In the second-to-last week of fiscal year 2020, the Department of Energy wrapped up its customer requirements review with the Department of Defense for the W87-1 intercontinental ballistic missile warhead, the Lawrence Livermore National Laboratory said.

W87-1, the replacement for W78, is arguably the civilian agency’s most ambitious nuclear modernization project of the 21st century. It involves everything from freshly made non-nuclear components to brand new plutonium-pit triggers, to be cast at yet-unfinished facilities at the Los Alamos National Laboratory and the Savannah River Site.

For now, DoE’s National Nuclear Security Administration (NNSA) remains on track to complete the W87-1 first production unit in 2030, said Livermore, the design agency for the weapon, in a press release late last week. That’s the same year its carrier missile, the in-development Ground Based Strategic Deterrent (GBSD) would begin replacing the current fleet of Minuteman III intercontinental ballistic missiles.

The NNSA has said that the first GBSD missiles might go into silos tipped with W87-0 warheads: a GBSD-adapted version of the current-generation W87 warheads that tip some Minuteman III missiles today. Last week a senior Air Force official said the first W87-0 flight tests could launch in three years or so.

The service has not said when W87-1 might get its first GBSD flight test. Unlike W87-0, which will be a refurb of existing parts, W87-1 will be a newly manufactured copy of an existing design.

The Government Accountability Office reported last month that the entire W87-1 program could cost anywhere between $7.7 billion to $14.8 billion, depending on whether the warhead “includes features that meet minimum safety and security requirements” or whether it uses “enhanced safety and security features.”

Among other things, a customer requirements review can establish the technical basis for real-world tests that precede mass production of a new weapon design, according to the NNSA’s latest annual Stockpile Stewardship and Management Plan, an unclassified summary of the agency’s nuclear weapons work.