The contrast between the replacement for the existing Collins class submarines and the F-111 strike fighter is instructive. Governments didn’t replace the F-111 with the similarly sized F15 fighter, let alone require a much bigger version to be designed. Other factors led to the choice of the smaller, shorter range F-35s and the F18 Super Hornets. The F15’s combat radius is 1,960 km: the F-35’s is 1,000 km and the Super Hornet’s 740 km.

Fighter planes can refuel, but so can subs. Even unrefuelled, Australia’s post-war subs have possessed a remarkably long range of 19,000 km compared to the chosen fighter jets. But there’s now a bipartisan consensus among politicians and commentators that Australia’s new subs must be bigger due to the distances they have to cover. Yet no government has ever given a substantive explanation for why Australia is embarking on the highly complex and expensive task of acquiring huge, conventionally powered submarines. Instead, all assert that Australia requires much bigger subs than the existing Collins class and the Oberons that served the nation well from 1960–2000.

The 2016 Defence White Paper’s $50 billion figure for building the new subs is already attracting adverse attention. Much less notice is paid to why we need such large submarines that will require extensive design changes to existing versions. Ignoring transparency, governments have ruled out acquiring medium-sized subs without a convincing explanation. Range isn’t an obstacle. Greece’s German-designed medium-sized subs have a stated range of 18,500 km. Later German versions can be configured to exceed the government’s requirement of a 19,000 km range.

Smaller subs have several notable advantages.

They’re much harder to find than big ones. That’s a significant consideration, as made clear by recently retired US navy chief Admiral Jonathan Greenert, who warned ^[1]that rapid advances in sensors and data processing speeds make it easier to detect and destroy big subs and ships. Smaller subs can operate in the shallower waters to Australia’s north and are much cheaper to buy and run.

The consensus favouring big subs ignores how the Japanese, French and German contenders in the competitive evaluation process are all at least double size of the Oberon subs imported from the UK in the 1960s, without necessarily expanding on the reasons behind that preference. Japan’s big Soryu class subs now in service can’t go nearly as far as the Oberons did. The others aren’t as bad, but their extra weight still acts as a drag on range. As stated by a participant in the bidding process, ‘you can’t beat physics’.

The Oberons only displaced about 2,300 tonnes, but their unrefuelled range was around 19,000 km. With stops to top up fuel, fix minor maintenance problems and let the crew stretch their legs, they had no trouble going long distances to snoop around the naval base at Vladivostok. The subsequent Collins class’ submerged displacement is 3,400 tonnes. Its range is also around 19,000 km.

Although the government’s publicly stated requirement for the new subs is that their range and endurance must be similar to the Collins, defence officials have told the contenders they must offer larger subs. The Germans won’t release how much their contender will displace, after amending an earlier design for a 4,335 tonne Type 216 sub. The French candidate is 4,800 tonnes. The Japanese contender will probably have to be redesigned to over 5,000 tonnes to meet the specified range of 19,000 km.

The 4,200 tonne Soryu’s range is only 12,000 km. A bigger version will save weight by not including an Air Independent Propulsion system—even though the Japanese claimed as recently as 13 December in an ABC television interview ^[2] that AIP was one of their subs’ great selling points. The ABC journalist wrongly stated the system was ‘unique’ to Japan’s subs.

Some observers argue AIP isn’t essential, despite allowing ultra-quiet operation in a target zone without needing to use the sub’s diesel engines to recharge batteries. Almost all operators of modern conventional subs, including Russia and China, now regard AIP as necessary to help subs survive when silence is crucial. The government’s decision not to require AIP is highly contentious. But it helped keep the Soryu in a competition the former Prime Minister Tony Abbott wanted it to win to gain a strategic one-up on China, even if his choice isn’t the best sub for Australia.

A reason for Soryu’s short range is that a large part of the space between its unusual double hull is reportedly filled with water ^[3]. Associated maintenance difficulties may help explain why its service life is only 20 years, compared to 30 or 40 for other subs. The double hull also makes crew space exceptionally cramped.

The Japanese have never exported a sub, let alone built one overseas as Australia requires. Since 1960, the Germans have supplied 163 diesel-electric subs to 20 navies; 123 were exported or built overseas. Israel has an advanced 2,400 tonne German sub and Singapore is buying a 2,200 version. The French have built a large number of various sized nuclear and conventional subs since 1960 and exported 107 to nine navies.

Some analysts see less need for Australian subs to focus on the seas around China, as countries such as Japan, South Korea, and Vietnam now have more subs in the vicinity. In an ASPI paper, Benjamin Schreer advocated focusing Australia’s submarine fleet on the east Indian Ocean and maritime chokepoints in the Indonesian archipelago. He stated that ‘while this could mean fewer and smaller boats, they would still make critical contributions to Australia’s security and to allied operations’.

German and French medium-sized subs are ideally suited to operating in those waters and could still travel as far as Vladivostok. Smaller sub-surface drones could supplement them in a future where plans to purchase large, expensive and easily detectable subs make less and less sense.