Mk 152

Rocket uses in

Functioning

Arming time

Vane span, inches

Body diameter, inches

Over-all length, inches

5.5

General: This fuze is identical to the Bomb Fuze AN-Mk 219, except that it has been partially armed fifty turns of the arming vanes and a metal fork has been inserted bet-ween the vane carrier and the fuze body to take up the space left by the pre-arming process. This fork must be removed before launching the fuzed rocket. In addition, the pitch of the vanes has been increased to 40 degrees instead of the 18 degrees on the AN-Mk 219.

The Bomb Fuze AN-Mk 219 must not be used in place of the Rocket Fuze Mk 152, and vice versa.

When installing the Fuze Mk 152 in a demolition rocket, be sure to use a regular adap-ter ring for the Bomb Fuze AN-Mk 219, the same as when installing the Bomb Fuze AN-Mk 219 in the nose of a depth bomb. The fuze cavity in the rocket body is deep enough to necessitate the addition of the following with the Fuze Mk 152: Auxiliary Booster Mk 2 (two inches long); Auxiliary Booster Mk 1 (three inches long); and one cardboard spacer approximately ½ inch thick placed below the auxiliary boosters. Tests have indicated that a high-order detonation can stille be expected if an additional cardboard spacer is used in place of the Auxiliary Booster Mk 2; however, use of the booster is preferred.

When the rocket is placed in the launcher, an arming wire, one end of which is atta-ched to the launhcer, replaces the safety pin. This assembly prevents fuzes of other rockets in the launcher from arming as a result of the blast from rockets already laun-ched. Both safety pin and arming fork must be replaced if the rocket is not fired.

Operation: There are two stages of arming. During the first stage, the upper gear is free to rotate and the lower gear, being attached to the hammer carrier locked by the inner sleeve, is held stationary. During the second stage, the hammer carrier has risen to clear the inner sleeve, and the lower gear is free to rotate, while the upper gear is held stationary, as it is attached to the arming shaft, which was threaded up until it locked against the shaft extension nut.

First stage: As the rocket is launched, the arming wire is withdrawn and the vanes are free to rotate. Through the system of reduction gears, the upper gear rotates to thread the arming shaft up until the head of the screw on the shaft locks against the shaft extension nut. A collar on the shaft lifts the hammer carrier and the entire arming assembly. Simultaneously with the locking of the arming shaft and the upper gear, the hammer carrier clears the inner sleeve to free the lower gear.

Second stage: The lower gear and hammer carrier are rotated in counterclockwise direction. The aligning lug on the hammer carrier engages the firing-pin carrier, lining up the firing-pin extension with the firing pin. Further rotation causes the firing-pin carrier to engage the detonator carrier, lining the firing pin up with the detonator. The hammer carrier, firing-pin carrier, and detonator carrier continue to rotate through 180 degrees, until the lip on the detonator carrier engages the inner sleeve. Simultaneously, the spring-loaded detent in the striker snaps into a recess in the hammer carrier, thus lock-ing the firing train components in an armed position. Since the upper and lower gears are now both locked, the two copper pins securing the lower gear to the hammer carrier are sheared and the vanes rotate freely. If the air speed is less than 300 m.p.h., the air pressure will not be sufficient to shear the pins, and the vanes will merely cease rotat-ing.

The fuze is now fully armed. On impact, the entire upper assembly of the fuze is for-ced inward. The shear wire in the arming shaft is cut as the upper part of the shaft te-lescopes into the lower part, and the shear wire through the firing pin into the detonator. The detonator sets off the auxiliary booster lead-in, booster lead-in, booster, and main charge successively.

Figure 156. Navy Nose Fuze (Rocket) Mk 152