These are the reasons why both the US and the UK went nuclear-only in submarines decades ago. Nuclear propulsion comes with a price tag, but if you can afford it, the gains are exponential. SSNs are especially well suited to Australia given the huge distances of the Indo-Pacific theatre. 

The Australians have therefore decided that this is the right direction of travel and that they can afford it (just). The next issue was how to do it. Just buying a fleet of the current in-build US SSN, the Virginia class, was off the cards. America cannot currently build these fast enough even to replace its own subs as they wear out, and as is being seen across Western shipbuilding in toto, if you let build capacity wither, getting it back is very difficult. While waiting for the Aukus boats America has said it will supply a few Virginias to the Aussies, but it can’t build their whole fleet.

The Australians also decided that creating their own infrastructure and expertise from scratch wasn’t realistic and were right to do so. Australia has no existing nuclear industry and developing an entire nuclear industrial base purely to support a few submarine powerplants would be absurdly expensive. Even for the UK, with an extensive existing nuclear industry, merely re-generating sub build capability after a break in production proved next to impossible without US help.

With all this in mind, Australia teaming up with the US and the UK makes perfect sense. On the one hand you are partnering up with the world’s dominant maritime power with a track record of producing high-quality nuclear submarines. On the other, you are teaming up with a long-standing ally who also builds and runs SSNs but does so at an operating scale much closer to what you need. Neither can simply give Australia what it needs, but with both working together, and Aussie investment added, the capacity is there to establish a powerful sub force in western Australia and so bring security to the Indo-Pacific.

The activity that leads to Australia having its own fleet of boats is phased. To start with, there is a training and familiarisation phase which we are currently in. As an example, US Submarine tender Emory S Land arrived at the HMAS Stirling naval base in Perth on Friday to prepare for a submarine tender maintenance period (STMP). Here a joint team of US and Australian engineers will work on whichever US Virginia puts in later this year. Other US visits are expected as part of this phase, as is a visit from whichever Astute boat sails as part of the British carrier strike deployment to the Indo-Pacific next year.

Phase 2 starts later this decade and sees more regular visits to Perth by UK and US submarines while Australia continues to build up its support infrastructure and expertise. Some believe this should be the limit of Aukus ambition – essentially the creation of a UK/US forward operating base. There are many reasons for this lack of optimism, one key part of which is that the success of the next phase – the permanent delivery of up to three US-built Virginias – depends on the US increasing their build rate from 1.33 boats a year to three. Will the US sort out the backlog for their own security reasons – probably. Will they do it for the greater good – not sure.

Then we get to the really difficult part as the three countries attempt to collaborate on designing and building a new submarine incorporating sensor, weapon, command and propulsion technologies which will form the backbone of Australian and UK submarine fleets for the next 40 years. This is where the different operating methodologies and mindsets between US and UK submarines might come home to roost.

To give one example, by the time a US submarine captain is appointed, he or she has spent half a career training as a nuclear propulsion engineer. US Navy nuclear training is tough and selective – it takes serious effort to progress through it.

In the RN, submarine captains have spent their careers concentrating pretty much entirely on manoeuvring and fighting the boat. The make-or-break course to be a British sub captain – the “Perisher”, as it’s known, which breaks nearly as many careers as it makes – is entirely about manoeuvring and combat. (That said, with only one British SSN able to go to sea at the moment, any discussion of how the RN operates SSNs is a bit abstract.)