Night Depth Charge Marker Mk 2

Over-all length, inches

Diameter, inches

Weight, pounds

Effective releasing altitude

Visibility

Burning time, minutes

Ignition time (after impact)

70 - 90 seconds

Use: The marker is employed to indicate the initial point of contact with submarines and provide a reference point for further search and attack during night operations.

Description: The marker is a sealed, cylindrical, metal container that has a centrally located tube, sealed on both ends by tear strips with a pull ring attached, and containing calcium phosphide. The main charge is calcium carbide that surrounds the central tube and is held in one end by a screen. This produces a concentration of weight at one end and allows the marker to float in an upright position.

Operation: After the two tear strips are pulled off, the marker is launched by throw-ing it overboard. Water enters through the small holes in the bottom and reacts both with the calcium carbide (producing an inflammable gas, acetylene) and with the calcium phosphide (producing a spontaneously ignited gas, phosphine). Both gases escape from the small holes in the top and ignite within 70 to 90 seconds after impact with the water. In extremely cold weather, the ignition delay may be somewhat longer. The resulting flame is about nine inches high. If it should be put out by rough water, the gases will ig-nite again.

Figure 186. Depth Charge Marker Mk 2