W80 ( nuclear warhead ) The W80 is a small thermonuclear warhead ( fusion or , more descriptively , two - stage weapon ) in the enduring stockpile with a variable yield of between 5 and 150 kt of TNT . It was designed for deployment on cruise missile s and is the warhead used in the majority of nuclear - armed US Air Force ALCM and ACM missiles , and their US Navy counterpart , the BGM - 109 Tomahawk . It is essentially a modification of the widely deployed B61 weapon , which forms the basis of most of the current US stockpile . The very similar W84 warhead was deployed on the BGM - 109G Gryphon GLCM . Dimensions . The W80 is physically quite small : the " physics package " itself is about the size of a conventional Mk . 81 bomb , in diameter and long , and only slightly heavier at about . Armorers have the ability to select the yield of the resulting explosion in - flight , a capability sometimes referred to as " dial - a - yield " but more properly variable yield . At one end of the scale , perhaps using just the boosted fission primary , the W80 has destructive power equivalent to around 5 kilotons of TNT ; at the other end , the yield is equivalent to around 150 kt . History . Early development . The Los Alamos National Laboratory began development on the W80 in June 1976 , with the brief of producing a custom weapon for the cruise missile s then under construction . The main differences between the W80 and W61 appear to relate to the physical packaging of the device , and to the removal of the 0 . 3 kt yield mode ; the W61 apparently needed this feature when deployed as a depth charge , a role for which the W80 was not intended . Production of the W80 Model 1 ( W80 - 1 or Mod 1 ) to arm the ALCM started in January 1979 , and a number of warheads had been completed by January 1981 when the first low - temperature test was carried out . To everyone ' s surprise the test delivered a much lower yield than was expected , apparently due to problems in the TATB based insensitive high explosive s used to fire the primary . This problem turned out to affect several models of the B61 - based line , and production of all weapons was suspended while a solution was worked on . Production restarted in February 1982 . In March 1982 , designers began working on a W80 variant intended for the Navy ' s Tomahawk program . The W80 Model 0 ( W80 - 0 or Mod 0 ) used " supergrade " fission fuel , which has less radioactivity , in the primary in place of the conventional plutonium used in the Air Force ' s version . " Supergrade " is industry parlance for plutonium alloy bearing an exceptionally high fraction of Pu - 239 ( > 95 % ) , leaving a very low amount of Pu - 240 which is a gamma emitter in addition to being a high spontaneous fission isotope . Such plutonium is produced from fuel rod s that have been irradiated a very short time as measured in MW - Day / Ton burnup . Such low irradiation times limit the amount of additional neutron capture and therefore buildup of alternate isotope products such as Pu - 240 in the rod , and also by consequence is considerably more expensive to produce , needing far more rods irradiated and processed for a given amount of plutonium . Submarine crew members routinely operate in close proximity to stored weapons in torpedo rooms , in contrast to the Air Force where exposure to warheads is relatively brief . This justified the additional costs of the premium supergrade alloy used on the Navy weapon . The first models were delivered in December 1983 and the Mod 0 went into full production in March 1984 . Production of the W80 was completed by September 1990 , although the exact date at which the respective Mod 0 and Mod 1 runs ended is not clear . A total of 1750 Mod 1 and 367 Mod 0 devices were delivered ; 1 , 000 Mod 1 devices were deployed on the original ALCM , another 400 on the later ACM , and 350 Mod 0s on the Tomahawk . A number of the original ALCMs equipped with the Mod 1 later had their warheads removed in order to use them with conventional explosives ( the CALCM conversion ) , and under START II only 400 ACMs would retain their warheads and the rest would be removed , apparently with all remaining ALCMs converted to CALCMs and their warheads removed to the " inactive stockpile " . With the fall of the START II treaty it is not clear what the current plans are , but it is highly likely they will take place as originally planned in order to remove the ALCM from service . Mod 0 armed Tomahawks are currently stored onshore , but there are / were plans to make this the primary US Navy nuclear weapon . 2007 nuclear weapons incident . On August 30 , 2007 , six cruise missiles armed with W80 - 1 warheads were mistakenly loaded onto a B - 52 and flown from Minot Air Force Base , North Dakota , to Barksdale Air Force Base , Louisiana , on a mission to transport cruise missiles for decommissioning . It was not discovered that the six missiles had nuclear warheads until the plane landed at Barksdale , leaving the warheads unaccounted for over 36 hours . This was the first time since 1968 that nuclear warheads were publicly revealed to have been transported on a US bomber . The munitions crews involved in mistakenly loading the nuclear warheads at Minot were temporarily decertified from performing their duties involving nuclear munitions .