OPINION | US and UK partners show the realities facing Australia's small submarine fleet

In 2056, 30 years from now, when Australia has eight nuclear-powered submarines (SSNs), we will have two deployable submarines consistently available. That’s assuming all goes well with AUKUS’ “optimal pathway” and we do in fact have eight SSNs in service.

Expecting a better outcome than this is likely to lead to disappointment, if the experience of our two AUKUS partners is any guide, and our own experience with the simpler but still complex diesel-electric Collins submarines has any lessons for us.

The problem with nuclear submarines is shared by all submarines: they are hugely complex electro-mechanical devices and they operate in extraordinarily demanding environments – both physical and threat.

However, nuclear submarines are even more complex than their diesel electric counterparts, compounding the maintenance and availability challenges. As the inaugural head of Australia’s Submarine Agency, Vice Admiral Jonathan Mead has said, nuclear submarines are, “more complicated than the Space Shuttle or the International Space Station”.

Complex machines like modern submarines are not available for operations all the time as they comprise many systems and sub-systems that need maintenance. In addition to the everyday maintenance performed dockside, submarines require periodic overhauls that take them out of the water for one, two or even more years, depending on the particular overhaul and the capacity of their supporting industrial base.

What that means is that world’s best practice is essentially a three-to-one ratio: for every three submarines a navy has, one is available for operations. However, not every navy is achieving world’s best practice and that ratio can increase depending on the complexity of the boats, their operating profile, capacity of maintenance yards, the ability of suppliers to provide parts, and so on.

Moreover, there is a vicious cycle of submarine availability and submariner availability—if submarines aren’t available, submariners can’t go to sea to train and qualify. But if you don’t have sufficient numbers of qualified submariners across the necessary critical skills, then you can’t take submarines to sea. So availability and deployability is a complex, interrelated challenge of both people and materiel that we can only skim over lightly here.

The Collins experience

Australia’s six Collins-class submarines have proven to be very capable diesel-electric boats. From a maintenance and availability perspective, the program overcame enormous challenges early in the fleet’s life, but only with concerted political attention and external intervention, notably through the Coles review.

In the early 2010s, Collins’ availability had crashed. The Coles review introduced a "usage and upkeep cycle" that sought to achieve world’s best practice in availability. Under this cycle, two of the six boats are in longer term maintenance – in activities like full-cycle dockings (FCDs) that take boats out of the water and pull them apart.

The remaining four are available to the Chief of Navy. Three of these are consistently available for tasking while one is in shorter-term maintenance. However, only two of them are consistently deployable. Defence has provided evidence at parliamentary committees that it has achieved this model (although there is no public data that would allow us to confirm actual submarine availability or days at sea).