Nuclear weaponsReplacing Aging Thermonuclear Warheads

Lawrence Livermore National Laboratory (LLNL) researchers passed their first program level key milestone in the W87-1 Modification Program (W87-1 Mod) on Sept. 24, keeping the program on schedule despite work stoppages due to the COVID-19 pandemic.

The W87-1 Mod will replace the W78 thermonuclear warhead with a modified design of the W87 warhead. The W78 is nearing the end of its functional lifespan after 37 years in service, perched atop the Air Force’s Minuteman III intercontinental ballistic missiles (ICBMs). The W87-1 will be paired with an updated Mark 21 reentry vehicle, called an Mk21A, and an ICBM system named the Ground-Based Strategic Deterrent (GBSD), both of which are being developed in parallel with the warhead. This new missile is slated to replace the ‘70s-era Minuteman III missiles, as well as the accompanying command and control systems. Upon completion, the U.S. ICBM force will consist of ICBMs with both the existing W87 warheads and W87-1 warheads. The W87-1 Program will require all new manufacturing of components, which has not been done since 1992.

The W87-1 milestone – called the Customer Requirements Review, or CRR – centered around the Department of Defense (DoD) and National Nuclear Security Administration (NNSA) concurring that the system requirements are complete, clear and consistently understood between stakeholders. This is a key step in ensuring the laboratories will develop a design that meets DoD requirements for weapon performance, safety, security and reliability.

As the lead nuclear design agency for the warhead, LLNL worked closely with a number of key partners to meet the milestone, including Sandia National Laboratory, NNSA, the U.S. Air Force and the DoD contractors responsible for developing the Mk21A and GBSD. In working toward completion of this milestone, the COVID-19 pandemic posed an unforeseen challenge to LLNL and their colleagues across the nuclear weapon enterprise.