Simon Cowan | The AUKUS nuclear submarine project needs a closer look

They were that the submarine couldn't be nuclear-powered, and that they had to be manufactured and assembled in Adelaide.

Together, these decisions ensured that little consideration would be given to existing diesel submarine designs. As with the Collins class itself, Australia would need a largely bespoke design, producing an "orphan" class submarine unlike any sub operated by our neighbours and partners.

This approach is far more risky. Time and cost overruns are the norm. Sometimes the end product simply never meets the ambitions set for it during procurement. When the technology is a step-change from the previous generation of equipment, those risks are magnified.

There is no good reason for us to take these risks. Having rightly abandoned the "no nuclear" prohibition in the later days of the Morrison government, Australia now needs to jettison the requirement for a local build.

It is important to understand that - while many in defence were on board with the diesel electric requirement and the home grown build for a variety of reasons - the rationale for these choices was largely political, not defence related.

The initial specs for the Future Submarine Project effectively described a submarine with all the features, capability and range of a nuclear submarine, but without the nuclear propulsion that many of those capabilities require.

In part, this was because of political concerns that the public wouldn't accept nuclear propulsion. Another big factor was the absence of local capability to produce or maintain nuclear submarines.

Of course, as was identified in the early 2010s, Australia lacked industry capable of manufacturing any submarines. That capability would have to be built before the submarines could be.

The exact extent to which this magnifies the cost and risk of the project is unclear; but it's a lot. Moreover, with unemployment below 4 per cent, many of these "new" jobs would simply be displacing workers already employed in other businesses.

People are already baulking at the enormous price tag of this project - possibly in excess of $350 billion by the second half of this century. And it would be a brave person who was willing to bet the project will come in under this estimate.

Historically, these projects have only increased in cost as they came closer to fruition.

Recent polls indicate that a majority of Australians are reluctant to cop higher taxes, or cut other services to fund this project. Ultimately this means we can't afford to blow out the cost of these submarines to appease the political sensibilities of the South Australian government.

There will be big enough challenges to get any nuclear submarine in the water.

Australia will have to massively expand our submarine crews; not only because the crew requirements for the new subs are much higher than the current subs but because we've repeatedly had trouble in crewing the smaller Collins class since they were brought into service.

These crews will also need to be significantly upskilled in nuclear submarine operations; especially the leadership of the submarines, who will all likely need a background in nuclear engineering and physics.

All of this is beside the more complex maintenance and operations requirements that come with nuclear submarines.

This may lead some to think these submarines are a distraction from more important priorities, or are a waste of money. Others have gone further, proclaiming that submarines are on the edge of being made obsolete anyway.

If a technological advance exists that would render subs obsolete, Australia would be wise to invest its $350 billion in developing that technology, as our rivals in the region have invested far more money than us in developing submarine technology.

However, it seems unlikely. What is more likely is that the nature of submarine operations will continue to change, as aircraft operations have: a greater reliance on unmanned vehicles and drones operated from a central platform well away from the area of operations.

The good news is that's exactly the area where nuclear submarines - with their greater size, endurance and energy generation - excel over diesel-electric submarines.

But it is clear that the absence of advocacy for this project aimed at the broader public from within the defence community is undermining support for this project.

It's not that those associated with defence - both inside and outside the defence force - don't have strong opinions on these issues. However, historically they largely communicate among themselves; unwilling to educate and inform the broader public, preferring to leave those tasks to the government of the day.

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This is an error. If defence wants to grow its share of the taxpayer-funded pie, it needs to step up and convince people that defence should be a priority; as former senior commanders do in the US for example.

It's no good hiding behind claims of national security. In practice, the general public has no need or interest in the level of detail that would constitute a threat to national security anyway.

But the absence of defence voices from this debate allows it to be dominated by politicians and others who have non-defence priorities (like South Australians who seemingly believe the number one priority for defence procurement is to generate and fund jobs in their state).

The political class has recently made some courageous decisions to prioritise defence needs over these handouts. With the announcement of the AUKUS pact, the Morrison government crossed the nuclear Rubicon.

This year, the Albanese government dented the local manufacturing requirements by committing to acquiring three Virginia class nuclear submarines from the US to fill the looming capability gap.

If that procurement is successful, those with an interest in our national defence should insist we abandon the ambitious plans to design and build our own nuclear submarines - and instead align ourselves completely with the US program.