Going nuclear: Battle for next-generation subs

Australians will shortly learn whether a US or UK design has been selected for the country’s future nuclear-powered attack submarines (SSNs), and where they will be built.

The nuclear-powered Astute-class submarines, such as HMS Ambush, pictured here during sea trials near Scotland, could be Australia’s next submarine design.

Should Defence Minister Peter Dutton adhere to a recent statement, Australians will shortly learn whether a US or UK design has been selected for the country’s future nuclear-powered attack submarines (SSNs), and where they will be built.

Dutton disclosed on March 13 that the successful design would be revealed “within the next couple of months” – surprisingly early considering the extensive 18-month scoping study for the multi-billion- dollar program that was announced only last September under the Australia/UK/US (AUKUS) security partnership. Interim arrangements would also be explained, Dutton added.

The choice for Australia’s next generation of submarines almost certainly lies between the US Virginia-class Block 1V and the UK Astute-class.

Both types are currently in production and service, both are highly rated, both feature the virtually unlimited range, extended endurance, impressive speed, and warfighting capability sought by the RAN – and both have caveats regarding availability.

The Virginia-class Block 1V entered service in 2020 as the latest evolution of a design dating back to 2004. The Block IV is 115m long, displaces 7900 tonnes, has a diameter of 10.06m, a notional top speed in excess of 25 knots, a crew of 135, and four torpedo tubes. Twenty-five internal spots are available for the Mk 48 CBASS heavyweight torpedoes in service with the USN and RAN and for Tomahawk Land Attack cruise missiles. Two external vertical launch cells can each store and launch six additional Tomahawks or other payloads.

The Astute-class boat entered service in 2010. The type is 97m long, displaces 7800 tonnes, has a diameter of 11.3m, a notional top speed of 30 knots, a crew of 98, and six torpedo tubes. Thirty-eight internal spots are available for a mix of Spearfish heavyweight torpedoes, Tomahawks, and Harpoon anti-ship missiles.

By contrast, the RAN’s six in-service Collins-class boats are 77.8m long and displace 3407 tonnes, have a submerged top speed of 20 knots, six torpedo tubes, a crew of 58, an internal mix of 22 Mark 48 CBASS torpedoes and SubHarpoon anti-ship missiles, and range and endurance limited by their diesel-electric propulsion.

The US Navy currently operates 52 SSNs including 19 Virginia-class, well below the 66 planned, albeit by 2048. This number will fall to 42 unless seven of the earlier Los Angeles-class SSNs receive full refits including reactor refuelling. Both US build yards are fully occupied with annual production of two Virginia SSNs and one Columbia-class ballistic missile submarine (SSNB), with the build rate eventually moving up to three Virginias and one Columbia per year. Additionally, the four repair yards handling submarine refuels and refits are overloaded, with SSNs coming last in priority after aircraft carriers and SSBNs.

Looking ahead, the first of 10 Virginia Block V boats, stretched to 140m and weighing 10,200 tons, is projected to enter US Navy service in 2025.

Eight of the Block Vs will boast a missile payload module containing an additional four seven-tube vertical launch cells for Tomahawks, future missiles (and potentially, uncrewed vehicles), and will provide a significantly greater land attack capability than the Astute, albeit at much greater cost.

The choice for Australia’s next generation of submarines almost certainly lies between the US Virginia-class Block 1V and the UK Astute-class.

The Royal Navy currently operates four Astute-class SSNs, one of which recently visited Australia for the first time.

The seventh and last Astute boat is optimistically scheduled to enter service in 2026, and the UK’s limited build capacity is already being taken up by the Dreadnought-class ballistic missile boats that will replace the RN’s four Vanguard-class SSNBs in the 2030s.

Work has already begun on the next generation of UK and US SSNs, respectively dubbed SSN(R) and SSN(X), and each is slated to enter service in the late 2030s or the early 2040s.

UK SSN(R) production is notionally seven boats but is rumoured to probably be limited to six – one and perhaps two less than Australia’s stated requirement.

Both are in the very early concept phases, but both are expected to be bigger and more expensive than the boats they replace, have X-plane hydroplane arrangements, and feature turbo-electric drive instead of direct drive from the steam turbines. Joining one of these next-generation projects would enable Australia to enter the nuclear submarine club at a higher level, but carry all of the first-of-class risk.

It’s far from clear whether either could progress in time to meet the SSN requirements articulated by Vice Admiral Jonathan Mead, head of Defence’s nuclear submarine taskforce; namely a mature design with a production run already in existence at the yet-to-be-determined start of the AUKUS build program.

While Virginia-class construction will continue to around 2040, Astute construction is due to finish in 2026 and production of its PWR2 reactor has almost ceased.

Potentially the more efficient, safer (and larger) but as yet unfielded PWR3 developed for the Dreadnought SSNBs – and also destined for the UK’s Astute-class replacement – could be utilised although this would clearly entail significant submarine redesign.

Given the AUKUS objective is for Australia to acquire nuclear-powered submarines “at the earliest achievable date”, barring heavyweight political intervention the pressure on US and UK shipyards to meet national requirements together with demands on operational assets, points to an Australian build as the only viable option to ensure SSNs are obtained within any rational period, although reactor modules would need to be pre-fabricated and imported from the US or UK.

The two-year life of type extension (LOTE) activity for each of the Collins-class starting with HMAS Farncomb in 2026 will update and renew mainly ship systems until the scheduled decommissioning of the last-of-class in 2048.

Meanwhile an influential school of thought is suggesting as an additional interim measure the urgent construction at ASC of several Collins boats with minimal design adaption, possibly available by 2030.

These would not only provide increased operational capability but also develop resources to train and qualify the larger crew numbers needed for the nuclear boats, in addition to readying the Australian submarine enterprise for the start of SSN construction in the early 2030s.

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Julian Kerr writes for Australian Defence Magazine, Jane’s Defence Weekly and Jane’s Navy International.