Dependent Deterrent? US Support for the UK’s New Nuclear Warhead

Last night, BBC Newsnight reported on a quiet but crucial drama playing out at the heart of UK–US defence relations. The UK has started a programme to build a new nuclear warhead for its submarine-launched ballistic missiles. The warhead depends on a parallel programme to build a new warhead in the US, called the W93. The link between the UK and US warhead programmes is already known, and has been the subject of analysis at RUSI and elsewhere, but the BBC report reveals some key new information and makes some startling new claims.

Three details are crucial. First, the BBC quotes an official (nationality not specified) claiming that the W93 warhead is a ‘joint project, in design terms’ between the UK and the US, an allegation of much closer cooperation than previously believed. Second, it claims that the UK’s lobbying for Congress to fund the W93 has given an exaggerated impression of how quickly the UK actually needs the US to begin work. Third, the BBC provides an estimate of the new warhead’s cost, at £10 billion over the next 15 years – something the UK government has so far refused to do. The Newsnight report represents the most high-profile national attention that has been given to this topic thus far, but its revelations raise just as many questions as they answer. It is essential that Parliament takes up the challenge of scrutinising the warhead programme in detail.

Design Links

When it comes to the BBC’s claims about the design links between the US W93 and the new UK warhead, details matter. It is already known that the W93 will be housed in a new re-entry vehicle called the Mk7. (A re-entry vehicle is a body containing electronics and various non-nuclear components in which the warhead, with its nuclear explosive package, re-enters the Earth’s atmosphere after being released by the missile).

If the BBC’s claim that the W93 is a ‘joint project’ actually refers specifically to the Mk7, this would confirm the tight relationship between the two programmes, but it would largely not be new information. The UK government told Parliament last year that the Mk7 will be common to both the W93 and the UK’s new warhead. As Newsnight noted, basic parameters of the UK warhead are set by the fact that it is deployed in a US aeroshell and on a US missile, implying a strong degree of similarity in the warheads. The Ministry of Defence (MoD) permanent secretary has acknowledged ‘a very close connection, in design terms and in production terms’ between the W93 and the new UK warhead. This falls short of suggesting, however, that the design of the two warheads will be identical.

The BBC broadcast claimed that the ‘design for the American and British versions of the new Trident warhead is essentially the same’. Given that the W93 programme is only in its early stages, which aim to study potential options, it is difficult to see how the warhead’s eventual design can yet have been fixed. But if the design of the W93’s nuclear explosive package were intended to be a ‘joint project’, as the BBC’s source suggests, that would be bigger news. It would be an admission of much closer cooperation on the most sensitive aspect of nuclear weapons than has been acknowledged publicly by UK officials. It would contradict what US officials have said about the nature of UK–US cooperation on the W93/Mk7, where the line has been that the nuclear explosive package is a ‘sovereign’ UK capability. It would also be likely to draw allegations that the UK and US are in breach of the spirit, if not the letter, of the Nuclear Non-Proliferation Treaty, charges which tend to reoccur whenever US–UK nuclear cooperation is in the news. Taking these factors into account, the MoD should consider clarifying for the record whether or not the replacement UK warhead will be based on a sovereign design.

Who’s Making the Running?

The Guardian reported last year that the UK defence secretary had written to members of Congress saying that their ‘support to the W93 program in this budget cycle is critical to the success of our replacement warhead program and to the long-term viability of the UK’s nuclear deterrent’. The implication was that the UK needed the W93 programme – which faced initial opposition from appropriators in the House of Representatives – to start now. Although the W93 was eventually funded by Congress, there has been concern in the US that the programme has been accelerated unnecessarily. In December, as Newsnight noted, the Democratic chairman of the House Armed Services Committee said about the W93: ‘Do we need the money right now? I think the U.K. is pushing a lot of that. Do they need it right now? We need to do it. Do we need to do it right now? That’s a tougher question’.

According to the BBC’s reporting, the UK timetable is not as urgent as it has been made out to be, because the UK nuclear weapons infrastructure is not yet capable of producing a new warhead. The UK’s lobbying efforts, writes Mark Urban, ‘appear designed to help the programme through a potentially difficult period when nuclear projects are coming under heightened political scrutiny rather than being driven by Britain's production schedule’. In last night’s broadcast, Urban said it seems that ‘the US–UK nuclear tag team is working its magic, and politically using its influence to convince people in Washington DC that this programme has to be got underway and funded as soon as possible’.

If the BBC is right, and the Biden administration and Democrats in Congress come to believe that the UK has exaggerated the urgency of its situation, this could harm the UK government’s credibility in Washington. It will also give ammunition to those who argue that spending on W93 should be delayed. But the relationship between the UK’s delayed infrastructure and its need for US design work to begin is more complex than it might appear. For one thing, starting design work does not necessarily require production infrastructure already to be in place. And design choices might well have an impact on the type of infrastructure the UK needs. For example, an MoD official told the Public Accounts Committee last year that plans for a new facility to handle enriched uranium, named Pegasus, are on hold until more information about the design of the new warhead is available.

If that is the case, depending on how closely the designs of the W93 and the UK warhead are linked, a delay in starting work on the W93 might potentially cause further delay to the UK’s infrastructure plans. If those delays increase, they could eventually put the timetable for UK warhead production at risk. Here, there is precedent: delays to a new facility for warhead components in the late 1980s became so severe that the Defence Committee raised concerns that the UK would not be able to produce new warheads in time to arm the full fleet of Trident submarines when they entered into service. Delays to the W93 could also potentially increase overall costs for the UK if it is forced to keep technical options open for longer than it would otherwise like.

How Much Will It Cost?

A final detail from the BBC’s report is the estimate that the new UK warhead, factoring in infrastructure needs, could cost £10 billion over the next 15 years. RUSI’s Malcolm Chalmers suggested in October last year that the overall costs could be considerably higher, between £15 billion and £30 billion over the lifetime of the procurement. The government has been refusing to provide any cost estimate, arguing that it is too early to do so, ‘as much will depend on the eventual design requirements’, and that ‘information relating to the programme may be subject to commercial and national security constraints’.

The 2006 White Paper on the future of the deterrent estimated the cost of a new warhead to be between £2 billion and £3 billion, but this very likely did not include the costs of infrastructure upgrades. An existing modernisation programme at the Atomic Weapons Establishment, the Nuclear Warhead Capability Sustainment Programme, has an overall budget of £21 billion spread from 2005–25. Parliament should urge the government to provide it with some estimate of costs for the new warhead, even if the estimate is a range rather than a specific figure.

Parliament should also ask the MoD to clarify the extent to which projected UK costs are dependent on decisions, such as the initiation of design work on the W93, that might be out of the UK’s hands.

The views expressed in this Commentary are the author's, and do not represent those of RUSI or any other institution.