Booster M21A1 and M24

General: These boosters are used with the Fuze M48A2 to form the Rocket Fuze M81. The Booster M24 has been standardized as an alternate for all modifications of the Boosters M21 Type and may be used in place of the M21A1 with the Fuze M48A2.

Booster M21A1: The M21A1 consists of a booster cup which contains a tetryl charge and threads into the base of the body containing a tetryl booster lead and the rotor as-sembly. The rotor assembly consists of a rotor containing the lead azide detonator, a safety lock pin, a rotor stop pin, a rotor lock pin, and a rotor lock-pin lock. The rotor is seated on the pivot pin and rotates under centrifugal force. The meachanism is covered by a thin brass disc which has a flash hole ¼ inch in diameter to permit the transmission of the fuze action to the detonator. The flash hole is covered by a thin disc of onion-skin paper.

When rocket is launched and reaches required rotational velocity, the safety lock pin moves outward against its spring under centrifugal force. This releases the rotor, which rotates on the pivot pin to the aligned or armed position. The rotor is locked in the armed position by the rotor lock pin, which moves outward into a cavity of the body under cen-trifugal force, and the rotor lock-pin lock moves forward by creep to prevent the rotor lock pin from returning to its original position. The booster is armed in flight, and the de-tonator is initiated by action of the fuze.

Booster M24: The rotor assembly of the M24 consists of a rotor which contains the detonator, a centrifugal rotor stop which holds the rotor in the unarmed position, a guide pin, and a plate which closes the rotor chamber.

When rocket is launched, centrifugal force causes the rotor stop to move outward against the spring and relesase the rotor, which turns so that the detonator is aligned with the flash hole and the booster lead. The rotor is locked in the armed position by the lock pin, which enters the lock pin cavity as far as the closing plug. The booster chare consists of a tetryl pellet. The booster is armed in flight, and the detonator is initiated by the action of the fuze.

Figure 142. Boosters M24 (below) and M21A1 (above)