PD Support Munitions
Mk25 Marine Marker
The Mk25 Marine Marker is a method used in sea-surface reference-point marking that calls for both smoke and flame. It has a variety of applications, such as charting the course of enemy submarines, locating a survivor during search and rescue operations, locating target areas in antisubmarine warfare or determining wind direction and velocity. It can be launched by hand or by sonobuoy launcher from either aircraft or surface ships.
The Mk25 marker is 18.5 inches long and 2.9 inches in diameter. It contains an Mk72 Mod 0 seawater-activated battery and electric squib. Prior to launch, the battery is activated by pushing in the base plugs. This exposes the battery cavity, which allows seawater to enter upon insertion into water. The water activates the battery, then the battery current initiates the electric squib, which in turn ignites the red phosphorous pyrotechnic composition. The gas buildup forces the valve assembly from the chimney in the nose, and yellow flame and white smoke are emitted. After 10-20 minutes of burning, the signal is expended and a scuttling charge sinks the container.
There are currently four variations of the Mk25 Marine Marker. Each functions identically, but Mod 2 contains two seawater-activated batteries and two squibs while Mod 3 variants contain only one of each. The Mod 4 variant uses the same number of batteries and squibs as the Mod 3 but features a plastic cover that is removed prior to launch to allow water to enter the cavity. Mod 3 also has an integral aluminum cover and arrow indicator placed in the safe arm position, which Mod 4 does not. Mod 3 is mostly used by the Air Force and Coast Guard, while the Navy uses Mod 4.