- NNSA and Navy complete the first W76 Mk4B production unit ahead of schedule
- The new reentry body is designed to support greater reliability
- Existing W76-1 and W76-2 warheads will transition to the Mk4B configuration
The National Nuclear Security Administration, in partnership with the U.S. Navy, has finished building the first production unit of the W76 Mark 4B reentry body, beating the original timeline by nearly three months.
What Is the W76 Mk4B Reentry Body?
The Mk4B is an advanced reentry body that shields the warhead of a submarine-launched ballistic missile during re-entry through Earth’s atmosphere. As part of the effort, every W76-1/Mk4A and W76-2/Mk4A in the stockpile will be converted to the newer Mk4B configuration, which offers greater reliability than its predecessor.
The W76 accounts for the largest share of the U.S. nuclear inventory and serves as a key component of the Navy’s Trident II D5 missile system, which supports the sea-based leg of the U.S. nuclear triad. The missile system is deployed aboard Ohio-class and Columbia-class submarines.
Which Entities Collaborated on the Program?
Sandia National Laboratories, Los Alamos National Laboratory and Lockheed Martin Space served as design agencies, with Sandia focused on non-nuclear components while overseeing system integration for the Mk4B.
NNSA and the Navy were reportedly able to deliver components early by utilizing production and qualification processes at Kansas City National Security Campus, Pantex Plant and Lockheed Martin Space. Pantex leveraged a previous readiness determination for the W76-1 program, while Kansas City National Security Campus accelerated production of key non-nuclear components. Sandia and Los Alamos also supported the schedule by issuing qualification evaluation releases.
The milestone supports U.S. military requirements by ensuring the sea-based leg of the nuclear triad remains reliable.
NNSA Administrator Brandon Williams said the agency is delivering on its commitment to accelerate production of the nation’s nuclear deterrent by handing over the first W76 Mk4B to the Navy ahead of schedule. A former nuclear submarine officer, Williams said the sea leg of the triad is essential to the nation’s assured second-strike capability, and that enhancing the W76 reentry body’s reliability will strengthen America’s national security.
