The B43 was developed from 1956 by Los Alamos National Laboratory, entering production in 1959. It entered service in April 1961. Total production was 2,000 weapons, ending in 1965. Some variants were parachute-retarded and featured a ribbon parachute.
The B43 was built in two variants, Mod 1 and Mod 2, each with five yield options. Depending on version, the B43 was 18 in (45 cm) in diameter, and length was between 12.5 ft (3.81 m) and 13.6 ft (4.15 m). The various versions weighed between 2,061–2,116 lb (935–960 kg). It could be delivered at altitudes as low as 300 ft (90 m), with fuzing options for airburst, ground burst, free fall, contact, or laydown delivery. Explosive yield varied from 70 kilotons of TNT to 1 megaton of TNT.
The B43 used the Tsetse primary design for its fission stage, as did several mid- and late-1950s designs.
The B43 was one of four thermonuclear gravity bombs carried by Canadian CF-104 jets while serving in Germany between June 1964 and 1972.
Carrier aircraft included most USAF, USN and USMC fighters, bombers and attack aircraft, including the A-3 Skywarrior, A-4 Skyhawk, A-5 Vigilante, A-6 Intruder, A-7 Corsair II, B-47 Stratojet, B-52 Stratofortress, B-58A Hustler, F-100 Super Sabre, F-105 Thunderchief, F-4 Phantom II, F-104 Starfighter, FB-111A strategic bomber variant, F-15E Strike Eagle, F-16 Fighting Falcon and the F/A-18 Hornet. The B-1B Lancer was also intended to carry the B43, though it remains unclear whether this particular aircraft was ever type-approved to carry the B43 prior to the B-1's reassignment to conventional strike roles. The B43 was also supplied for delivery by Royal Air Force Canberra and Valiant aircraft assigned to NATO under the command of SACEUR.
The B43 was never used in combat, but it was involved in a nuclear accident when an A-4E Skyhawk, BuNo 151022, of the USS Ticonderoga (CVA-14) (from Attack Squadron VA-56), was lost off the coast of Japan on 5 December 1965 when it rolled off an elevator, in 16,000 ft (2,700 fathoms; 4,900 m) of water in the Pacific Ocean, 80 mi (130 km) from Kikai Island, Kagoshima Prefecture, Japan. The Skyhawk was being rolled from the number 2 hangar bay to the number 2 elevator when it was lost. The pilot LTJG D. M. Webster, airframe, and the bomb were never found. No public mention was made of the incident at the time and it would not come to light until a 1989 Pentagon report revealed that a one-megaton bomb had been lost. Japan then asked for details of the incident.
- Clearwater, John, "Canadian Nuclear Weapons: The Untold Story of Canada's Cold War Arsenal", Dundurn Press, 1998, ISBN 1-55002-299-7, Chapter 3
- Maruyama Kuniaki 丸山邦明 (2005). "Gunji kichi mondai to Amami 軍事基地問題と奄美". In Kagoshima-ken chihō jichi kenkyūsho 鹿児島県地方自治研究所. Amami sengo-shi 奄美戦後史 (in Japanese).
- "Archived copy". Archived from the original on 2010-12-06. Retrieved 2010-03-28.CS1 maint: Archived copy as title (link)
- Broken Arrows at www.atomicarchive.com. Accessed Aug 24, 2007.
- Washington, D.C.: Washington Post, Reuter, "U.S. Confirms '65 Loss of H-Bomb Near Japanese Islands", Tuesday, 9 May 1989, page A-27.
- Washington, D.C.: Washington Post, "Japan Asks Details On Lost H-Bomb", Wednesday, 10 May 1989, page A-35.