|Unit cost||$28 million (Mod 12)|
|Produced||1968 (full production)|
|Mass||715 pounds (324 kg)|
|Length||141.6 inches (3.60 m)|
|Diameter||13.3 inches (34 cm)|
|Blast yield||Believed to be either 0.3–340 kt or 0.3–400 kt in the weapon's various mods.|
The B61 is of the variable yield ("dial-a-yield" in informal military jargon) design with a yield of 0.3 to 340 kilotons in its various mods. It is a Full Fuzing Option (FUFO) weapon, meaning it is equipped with the full range of fuzing and delivery options, including air and ground burst fuzing, and free-fall, retarded free-fall and laydown delivery. It has a streamlined casing capable of withstanding supersonic flight and 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. 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.
In 1961 a report was issued indicating Navy and Air Force interest in a lightweight bomb to replace existing weapons, but that both services had considerably different military requirements for such a weapon. However, the authors of the report believed that due to advances in technology it was possible for a single weapon to fulfill both requirements. This was followed by a report from Sandia in mid-1962, that believed that a lightweight nuclear bomb with full fuzing option was possible and that such a program could be completed in a short time-span, possibly by 1965 or 1966.
Development of the weapon that would become the B61 was authorized in December 1962. The justification for the program was that the new weapon would modernize the nuclear arsenal, improve the capability of aircraft and simplify the nuclear weapons inventory by replacing lower-yield versions of the B28 and B43 nuclear bombs. The desired production date was June 1965.
The weapon was designated the TX-61 in January 1963. Due to the short time-scales, it was decided to make maximum use of off-the-shelf components such as those developed for the B57 nuclear bomb. Environmental conditions specified included an indefinite temperature range of −60 °F (−51 °C) to 160 °F (71 °C), shocks of up to 40g, and in flight temperatures of up to 275 °F (135 °C) for up to 40 minutes. Parachute deployment was specified to produce a maximum load of 255 g (2,500 m/s2).
The weapon was designed and built by the Los Alamos National Laboratory in New Mexico. Production engineering began in 1965, with the first war-reserve B61-0 weapon accepted by the AEC in December 1966. However production was halted in May 1967 for design modifications to be made before resuming in January 1968. 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.
During testing, spin motors were added to the weapon to produce a spin of 5 revolutions per second. This was to improve stability and decoupling during high speed delivery. Three alternatives to the weapon were also explored for still-classified reasons. The first alternative was halted due to its similarity to the original TX-61 design, and the Department of Defense was unfavorable to the second option which halted its exploration. The TX-61 design was ordered to "proceed along the lines" of the third alternative in May 1964, though it is unclear what that means.
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
The B61 has been deployed by a variety of US military aircraft. US aircraft cleared for its use have included the
B61 tactical variants are deployed with NATO allies in Europe as part of the
The B61 is a variable yield ("dial-a-yield" colloquially) dual use tactical and strategic bomb equipped with Full Fuzing Option (FUFO) designed for external carriage by high-speed aircraft. It has a streamlined casing capable of withstanding supersonic flight. The original B61-0 weapon was 141.6 inches (3.60 m) long, with a diameter of 13.3 inches (340 mm) and a basic weight of 715 pounds (324 kg) with most later weapons having approximately the same dimensions and weight, except for the Mod 11 version which has a weight of approximately 1,200 pounds (540 kg).
The B61 is armed by ground-based personnel via an access panel located on the side of the bomb, which opens to reveal nine dials, two sockets, and a T-handle which manually triggers the "command disable" function. One of the sockets is for a MC4142 "strike enable" plug which must be inserted in order to complete critical circuits in the safety/arming and firing mechanisms. The other socket is the
The B61 "command disable" mechanism functions as follows: after entering the correct three-digit numeric code it is then possible to turn a dial to "DI" and pull back a T-shaped handle which comes away in the user's hand. This action releases a spring-loaded firing pin which fires the percussion cap on an MC4246A thermal battery, powering it up. Electrical power from the thermal battery is sufficient to "fry" the internal circuitry of the bomb, destroying critical mechanisms without causing detonation. This makes the bomb incapable of being used. Any B61 which has had the command disable facility activated must be returned to Pantex for repair.
Fuzing and delivery
The B61 can be set for airburst or groundburst detonation, and by
The Mod 11 is a hardened penetration bomb with a reinforced casing and a delayed-action
The B61 has 13 variants, referred to as Mod 0 through Mod 12.
|Mod||Status||Date[Note 1]||Number produced||Role||Yields||PAL type||Notes|
|0||Retired||1/67 to 9/93||500||Tactical||10 to 300 kt||Cat B||First production weapons|
|1||Retired||2/69 to 9/89||700||Strategic||10 to 340 kt||None|
|2||Retired||6/75 to 9/94||235||Tactical||10 to 150 kt||Cat D|
|3||Active||10/79 to present||545||Tactical||0.3, 1.5, 60, or 170 kt||Cat F|
|4||Active||8/79 to present||695||Tactical||0.3, 1.5, 10, or 45 kt||Cat F|
|5||Retired||6/77 to 9/93||265||Tactical||10 to 150 kt||Cat D|
|6||Never entered production||10 to 150 kt||Cat D||Conversion of Mod 0. Cancelled February 1992.|
|7||Active||9/85 to present||600||Strategic||Allegedly 4 yield settings, including 10, or 340 kt.||Cat D||Conversion of Mod 1, conversion completed by April 1990|
|8||Never entered production||10 to 150 kt||Cat D||Conversion of Mod 2 and Mod 5. Cancelled February 1992.|
|9||Never entered production||10 to 300 kt||Cat F||Conversion of Mod 0. Cancelled September 1991.|
|10||Inactive stockpile||8/90 to present||215||Tactical||0.3, 5, 10, or 80 kt||Cat F||Remanufactured from retired Pershing II W85 warheads.|
|11||Active||12/96 to present||50||Strategic||Disputed, either same as Mod 7 or 400 kt||Cat F||Conversion of Mod 7, earth penetrating weapon.|
|12||Active||First production unit 11/21||400 to 500 weapons planned||Tactical/Strategic||0.3, 1.5, 10, or 50 kt||Cat F||Conversion of Mod 4. To replace the Mods 3, 4 and 7.|
B61 Mod 3 and 4
A Sandia document on the dates of the development phases of the US nuclear stockpile describes the B61-3 as an "improved Mod 2 w/IHE" and the B61-4 as "same as Mod 3 ex. Hi-Y".
B61 Mod 5
A 1978 report on reducing or substituting beryllium in nuclear weapons noted that the B61-5 contained beryllium and that if the use of beryllium were to be restricted, the B61-5 could probably be replaced by the B61 Mod 3.
B61 Mod 6 and 8
The B61 Mod 6 and Mod 8 bombs were developed for use by the US Navy beginning in March 1987 and cancelled at the end of the Cold War. The weapons weighed 350 kilograms (770 lb), had a length of 3,597 millimetres (141.6 in) and a diameter of 338 millimetres (13.3 in), and were one-point safe, used insensitive high explosives (IHE) in their primary stages and utilized enhanced electrical safety (EES).
The weapons were to be built by converting existing B61-0, −2 and −5 weapons into Mod 6 and 8 weapons and the weapons were to use B61-7 weapon parts where possible. By mass, the largest deviations from the B61-7 were the Acorn assembly, MC4137 TSSG (trajectory sensing signal generator) and the JTA (described as "ballast for WR").
The weapon's computer was the MC4139 Programmer, two of which are used on independent channels, and is identical to the programmer used on the B61-7. The MC3656 Main Battery is identical to the battery used on the B61-7 and is thermally operated, providing 120 seconds of power for the weapon, but initial power is supplied by the MC2238 Pulse Batteries which are activated by the weapon's pullout switches during separation from the aircraft.
The weapon contained two neutron generators for initiation, used a 2400 volt 0.6 μF capacitor for neutron generator firing and a 3300 volt 2.0 μF capacitor for the firing set. If neither the radar fuze or the contact crystals actuated, the weapon would detonate at 120 seconds from arming.
The weapons were to initially use the MC4175 Trajectory Sensing Signal Generators which are identical to the TSSG found in the B61-7, but starting from 1991, the Mod 6 was to get a new MC4137 Trajectory Sensing Signal Generator. The MC4175 stored the arming signal for the trajectory stronglink it its memory, so it featured a pair of rolamite acceleration switches designed to prevent the possibility of the signal being transferred to the stronglink before the rolamites were actuated by the spinning of the weapon in flight. The MC4137 instead is provided the unique signal from the MC4139 Programmer, which stores it in a volatile memory that erases after approximately seven seconds of lost power, meaning that without intent from the MC4139 and continuously applied power the MC4137 does not know how to arm the safelink.
The weapon was to feature a number of weapon stronglinks. Stronglinks are part of the weapon's safety systems and are designed to be robust enough that they can survive abnormal environments long enough for the weapon's weaklinks to fail. This requires weak and stronglinks to be colocated so they are exposed to the same environmental conditions in an accident.
The first stronglink was the MC2969 Intent Stronglink Switch which was also used on the B61-3, −4 and −7, W78, W80 and B83 weapons. The MC2969 consisted of a 14-pin ceramic-insulated bank of switches that would close upon the receipt of the proper intent unique signal (IUQS) to its electromechanical decoder. Receipt of the wrong signal would lock the MC2969 in the open position until a specific unlock signal was received.
The second stronglink was the MC2935 Trajectory Stronglink Switch of which there were two, one for each channel of the weapon's firing set. Like the MC2969, it mechanically locked if it received the wrong input signals, but unlike the MC2969 it could only be manually unlocked, which could only take place at the factory. Signals for the MC2935 come from either of the two MC4175s or the MC4137 Trajectory Sensing Signal Generators.
A third stronglink existed inside the first exclusion region of the weapon and was involved in weapon arming. Details of the system are still classified.
B61 Mod 12
As of 2013 the Pentagon saw the
In 2013, the Pentagon and NNSA stated that if B61 refurbishment did not begin by 2019, components in the existing weapons could begin to fail. In 2013 Tom Collina of the Arms Control Association said that the new development could complicate arms control efforts with Russia.
In 2014, Congress slashed funding for the project and called for alternates to be studied. In January 2014, former Air Force Chief of Staff
In 2014 critics said that a more accurate and less destructive nuclear weapon would make leaders less cautious about deploying it, while Schwartz said it would deter adversaries more because the U.S. would be more willing to use it in situations where necessary. The improved accuracy would make it more effective than the previous Mod 3/4 currently deployed to the continent. F-16 and Panavia Tornado aircraft cannot interface with the new bomb due to electronic differences, but NATO countries buying the F-35 would be able to utilize it. The first flight test for an inert Mod 12 was conducted in 2015, with a second successful test in August 2017.
Despite claims the Mod 12 has an earth penetrating capability, the weapon does not have the reinforced structure like that of the Mod 11, which is required to function as an earth penetrating weapon. The Mod 11 will be retained in service for the ground penetrating mission.
The Mod 12 Life Extension Program continued in 2018 and on 29 June 2018 two successful non-nuclear system qualification flight tests at Tonopah Test Range were reported. In October 2018, the Mod 12 guided tail-kit assembly received Milestone C approval to enter the production phase; the TKA went through the traditional test program in under 11 months, achieving a 100% success rate for all 31 bomb drops. The B61-12 nuclear bomb completed its successful flight tests with the US Air Force's F-15E in June 2020. It was dropped from above 25,000ft and was in the air for approximately 55 seconds before hitting the target.
The first B61-12 bomb was produced in November 2021. The weapon replaces the B61 mod 3, mod 4 and mod 7 bombs while the B61-11 will be retained in the stockpile. It is expected that the LEP will extend the B61's life by at least 20 years. Politico reported in October 2022 that the US military planned to accelerate the deployment of the Mod 12 in Europe. This drew criticism from the Russian Deputy Minister of Foreign Affairs Alexander Grushko, who accused the US government of "reducing the nuclear threshold" with the weapon's increased accuracy.
B61 Mod 13
The NNSA Stockpile Stewardship and Management Plan anticipates Phase 1 development for the B61 Mod 13 Life Extension Program (LEP) beginning in 2037 with first production of the weapon in 2050.
W61 Earth Penetrator Warhead
A W61 Earth Penetrator Warhead (EPW) with a yield of 340 kilotonnes of TNT (1,400 TJ) was developed for the AGM-129 Advanced Cruise Missile and the MGM-134 Midgetman small ICBM. The weapon entered Phase 1 initial development in January 1985 and phase 4 production engineering in September 1992 before being cancelled in December of that year.
In the Advanced Cruise Missile role, the weapon was to replace aging B53 bombs, but after the W61 cancellation the role was filled by the B61-11 bomb.
A declassified technical report on the automation of pit handling at Pantex indicates that the B61-2 and B61-5 share a common pit design, as do the B61-3, B61-10 and W85. The B61-0 and B61-4 do not share a pit with any other weapon. As the B61-7 was a retrofit of the B61-1 and the B61-11 was a retrofit of the B61-7, they presumably share a common pit.
In May 2010 the National Nuclear Security Administration asked Congress for $40 million to redesign the bomb to enable the Lockheed Martin F-35 Lightning II to carry the weapon internally by 2017. This version is designated Mod 12. The four hundred Mod 12 bombs will be used by both tactical aircraft (such as the F-35) and strategic aircraft (such as the B-2) and the Tail Subassembly (TSA) will give them Joint Direct Attack Munition levels of accuracy, allowing the fifty kiloton warhead to have strategic effects from all carrying aircraft. However, refitting the 400 weapons is now expected to cost over $10 billion. The Mod 12 tail assembly contract was awarded to Boeing on November 27, 2012 for $178 million. Boeing will use their experience with the Joint Direct Attack Munition to yield JDAM-equivalent accuracy in a nuclear bomb. This contract is only the first part of the billion-dollar expense of producing and applying the tail kits, over and above the $10 billion cost to refurbish the warheads. The Mod 12 uses an internal guidance system and can glide to its target. On 1 July 2015, the National Nuclear Security Administration (NNSA) conducted the first of three flight tests of the Mod 12 tail kit assembly.
- List of nuclear weapons
- Joint Direct Attack Munition
- B61 Family
- Weapons Storage and Security System
- B83 nuclear bomb
- In this context, date means from the start of Phase 6 full scale production to the retirement of the final weapon at the end of Phase 7.
- Kristensen, Hans (2013-01-16). "B61-12: NNSA's Gold-Plated Nuclear Bomb Project". Archived from the original on 16 January 2013. Retrieved 2012-07-26.
- History of the TX-61 Bomb (Report). Sandia National Laboratories. August 1971. Archived from the original on 2021-03-30. Retrieved 2021-02-05.
- "The B61 Bomb". Nuclear weapon archive. 9 January 2007. Archived from the original on 27 February 2009. Retrieved 2018-03-28.
- Sublette, Carey (9 January 2007). "The B61 Bomb". Nuclear Weapon Archive. Archived from the original on 27 February 2009. Retrieved 2012-06-09.
- "The B61 Life Extension Program" (PDF). Union of Concerned Scientists. May 2013. Archived (PDF) from the original on 16 June 2015. Retrieved 8 July 2017.
- "Window on Heartland: Geopolitical notes on Eastern Europe, the Caucasus and Central Asia". February 2012. Archived from the original on April 24, 2013.
- Gertz, William ‘Bill’ (April 1, 1997), "Moscow builds bunkers against nuclear attack", The Washington Times, Global security, archived from the original on March 9, 2014, retrieved May 12, 2014
- "Kosvinsky Mountain, Kos'vinskiy Kamen', Gora, MT 59°31'00"N 59°04'00"E, Russia". Global Security. Weapons of mass destruction. Archived from the original on 2014-08-05. Retrieved 2014-05-12.
- "The Bulletin of the Atomic Scientists", 26 October 2013
- De Boeck, Ann (July 16, 2019). "Eindelijk zwart op wit: er liggen Amerikaanse kernwapens in België". De Morgen. Archived from the original on July 16, 2019.
- Kristensen, Hans M. "New Report: US and Russian Non-Strategic Nuclear Weapons." Archived 2013-01-30 at the Wayback Machine Federation of American Scientists, 2 May 2012.
- Borger, Julian (21 April 2013). "Obama accused of nuclear U-turn as guided weapons plan emerges". The Guardian. Archived from the original on 4 November 2013. Retrieved 11 June 2013.
- Kristensen, Hans M. (30 October 2013). "Capabilities of B61-12 Nuclear Bomb Increase Further". Federation of American Scientists. Archived from the original on 2013-11-01. Retrieved 30 October 2013.
- "the nuclear information project: the B61-11". Nukestrat.com. Archived from the original on 2012-09-10. Retrieved 2012-06-09.
- "Glenn's Computer Museum-B61 Preflight Controller". Glennsmuseum.com. Archived from the original on 2012-04-25. Retrieved 2012-07-08.
- Developing and Producing the B-61. US Department of Energy. 1970s. Event occurs at 11m 56s. Archived from the original on 12 December 2016. Retrieved 10 July 2017.
- Final Development Report for the B61-7 Bomb (Report). Sandia National Laboratories. 1985.
- "NNSA Completes First Production Unit of B61-12 Life Extension Program". Energy.gov. Archived from the original on 2022-10-04. Retrieved 2022-11-19.
- "B61-12 Life Extension Program" (PDF). Archived from the original (PDF) on 2017-05-15. Retrieved 2018-02-03.
- "B61-12: The New Guided Standoff Nuclear Bomb" (PDF). Archived (PDF) from the original on 2017-12-02. Retrieved 2018-02-03.
- "Video Shows Earth-Penetrating Capability of B61-12 Nuclear Bomb". Archived from the original on 2016-06-30. Retrieved 2016-06-04.
- Special Task Group Report – Beryllium: Substitute Materials for Be and BeO in Nuclear Weapons Volume II – Impact on United States Department of Energy National Defense Programs of proposed Department of Labor (Occupational Health and Safety Administration) Beryllium Standards (Report). United States Department of Energy. 1 May 1978. Archived from the original on 7 June 2021. Retrieved 7 June 2021.
Of the LASL devices currently entering stockpile, the B61-3 and B61-4 do not contain beryllium. The B61-5 does, but the B61-3 could probably be substituted for it.
- Interim Development Report for the B61-6,8 Bombs (Report). Sandia National Laboratories and Los Alamos National Labs. May 1989. p. 9. SAND88-2986. Archived from the original on 2021-07-20. Retrieved 2021-05-28.
- Interim Development Report for the B61-6,8 Bombs, p. 9.
- Interim Development Report for the B61-6,8 Bombs, p. 11.
- Interim Development Report for the B61-6,8 Bombs, p. 16.
- Interim Development Report for the B61-6,8 Bombs, p. 21.
- Interim Development Report for the B61-6,8 Bombs, p. 26.
- Interim Development Report for the B61-6,8 Bombs, p. 31.
- Interim Development Report for the B61-6,8 Bombs, p. 17.
- Interim Development Report for the B61-6,8 Bombs, p. 36.
- Interim Development Report for the B61-6,8 Bombs, p. 37.
- Interim Development Report for the B61-6,8 Bombs, p. 22.
- Interim Development Report for the B61-6,8 Bombs, p. 48-50.
- Interim Development Report for the B61-6,8 Bombs, p. 41.
- Interim Development Report for the B61-6,8 Bombs, p. 18.
- Interim Development Report for the B61-6,8 Bombs, p. 19, 43.
- Interim Development Report for the B61-6,8 Bombs, p. 42-43.
- "Cold War Relic", Air force mag, 4 November 2013, archived from the original on 9 November 2013, retrieved 23 January 2014
- Reif, Kingston (2013-10-25). "Pentagon Pushes for Billions to Refurbish Nuclear Bombs". Bulletin of the Atomic Scientists. Archived from the original on October 29, 2013. Retrieved October 25, 2013.
- Rabechault, Mathieu (6 November 2013). "US to spend billions 'modernizing' nuclear arsenal". AFP. Archived from the original on 19 November 2013. Retrieved 7 November 2013.
- Guarino, Douglas P. (16 January 2014). "Nuclear Security and Omnibus Legislation: What's Up and What's Down". Nuclear Threat Initiative. Global Security Newswire. Archived from the original on 18 January 2014. Retrieved 16 January 2014.
- "General Confirms Enhanced Targeting Capabilities of B61-12 Nuclear Bomb", Federation of American Scientists, Fas, 23 January 2014, archived from the original on 22 December 2015, retrieved 12 December 2015
- Keck, Zachary (13 July 2015). "America and Russia Test New Tactical Nuclear Missiles". National interest. The National Interest. Archived from the original on 31 August 2021. Retrieved 13 July 2015.
- US conducts first flight test of guided B61-12 nuclear bomb, Flight global, 10 July 2015, archived from the original on 11 July 2015, retrieved 10 July 2015
- Video Shows Earth-Penetrating Capability of Mod 12 Nuclear Bomb Archived 2016-06-30 at the Wayback Machine – Fas.org, 14 January 2016
- Miles, Aaron (18 May 2019). "Is the Air Force Really Testing an 'Earth-Penetrating' Nuclear Bomb?". nationalinterest.org. Center for the National Interest. Archived from the original on 7 June 2019. Retrieved 7 June 2019.
- NNSA, Air Force complete successful end-to-end Mod 12 Life Extension Program flight tests at Tonopah Test Range Archived 2018-07-02 at the Wayback Machine GlobalSecurity.org
- US Air Force's Mod 12 nuclear bomb new guided tail-kit assembly enters production phase Archived 2018-12-15 at the Wayback Machine. Air Recognition. 10 December 2018.
- "B61-12". June 2020. Archived from the original on 2021-01-26.
- "Russia says US lowering 'nuclear threshold' with newer bombs in Europe". South China Morning Post. 30 October 2022. Archived from the original on 29 October 2022. Retrieved 29 October 2022.
- Kristensen, Hans (2021-12-15). "NNSA Removes F/A-18F Super Hornet From Nuclear Bomb Fact Sheet – Federation Of American Scientists". Fas.org. Archived from the original on 2022-02-12. Retrieved 2022-03-09.
- Nuclear Weapons Surety – Annual Report to the President 1988 (PDF) (Report). Department of Defense and Department of Energy. September 1989. p. 63. Archived (PDF) from the original on 2022-03-05.
ACM[EPW]/W61 schedule for which Phase 2A has been completed (Phase 3 is planned in the next few months) and will permit the removal of the B53 from standing alert.
- "NNSA Seeks $40M for Nuke Refurbishment Study", Global security news wire, May 18, 2010, archived from the original on July 6, 2010, retrieved May 19, 2010
- Kristensen, Hans. "B61 LEP: Increasing NATO Nuclear Capability and Precision Low-Yield Strikes." Archived 2016-09-15 at the Wayback Machine FAS, 15 June 2011.
- Kristensen, Hans. "B61-12: NNSA’s Gold-Plated Nuclear Bomb Project." 26 July 2012Archived 2013-01-16 at the Wayback Machine FAS, 26 July 2012.
- Boeing to Upgrade B61 Nuclear Free Fall Bomb, Deagel, November 27, 2012, archived from the original on April 6, 2013, retrieved November 28, 2012
- Boeing Receives $178 Million Contract for B61 Tail Kit Assembly, Media room, archived from the original on 2012-12-03, retrieved 2012-12-02
- Kristensen, Hans. "$1 Billion for a Nuclear Bomb Tail." Archived 2013-07-18 at the Wayback Machine FAS, 12 April 2013.
- "As U.S. Modernizes Nuclear Weapons, 'Smaller' Leaves Some Uneasy", The New York Times (information), 11 January 2016.
- Developing and Producing the B-61 (Google You tube), AEC.
- "B61", Weapons of mass destruction (information), Global Security.
- B61-11 Concerns and Background, Los Alamos Study Group, 1997, an anti-nuclear weapons organization
- Nelson, Robert W (January–February 2001), "Low-Yield Earth-Penetrating Nuclear Weapons", Science and Global Security, Federation of American Scientists, 54 (1): 1–20, S2CID 123478310.
- Norris, Robert S; Kristensen, Hans M; Handler, Joshua (2003), "The B61 family of bombs", , retrieved 2006-01-16.
- B61 Nuclear Bomb Preflight Controller Unit, Glenn’s museum.