Inside the Fast-Track Build of the B61-13 Nuclear Bomb

Source: US DOE | Flickr
Secretary of Energy Chris Wright quality stamps the B61-13 First Production Unit Monday May 19, 2025 at Pantex. Pictured are Joseph M. Oder, from left, Jason Armstrong, PFO, Secretary Chris Wright, Kelly Beierschmitt, PXD, Tom Mason, LANL, Rich Tighe, Y-12, and John Evans, NA-12. (Photographer Michael Schumacher)

David A. Hoagland of War on the Rocks reports that the B61 nuclear gravity bomb, first developed after the Cuban Missile Crisis, remains a cornerstone of the U.S. nuclear arsenal due to its adaptability. Over 60 years and 13 modifications later, the latest version—the B61-13—has been rapidly developed to address evolving threats, especially hardened and deeply buried targets. Built using lessons and infrastructure from the B61-12, the B61-13 features improved accuracy and yield without increasing the overall nuclear stockpile. Its accelerated development reflects a more agile U.S. nuclear modernization strategy amid growing global nuclear tensions. Hoagland writes:

Within months of the Cuban Missile Crisis, weapons designers at Los Alamos National Laboratory began engineering what would become the longest-serving and most adaptable weapon in America’s nuclear arsenal. Although it was ballistic missiles that had sparked the crisis in Cuba and came to symbolize the nuclear age, the new B61 would be an air-delivered gravity bomb. So named because it is dropped from an aircraft, gravity bombs had been a feature of aerial warfare since wooden biplanes released them over the trenches in World War I. But the B61 was a revolutionary weapon, featuring a versatility not seen in a nuclear munition before or since.

Sixty years later, it remains the primary family of gravity bombs in the U.S. nuclear stockpile. The B61’s longevity attests to both the timelessness of its role and the modularity of its original design. Indeed, there is no longer a single B61 today but an ensemble of weapon systems that all derive from the same progenitor. Thirteen variants, or modifications, have been developed, each with distinct characteristics and missions. A variety of modifications  can be delivered by a broad range of U.S. and allied aircraft, from strategic platforms like the B-2 stealth bomber to dual-capable fighters such as the F-15, F-16, F-35, and the European Tornado, as well as next-generation systems like the B-21 Raider. In various configurations, the bombs can be released in free-fall mode or with a speed-retarding parachute that when packed is denser than hardwood.

The latest descendant in this bloodline is the B61-13, whose first production unit the National Nuclear Security Administration heralded this week as part of the comprehensive modernization of the U.S. nuclear stockpile. […]

The B61-13 represents an intermediate answer to these edicts as even more effective instruments are being evaluated. While the bomb will provide new military capabilities, it will not be a novel weapon in the sense of being assembled from wholly new components and materials. Rather, the system is a modification, a subset of weapon modernizations that upgrade existing warheads with new operational characteristics. Most of the weapons in the U.S. nuclear arsenal were built in the 1970s and 1980s, and the B61 is one of seven systems undergoing modernization to extend their operability or add further capabilities. The planned W93 warhead, by contrast, will be an altogether new, modern weapon. […]

Even then, there was reason for optimism that nuclear weapons would continue to recede in relevance, as they had in the decade prior. Yet the behavior of America’s adversaries in the intervening years has made clear that nuclear deterrence will remain a dominant feature of the global landscape for the foreseeable future. Deterrence is not magically achieved by reaching an arbitrary threshold of missiles and bombs — it is a condition painstakingly attained and preserved by fielding the right number of the right weapons in the right places. The B61-13 is merely the latest output of the formula used to shape America’s nuclear arsenal, whose wisdom will ultimately be affirmed if these weapons never have to be used.

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