False Target Shell Mk 1 Mod 0

Length, inches

18.0

Diameter, inches

Delay, seconds

Persistance of echo, minutes

4 to 18

Use: These shell is used to confuse and disrupt enemy underwater echo ranging.

Description: The external appearance is similar to the Submarine Emergency Signal Mk 2 Mod 2. The shell holds six metal cups 2.75 inches in diameter and 1.875 inches in depth, filled with a lithium hydride paraffin mixture. The base of the shell contains a pri-mer, time fuse and 20-gram charge of smokeless powder. Attached to the base is a firing mechanism which is used with the standard emergency identification signal ejector.

Operation: The shell is projected from the standard emergency identification signal ejector, using 200 pounds per square inch air pressure if possible. The shell is fired by a lug at its base which projects beyond the side of the shell and rides in a groove in the ejection tube. As the shell is forced through the tube, the extended lug reaches the end of the groove just before the base of the shell passes the muzzle door. The tripping lever is pulled back, thereby cocking and releasing the firing pin lever and firing pin. The firing pin strikes the primer, and the flash from the primer ignites a length of time fuse coiled in the base of the shell. The time fuse burns for 27 seconds, and then ignites the 20-gram charge of smokless powder, which ejects six cups of lithium hydride. When the lithium hydride touches the water, a chemical reation occurs which yields fine hydrogen bubbles. The hydrogen bubbles return an echo of the same order and magnitude as that returned by a submarine.

Remarks: False target shells should be segregated from pyrotechnics and other am-munition components, and should be kept in a dry atmosphere.

When visibility is such that surface disturbance may be a hazard, false target shells should not be released from depths less than 150 feet, because small bubbles or a sur-faced canister may result.

Figure 220. False Target Shell Mk 1 Mod 0