B61 nuclear bomb

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B61 bomb in various stages of assembly.

The B61 nuclear bomb is the primary thermonuclear weapon in the U.S. Enduring Stockpile following the end of the Cold War.

1 Development
2 Design
3 See also
4 External links

[edit] Development

The B61, originally known (before 1968) as the TX-61, was designed in 1963. It was designed and built by the Los Alamos National Laboratory in New Mexico. It began from a program for a lightweight, streamlined weapon launched in 1961, and was formally designated TX-61 in 1963. Production engineering began in 1965, with full production beginning in 1968 following a series of development problems.

Total production of all versions was approximately 3,155, of which approximately 1,925 remain in service as of 2002, and some 1,265 are considered to be operational. The warhead has changed little over the years, although early versions have been upgraded to improve their safety features.

Nine versions (or 'Mods') of the B61 have been produced. Each shares the same 'physics package,' with different yield options.

The newest variant is the B61 Mod 11, deployed in 1997, which is a ground-penetrating bunker buster.

The B61 has been deployed by a very wide variety of U.S. military aircraft. Aircraft cleared for its use have included the B-1, B-2, B-52, and FB-111 strategic bomber aircraft; the F-100 Super Sabre, F-104 Starfighter, F-105 Thunderchief, F-111 and F-4 Phantom II fighter bombers; the A-4 Skyhawk, A-6 Intruder, and A-7 Corsair II attack aircraft; the F-15 Eagle and F-15E Strike Eagle, F-16, F/A-18 Hornet and Super Hornet; and the F-117 (although some sources claim the F-117 was never wired to carry nuclear weapons). German and Italian Panavia Tornado IDS aircraft can also carry the B61. It is likely (although currently unconfirmed) that the F-22 Raptor and F-35 will be capable of employing the B61, likely on external pylons since the bomb is too large for either aircraft's internal weapons bays (unlike the F-117, which has sufficient clearance), compromising their stealthiness.

Approximately 480 are deployed with USAF units in the United Kingdom, Germany, and Turkey, 150 of which are held in U.S. custody for use by NATO squadrons in Belgium, Germany, Italy, the Netherlands, and Turkey under a nuclear weapons sharing agreement [1]. The remainder are generally stored with the USAF's 4th Fighter Wing at Seymour Johnson Air Force Base and the 27th Fighter Wing at Cannon Air Force Base.

The B61 gravity bomb should not be confused with the MGM-1 Matador cruise missile, which originally was developed under the bomber designation B-61.

[edit] Design

A B61 bomb undergoing disassembly.

The B61 is a variable-yield bomb designed for carriage by high-speed aircraft. It has a streamlined casing capable of withstanding supersonic flight speeds. The weapon is 11 ft 8 in (3.58 m) long, with a diameter of about 13 in (33 cm). Basic weight is about 700 lb (317.5 kg), although the weights of individual weapons may vary depending on version and fuse/retardation configuration.

The newest variant is the B61 Mod 11, a hardened penetration bomb with a reinforced casing (according to some sources, containing depleted uranium) and a delayed-action fuse, allowing it to penetrate several metres into the ground before detonating, damaging fortified structures further underground [2]. The Mod 11 weighs about 1,200 lb (541 kg). Developed from 1994, the Mod 11 went into service in 1997 replacing the older megaton-yield B53 bomb, a limited number of which had been retained for anti-fortification use. About 50 Mod 11 bombs have been produced, their warheads converted from Mod 7 bombs. At present, the primary carrier for the B61 Mod 11 is the B-2 Spirit.

Most versions of the B61 are equipped with a parachute retarder (currently a 24-ft (7.32 m) diameter nylon/Kevlar chute) to slow the weapon in its descent, giving the aircraft a chance to escape the blast (or to allow the weapon to survive impact with the ground in laydown mode). The B61 can be set for airburst, ground burst, or laydown detonation, and can be released at speeds up to Mach 2 and altitudes as low as 50 feet (15.24 m). Fusing for most versions is by radar.

The B61 is a variable-yield, kiloton-range weapon. Tactical versions (Mods 3, 4, and 10) can be set to 0.3, 1.5, 5, 10, 60, 80, or 170 kiloton explosive yield (depending on version). The strategic version (B61 Mod 7) has four yield options, with a maximum of 340 kilotons. Sources conflict on the yield of the earth-penetrating Mod 11; the physics package or bomb core components of the Mod 11 are apparently unchanged from the earlier strategic Mod 7, however the public declassified 2001 Nuclear Posture Review [3] states that the B-61-11 has only a single yield; some sources indicate 10 KT, others suggest the 340 kiloton maximum yield as the Mod-7.

The early Mods 0, 1, 2, and 5 have been retired (Mods 6, 8, and 9 were cancelled before production), and the Mod 10 has been moved to the inactive stockpile, leaving the Mods 3, 4, 7, and 11 as the only variants in active service.

The U.S. is refurbishing the B61 bombs under its Life Extension Program with the intention that the weapons should remain operational until at least 2025.[4]