Over-all length: 1.9 meters.

Weight of explosive: 3.5 kilograms.

Diameter: 0.3 meters.

Weight of propellant: 15.0 kilograms.

Maximum speed: 100 m./sec.

Total weight: 315 kilograms.

General description: Design work on this bomb was originally started in 1935, and pro-duced the Basic 3 No. 25 Mk 4 bomb, which was used for all early Japanese Navy rocket testing and research. Production commenced on the type 3 bomb in 1943, and a reaso-nable number of the bombs had been produced or were in the process of production at the end of the war.

This bomb is an example of the early ideas on the use of rocket power. It is essentially an armor-piercing bomb, designed to utilize rocket power to increase penetration. How-ever, as finally produced, the bomb had a maximum velocity of only 100 m./sec., and consequently was of little value.

The bomb consists of an armor piercing explosive nose section, a rocket motor tail sec-tion and a cylindrical center section joining the two, and carrying the fuzes for both sec-tions. The armor piercing nose is of extremly heavy construction, and is fuzed in the base with a fuze incorporating a short delay. A very small explosive charge, approxima-tely 3.5 kilograms in weight, is used as a burster. Type 91 explosive is used, as in all other Japanese Navy armor piercing ammunition. The rocket motor tail section about half of the overall length of the bomb, and carries 15 kilograms of propellant of the ballistic type. It is fuzed at its forward end for ignition of the propellant, with a fuze which ope-rates after the bomb leaves the plane. The tail section is equipped with standard fins for stabilization of the bomb in flight.

The cylindrical center section of the bomb has the function of joining the nose and tail sections and of carrying the fuzes for both. Both fuzes, situated at the center of the bomb are equipped with arming vane extensions which project out of the side of the bomb. Two hinged doors in the side of the bomb allow access to the fuzes.

The data on this bomb are the result of incomplete investigation, and must not be consi-dered as specific, accurate information.

Figure 54 - Type 3 No. 25 Mk 4 Bomb Modification 1.