Over-all length: 80.3 inches.

Maxium diameter: 11.8 inches (300 millimeters).

Description: This unit is designed as an integral type bomb pusher for launching 250-kilogram bombs from ground launcher for land bombardement. The motor described here is specifically designed to fit type 98 No. 25 land use bombs. Another motor is reported to be designed as a pusher unit for type 99 No. 25 ordinary bombs. This motor has never been recovered but is reported to be only slightly different from the recovered model.

Weight of complete motor: 429.2 pounds (194.8 kilograms).

Weight of propellant: 178.2 pounds (81 kilograms).

Length of propellant stick: 21.65 inches.

Depth of propellant stick: 3 5/16 inches (39.3 millimeters).

Weight of ignition charge: 150 grams.

Propelltant: The propellant charge consists of 20 sticks of 343 special D.T.₂ (code de-signation). The chemical analysis is not known as the motor has never been recovered complete. The 20 sticks are arranged in 2 groups of 10 sticks each, 1 group directly aft of the other.

Igniter: The igniter consists of an igniter body, electric cap and igniter charge of black powder. The igniter is inserted in the forward end of the motor and is ignited by a hand generator.

Launcher: A crude wooden trough mounted on a bipod forward and a steel base plate aft.

Remarks: The 250-kilogram bomb pusher unit unlike the 60-kilogram units remain with the explosive head throughout flight.

Figure 90 - Special Mk 1 Rocket Motor Model 21.