When Australia decided to buy a fleet of new nuclear-powered attack submarines earlier this month, it sparked international outrage. China labelled it a “cold war, zero sum mentality”. France was enraged at being left out. The deal will cost Australia $100 billion, and hand UK and US technology to a fleet of attack submarines, the apex predators of naval warfare. But by the time they are delivered in 20 years’ time, these submarines could be obsolete.
No one really knows how these submarines would perform in a conflict situation. It’s true that submarines have occasionally launched cruise missiles at land targets, but there has been no real submarine combat since 1982, when HMS Conqueror torpedoed the General Belgrano off the Falklands. Exactly how well submarines fare against modern anti-submarine warfare (ASW) forces is a continuing debate.
“There is a natural arms race between submarines, particularly nuclear-powered ones, and surface navies,” says submarine warfare author HI Sutton. “Broadly, submarines still appear to have the advantage.” Sutton says that Australia’s decision to tear up its 2016 contract for a diesel-powered submarine fleet with France and go nuclear instead was driven by the need for endurance provided by nuclear power, which enables a sub to stay underwater for literally years at a stretch, making its own oxygen.
But new technologies have emerged; in another five years they are likely to be mature, and five years later they could be in service with many of the world’s navies.
“Highly specialised systems like subs are especially vulnerable to fast extinction when the world changes,” says Roger Bradbury, Professor Emeritus of Complex Systems at Australian National University. Submarines are apex predators that depend on stealth — so were sabre-toothed tigers, he argues, and they’re extinct.
Once detected, submarines can be destroyed: hull breaches are catastrophic, and in the case of a nuclear ship, the damage to a nuclear reactor cannot be fixed like a diesel turbine. They survive because they are fiendishly difficult to find. While there is occasional talk of radical new technology to ‘make the sea transparent’, the best tools are still sonar and magnetic sensing, both of which have limited range. Roughly, magnetic is a kilometre or two, sonar can be five to fifty kilometres depending on the submarine, the sensor and the ocean conditions.
In 2021 a submarine captain’s main concerns are other submarines, sonar-equipped destroyers, and a few specialist aircraft and helicopters capable of detecting them if they know where to look. By the time Australia’s nuclear submarines are up and running in the 2040s, a new breed of submarine hunter could be widespread: smaller and autonomous robot submarines, surface vessels and aircrafts, all powered by new technology.
Previously, unmanned underwater vehicles (UUVs) typically resembled the US Navy’s torpedo-size Knifefish. They are tethered to a mothership so the operator can control them directly, used for limited roles like underwater surveys and to locate and destroy mines. Now, much larger and truly autonomous uncrewed submarines like the US Navy’s Orca XLUUV, based on Boeing’s 15-metre Echo Voyager, can trawl the ocean’s depths for up to six months with minimal human supervision.
XLUUVs’ main role might be as weapon carriers: when other sensors spot a sub, they can torpedo it. This would give away the XLUUVs position but, unlike crewed submarines, they are expendable.
David Strachan, senior analyst at warfare intelligence company Strikepod Systems, says that the Orca XLUUVs could also lay fields of anti-submarine Hammerhead mines. “The Hammerhead is moored to the seabed, and is equipped with a variety of sophisticated acoustic, magnetic and pressure sensors to detect, identify and engage adversary submarines using a Mk 54 torpedo,” says Strachan. “Orcas would be used to clandestinely deploy minefields of Hammerheads at strategic points.”
Submarines will also have to watch out for the threat from above, with hunter robots capable of detecting them from the surface. Sea Hunter is a fast, lean-looking 40-metre crewless trimaran developed by US agency DARPA to hunt submarines. After successful trials, including some to show how onboard AI could sail it autonomously in crowded shipping lanes, it was given to the US Navy in 2018. A sister vessel, Sea Hawk, was added this April and more are on the way.
Circling above them, drones are also making inroads into long-range anti-submarine patrols. The limitation has always been fuel, but solar power offers the potential for eternal aircraft which can stay aloft using sunlight by day and battery power by night. Solar Impulse II was the first aircraft to circumnavigate the world this way in 2016. Now the US Navy has commissioned Skydweller Aero, a drone based on the Solar Impulse airframe for long-range maritime patrols, and in the next year it will fly for 90 days at a time, scanning the seas below with a range of advanced sensors.
The new sub hunters are much smaller and cheaper than their crewed counterparts. Sea Hunter displaces 145-tons of sea, compared to 9,000 tons for the US Navy’s Arleigh Burke class destroyers, the mainstay of anti-submarine warfare. This means they can be procured in much larger numbers. They can also be made rapidly — the US Navy commissioned five Orca XLUUVs in 2019, with delivery expected by 2022. That’s much quicker than traditional submarines. Pricing also works in favour of the smaller vehicles. The Sea Hunter prototype was just $20m, compared to $1.8bn for a destroyer. The Orca XLUUVs are $10m apiece, compared to $2.8bn for a Virginia class submarine.
“They [the Australian navy] will be fighting technology that improves on a scale of years with boats that improve on the scale of decades, if at all,” says Bradbury. While submarines are likely to become harder to detect with sonar, Bradbury says that if sonar does not identify them, they’ll be picked up by sensors detecting magnetic, nuclear, gravitational and other anomalies.
Crucially, it is not just the Americans who are exploring this technology. The Chinese, the target of the AUKUS deal, launched a clone of Sea Hunter in 2019. They paraded their own giant robot submarines known as HSU001 on trucks during an event in Beijing in 2019 , and open-source documents reveal they are already experimenting with them in sub-vs-sub combat. And they have solar powered drone projects too. All of this suggests they are just a few years behind the US.
Simply increasing the number of hunters will not necessarily be enough to end submarines’ dominance in the sea, argues Sutton. “The big picture will remain that submarines, if operated well, are very hard to find,” he says. Sutton believes that robots will threaten surface vessels before they challenge submarines.
However, there is one thing that submarines would find impossible to hide from: covering the sea with submarine-locating sensors from horizon to horizon. This is DARPA’s Ocean of Things (OoT), an array of solar-powered floats which drift with the currents and send back sonar data by satellite.
The 14-kilo, solar powered fishing floats have a battery life of a few hours. OoT takes advantage of cloud computing and machine learning to crunch through the mass of data collected by the floats to pick out the sonar signature of submarines trying to sneak through the array.
DARPA tested thousand-float arrays in the Gulf of Mexico in 2020, and is planning arrays of tens of thousands. Each float can observe an area of twenty square kilometre, then pass data to XLUUVs or other craft to make the kill. China will be watching the OoT with interest. Plans for a Great Underwater Wall were revealed in 2016, combining networked underwater sensors with small robots submarines.
“It will become increasingly difficult for submarines to operate unmolested,” says Strachan. He believes they could be withdrawn from the front line and take on a role as motherships for a variety of uncrewed systems — aircraft carriers rather than battleships. This is probably not what Australia had in mind.
Being relegated to a transport role for a swarm of robots doing the real work would be a comedown for a prestigious fleet of brand-new nuclear submarines. But it’s better than extinction.
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This article was originally published by WIRED UK
