# SSN-AUKUS

The SSN-AUKUS, also known as the SSN-A, is a planned class of nuclear-powered fleet submarine (SSN) intended to enter service with the United Kingdom's Royal Navy in the late 2030s and Royal Australian Navy in the early 2040s. The class will replace the UK's Astute-class and Australia's Collins-class submarines.
The UK commenced an Astute class replacement project in 2018, which was later named the Submersible Ship Nuclear Replacement (SSNR). The ongoing SSNR design was renamed SSN-AUKUS in March 2023, under the 2021 AUKUS trilateral security partnership, when Australia joined the programme and additional US technology was incorporated into the design.
Australia plans to build five SSN-AUKUS submarines in addition to acquiring three nuclear-powered Virginia-class submarines from the United States.
When in service with the Royal Navy and the Royal Australian Navy, submarine crews will train and patrol together and undertake joint maintenance and support. Components and parts will be shared with the US.
The class will be powered by Rolls-Royce's pressurised water reactors (PWR). The submarines will displace over 10,000 tonnes.

## Development
### UK SSNR design

The United Kingdom began planning for the replacement of the Astute class of submarines in early 2018. Initially, the programme was known as the Maritime Underwater Future Capability (MUFC). The concept phase was scheduled to last for three years to assess requirements and consider options but was suspended for two years due to delays in the Astute-class and Dreadnought-class delivery programmes. In 2020, the Ministry of Defence recruited for a Submarine Delivery Agency Project Manager to work on the SSNR design and development process.
In March 2021, the government's defence paper Defence in a Competitive Age committed to funding the SSNR project. This was followed in September 2021 by an investment of £170 million by the government in the form of two £85 million contracts to BAE Systems and Rolls-Royce Holdings for early design work on the SSNR. The investment will support 350 jobs for the UK economy.
In November 2022, MSubs Ltd was awarded a £15.4m contract to build an XLUUV (Extra Large Uncrewed Underwater Vehicle) vessel which is to be delivered to the Royal Navy within two years. The 17-tonne vessel (known as Project CETUS) is described as being "the next step in developing autonomous underwater warfare capability" and is also to feed into the design of SSNR.
In January 2023, it was reported that the submarines were likely to incorporate a vertical launch system (VLS) for land-attack missiles. This would be a first for Royal Navy SSNs, which currently launch land-attack missiles via their torpedo tubes. A VLS system was described as likely to increase interoperability options with the US Navy since future US land attack missiles may not have a horizontal launch option.

### AUKUS

Following an 18-month consultation starting in September 2021, the design was renamed SSN-AUKUS in March 2023 when Australia joined the programme and additional US technology was incorporated, both as part of the AUKUS agreement. The British Prime Minister Rishi Sunak announced in March 2023 that the UK would boost defense spending by additional £5 billion over two years, some of which would go towards funding "the next phase of the AUKUS submarine programme."
The first SSN-AUKUS class boat for the Royal Navy will commence construction in Barrow-in-Furness as early as the late 2020s and is expected to be operational as early as the late 2030s. The Royal Navy boats will be built by BAE Systems. As of 2023, the workforce at Barrow-in-Furness was being expanded from 10,000 to 17,000 to support both the Dreadnought class program and the SSN-AUKUS class.
The SSN-AUKUS class will be powered by a Rolls-Royce pressurised water reactor (PWR), manufactured at an expanded Rolls Royce Raynesway site in Derby. Australia is to invest A$4.6 billion (£2.4 billion) to allow the expansion of Rolls Royce's Derby site, and alongside funding from the UK Ministry of Defence, the site will double in size creating a further 1170 jobs needed to support the delivery of the Australian boats.
In October 2023, the UK government announced a series of contracts with BAE Systems, Rolls-Royce and Babcock, collectively worth £4 billion, to support the design and development of the submarine class up to 2028. These contracts will fund the finalization of the submarine design, as well as procure long-lead items for the first UK submarine.
The Royal Australian Navy will acquire five SSN-AUKUS class boats that will be built at the Osborne Naval Shipyard in South Australia. A new submarine construction yard will be constructed at Osborne to be known as the Submarine Construction Yard. The Royal Australian Navy boats will be built by a joint venture between ASC, who constructed and maintain the Collins class, and BAE Systems. The building of the first boat is to begin by the end of the 2030s with the boat delivered in the early 2040s. A boat will be built every three years.
Australia will operate two submarine classes, and if the build schedule for the SSN-AUKUS falls behind, has the option of purchasing up to two additional Virginia class boats from the United States. As a non-nuclear weapon state under the IAEA, Australia will not produce nuclear fuel for its SSNs. The UK and US intend to provide Australia with nuclear material in complete, welded nuclear power units.
In March 2023, Vice Admiral Jonathan Mead, head of the Australian Nuclear Powered Submarine Task Force, said the SSN-AUKUS design was "about 70 per cent mature".
The SSN-AUKUS class "will incorporate US technology such as propulsion plant systems and components, a common vertical launch system and weapons", and "will have a high degree of commonality" with the Virginia class, including "sharing elements of the propulsion plant, combat system and weapons", enhancing interoperability and Australia's transition to SSN-AUKUS.
In November 2023, Australian Minister for Defence Industry Pat Conroy said the submarines would use an "evolved" version of the AN/BYG1 Combat Management System in use with the Virginia-class and Collins-class and will be armed with Mk-48 torpedoes.
In January 2025, Rolls-Royce was awarded a c. £9 billion, 8 year contract, named "Unity", by the UK Ministry of Defence. This contract includes the design, manufacture and support of all nuclear reactors in Royal Navy submarines. This will support the beginning of the previously announced SSN-AUKUS contracts.