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AUKUS-SSNs/SSN(R) Astute Replacement Programme [UK]

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Last reviewed: 13th July 2026

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 up to 12 SSNs will be delivered during the lifetime of the programme.

Summary

Programme value:
$44.6 billion (Estimated)
Units required:
12 (Actual)
Award year:
2028
Status:
Selected
Type:
Procurement - new
Systems:
SSN AUKUS - Downselected
Unit cost:
$3.7 billion (Modelled)
PGO:
95% ?

Annual expenditure

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Annual units funded

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Summary

Programme value:
$44.6 billion (Estimated)
Units required:
12 (Actual)
Award year:
2028
Status:
Selected
Type:
Procurement - new
Systems:
SSN AUKUS - Downselected
Unit cost:
$3.7 billion (Modelled)
PGO:
95% ?

Bids and suppliers

BAE Systems - SSN AUKUS - UK

BAE Systems - SSN AUKUS - UK

Downselected

 
Supplier
Equipment Category
Subcategory
System Name
 
Prime BAE Systems
Manufacturer:BAE Systems
Equipment Category:Vessels
Equipment Category: Submarines: nuclear/attack
System Name:SSN AUKUS
View Entry
Babcock International Group
Manufacturer:Babcock International Group
Equipment Category:Vessels
Equipment Category: --
System Name:TBC
Rolls-Royce
Manufacturer:Rolls-Royce
Equipment Category:Vessels
Equipment Category: --
System Name:TBC
-
Manufacturer:-
Equipment Category:C4I systems
Equipment Category: Naval: Combat Management Systems
System Name:TBC
-
Manufacturer:-
Equipment Category:C4I systems
Equipment Category: Naval: shipboard communication systems
System Name:TBC
Thales Underwater Systems
Manufacturer:Thales Underwater Systems
Equipment Category:Sensors
Equipment Category: Sea: sonar systems
System Name:TBC

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.

According to evidence given to the UK Parliamentary Defence Committee by Sir Stephen Lovegrove in December 2025, the UK plans to procure "up to 12" SSN's for the RN. However, currently the infrastructure the Barrow-in-Furness does not allow for this and requires significant investment to be ready for future SSN production.

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.

On 20 March 2026, the US announced a potential Foreign Military Sale (FMS) to the UK worth up to $1 billion. The FMS referred to the "design and development of AUKUS-specific vertical deployment tubes" and "common weapons launchers". This suggests a common VLS for the Australian and UK SSNs. 

In June 2026, the UK Defence Investment Plan (DIP) revealed that the steel cut for the first AUKUS SSN was scheduled for 2027. 

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

According to evidence given to the UK Parliamentary Defence Committee by Sir Stephen Lovegrove, the UK plans to procure "up to 12" SSN's for the RN. However, currently the infrastructure the Barrow-in-Furness does not allow for this and requires significant investment to be ready for future SSN production. 

This was further outlined in the 2026 DIP which committed to "building up to 12" AUKUS SSNs. 

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. However, given the UK have reaffirmed that it is seeking "up to 12" AUKUS SSNs, the programme could have a total value of around $44.64 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 with the first steel cut in 2027. 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. However, if 12 are procured, the programme could be pushed to completion in the early 2060s. 

The UK AUKUS SSNs are expected to be delivered in an 18 month "drumbeat" schedule.

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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Related Newsletters

Summary

Programme value:
$44.6 billion (Estimated)
Units required:
12 (Actual)
Award year:
2028
Status:
Selected
Type:
Procurement - new
Systems:
SSN AUKUS - Downselected
Unit cost:
$3.7 billion (Modelled)
PGO:
95% ?

Related News & Analysis

Latest updates

Field Old Value New Value Date
Quantity Required 7 12 21/04/2026
Value 26040000000.0 44640000000.0 21/04/2026
Contact Stage ca selected 12/09/2024
Award Year 2023 2028 12/09/2024
Award Year 2030 2023 19/10/2023
Contact Stage announced ca 10/10/2023
Value 15260000000.0 26040000000.0 10/10/2023
Value Confidence modelled estimated 10/10/2023
First Delivery 2040 2039 10/10/2023
Unit Cost $2,180,000,000 $3,720,000,000 10/10/2023

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