The W87-1 warhead modification program recently moved into development engineering, also called Phase 6.3, following approval from the National Nuclear Security Administration, the Department of Defense and the Nuclear Weapons Council. 

During this phase of the nuclear weapons lifecycle process, NNSA will continue to work closely with the Defense Department to conduct experiments, tests and analyses to develop and validate the warhead’s selected design, according to a release posted Monday on Lawrence Livermore National Laboratory’s website. 

During Phase 6.3, which began on an undisclosed date, the national laboratories have been initiating and continuing product development activities and producing test hardware, according to Livermore’s statement. The NNSA did not respond to queries on Wednesday about the approval date for Phase 6.3 and the expected duration of the engineering development phase.

The W87-1 is scheduled for deployment in the early 2030s, alongside the W87-0 warhead on the Sentinel intercontinental ballistic missile formerly known as the Ground-Based Strategic Deterrent (GBSD). 

W87-1 will be a newly manufactured copy of the W78 warhead currently deployed on Minuteman III missiles. The warhead will also include a fresh plutonium pit cast at the Los Alamos National Laboratory some time in the late 2020s or early 2030s. W87-0 will be a version of the existing W87 adapted for flight on Sentinel missiles. 

Following authorization from the Nuclear Weapons Council in September 2018, the W87-1 restarted the 6.2 feasibility study and design options phase in January 2019. The program completed Phase 6.2 and entered Phase 6.2A, a design definition and cost study, in the fourth quarter of fiscal year 2021, according to Livermore. 

“Reaching Phase 6.3 for the W87-1 Modification program is an important milestone for the warhead program as we remain synchronized with the U.S. Air Force for the Sentinel program and development of the updated Mark 21A reentry vehicle,” said Marvin Adams, NNSA deputy administrator for defense programs. “Delivery of this warhead, planned to be 100% newly manufactured, will be an important step in the modernization of the nation’s nuclear deterrent.”