How the US Navy could sink AUKUS

The US Navy has 49 attack submarines, with the goal of growing the submarine fleet to 66 boats. Some planning documents have suggested increasing this to 78.

The fleet is a mix of older Los Angeles- and Seawolf-class submarines and the new Virginia-class submarines, which have been in production since 2000.

The US Navy plans on the basis it will acquire two new Virginia-class submarines every year.

But this is not actually growing the size of the fleet for two reasons: production is actually languishing at an average of 1.2 to 1.3 boats per year; while new boats when delivered are replacing retiring LA-class vessels.

According to the Congressional Research Service, the navy expects the size of the attack submarine fleet to shrink to 46 boats by 2030, return to 50 boats in 2032, and grow beyond 50 from 2036. The earliest the navy will reach 66 submarines is 2049.

The reason for the dip in numbers is a legacy of the Cold War. Once that ended in the early 1990s, the US Navy, like many militaries, cut back its spending and procurement.

Under AUKUS, the US has promised to sell the first of at least three Virginia-class submarines to the Australian navy from 2032. However, a clause in the legislation requires the US president to show Congress the transfer “will not degrade the United States’ undersea capabilities” – essentially ensure the US fleet will not go further backwards.

To avoid this, American and Australian taxpayers are spending $US17.5 billon over the next five years to boost the US submarine industrial base, including increasing workforce and supply chains and improving shipyard efficiency, with the aim of lifting the rate of production to two submarines a year from 2028, and 2.3 a year at some point after that.

That 2.3 rate of production is the magic number that will free up submarine hulls to be transferred to Australia without worsening the US shortfall.

There is another way to avoid a shortage, and that is to increase the availability of the US’ existing submarines. Of the 49 submarines, 16 are in maintenance or idle. In 2015, the unavailability rate was 19 per cent, which is the Navy’s target.

Just as with slow production rates, the maintenance backlog is blamed on a lack of workers, facility constraints at shipyards, and lack of spare parts. Some of the $US17.5 billion is going towards reducing the backlog.

The other major strain on the US submarine fleet is production of the bigger Columbia-class nuclear-powered submarines, which carry ballistic nuclear warheads.

The ballistic missile-equipped submarines are essential to the defence of the US mainland and forms part of the country’s nuclear-deterrent triad, along with strategic bombers and land-based ballistic missiles.

The Navy’s shipbuilding plan calls for one Columbia-class submarine to be built each year alongside the two Virginia-class boats.

“Policymakers and other observers have expressed concern about the industrial base’s capacity for executing a 1+2 workload without encountering bottlenecks or other production problems in one or both of these programs,” a Congressional Research Service report said last month.