B61

Development of the B61 was authorized in December 1962 to modernize the United States nuclear arsenal and simplify the inventory by replacing older nuclear bombs. Designated the TX-61 in January 1963, the program utilized components from existing weapon designs to meet development schedules. Environmental specifications required operation across wide temperature ranges and high shock thresholds. The first war-reserve B61-0 was accepted in December 1966. Following design modifications, production resumed in January 1968. Testing was conducted at the Nevada Test Site between 1963 and 1968, including the Flintlock Halfbeak test in June 1966.

The B61 is a two-stage radiation implosion thermonuclear gravity bomb featuring a variable yield design. It is a Full Fuzing Option weapon, configured for air burst, ground burst, free-fall, retarded free-fall, and laydown delivery. The bomb has a streamlined casing for supersonic release and is equipped with spin motors to provide stability during high-speed delivery. Ground arming is performed via an access panel, which includes a command disable mechanism that uses a thermal battery to disable internal circuitry without causing detonation. Certain variants utilize a parachute retarder for low-altitude or laydown delivery. The Mod 11 variant is a hardened ground penetrator with a reinforced casing and delayed-action fuze for striking underground structures. The Mod 12 variant incorporates an internal guidance system and a guided tail-kit assembly that allows the weapon to glide to its target, improving accuracy and enabling lower-yield options to achieve strategic effects. The Mod 13 is a high-yield variant designed for strategic delivery.

The B61 is widely deployed by the United States and several NATO allies. Under the NATO nuclear sharing arrangement, the weapon is stored at bases in Belgium, Germany, Italy, the Netherlands, and Turkey, with the United Kingdom also participating in the dual-capable aircraft mission. Certified delivery platforms include strategic bombers, such as the B-2 Spirit, and fighter aircraft, including the F-35A Lightning II, F-15E Strike Eagle, F-16 Fighting Falcon, and Panavia Tornado IDS. The forthcoming B-21 Raider is planned to carry the weapon.