Variable yield

Variable yield—or dial-a-yield—is an option available on most modern nuclear weapons. It allows the operator to specify a weapon's yield, or explosive power, allowing a single design to be used in different situations. For example, the Mod-10 B61 bomb had selectable explosive yields of 0.3, 5, 10 or 80 kilotons, depending on how the ground crew set a dial inside the casing when it was loaded onto an aircraft.

Variable yield technology has existed since at least the late 1950s. Examples of variable yield weapons include the B61 nuclear bomb family, B83, B43, W80, W85, and WE177A warheads.

Most modern nuclear weapons are Teller–Ulam design type thermonuclear weapons, with a fission primary stage and a fusion (or fission) secondary stage which is collapsed by the energy from the primary. These offer at least three methods to vary yield:

All current British nuclear warheads incorporate variable yield technology as standard.

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