U.S. nuclear warheads, 1945–2009
By Robert S. Norri s & Hans M. Kristensen
The United States has produced an estimated 66,500 nuclear bombs and warheads of 100 types and modifications for its operational stockpile since 1945. The accompanying table, “U.S. nuclear weapons designs, 1945–2009,” lists all types of U.S. weapons produced, from Little Boy to the W88.
The table includes some, but not all, canceled warhead programs.1 Some 5,200 warheads remain in the Defense Department stockpile, representing eight basic types of warheads and 15 modifications.2
All U.S. warheads were developed at one of two nuclear design laboratories, Los Alamos or Lawrence Livermore national laboratories.
Los Alamos has been the predominant design laboratory with 77 types to its credit, while Lawrence Livermore has designed 23 types. Today, Los Alamos maintains 11 types of weapons and Livermore four. All four services have had nuclear weapons: The air force has adopted 52 types, the navy 35 types, the army 26, and the marines 15. Today, the air force has 11 types and the navy 4; the army and marines have none.
The wide variety of warheads and bombs is evident in the profusion of weapon systems developed and adapted to accommodate them, and some warheads and bombs were adopted by more than one service. The earliest bombs weighed approximately 5 tons and could only be carried by large bombers. By the early 1950s, scientists had designed lighter-weight, smaller-diameter bombs that were adapted to dozens of types of air force, navy, and marine aircraft.
After thermonuclear bombs entered the stockpile in 1954, the megatonnage of the stockpile rose dramatically, reaching a peak of more than 20,000 megatons (the equivalent of 1,360,000 Hiroshimasized bombs) in 1960. The yields of individual weapons have varied from 100 tons (0.10 kilotons) to 25 megatons (25,000 kilotons).
Throughout the 1950s and 1960s, the military requested a nuclear weapon for nearly every conceivable mission, including ballistic and cruise missiles, from short- to intercontinental-range, to be launched from both land and at sea. At one point, the air force even proposed launching a ballistic missile from an airplane, but the program—referred to as Skybolt—was cancelled. The air force had two types of air-to-air nuclear-armed missiles (known as the Falcon and Genie) and a high-altitude, surface-to-air, air-defense missile (known as the BOMARC), which was intended to be used to shoot down Soviet bombers. The navy adopted several types of nuclear weapons for anti-submarine warfare and surface ship air-defense missions, and its special forces carried backpack nuclear munitions.
The army had a variety of weapons intended to be used on the nuclear battlefield, including several calibers of artillery, ballistic missiles with ranges up to 1,750 miles (2,816 kilometers), air-defense missiles, and landmines. The marines shared some of these systems and had its own types of nuclear bombs.
The U.S. stockpile reached a peak of more than 32,000 warheads in 1967 but decreased by 30 percent during the next 20 years as the number of missions contracted and arms control limitations entered into force. Since the end of the Cold War, the stockpile has been cut by an additional 75 percent to approximately 5,200 warheads.
The Cold War tempo of warhead and bomb proposal, testing, development, production, deployment, and retirement has long ended. The last of more than 1,000 nuclear weapons tests since 1945 was conducted in 1992, and new warhead production ceased in 1992. Yet the military continues to introduce modified versions of warheads, with the B83 mod 1 introduced from 1993 to 1995, the B61 mod 11 introduced from 1997 to 2001, and the W76 mod 1 introduced beginning in 2008.
Nuclear Notebook is prepared by Robert S. Norris of the Natural Resources Defense Council and Hans M. Kristensen of the Federation of American Scientists.
1. Beyond the six cancelled warheads listed, other programs were cancelled: B10,
B/W13, B20, B22, B26, B/W29, Mk32, W35, W37, W42, B/W46, W51, W60, W63, W64,
W65,W67, W73, W74, W75, W86.
2. For a description of the current U.S. nuclear arsenal, see: Robert S. Norris and
Hans M. Kristensen, “Nuclear Notebook: U.S. Nuclear Forces 2009,” Bulletin of the
Atomic Scientists, March/April 2009, vol. 65, no 2, pp. 59–69.
Copyright © 2009 Bulletin of the Atomic Scientists
“U.S. nuclear weapons designs, 1945–2009,” lists all types of U.S. weapons produced, from Little Boy to the W88.