Fortunately we were never in a position to test either version. One of our USN exchange pilots when asked told us it was classified US only … information … which means he didn’t know either.
Found this, the Brits took theirs to the Falklands War … who knew? Variable yield, don’t recall mention of that in the training. I was in Portsmouth when the Brits were packing up to head south with the NATO fleet. The sparkling modern British Destroyer that was also assigned to the fleet was taken away and they tossed us an old Dido class frigate to take it’s place.
Tim
https://en.wikipedia.org/wiki/Nuclear_depth_bomb#:~:text=A%2….
A nuclear depth bomb is the nuclear equivalent of the conventional depth charge, and can be used in anti-submarine warfare for attacking submerged submarines. The Royal Navy, Soviet Navy, and United States Navy had nuclear depth bombs in their arsenals at one point.
Due to the use of a nuclear warhead of much greater explosive power than that of the conventional depth charge, the nuclear depth bomb considerably increases the likelihood (to the point of near certainty) of the destruction of the attacked submarine.
Some aircraft were cleared for using these, such as the P2V Neptune, but none were used against any submarines.
Because of this much greater power some nuclear depth bombs feature a variable yield, whereby the explosive energy of the device may be varied between a low setting for use in shallow or coastal waters, and a high yield for deep water open-sea use. This is intended to minimise damage to peripheral areas and merchant shipping.
During the Falklands War, Britain’s naval task force carried 31 nuclear depth charges.