What do we know about the UK’s nuclear warhead plans?

Why has this been in the news recently?

In early February, as part of the annual process of setting the Federal Budget, the US government requested funding for a new nuclear warhead programme, the W93. This would be the first new warhead design in decades. In a statement to the Senate Armed Services Committee, the head of the US Strategic Command, said that the W93 programme would “support a parallel Replacement Warhead Programmme” in the UK.  Alan Shaffer, another US defence official, also spoke of the two programmes sharing technologies at a conference. Unsurprisingly, the press picked up on this, despite there being no official announcement from the UK government.
Has the UK government said anything?

Yes, an official announcement was made to Parliament on 25th February. No details were given, other than to say the government was planning to replace the warhead.
Will Parliament be given a vote?

The announcement did not mention this, so it looks like the government will try and avoid one.
So we don’t know anything about their plans for the new UK warhead?

Not really. We know quite a lot more about the US programme though. They are asking for funding to start the ‘Concept and Assessment’ phase of the W93, and they want 53m in the next financial year (Fiscal Year 2021). That is intended to go up to 80m in 2022, 175m in 2023, 440m in 2024 and 1,105m in 2025. The programme is part of a huge planned increase in funding for the National Nuclear Security Administration, who are asking for a budget of 19.8bn in the next financial year, an increase of 18%

Nearly half the 2021 W93 budget is for work at Sandia National Laboratories, with most of the rest being spent at Los Alamos National Laboratory. The programme is intended to be a seven phase process, with the final phase being production and delivery.
Do we know anything about the actual warhead the US is planning?

A big part of this ‘Concept and Assessment’ phase will be setting out the technical criteria for the warhead design and outlining different ‘concepts’ for the warhead, including risks and cost estimates. The technical specifications for the warhead will only begin to be settled once one of those concepts has been chosen as the preferred design.

However, from press briefings we know that they are planning to base the design on existing warhead designs and components, but they are likely to consider changing the internal layout of the weapon and including new components. The one thing they have categorically said is that it will be ‘safer’. In this context that presumably means that it will be designed to make an accident or an unplanned detonation less likely, not that it will kill less people if it is used, or that it will be less likely to be used.
Has this W93 plan just come out of nowhere?

The US has previously talked about developing a new warhead design, so no. Previous plans referred to a ‘Next Navy Warhead’ and ‘Interoperable Warhead 2’. At the moment it’s not clear what relation the W93 bears to these earlier plans, but the picture is likely to become clearer once some technical details emerge.
Will the W93 be mounted on a Trident missile?

Yes, both UK and US nuclear-armed submarines will be firing Trident missiles for the foreseeable future. Until recently it was thought that a replacement missile would be developed part-way through the life of the Dreadnought and Columbia-class submarines, but it now looks as if the US will just do another life extension to the Trident missiles instead.
Is the US planning to test the W93

Apparently not, according to press briefings. US officials say that the fact it will be based on an existing design means there is no need for live testing of the W93.
Will the W93 breach the New-START agreement?

Although it looks increasingly likely that the New-START treaty between the US and Russia will expire in January 2021, long before the W93 comes into service, defence officials are keen to point out that it will not breach the terms of New-START because it will be a one-to-one replacement for a warhead already in service, probably the W88.
What does this mean for the UK warhead?

It seems the new UK warhead will have a number of components and design features in common with the W93. Whether that means they will be functionally identical remains to be seen.

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