B61 Mod 11

B61
B61 training unit intended for ground crew. It accurately replicates the shape and size of a "live" B61 (together with its safety/arming mechanisms) but contains only inert materials
Type	Nuclear bomb
Service history
Used by	United States
Production history
Designer	Los Alamos National Laboratory
Designed	1963
Manufacturer	Pantex Plant
Produced	1968 (full production)
No. built	3,155
Variants	12
Specifications
Weight	700 pounds (320 kg)
Length	11 feet 8 inches (3.56 m)
Diameter	13 inches (33 cm)
Blast yield	0.3-340 kilotons

The B61 nuclear bomb is the primary thermonuclear gravity bomb in the U.S. following the end of the Cold War. It is a low to intermediate-yield strategic and tactical nuclear weapon featuring a two-stage radiation implosion design.

The B61 is of the variable yield ("dial a yield") design with a yield of 0.3 to 340 kilotons in its various mods. It has a streamlined casing capable of withstanding supersonic flight speeds. The weapon is 11 ft 8 in (3.56 m) long, with a diameter of about 13 inches (33 cm). Basic weight is about 700 pounds (320 kg), although the weights of individual weapons may vary depending on version and fuze/retardation configuration.

The B61, 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. 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 540 remain in active service, 415 in inactive service and 520 are awaiting dismantlement as of 2012^[update].

180 B61 bombs (in tactical variants) are deployed with NATO allies in Europe as part of the Nato Nuclear Weapons Sharing Program. NATO has agreed to vastly improve the capabilities of this force with the increased accuracy of the B61 Mod 12 upgrade and the delivery of the stealthy F-35. This will, for the first time, add a modest standoff capability to the B61.

Nine versions 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 Russian Continuity of Government facility at Kosvinsky Kamen, finished in early 1996, was designed to resist US earth-penetrating warheads and serves a similar role as the American Cheyenne Mountain Complex. The timing of the Kosvinsky completion date is regarded as one explanation for U.S. interest in a new nuclear bunker buster and the declaration of the deployment of the B-61 mod 11 in 1997: Kosvinsky is protected by about 1,000 feet (300 m) of granite.