The W81 was a planned American warhead to be mounted on the SM-2 surface-to-air missile used by the United States Navy. The W81 was believed to be derived from the B61 nuclear bomb which forms the backbone of the current US nuclear gravity bomb arsenal and from which the W80 cruise missile warhead is derived. The weapon was being designed at Los Alamos National Laboratory (at the time called Los Alamos Scientific Laboratory). [1]
The W81 went through several design iterations, starting with an enhanced radiation model, then a pure fission model and cancelled in 1986. [1]
Characteristics are not known in detail, but the B61 it is derived from has a physics package (bomb core) of about 12 inches (30 cm) diameter with length of 32 inches (81 cm), weighing around 300 pounds (140 kg) (see the W80, another B61 derived design). Available LASL images show a much shorter weapon, perhaps 12 by 16 to 18 inches (30 by 41 to 46 cm), probably the final fission-only W81 concept, corresponding with the size of the B61 fission primary alone. [2]
The LASL image clearly shows the warhead taking up most, but not all, of the 13.5 inches (34 cm) SM-2 body diameter.
A warhead is the forward section of a device that contains the explosive agent or toxic material that is delivered by a missile, rocket, torpedo, or bomb.
A neutron bomb, officially defined as a type of enhanced radiation weapon (ERW), is a low-yield thermonuclear weapon designed to maximize lethal neutron radiation in the immediate vicinity of the blast while minimizing the physical power of the blast itself. The neutron release generated by a nuclear fusion reaction is intentionally allowed to escape the weapon, rather than being absorbed by its other components. The neutron burst, which is used as the primary destructive action of the warhead, is able to penetrate enemy armor more effectively than a conventional warhead, thus making it more lethal as a tactical weapon.
Nuclear weapon designs are physical, chemical, and engineering arrangements that cause the physics package of a nuclear weapon to detonate. There are three existing basic design types:
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.
The B61 nuclear bomb is the primary thermonuclear gravity bomb in the United States Enduring Stockpile following the end of the Cold War. It is a low to intermediate-yield strategic and tactical nuclear weapon featuring a two-stage radiation implosion design.
The Mk/B53 was a high-yield bunker buster thermonuclear weapon developed by the United States during the Cold War. Deployed on Strategic Air Command bombers, the B53, with a yield of 9 megatons, was the most powerful weapon in the U.S. nuclear arsenal after the last B41 nuclear bombs were retired in 1976.
The W80 is a low to intermediate yield two-stage thermonuclear warhead deployed by the U.S. enduring stockpile with a variable yield ("dial-a-yield") of 5 or 150 kilotonnes of TNT.
A thermonuclear weapon, fusion weapon or hydrogen bomb is a second-generation nuclear weapon design. Its greater sophistication affords it vastly greater destructive power than first-generation nuclear bombs, a more compact size, a lower mass, or a combination of these benefits. Characteristics of nuclear fusion reactions make possible the use of non-fissile depleted uranium as the weapon's main fuel, thus allowing more efficient use of scarce fissile material such as uranium-235 or plutonium-239. The first full-scale thermonuclear test was carried out by the United States in 1952; the concept has since been employed by most of the world's nuclear powers in the design of their weapons.
The W88 is an American thermonuclear warhead, with an estimated yield of 475 kilotonnes of TNT (1,990 TJ), and is small enough to fit on MIRVed missiles. The W88 was designed at the Los Alamos National Laboratory in the 1970s. In 1999, the director of Los Alamos who had presided over its design described it as "the most advanced U.S. nuclear warhead". As of 2021, the latest version is called the W88 ALT 370, the first unit of which came into production on 1 July, 2021, after 11 years of development. The Trident II submarine-launched ballistic missile (SLBM) can be armed with up to eight W88 warheads or twelve 100 kt W76 warheads, but it is limited to eight warheads under the Strategic Offensive Reductions Treaty.
W70 was a two-stage, thermonuclear warhead that was developed for the MGM-52 Lance missile by the United States. Designed by Lawrence Livermore National Laboratory, the Mod 1 and Mod 2 version of the weapon entered service in 1973, while the enhanced radiation Mod 3 weapon entered service in 1981. The last W70 warhead was dismantled in February 1996.
The W71 nuclear warhead was a US thermonuclear warhead developed at Lawrence Livermore National Laboratory in California and deployed on the LIM-49A Spartan missile, a component of the Safeguard Program, an anti-ballistic missile (ABM) defense system briefly deployed by the US in the 1970s.
The W66 thermonuclear warhead was used on the Sprint anti-ballistic missile system, designed to be a short-range interceptor to shoot down incoming ICBM warheads.
The W84 is an American thermonuclear warhead initially designed for use on the BGM-109G Gryphon Ground Launched Cruise Missile (GLCM).
The Mark 6 nuclear bomb was an American nuclear bomb based on the earlier Mark 4 nuclear bomb and its predecessor, the Mark 3 Fat Man nuclear bomb design.
The W73 was a planned nuclear warhead for the AGM-53 Condor air to surface missile and designed by Los Alamos Scientific Laboratory. The W73 warhead was cancelled in 1970 in favor of a purely conventional warhead for Condor. Condor was approved for production in 1975 with a expected production run of 250 missiles, but was cancelled in early 1976 due to high cost.
The B61 Family is a series of nuclear weapons based on the B61 nuclear bomb.
The Mark 27 nuclear bomb and closely related W27 warhead were two American thermonuclear bomb designs from the late 1950s.
The W64 nuclear warhead was the Los Alamos Laboratory's entry into a brief competition between Lawrence Livermore Laboratory and Los Alamos to design an "enhanced-radiation" nuclear warhead for the United States Army's MGM-52 Lance tactical surface-to-surface missile. In July 1964, both Livermore Labs and Los Alamos started developing competing warheads for the Lance. The Los Alamos design, the W64, was canceled in September 1964 in favor of Livermore's W63. In November 1966, the W63 was canceled in favor of the W70, the model that finally entered production.
The uranium hydride bomb was a variant design of the atomic bomb first suggested by Robert Oppenheimer in 1939 and advocated and tested by Edward Teller. It used deuterium, an isotope of hydrogen, as a neutron moderator in a uranium-deuterium ceramic compact. Unlike all other fission-based weapon types, the concept relies on a chain reaction of slow nuclear fission. Bomb efficiency was adversely affected by the cooling of neutrons since the latter delays the reaction, as delineated by Rob Serber in his 1992 extension of the original Los Alamos Primer.
USN Standard SM-2 SAM warhead; PAL F; variant of Mk/B-61 warhead, enhanced radiation version initially planned, later converted to fission only,