B61 nuclear bomb
The B61 nuclear bomb is the the primary thermonuclear weapon in the U.S. Enduring Stockpile following the end of the Cold War.
Developed in the 1960s, the B61 is a variable-yield bomb designed for carriage by high-speed tactical aircraft. It has a streamlined casing capable of withstanding supersonic flight speeds. It is 11' 8" (3.58 m) long, with a diameter of about 13" (33 cm). Basic weight is about 700 lb (317.5 kg), although some versions are heavier.
Most versions of the B61 are equipped with a parachute retarder (currently a 24' (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 released at speeds up to Mach 2 and altitudes as low as 50 feet (15.24 m). Fusing for most versions is by radar, although the B61 Mod 11 is a hardened penetration bomb with a delayed-action fuse, intended to penetrate fortifications before detonating.
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 350 kilotons. The earth-penetrating Mod 11 apparently has a single, undisclosed yield.
The basic "physics package" of the B-61 is shared with the W80 warhead used by several U.S. cruise missiles.
The B61 was designed in 1963. Testing began in 1966, with full production beginning in 1968. Total production of all versions was approximately 3,155, of which approximately 1,925 remain in service as of 2002. The warhead has changed little over the years, although early versions have been upgraded to improve their safety features.
The B61 can be deployed by a very wide variety of U.S. military aircraft including:
German and Italian Panavia Tornado IDS aircraft can also carry the B61.
It is likely (although currently unconfirmed) that the F/A-22 Raptor and F-35 will be capable of employing the B61.
Approximately 150 are deployed with USAF units in Great Britain, Germany, and Turkey, and held in U.S. custody for use by NATO squadrons in Belgium, Germany, Italy, the Netherlands, and Turkey.