The Kaiten (Japanese:, literal translation: "Return to the sky", commonly rendered as: "The turn toward heaven", "The Heaven Shaker" or "Change the World" ) were manned torpedos and suicide craft, they were used by the Imperial Japanese Navy in the final stages of World War II.
Towards the end of 1943 the Japanese command in response to unfavorable progress in the war heard suggestions for various suicide craft. These suggestions were initially rejected but later deemed necessary. For the naval department this meant kamikaze planes, suicide boats, submarines and human mines. While the kamikaze were somewhat successful the next most successful of these was the kaiten.
Research on the first kaitens began in February 1944. Followed on 25 July of the same year by the first prototype. By 1 August an order had been placed for 100 units.
The very first kaiten was nothing much more than a type 93 torpedo engine compartment attached to a cylinder that would become the pilot's chamber and trimming ballast in place of the warhead and other electronics and hydraulics. The torpedo's pneumatic gyroscope was replaced by an electric model and controls were linked up to give the pilot full control over the weapon.
The original designers and testers of this new weapon were Lieutenant Hiroshi Kuroki and Lieutenant Sekio Nishina. They were both to die at the controls of kaitens, Lieutenant Kuroki being in a very early training prototype.
In total six models of kaiten were designed, the types 1, 2, 4, 5 and 6 were based on the type 93 torpedo. The Type 10 was the only model based on the type 92 torpedo. Types 2, 4, 5, 6 and 10 were only manufactured as prototypes and never used in combat.
Early designs allowed the pilot to escape after the final acceleration toward the target. There is no record of any pilot attempting to escape or intending to do so and this provision was dropped from later kaitens so that, once inside, the pilot could not let himself out. The kaiten was fitted with a control for self destruction, intended for use if an attack failed or the impact fuse failed. source