The US Navy’s robo-subs will sink Chinese ships without using torpedoes, missiles or guns

Submarines and warships of the Chinese fleet on manoeuvres. US plans to lay mines using unmanned submarines could present a threat to any invasion of Taiwan
Submarines and warships of the Chinese fleet on manoeuvres. US plans to lay mines using unmanned submarines could present a threat to any invasion of Taiwan - Guang Niu/AFP

The US Navy’s new robot submarine is primarily a minelayer, the official leading the program has revealed. The 84-foot Orca is designed to lay so-called “clandestine-delivered mines,” Captain Matt Lewis – a submariner and program manager for the Navy’s Unmanned Maritime Systems office – told The War Zone. “That’s the initial concept,” Lewis said.

This makes sense. Minelaying is the most straightforward task fleet leaders could assign to the Boeing-made Orca as the type undergoes intensive testing this year ahead of its formal entry into front-line service. The US Navy could acquire dozens of the autonomous submarines in the coming years, spending $50 million per boat to help fill an anticipated shortfall in manned submarines as old Cold War vessels decommission.

Sea mines could be some of the most effective – and most efficient – weapons for the most urgent crisis the American fleet could face in the next few years: a Chinese invasion of Taiwan. Assuming US President Donald Trump honours the longstanding American commitment to defend Taiwan – hardly a safe assumption, given Trump’s day-one executive order halting all US foreign aid – Orcas dispensing keel-breaking mines could transform the Taiwan Strait into a watery graveyard for the Chinese fleet.

The diesel-electric Orca was around 50 feet in length before the US Navy got its hands on the design a few years ago. The service added a 35-foot payload module with doors on the top and bottom. To deploy a payload – a mine, a sensor or some other object – the Orca just opens the lower doors. “I think the best way I can describe this is that it’s gravity-dropped,” Lewis explained.

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With the module, an Orca displaces around 85 tons of water. It can sail autonomously as far as 6,000 miles, periodically surfacing and raising antennae to communicate with its faraway operators, and probably running its diesel to charge its batteries. While the US Navy is developing tiny torpedoes that might one day arm the Orca flotilla, mines are ready today. And laying those mines, each powerful enough to sink all but the largest Chinese ships, isn’t terribly demanding for an immature robotic system.

Mines are simple but potent weapons. The American strategy for defending Taiwan primarily depends on submarine-launched torpedoes and air-launched anti-ship missiles, but mines are important, too. “Mines have the advantage of obviating the requirement for precise targeting of the Chinese fleet,” the Center for Strategic and International Studies in Washington DC explained. “Once the Chinese select an invasion beach, any mine dropped there will eventually hit a ship.”

It’s not for no reason that Iran leans heavily on mines in its strategy for closing the strategic Strait of Hormuz. Unsurprisingly, Taiwan is also an enthusiastic user of mines. Between 2019 and 2021 the Taiwanese navy commissioned four new Min Jiang-class minelayers, each displacing 350 tons. If tensions across the Taiwan Strait escalate to the point where violence seems likely, the Min Jiangs would deposit their munitions along the likeliest routes for a Chinese invasion fleet.

They might have help from the Americans – and from the air. Many US Air Force and Navy warplanes can drop mines. The US Air Force’s Boeing B-52 bombers are among the most capacious minelayers. The B-52s routinely haul a whopping 15 Quickstrike air-dropped mines, each weighing up to 2,000 pounds. Quickstrike mines guide themselves to their preset laid location as they fall, so the dropping plane doesn’t have to fly low and slow.

It’s not clear how many mines an Orca might carry in a single, potentially weeks-long mission slowly sailing along the Taiwan Strait. It’s likely fewer than a single B-52 carries in a sortie lasting just hours. But a B-52 is a big fat target for Chinese air defences. The US Air Force is mitigating this vulnerability by adding pop-out wings to Quickstrike mines – wings that can carry a mine potentially dozens of miles when dropped from high altitude.

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The Orca needs no such help. Running silent at a top speed of just a few knots, an Orca should be almost impossible for Chinese forces to detect. The robotic sub could slip into the Taiwan Strait, lay its mines then slip out. Chinese sailors may have no idea they’re in danger until the instant their ship explodes.

There’s a downside to this creeping stealth, of course. The Orca is silent because it’s slow. It’s slow because it has a conventional engine instead of the nuclear reactor that’s standard on the US Navy’s 50 or so manned submarines. It might take weeks for an Orca to sail from some secure port to a potential war zone and then back.

So if the Americans are going to deploy Orcas to mine the Taiwan Strait, they’d better plan ahead – and be ready to launch the robotic subs at the first sign of a Chinese mobilisation.