The government has announced a defence strategic review ^[1] to ensure Australia ‘has the right capabilities that are postured to meet the growing strategic challenges that Australia and its partner countries will face in the world in coming years’. Earlier in this series, we looked at Australia’s transition in undersea warfare capability and highlighted the risks involved in that long process ^[2]. One of the review’s highest priorities will be to address those risks.

While there are several broad paths to mitigating them, the acquisition of a new conventional submarine has garnered the most public attention. It seems likely that the review will consider the merits of the concept. Its analysis will be informed by the nuclear-powered submarine taskforce ^[3]’s assessment of the optimal pathway to acquire these nuclear-powered attack submarines (SSNs).

We look here at whether a new conventional submarine could address the transition risk. It would need to address three broad challenges to win the review’s support:

• capability deficiencies, namely that the Collins-class submarine ceases to meet Australia’s undersea warfare requirements
• platform availability, namely that the Royal Australian Navy no longer has sufficient submarines to meet its requirements
• workforce availability, namely that the navy doesn’t have sufficient submarines to generate the uniformed workforce needed to transition to SSNs.

Of course, these are intertwined; there’s no point having lots of submarines if they’re not survivable, for example. There are quality and quantity risks, and we should be mindful of the transition from the Oberon class to the Collins. By the time the first Collins was commissioned in 1996, Australia’s submarine fleet had fallen from six to two and the navy was struggling to maintain its workforce. It took years to recover.

It’s hard to discuss quality issues, particularly since Defence itself doesn’t seem to have a clear view on what comprises a viable capability. For years, senior officials told the Senate the Attack class would remain a ‘regionally superior capability’. Yet, shortly after its cancellation, former prime minister Scott Morrison said it was the unanimous view of Defence’s senior leadership that the Attack class would have been obsolete the moment it was launched.

If our capability requirements can only be met by an SSN, then no conventional submarine can ever meet them. Nor can the Collins, even after going through a robust life-of-type extension (LOTE). But since many advanced nations are still designing, building and operating conventional submarines, it would appear there’s some life left in the concept.

One might argue that the LOTE program will ensure the Collins will continue to deliver adequate capability throughout its very long life with new diesel generators, main motors, electrical distribution systems and optronic sensors in place of periscopes.

But it’s unlikely that the LOTE will substantially improve available power, the submarine’s capacity to sustain longer patrols, faster transits or noise generated from the current hull shape. In addition, many more modern submarines have adopted impellor arrangements to reduce the noise and cavitation issues associated with their propellers. Defence has also rejected incorporating air-independent propulsion (AIP) that would allow the submarine to remain submerged for longer. It is highly doubtful that the Collins upgrades will keep pace with China’s growing submarine and anti-submarine capabilities, and those of other potential adversaries.

However, more modern submarine designs than the Collins are now available. Ten years ago, on Defence’s recommendation, the government rejected an off-the-shelf design for the Collins’ replacement, but submarine design has progressed significantly since then, and dramatically since the Collins design was completed in the 1990s. Certainly, smaller European designs don’t have the range of the Collins, let alone of the Attack class, but they do have enhancements such as AIP. And large conventional designs, such as those of the Japanese and Koreans, are in a similar class to the Collins while possessing advantages such as AIP and lithium–ion batteries.

But it’s highly likely Defence will have to moderate its requirements and accept the art of the possible. Arguably, the Attack class collapsed under the weight of its own contradictions because we sought to design a conventional boat with many SSN capabilities. If Defence follows the same path now, it will meet the same result.

One approach could be a high–low capability mix, with Collins then the SSN providing the high end and an off-the-shelf design providing the low end. Considering Chinese warships are now frequent visitors to our near region, a small but stealthy submarine could provide useful capability close to home.

Turning to quantity, or platform availability, it’s important to remember that with a minimum of three boats needed to reliably deploy one, the best we can hope for from the six-boat Collins fleet is two deployable boats—and that’s world’s best practice. That’s despite the government stating in the 2009 defence white paper that we need more submarine capability and every subsequent government reinforcing that assessment.

The LOTE can’t improve on that, and there’s a distinct possibility of availability declining. Each LOTE installation is intended to fit inside the two-year full-cycle-docking window currently built into the Collins’ maintenance cycle. But if technical risks associated with a very ambitious program of modification push that schedule out, the boats will spend more time out of the water and less time in training or on operations. And there’s no way the LOTE can replace every ageing component on boats that will need to serve into their forties. Unplanned defects will increasingly see boats out of service for maintenance. Australia’s submarine force could experience a re-run of the Oberon–Collins transition, with capability falling to catastrophic lows.

Delivering new conventional submarines could increase quantity—but only if Australia exercises discipline. Much of the benefit will be undone if we must wait until the mid- to late 2030s for any new boats. That means sticking as close as possible to an existing design and making hard prioritisation decisions, such as choosing a rapid schedule over integrating the US combat system.

It also means some very hard thinking about where to build them. There will no doubt be political pressure to construct them in Australia. There will also be concerns raised about our ability to build both the conventional boat and the SSN here. But we can’t procrastinate and repeatedly change course for 13 years and expect to have the same freedom of choice as when we started down the submarine replacement path in 2009. Just as we need to consider all industrial strategies when it comes to SSNs, we need to consider all approaches to the new conventional boat. We could prioritise building the SSNs here and acquire the new conventional boat overseas—or the other way around. But the days when the mere thought of building any vessels overseas was anathema are long gone.

The quantity of boats is closely related to the third risk: the number of submariners. It’s no coincidence that Defence and its industry partners’ efforts in achieving world’s best practice in submarine availability have allowed the navy to finally generate the number of submariners it needs to operate the Collins fleet. That’s around 750 (a crew of 56 times 6 boats times a redundancy factor of 2–2.5). But by the time the SSNs are all in service, that force will need to be more than 2,000, perhaps even 2,500. It goes without saying that the navy can’t get from 750 to 2,500 overnight. But even finding the personnel for the first SSN—potentially 140 for a single US boat—from a pool of 750 will be challenging when the bulk of that pool is still needed for the Collins.

In short, the navy needs a way to grow a workforce at an achievable rate at a time when Collins availability will likely be declining. We have examined a range of options to increase submariner numbers. While this analysis is not exhaustive, it indicates that an additional four conventional submarines supplementing the six Collins would provide the most achievable growth path to a fleet of eight nuclear boats. That scenario would require an ambitious but manageable average annual workforce growth of around 4%, smoothing out a growth rate that could be twice as high if the navy went straight from the Collins to SSNs.

Of course, no number of conventional submarines will address the other part of the workforce requirement, namely the ability to safely operate a nuclear submarine. That will require nuclear specialists within and outside Defence. The navy will need to learn how to operate submarines very differently, both tactically and strategically.

While some nascent workforce capability could be developed through participation in US and/or UK nuclear submarine programs and joint crewing, it will be difficult to establish and sustain a critical mass of nuclear-qualified workers until SSNs are available to Australia. It may be that the SSN delivery schedule is driven more by Australia’s capacity to expand its nuclear workforce than by construction capacity.

In sum, another conventional boat could mitigate some of the key risks we face in our long submarine transition. But the review team needs to remind Defence that the perfect (whether it be military capability or local industry involvement) is the enemy of the good and its quest for submarine perfection has so far delivered nothing. Australia’s ambitions in both areas must be moderated if it is to get a new conventional submarine in time to help address those risks.

The other unavoidable issue that must be factored into the review’s considerations is, of course, funding. An additional conventional submarine will come at great cost. We have previously outlined ^[4] the pressures on the defence budget that SSNs will only exacerbate. With substantial new funding looking unlikely with the broader pressures on the public purse, finding the money for a new conventional submarine would involve cancelling other capabilities in Defence’s investment program. That will likely require strong recommendations from the review, and resolute backing from the government.