page_title: B61 nuclear bomb
section_title: Development
hierarchical_section_title: B61 nuclear bomb / Development
caption_attribution_description: English: B61 nuclear bomb casing, MAPS Air Museum, North Canton, Ohio.
context_page_description: The B61 nuclear bomb is the primary thermonuclear gravity bomb in the United States Enduring Stockpile 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 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, is 11 ft 8 in long, with a diameter of about 13 inches. Basic weight is about 700 pounds, although the weights of individual weapons may vary depending on version and fuze/retardation configuration. As of 2020, it is undergoing a 12th modification. According to the Federation of American Scientists in 2012, the roughly 400 B61-12s will cost $28 million apiece.
context_section_description: 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. Shot Flintlock Halfbeak in June 1966 may have been a full yield test of the weapon with other tests conducted between 1963 and 1968 at the Nevada Test Site.
  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.
  13 versions of the B61 have been designed, known as Mod 0 through Mod 12.  Of these, nine have entered production. Each shares the same physics package, with different yield options. The newest variant is the Mod 11, deployed in 1997, which is a ground-penetrating bunker busting weapon. 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 Mod 11 in 1997: Kosvinsky is protected by about 1,000 feet (300 m) of granite.
  The B61 unguided bomb should not be confused with the MGM-1 Matador cruise missile, which was originally developed under the bomber designation B-61.
caption: B61 bomb casing; MAPS Air Museum, North Canton, Ohio.
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