The W93 warhead will notionally be based on previously deployed nuclear-explosive components, the head of the Department of Energy’s National Nuclear Security Administration (NNSA) said here Tuesday. 

The W93, a planned submarine-launched warhead and the first U.S. nuclear weapon since the Cold War that isn’t a copy or iteration of an existing weapon, has been a hot topic in the initial hearings on the Trump administration’s fiscal 2021 budget request. What is broadly known is that the warhead will integrate existing nuclear-weapons parts that have not previously been jammed together into the same reentry vehicle. Futher details are scarce.

The NNSA requested $53 million for early work on the W93 in the budget year beginning Oct. 1. For “right now, it is based on previously deployed and also previously tested nuclear-explosive components,” NNSA Administrator Lisa Gordon-Hagerty said Tuesday during a hearing of the House Armed Services strategic forces subcommittee. 

That answer could change, Gordon-Hagerty said, because the NNSA and the Navy, the customer for the weapon, have yet to winnow down their options for building the proposed warhead, which will tip the eventual successor to the Trident II D5 missiles now carried on U.S. ballistic missile submarines. W93 was previously known as the Next Navy Warhead, and as Interoperable Warhead 2, prior to that.

Meanwhile, Gordon-Hagerty said, it would be “premature” to say whether the W93 will need brand new plutonium pits — the fissile cores of nuclear weapons.

If it does, the Navy will have to take a number.

The NNSA is upgrading a pit plant at the Los Alamos National Laboratory in New Mexico and designing a brand new factory at the Savannah River Site in South Carolina. Those facilities, for this decade at least, have been tapped to produce W87-1-style pits for the Air Force’s planned Ground-Based Strategic Deterrent missiles: the silo-based replacement for the Minuteman III, which the Air Force wants to start phasing out around 2030.

For the planned pit complex alone, the NNSA requested $1.4 billion for 2021, up from roughly $800 million appropriated for 2020. The agency estimates it will cost about $30 billion to build and operate the two pit plants over the course of several decades. 

The agency’s nearly $20 billion budget proposal for 2021 is 25% higher than the 2020 appropriation of more than $16.5 billion, and billions of dollars more than the NNSA thought in 2019 it would need for the coming fiscal year.

Gordon-Hagerty is scheduled to return to Capitol Hill this afternoon for a hearing before the House Appropriations energy and water development subcommittee, which writes the first draft of the NNSA’s annual budget bill. Subcommittee Chair Marcy Kaptur (D-Ohio) said last week she intends to trim the agency’s budget request.