The Labor government has announced that work needs to “begin” in defining the type of submarine that should be designed to replace the Collins class (I say “begin” as there has been consideration of this for years within Defence).
Australia is different from the vast majority of other nations operating submarines in that our geography is vast, and areas of operation (AO) of interest are many thousands of kilometres distant. Hence the former Labor Defence Minister Kim Beazley suggesting that we need to double the number of submarines we have now. This presents some challenges for our force structure planners.
Conventional submarines are compromised in two important ways. First, there is the necessity to periodically charge batteries (and replenish air) using a snort mast (snorkel) to allow air to be drawn in to run the diesel generators. In an operational sense, when in the AO, so called air independent propulsion such as fuel cells allows advanced conventional submarines to remain submerged well over a week if the speed is kept very low. In this way, the indiscretion ratio problem (the percentage of time snorting) can be significantly reduced when in the AO.
The second problem that is more critical for our region is the issue of transit speed. For a variety of reasons, conventional submarines can only transit at about 10 knots. That means getting to the closest potential AO will take more than a week from where the submarines are based at Fleet Base West, and for most AO’s it will be considerably more than that. The long transit time required (both to and from the AO) clearly indicates that a significant portion of any deployment will be “wasted” in the transit.
Submarines are being tasked to carry out more varied tasks, and Australia’s next submarines will probably need to carry land attack cruise missiles. If this were the case with the Collins, it would come at the expense of some Harpoon anti-ship missiles or heavyweight torpedoes. Additionally, these rounds would have to be fired through the torpedo tubes.
With US attack submarines, small vertical silos housing Tomahawk cruise missiles have become de rigueur since the advent of the Improved Los Angeles class submarines. Our next generation submarine will probably also need to have this arrangement to give the operational flexibility required (and to ensure that we don’t end up with a reduced weapons load in other ways compared to now). This means a larger submarine and the Collins replacement will have to become larger for reasons I have outlined.
The next generation submarine will probably also need to deploy unmanned underwater vehicles (UUV). Once again, UUV’s will take up more space, and problematically, will probably require charging of batteries from the host submarine, which will be a further drain on electrical resources.
In comparison, nuclear submarines are able to transit at 30 knots or more, therefore the submarine and its crew spend significantly greater portions of a deployment doing productive work.
Traditionally, the major operational compromises associated with nuclear submarines have been size and noise levels. First, with noise levels, the submarines have become far quieter as a result of so-called natural coolant circulation reactors, where, at slow speeds in the AO coolant pumps are not required (as was the case with conventional reactors). With size, as previously stated, conventional submarines are becoming larger by necessity.
When all these factors are taken into account, a submarine probably of the order of 5,000-6,000 tonnes, requiring a lot of power and volume (and growth potential) and a high transit speed is needed. If we were only looking at the issue from a perspective of optimising the design for operational considerations, the conclusion would have to be that the submarine should be nuclear. The high transit speed would mean a greater percentage of mission time on station, requiring fewer submarines. We are having significant problems crewing our current fleet, so anything that can be done to reduce the total number of submariners required would be welcome.
The submarine would undoubtedly cost more, and Australia would have to source the reactor from the USA (as does the UK). We could probably come to an arrangement for the US to take the powerplant back at the end of the submarine’s life (reactors no longer require a mid-life refuel). We could still design and build the submarine in Australia and just use the US reactor.
In my view, it is imperative for the government to realistically and closely evaluate the nuclear option regardless of ideological sensitivities.
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