WASHINGTON — Production has completed on America’s newest submarine-launched nuclear warhead, according to the National Nuclear Security Administration (NNSA).
The last production unit of the W88 Alt 370, an upgraded version of the legacy W88 used on Ohio-class ballistic missile submarines, rolled off the line recently, NNSA announced on Tuesday. Design work began in 2013, but it took only about four years from first production unit to last production unit; total program costs are estimated to be around $3.4 billion, according to an October 2024 NNSA document.
While the Defense Department has oversight on the delivery systems for nuclear weapons, nuclear warhead modernization is run through the NNSA, a semi-independent branch of the Department of Energy.
“Completion of the last W88 Alt 370 testifies to the successful collaboration we’ve had with our U.S. Navy and Department of War partners,” David Hoagland, NNSA Acting Deputy Administrator for Defense Programs, said in the statement. “The momentum built through the production and delivery of the W88 Alt 370 will continue into our expanding weapons modernization programs and additional stockpile efforts in the coming years.”
The Alt 370 is not a “new” warhead as counted by nonproliferation regimes. Instead, it’s an upgrade to existing nuclear warheads, updated for both safety and capability. According to the release, the Alt 370 “included replacing the warhead’s arming, fuzing, and firing assembly, adding a lightning arrestor connector, refreshing the conventional high explosives within the weapon, and concurrently replacing limited-life components.”
The Alt 370 is the second part of a major nuclear warhead modernization effort, launched under the Obama administration, to achieve its goals. In January, NNSA announced it had wrapped production on the B61-12 gravity bomb design. A lower-yield version, the B61-13, was announced by the Biden administration in 2023 and completed its first production unit in June of this year.
There are two other navy warhead modernization efforts underway. The first is the creation of a sea-launched cruise missile, or SLCM-N. (Notably, the announcement also states that the staff who worked on the Alt 370 effort will now pivot to focus “more fully on acceleration” of that effort.) The second is the W93, for deployment on Ohio- and Columbia-class subs and is expected to also be equipped on British subs.
