Do you know how we modify those designs? We paint kangaroos on them.

Then we find that those aircraft work. They do just what it says on the tin. But of course they do: the same design was already working for the Americans when we signed the contract.

Guess how much they cost.

They cost just what we expect. If the development phase is complete and the factories have settled down into volume production, the price is quite predictable.

Now you can answer the next question: when do they turn up?

Correct. They turn up on time.

Doctors tell us about the risk factors for disease. Similarly, there are risk factors for Australian defence projects, the elements that make them more likely to miss specifications, run over budget, deliver late, or all three.

The risk factors are: A, making the product in Australia; B, modifying the foreign design that we've chosen; and, C, choosing an immature design, one that is still in development.

If any of those factors is present, one more comes into play: D, complexity of the design. Call it the exacerbator.

When we buy aircraft from foreign factories and use exactly the same designs that another country has in service, none of A, B or C apply, so the exacerbator is irrelevant. For example, the air force is taking delivery of P-8A Poseidon maritime patrollers, which are unusually complicated aeroplanes. But the US Navy is already using Poseidons and we're getting ours from a Boeing factory without changes.

So, no worries, mate.

The F-35 Lightning program had risk factor C: it was not mature when we committed to buying it. D was therefore invoked. The program went badly at first, though it has been stable for more than a decade.

Fifteen years ago, the navy was struggling in its effort to acquire Seasprite helicopters, because it had insisted on huge modifications to the original US design and the result was to be a complicated product. That went so badly that we eventually walked away from it and wrote off $1.3 billion.

Almost all our warship programs now have risk factor A. We build in Australia, supposedly to increase self-reliance but really so prime ministers can pose in hard hats and so the navy can harness political enthusiasm to get the ships it wants.

The current Hunter-class frigate program has all three primary risk factors, especially B (huge modifications from the original British design), and lashings of complexity. And it's an utter mess - the Seasprite multiplied many times over.

Worse than the expected underperformance and excessive cost is the frigates' lateness, which is simply dangerous as we watch a rising threat from China.

And the nuclear submarines? If we build in Australia, we'll have risk factor A. We'll have B, too, if the navy is allowed to fool around with the design.

And the complexity exacerbator for a nuclear submarine? Massive, super-dooper-maximo, run-for-the hills-screaming-in-terror.

Meanwhile, US shipyards pop them out just as Boeing pops out those Poseidons. Think about that next time the government "promises" to build the submarines here.

"Threatens" would be a better word.

The Hunters are running so late that the Spanish company Navantia realistically proposes to get three ships of another design into our hands before even the first made-in-Adelaide frigate arrives. It's basically offering to knock out three more destroyers of our recently commissioned Hobart class, which it designed.

Let's assess the offer in terms of our risk factors.

One of them is a maybe, because the government will have the option to build in Australia. Next, we will want some design changes, mainly to update technology; Navantia has probably already offered those modifications. The basic design has been in service here and elsewhere for many years, so risk factor C isn't present.

The ships are complicated, so the exacerbator applies.

MORE AGE OF THE DRAGON:

Taking all that together, a reasonable judgment is that this project poses some risk but far less than the Hunter class, and it would be even more dependable (and quicker and cheaper) if we ordered from a Navantia shipyard in Spain.

But consider what the air force would do if it were in the business of buying destroyers. It would just order whatever the US Navy was using, get the things built by the same suppliers, and leave the design alone.

What the US Navy uses is famous. It's the Arleigh Burke class, which has been in production for more than three decades in successively updated batches.

There would be very little risk in buying Burkes from the US.

Ordering such ships would bring other benefits, too, not the least of which is that their greater size (and probably cost) brings greater weapon stowage. They each have not 48 missile cells, as in the Hobarts, but 96.

That's crucial. Surface warships are severely threatened by missile attack, which they face mainly by firing volleys of defensive missiles. When they run out of those interceptors, they're not much more than sitting ducks.

By buying Burkes, the navy would in fact be reliving its happy experience with excellent submarines and frigates that it bought off-the-shelf from British and US shipyards from the 1960s to 1980s.

Yes, that's right: our navy used to avoid risk factors A, B and C and therefore didn't have to worry about D.

It's high time government considered forcing it to do so again.