The depth charge is the most primitive dedicated ASW weapon. Even more primitive, but not dedicated, are only ramming and gunning if the enemy is on the surface; both variants of submarine "hunting" were exercised at all times but were the only options available to a stunned Royal Navy in the first three years of World War I.
It was an extraordinarily crude weapon - basically just a can filled with explosives and a hydrostatic fuze measuring the pressure of water around the weapon and detonating it at a certain, pre-set depth. It was an okay weapon for WWI - any attack would require the enemy to have been close to the surface, so he could be seen, and the depths to which submarines might dive were not great. The Royal Navy introduced the new weapon in 1916 and scored the first success with it on December 13th, 1916, against UB-29, a German submarine. Two depth charges had sufficed for her destruction, and indeed, the numbers dropped for each kill in WWI gave a serious underappreciation of what the Navy would need to drop in the future.
Two month after that success, and even before the U.S. entered the war, the USN began to develop a depth charge of their own, which was too weak to be successful. However, after the U.S. entry, the Royal Navy provided an example of their depth charges, which the U.S. fitted with a hydrostatic fuze of their own.
The final U.S. WWI depth charge could detonate at up to 300ft depth and
carried 300lbs explosives.
During the inter-war years, there was little effort for better depth charges, but the 600lbs variant was adopted for stern racks because of its better chance of success; the 300lbs variants were retained for the projectors.
for the ASW department with essentially the same weapon it had ended WWI
with, and development concentrated on increasing the depth in which a submarine
might be successfully attacked; coupled with that, the sinking speed of
the depth charges had to be increased.
Depth charges were abandoned by the U.S. Navy not much after World War II, the Navy preferring torpedos and ahead thrown proximity & contact weapons. Helicopters were the last U.S. weapons platform to retain depth charges, and many brown-water navies continue to use the depth charge today, in lieu of the hardly effective homing torpedos (since their sonar has problems distinguishing the bottom of shallow waters from a potential target).
The standard method of deploying a depth charge was by running it down a rail on the aft end of a ship. Different depth charges would be set a different depths, so a nice pattern would result and the submarine would, hopefully, end up in pieces.
This was a useful strategy in WWI, but a submarine could evade this if
it had already dived some time before. A more widespread pattern was needed
to catch such a target. The obvious solution to this problem was throwing
the depth charges far to the side, so as to create a sort of depth charge
carpet. For this purpose, the Y-gun was created.
This was a projector, firing depth charges using a small explosive charge, located on the centerline of a ship and having two "exits", forming a Y. On each exit, a depth charge was tied, to be fired off in support of the other charges, and landing some hundreds of yards outboard.
an effective addition to the ASW forces, with one major flaw: it could
only be mounted on the centerline, a location were traditionally little
room is available.
Several of these could be and were mounted on each destroyer. They were the fleet destroyers' main and most effective ASW weapon, as those didn't receive Hegehog.
||Mk 6 (Early War)
Weight: 338 kg / 745lbs
Charge: 272 kg / 600lbs Torpex
Sinking Speed: 2.4m/s / 8f/s later mods (mid-1942) 3.7m/s / 12f/s
Depth: 9 - 91m / 30 - 300ft later mods (mid-1942) up to 183m / 600ft
Mk 9 (Late War)