The federal government has confirmed it will buy at least three American Virginia-class nuclear submarines (potentially second-hand) in the early 2030s - subject to Congressional approval. There will also be an option to buy two more Virginias under the AUKUS defence and security pact.

The Virginia-class are nuclear-powered cruise missile fast-attack submarines. They are the US Navy's most recent submarine model, incorporating the latest in stealth, intelligence gathering, and weapons systems technologies. Virginias are designed for a broad spectrum of open-ocean and littoral missions, including launching cruise missiles, anti-submarine warfare and intelligence gathering operations. They have been in service with the US Navy since 2004. Virginias have a designed service life of 33 years and are expected to remain in US Navy service until well into the 2070s.

Meanwhile, design and development work will continue in Australia and the UK on a new SSN, to be known as the SSN-AUKUS, building on work the Brits have already done to replace their Astute-class nuclear submarines. The SSN-AUKUS submarines will eventually be operated by both the UK and Australia, using American combat systems. One is to be built in Adelaide every two years from the early 2040s through to the late 2050s, with five SSN-AUKUS boats to be delivered to the RAN by the middle of the 2050s.

Eventually the AUKUS fleet will include eight Australian-built nuclear submarines, with the federal government leaving open the option of taking some from British shipyards.

Turning to the cost aspect - Virginias are estimated to cost US$3.45 billion each. Then there will be substantial additional costs relating to nuclear submarine basing and maintenance and subsidising the manufacturing process in the US and South Australia. All of that is expensive but affordable.

It seems that the bulk of the $268-368 billion is to be spent on building the new SSN-AUKUS submarines in Australia.

An important question is whether we need or can manage that many nuclear submarines, and whether it's overkill to buy three Virginias with an option for two more - and at the same time have a domestic nuclear submarine building program, with the inevitability of delays and cost blowouts.

The RAN believes it needs eight because our AUKUS partners will expect us to carry a much greater share of the load of patrolling our region and beyond. Navy thinks it won't be possible to do it with less than eight. That's assuming we become a more assertive maritime power. It's also intended to counter the capability build-up of China, which has six active second-generation SSNs, with third generation SSNs under development.

The SSN-AUKUS submarine program is clearly intended to deter China - but an important question is how many Western nuclear submarines will that take? A saner approach might be for the AUKUS partners to negotiate with China on an arms control agreement to cap the number of nuclear submarines, and avoid a hugely expensive arms race for all concerned.

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Turning to the crewing aspect - a Virginia submarine has a crew of 130 and each submarine would normally have two or three crews to keep them at sea as much as possible, for up to three months at a time.

We currently have six Collins-class conventionally powered submarines that each has a crew of 60. The RAN submarine force has grown from a low point of 450 before the Collins-class review to over 900 now. According to Navy, sustainment issues have been rectified and the length of time each Collins is spending at sea has risen. However, if we had three Virginias, we would probably need 2000 submariners to maintain a substantial submarine patrol program.

It remains to be seen whether the navy can get the crew numbers for three Virginias in a competitive labour market and retain them. Working on a nuclear-powered submarine is a bit more glamorous than working on a conventionally powered one. The crew will be working in a challenging work environment with leading-edge nuclear technology - and being well paid for doing so.

However, working on a nuclear submarine will mean working 24/7 for weeks - possibly months - at a time in artificial light, breathing recycled air, living in confined conditions, eating processed food, not having access to a mobile phone or the internet, and cut off from friends and family and a normal Australian lifestyle. Retention could therefore be a major problem.

It would seem more sensible to acquire three Virginias and see whether we are able to keep them crewed and at sea before committing further to a domestic nuclear submarine building program that threatens to be a disastrous waste of taxpayers' money.

Instead, the money could be spent on a new national road and rail network, and building national resilience - all of which would have important long-term strategic and economic benefits. Spending the money on national infrastructure would not only create jobs in South Australia, but throughout Australia.