AUKUS-SSNs/SSN(R) Astute Replacement Programme [UK]
Last reviewed: 24th January 2025
Snapshot
The UK Ministry of Defence (MoD) has begun the planning process for the Astute class replacement programme referred to as SSN-Replacement (SSN(R)). In September 2021, it was announced that BAE Systems and Rolls-Royce had been funded by the UK MoD to undertake early design and concept development work for the SSN(R) programme, which will replace the Royal Navy's Astute-class from 2040. This followed a three-year programme, definition and design (PDD) phase for a capability solution for the MoD's Maritime Underwater Future Capability (MUFC) programme.
Following a similar pattern to the Astute-class, the SSN(R) programme has been speculatively forecast to cost around $26 billion. A construction contract is expected to be awarded in the late 2020s, and seven like-for-like replacements will be delivered in the 2040s.
Summary
- Programme value:
- $26.0 billion (Estimated)
- Units required:
- 7 (Estimated)
- Award year:
- 2028
- Status:
- Selected
- Type:
- Procurement - new
- Systems:
-
AUKUS SSN - Downselected
- Unit cost:
- $3.7 billion (Modelled)
- PGO:
- 95% ?
Summary
- Programme value:
- $26.0 billion (Estimated)
- Units required:
- 7 (Estimated)
- Award year:
- 2028
- Status:
- Selected
- Type:
- Procurement - new
- Systems:
-
AUKUS SSN - Downselected
- Unit cost:
- $3.7 billion (Modelled)
- PGO:
- 95% ?
Bids and suppliers
BAE Systems - AUKUS SSN - UK
Downselected
Additional Information
Programme Background
Requirements
The UK MoD has begun the planning process to replace the seven Astute-class nuclear attack submarines (SSNs) under the SSN-Replacement (SSN(R)) programme from the 2040s. The current Astute-class is still under construction for the UK's Royal Navy (RN), replacing the Trafalgar-class, but development and design took a considerable amount of time.
In January 2023, Naval News reported that the next-generation SSN would likely be fitted with VLS. This technical decision is intended to enhance interoperability with the USN.
Timeline
In order to ensure the SSN vital capability will be ready to replace the Astute-class submarines when they come out of service, the MoD has already invested millions of pounds into the plan, which also helps to support and maintain high-skilled jobs across the Midlands and North West of England admit a worldwide shortage in nuclear engineers.
Prior to an award placed in 2021, a three-year programme, definition and design (PDD) phase for capability solution for the MoD's Underwater Future Capability (MUFC) programme was undertaken. During 2019-20, work progressed around a MUFC and approval was received to enter a Programme, Definitions and Design (PDD) phase from April 2020, considering a range of potential capability delivery options and delivery arrangements, including a manned nuclear-powered submarine (known as the Submersible ship Nuclear (Replacement) (SSN(R)) and autonomous vehicles, to inform a future capability decision.
The Defence Command Paper published in March 2021 which followed the UK government's Integrated Review of Security, Defence, Development and Foreign Policy, committed to funding the next generation of nuclear submarines to guarantee security well into the second half of the century. As well as listing the SSN(R) as a key work area in the SDA Corporate Pan 2020-2023, the agency plans to deliver submarines faster and cheaper, with greater confidence and certainty.
The MUFC's PDD phase will see the Submarine Delivery Agency (SDA) work with BAE Systems, Babcock and Rolls-Royce to consider a range of capability options and delivery arrangements. Ian Booth, CEO of the SDA, said in September 2021 that 'although it is too early to determine what the capability solution will be, designing and building submarines is one of the most complex and challenging feats of engineering' and the work will, therefore relies on some of the nations most experienced defence nuclear experts from the very beginning of the design phase.
On 13 March 2023, the leaders of Australia, the UK and the US assembled at Naval Base Point Loma in San Diego to jointly announce the ‘optimal pathway’ forward in Canberra’s ambition to field SSNs. Australia will receive what are called SSN-AUKUS boats, representing the UK's next-generation design that incorporates technology from all three nations, including US submarine technologies. The design will be completely common between the UK and Australia to maximise the benefits of working together.
In effect, Australia is attaching itself to the UK’s existing effort to develop the SSN(R), the successor to the RN’s Astute-class boats. Indeed, the UK programme will now take a different tack, and this will present time and budgetary risks.
The first UK boats will properly take shape once BAE Systems in Barrow has finished work on the Dreadnought-class SSBNs. Australian SSN-AUKUS boats will be built in Adelaide.
Contract Awards
On 17 September 2021, BAE Systems was awarded an £85 million ($116 million) contract to support early design and concept work on the RN's next generation of submarines. Rolls-Royce has also received funding to undertake early design and concept development work, taking the contracts placed through the MoDs SDA to £170 million ($233 million). The contracts will deliver design work that will inform a future decision, which will help decide the replacement approach for the Astute-class submarines.
BAE's contract will enable to Company's Submarine business to progress in the early stages of the programme to deliver a replacement for the Astute-class but will also help sustain the UK's future underwater military capability, supporting 250 highly-skilled jobs in Barrow-in-Furness, Cumbria in the process.
A spokesperson for Rolls-Royce Submarines told Shephard, "This contract brings vital stability and reassurance, allowing our business to mature the Nuclear Steam Raising Plant programme into its final design phase. This programme is significant in bringing medium to long term stability to the business with the opportunity to productionise reactor technology whilst modernising our approach to meet the future demands of the Submarines Enterprise."
Ben Wallace, the Secretary of State for Defence, said, “Marking the start of a new journey in submarine development, British designers and engineers will lead the way in building submarines for our Royal Navy."
On 1 October 2023, the UK MoD awarded £3.95 billion ($4.85 billion) to BAE Systems for development work until 2028. The funding will enable BAE Systems to move into the detailed design phase of the programme and begin to procure long-lead items.
In January 2025, Rolls Royce signed a £9 billion 8-year 'Unity contract' with the UK MoD to supply PWR-3 nuclear reactors and in-service support for Dreadnought and SSN-AUKUS submarines. The contract will also provide full support for the in-service UK Royal Navy submarine fleet (Astute-class and Vanguard-class) throughout the period.
Forecast Methodology
Quantity
The below calculations are based on the assumption that the AUKUS-SSN/SSN-Replacement will take place on a like-for-like basis. Thus, Shephard estimates up to seven units could be procured.
Programme Value & Unit Cost
Australia's planned Attack-class submarines, prior to being cancelled, had risen to a programme value in the region of A$90 million ($70 million), but it did include the future sustainment cost of 12 submarines with the completion of the class expected in the 2050s.
Looking at the baseline unit cost only of nuclear-powered submarines, the UK Astute-class is being used as a reference point. The seventh Astute-class submarine, according to a 2015 National Audit report, cost around £1.64 billion ($2.25 billion). By inflating the value to 2023, a 7400t Astute-class submarine would now cost around $2.9 billion.
The SSN-AUKUS is likely to have much in common with the Dreadnought-class SSBNs. Assuming they will have the same PWR3 nuclear reactor, they would have the same pressure hull diameter as Dreadnought – around 12.8m. SSN-AUKUS would, therefore, be substantially larger than Astute, although shorter than Dreadnought. Another key difference between Astute and SSN-AUKUS is likely to be the inclusion of payload modules for vertical launch of missiles, medium-sized UUVs or seabed sensors.
From the 5200t Trafalgar-class to the 7400t Astute-class, the total displacement increased by 42%. By applying a similar tonnage-increase ratio to the SSN-AUKUS submarines, the future boats could displace around 10500t. This value aligns with the CBO estimate of the future SSN(X).
However, Shephard estimates the SSN-AUKUS will be smaller than the SSN(X), with a total displacement of 9500t.
Considering a potential displacement of 9500t and applying a proportion with the Astute-class, Shephard forecasts the SSN-AUKUS could cost around $3.72 billion.
By comparison, the US Navy estimates that each SSN(X) would cost $5.6 billion.
Shall the Royal Navy procure seven boats, the whole programme could cost around $26.04 billion.
Programme Years
The programme value years have been estimated by spreading the estimated unit cost of $3.72 billion across a nine-year construction period.
Construction & Delivery Timeline
Each submarine is expected to take eight to ten years to construct, but works are also expected to begin in the late 2020s when the construction of the Dreadnought will be almost completed. On this basis, delivery of the first submarine is expected to take place in the late 2030s.
One submarine is loosely forecast to be delivered every two years, meaning the completion of the programme will be around the early 2050s, should seven boats be eventually procured.
Please note that this is a highly speculative timeline and may not represent the likelihood of the programme advancing at that speed.
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