The US National Nuclear Security Administration (NNSA) has finished production of the W88 Alt 370, an upgraded nuclear warhead for Ohio-class ballistic missile submarines. The completion of the $3.4 billion modernization program marks a key milestone in refreshing America’s sea-based nuclear deterrent, with future efforts now accelerating toward next-generation warheads.
In a significant update to the nation’s underwater nuclear arsenal, the final unit of the W88 Alt 370 warhead has rolled off the production line. Announced by the National Nuclear Security Administration (NNSA) this week, the upgrade program began design work in 2013 and moved rapidly from its first production unit to completion in about four years. While not classified as an entirely new warhead under nonproliferation rules, the Alt 370 represents a substantial modernization of the legacy W88, incorporating critical enhancements for safety, reliability, and performance.
“Completion of the last W88 Alt 370 testifies to the successful collaboration we’ve had with our U.S. Navy and Department of [Defense] partners,” stated David Hoagland, NNSA Acting Deputy Administrator for Defense Programs. According to the NNSA release, the momentum from this program will now fuel other expanding modernization efforts in the coming years.
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The upgrades are substantial but focused on the warhead’s internal systems. The Alt 370 project involved replacing the arming, fuzing, and firing assembly, adding a lightning arrestor connector, refreshing the conventional high explosives, and swapping out limited-life components. This meticulous refurbishment ensures the warheads deployed on Ohio-class submarines remain effective and secure for decades to come.
This program is the second major leg of a nuclear warhead modernization initiative launched under the Obama administration to be completed. Earlier this year, the NNSA wrapped up production of the B61-12 guided nuclear gravity bomb. A higher-yield variant, the B61-13, saw its first production unit completed in June 2024.
With the W88 Alt 370 program concluded, the skilled workforce is shifting to other pressing naval nuclear projects. The announcement notes that staff will now focus “more fully on acceleration” of two other key efforts. The first is the controversial sea-launched cruise missile (SLCM-N) program. The second, and arguably more significant for the long-term, is the development of the completely new W93 warhead. This future warhead is intended for deployment on both American Ohio- and Columbia-class submarines, as well as on future British ballistic missile submarines.
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The completion of the W88 Alt 370 is more than a manufacturing checkbox. It represents the steady, behind-the-scenes work of maintaining a credible nuclear triad—the combination of land-based missiles, strategic bombers, and submarine-launched weapons that form the backbone of U.S. strategic deterrence. As geopolitical tensions underscore the importance of a reliable and modern nuclear deterrent, this successful program ensures one leg of that triad remains at peak readiness while paving the way for its eventual successor.
