The Mark 10/11 “Hedgehog” Projector
By Robert F. Sumrall (DD 762)
The Mark 10 and Mark 11 were ahead-throwing weapons that could launch a pattern of twenty four Mark 6, 7.2-inch projector charges ahead of the attacking vessel. As part of the 1950 armament conversion program, all active SUMNERs, GEARINGs, and FLETCHERs were fitted with MK 10 or MK 11 projectors.
The projector was fixed to the deck and consisted of a base frame and blast shield, cradles and spigots, and a roll correction gear assembly. The firing mechanism was attached to the back of the blast shield. There were four longitudinal tilting cradles, each carrying six fixed spigots tipped with firing pins. The tail of the charge fitted over the spigot and seated on the retaining nut of the firing pin. The spigots were positioned so that, when fired, the charges would describe either an elliptical or circular pattern when entering the water. The pattern could be varied by changing the tilt angle of the spigots. They were fired electrically, in pairs, at intervals of a 0.10 second through a ripple switch in the controls.
The MK 10 and MK 11 were nearly identical, differing in the shape and distance that their patterns were projected. The MK 10 fired an elliptical pattern approximately 140 by 120 feet out to a maximum of 200 yards while the MK 11 fired a circular pattern approximately 200 feet in diameter out to a maximum of 188 yards. The MK 6 projector charge was 7.2 inches in diameter, 3.88 feet long, and weighed between 50 and 53 pounds.