The B83 was based partly on the earlier B77 program, which was terminated because of cost overruns. The B77 was designed with an active altitude control and lifting parachute system for supersonic low-altitude delivery from the B-1A bomber. B77 nuclear component test firings were attributed to the Operation Anvil series in 1975 and 1976, specifically the "Cheese" test shots in Anvil:[2]
Anvil Kasseri – 28 October 1975, 1,200 kilotonnes of TNT (5,000 TJ) (B77/B83 full yield)
The B83 nuclear components have been attributed as the same as the earlier B77.
The B83 replaced several earlier weapons, including the B28, B43, and to some extent the ultra-high-yield B53. It was the first U.S. nuclear weapon designed from the start to avoid accidental detonation, with the use of "insensitive explosives" in the trigger lens system. Its layout is similar to that of the smaller B61, with the warhead mounted in the forward part of the weapon to make the bomb nose-heavy. It was intended for high-speed carriage (up to Mach 2.0) and delivery at high or low altitude. For the latter role, it is equipped with a parachute retardation system, with a 46-foot (14 m) Kevlarribbon parachute capable of rapid deceleration. It can be employed in free-fall, retarded, contact, and laydown modes, for air-burst or ground-burst detonation. Security features include next-generation permissive action link (PAL) and a command disablement system (CDS), rendering the weapon tactically useless without a nuclear yield.[2]
With the dismantling of the last B53 bomb in 2011, the B83 became the highest yield nuclear weapon in the U.S. arsenal.[3] In 2022, the Biden administration announced plans to retire the B83.[4] The B61-13 is planned to replace the B83. Although its yield is lower at 360 kilotonnes of TNT (1,500 TJ), it incorporates guidance features of the B61-12 for better accuracy while being more powerful than that version to strike harder and large-area targets.[5]
Design
The bomb is 12 feet (3.7 m) long, with a diameter of 18 inches (460 mm). The actual nuclear explosive package, judging from published drawings, occupies some 3 to 4 ft (0.91 to 1.22 m) in the forward part of the bomb case. The bomb weighs approximately 2,400 pounds (1,100 kg). The location of the lifting lugs shows that the greater part of the total mass is contained in the nuclear explosive.
The bomb has a variable yield: the destructive power is adjustable from somewhere in the low kiloton range up to a maximum of 1.2 megatonnes of TNT (5.0 PJ), some 80 times the explosive power of the bomb dropped on Hiroshima. The weapon is protected by a Category "D"Permissive Action Link (PAL) that prevents the enabling or detonation of the weapon without proper authorization.[6][7]
About 650 B83s were built, and the weapon remains in service as part of the United States "Enduring Stockpile".[2]
Aircraft capable of carrying the B83
The following aircraft are certified for carrying the B83 bomb:
Nuclear capability has been removed from the B-1B, mostly attributed to START I & START II,[10][11] and the B-52 no longer carries gravity nuclear bombs.[9]
The physics package contained within the B83 has been studied for use in asteroid impact avoidance strategies against any seriously threatening near earth asteroids. Six such warheads, configured for the maximum 1.2 megatonnes of TNT (5.0 PJ), would be deployed by maneuvering space vehicles to "knock" an asteroid off course, should it pose a risk to the Earth.[12]
