However, before we buy American submarines, we should have them carefully checked to ensure we aren't acquiring expensive problems - and we shouldn't pay too much for them in our eagerness to embrace a nuclear-powered submarine capability.

Australia is to buy three second-hand, but apparently near-new, Virginia-class attack submarines from the US in the early 2030s, with the option of buying two more later.

The deal is yet to be approved by the US Congress, but we're told that it has across-the-board political support.

The US offer to make available nuclear-powered submarines has not been made to any other nation, but our sometimes naive political leaders (when it comes to buying foreign defence equipment) need to be careful about what we accept, and how much we pay for them.

Defence Minister Richard Marles has said we will initially be getting Virginias with 20 years life left in them.

That means submarines built around 2020, given that the designed operational life of the Virginias is 33 years.

The first Virginias were built from 2000 and entered service with the US Navy in 2004. These were Block I submarines - which means Model 1.

The Americans are now up to Block V. The four Block I Virginias were built over seven years, the six Block IIs over six years, the eight Block IIIs over five-and-a-half years, and the 10 block IVs over five years. The latest version is the Block V - 10 of which started construction in 2020.

The Block V is 22 per cent larger than the earlier Virginias and is said to have triple the weapons capability of the earlier Blocks.

For example, it carries 40 Tomahawk cruise missiles, while the earlier models carry only 12. The US Navy expects to buy 66 Virginias and operate them well into the 2070s.

Australia will presumably be offered Block IVs. We would not want Virginias older than that.

Like everything else, the cost of building submarines has gone up over the years.

The early ones cost $4.2 billion to build while the Block 5s will cost $5.2 billion plus. America, being the home of capitalism, will obviously want to make a good profit on any sale to Australia, but we should not be paying much more than the new construction cost for superseded second-hand models.

The reason to be wary is that the US has not always been trustworthy with its sale of naval vessels to Australia.

In 1994, the RAN bought two US Navy Newport-class tank landing ships for the combined price of $61 million, with the intention of converting them to a combined pocket helicopter carrier and amphibious warfare transport.

After both ships had arrived in Australia and were commissioned as HMAS Kanimbla and HMAS Manoora, extensive corrosion was discovered in both ships. Refitting them cost more than $400 million.

In 2010, they were taken out of service because of ongoing corrosion problems, faults with the deck crane and alarm systems; a need to overhaul the propulsion system, power generators, and air-conditioning; and a need to upgrade the communications suite.

The additional work would have been prohibitively expensive. As a result, both vessels were sold for scrap in 2013.

The sale price was not disclosed but was probably not more than $5 million for both ships.

After this expensive fiasco, Howard government Defence Minister Ian McLachlan said no Australian government should ever again buy used ships from the Americans.

While we should be cautious about American used-sub sellers, nuclear-powered submarines make much more sense for Australia's extensive maritime environment than conventionally powered ones - although I believe the military threat from China has been greatly exaggerated.

Once the RAN has Virginias in service, they could be operated into the 2070s.

(They will be in operational service with the US Navy well into the 2070s - and probably beyond.)

That means a domestic construction program to build SSN-AUKUS nuclear-powered submarines should be unnecessary.

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It's a program that will inevitably be beset with design problems, delays, and cost blowouts that are likely to lift the cost well beyond the $368 billion projected.

The first Australian-produced SSN-AUKUS submarine is scheduled to be delivered by the early 2040s.

Noting the history of past delays, that seems more likely to be the 2050s. It's quite possible by then that the era of the manned nuclear attack submarine as the "apex predator" will have passed.

Over the next 30 years, the oceans will become increasingly "transparent" and made much more dangerous for submariners.

This is due to the development of relatively cheap detection sensors, smart sea mines, and unmanned underwater vehicles (UUVs) capable of destroying enemy submarines.

Some analysts believe that by the 2050s, long-range power projection by manned nuclear attack submarines will no longer be viable.

Today's politicians won't be the ones in the hot seat if the SSN-AUKUS program goes pear-shaped, and it won't affect most of us either - it's our children and grandchildren as taxpayers who will pay through the nose for an unwise commitment by today's politicians.