W41 (nuclear weapon)
For technical reasons, this article heading is W41 for a device actually designated B41
- B41Y1: "dirty" high-fallout with a yield of 25 Mt[note 1]
- B41Y2: "clean" less than 10 Mt yield.
It is unclear if the Soviets ever deployed a weapon in this range; their 58-megaton[note 1] "Tsar Bomba", which is generally believed to be the Primary and Secondary only for a 100-megaton device, was experimental although sufficiently weaponized to be dropped from a modified bomber. Only the Soviets and Americans ever tested devices with greater than 10 Mt yield.
The B41Y1 was the only three-stage device (see fusion device) ever built by the United States. As opposed to the usual fission Primary and fusion Secondary of a Teller-Ulam design, this bomb's uranium tamper constituted a Tertiary. The Y2 version lacked the Tertiary.
In the Y2 version, the device had the highest weight-to-yield ratio of any United States nuclear weapon. Carey Sublette quoted Theodore Taylor as saying the maximum practical ratio was 6.0 kt yield per kilogram of nuclear weapon; the deployed weapon, with parachutes and other weight that was not part of the ratio calculation, was 10,670 pound (4,840 kg). Test devices from which the B-41 was weaponized, however, were in the 9,100 pound (4,128 kg) range, consistent with Taylor's estimate.
Approximately 500 were built, between September 1960 and June 1962, and were in service from November 1963 to July 1976. It was replaced by the 9 Mt B53, which also was implemented as the W53 warhead for the UGM-27 Titan II intercontinental ballistic missile.
- The energy yields of nuclear weapons are commonly expressed in units of TNT equivalent, meaning the energy yield from the explosion of a stated amount of trinitrotoluene (TNT). The commonly used units are a kilotonne or a megatonne of TNT equivalent. A kilotonne (kt) of TNT equivalent is equal to 1012 joules and a megatonne (Mt) of TNT equivalent is equal to 1015 joules. The kilotonne and megatonne are often taken to be synonymous with kiloton and megaton.
- Globalsecurity.org, B-41
- Sublette, Carey, "The B-41 (Mk-41) Bomb: High yield strategic thermonuclear bomb", Nuclear Weapon Archive