adapted to two 30mm cannons, although the J8M2 version for the Navy lost one of these cannons to gain more fuel space. This engine, the Ro.2, burned the same volatile propellants as the German original.
By mid-1945, the Japanese defense industry was already on the verge of mass production, and the tooling for both the J8M1 and J8M2 was well advanced. However, all work on the J8M stopped with the war’s end on August 15, 1945. All examples of the type were taken by the Allies and ultimately scrapped. As was the case with numerous other wartime innovations, the J8M project proved to be a technological dead end, with no discernable tactical purpose. The turbojet engine soon made rocket-powered interceptors obsolete.
Ultimately, the J8M Shūsui is a fascinating chapter in the history of military aviation, reflecting in equal measure the ingenuity and desperation of wartime innovation.