This is a nozzle of a rocket motor that powered the Japanese Ohka bomb of World War II. The Ohka was a small, anti-ship, manned suicide aircraft. Known to the Americans as the Baka (Foolish) bomb, it was fitted with three rockets. The motors used a solid fuel and produced a thrust of 7,500 N (1,700 lb.) for ten seconds. Ohkas were carried by a Betty bomber and launched from an altitude of about one mile and a distance of 10 km (6-7 mi.) from the target ship.

Ohkas glided towards the target and the rocket motors in the rear were usually fired close to the target to give the bomb more speed. It was first used in combat in the Pacific in 1945 and damaged the U.S. battleship West Virginia and other vessels. This nozzle was transferred to the Smithsonian in 1966 by the U.S. Air Force.