Down Underwater: Australia’s Submarine Replacement Challenge

With operating ranges far in excess of diesel-electric norms but insufficient nuclear industry to go with SSNs, Australia’s new submarine must come up with an innovative solution

Australia’s future submarine project is approaching a significant milestone, with a government decision due on which of three competing partners will be chosen to design and build between eight and twelve boats. The new fleet, which is likely to cost around AUD$20 billion, will replace the six Collins-class submarines as they are retired from the mid-2020s onwards. Despite a negative public perception in Australia, the Collins is a very capable submarine, and there is likely scope for some life extension work, but its basic design dates back to the 1980s.

Unlike other countries in the market for diesel-electric submarines, Australia cannot simply purchase an ‘export-ready’ design because none of the established exporters have a design suited to a continent-sized defence challenge. To put it in perspective, the distance between the Royal Australian Navy’s two fleet bases in Sydney and Fremantle is 50 per cent greater than the distance between Moscow and London. Furthermore, given that the operational areas of interest are up to 3,000 nm away from Australia’s own waters, the requirement is for a boat with substantial range and endurance.

The detailed Collins specifications remain classified, but missions can last sixty days or more. With an average transit speed of 8 knots, which is typical of a large diesel-electric boat, that level of endurance can provide for about thirty days on patrol at the required range. The current six-boat fleet provides for a sustained presence of only one vessel at such long range, with essentially no spare capacity – which is likely the basis for the planned expansion of the fleet to eight or more. The 2009 Defence White Paper specified twelve, but that is believed to have been scaled back.

Ambitions for the future submarine’s performance have also been reduced since 2009. Then the aim was for a conventional submarine with greater speed and endurance than the Collins. Even today, the range and endurance requirements that produced the Collins class are technologically challenging, and attempting to better them would raise the project risk profile, and almost certainly the cost. Today the Australian Defence Department’s future submarine project team speaks in public briefings of a boat of ‘similar speed and endurance characteristics as the Collins, but with greater stealth and with better weapons and sensors’.

In truth, Australia’s submarine requirements would be best fulfilled by nuclear propulsion, and there is a small but solid lobby in Australia promoting that option. However, there are substantial obstacles to a nuclear-powered attack submarine (SSN) solution for Australia. There is no domestic nuclear industry, and hence only a very small cadre of nuclear-trained technicians and essentially no infrastructure to support a nuclear fleet. Furthermore, despite the substantial price tag of a conventional fleet, an SSN solution would be more expensive still, representing a large opportunity cost to the rest of the defence budget.

As a result, Australia has little option but to pursue a unique design tailored to meet its requirements. The current competition between two commercial European firms – TKMS from Germany and DCNS of France – and the government of Japan is the result of several studies of potential alternatives and some byzantine Australian politics revolving around local shipbuilding jobs. It now seems inevitable that almost all of the build work will be done in Australia. Swedish manufacturer Saab, now the owner of Kockums which designed the Collins class and hence has some political baggage in Australia, was excluded from the competition. This decision precluded what seemed a natural option of proving new technologies during Collins upgrades and life-extension work that could transition into a new hull later.

The Japanese government is offering a design based on the Soryu class, which, as a large conventional submarine, is probably the boat currently in the water that most closely meets Australia’s requirements. However, even a Soryu-based solution will be far from ‘off the shelf’, as Japan’s submarine concept of operations is for relatively short patrols at modest distances from home bases. Exporting a submarine build to Australia would be a big step for Japan. It has not been active in arms exports previously, and the Japanese polity required substantial convincing before it approved the offer. However, the Japanese government has now mobilised its defence, foreign affairs and industrial clout to make a strong bid, even to the point where Australia might have some relationship management to do if Japan loses out.

The European firms are both offering new designs. TKMS has concept designs for a ‘large ocean going submarine’ and a Type 216, both of which draw on experience with the Type 212 and 214 diesel-electric designs. However, both concepts are significantly larger than the 212/214 family, which has implications for engine capacity and energy generation and storage. DCNS has briefed about a solution moving the other way – a scaled back version of the Barracuda SSN, with its nuclear propulsion replaced by a diesel-electric system.

In both cases, getting the propulsion system right for a boat that might come in around 4,000 tonnes will be critical. That was long an Achilles heel for the Collins class. Kockums had no experience with a 3,000-tonne submarine, and the chosen solution for the diesel engines, generator and batteries caused significant problems for years afterwards – further exacerbated by poor management of the fleet by the navy and government. One of the investments made to date is a land-based test facility for propulsion systems, a step intended to identify and manage risks before installation in the boats.

Two points of interest will be whether the chosen solution has an air-independent propulsion (AIP) system, and which type of battery is chosen. These are related issues. The three competitors all have AIP systems in other designs, and would be well-placed to offer it to Australia. AIP provides a tactical benefit by allowing extended periods of quiet submerged operation, but also takes up a great deal of space and has relatively low energy density (4.5 MJ/L for fuel cells, for example) compared to diesel fuel (35 MJ/L). So for a given submarine size, AIP reduces overall range and endurance.

In the past, the difference in energy storage efficiency between lead-acid batteries (typically around 0.4 MJ/L) and AIP systems meant that the tactical advantages of longer operation than batteries offered by AIP could support outweighed the space and weight penalty. Today, lithium-ion batteries can achieve much better energy densities than their lead-acid predecessors (up to 2.5 MJ/L), which substantially lowers the differential. Evaluating the maturity of lithium-ion battery solutions will be a critical part of the project process.

Finally, it is fairly certain that the new Australian submarine will field an American combat system. That was the eventual solution for the Collins class, after two false starts, and continuity remains a strong preference of the Royal Australian Navy. That will require the US to work with whichever industrial partner is chosen, making it in practice a three-way collaboration. That might point the way to the likely outcome. From a US perspective, it would make good strategic sense for its two most reliable Pacific allies to work together on a critical capability. While the public American position on Australia’s choice is appropriately neutral, it is likely that, behind closed doors, Washington’s preference is for a Japanese solution.

Andrew Davies
Director of the Defence and Strategy Program at the Australian Strategic Policy Institute.

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