ROCKETS USED IN

FUNCTIONING

ARMED CONDITION

FUZES USED WITH

MAX. BODY DIAMETER

OVERALL LENGTH

GENERAL:

The M81 consists of the M4A2 fuze described on page 63 with a .05 second delay and an M21A1 booster staked in place. The M24 booster has been standardized as an alternate for all modifications of the M21 booster and may be used in place of the M21A1 with the M4A2 fuze.

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 assembly. The rotor assembly consists of a rotor containing the lead azide detonator, a safety lock pin, a rotor stop pin, and a rotor lock pin lock. The rotor is seated on the pivot pin and rotates under centrifugal force. The mechanism is covered by a thin brass disc which has a flash hole 1/4 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 un-der centrifugal 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 detonator 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 plate which closes the rotor chamber.

When rocket is launched, centrifugal force causes the rotor stop to move outward against the spring and release 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 charge consists of a tetryl pellet. The booster is armed in flight and the detonator is initiated by the action of the fuze.