Cruiser Mine (UK)
The British Cruiser Mine was a depth charge created by fitting a spherical Service mine with a hydrostatic firing mechanism. It is described in the Annual Report of the Torpedo School, 1915. A Mark I weapon was produced early in the war, but was not very good. The Mark II was ready in late 1915, but were produced in limited number as a stop-gap measure, as better choices were becoming available.
Adapted from a spherical service mine, 250 pounds of gun cotton were initiated by a G.C. primer of 2.25 pounds, producing a blast with an estimated danger radius of 52 feet.
A hydrostatic trigger set the weapon off at 45 feet depth. The overall weight was 1150 pounds, giving it a sink rate of 5-6 feet per second.
Deployment and Use
The Mark I devices had been hastily conceived and constructed early in the war, employed external ballasting. They were noted as being unsatisfactory except from the standpoint of safety – a little reading between the lines indicates they'd perhaps failed to kill anyone at all.
Issue of the Mark II cruiser mines, incorporating the same Mark IV trigger used in the spherical Service mine commenced in October 1915. They were to be used only by local patrol vessels after the Type D depth charge became available, as they were large and heavy for the bang they delivered. Only about 180 in all were produced.
- Annual Report of the Torpedo School, 1915. Plate 88.
- Annual Report of the Torpedo School, 1915. Plate 89.
- Annual Report of the Torpedo School, 1915. pp. 164-5, 174-5, Plate 73, Plates 88-9.