Swarming systems — either fired from a ship or dropped by a plane or a mother ship — are small, lightweight, cheap, numerous, and, networked together to cooperate like bees from the same hive. Credit US Navy photo.

“Think of a flotilla of 20 low cost Chinese ‘trawlers’ all peacefully ‘catching fish’,” says submarine analyst Peter Coates.

“But actually … acting as a mother-ship each for 200 low-cost mass-produced mini-UUVs … this flotilla could be assisted by the fixed seabed and tethered anti-submarine sonar sensors China is already stringing across East Asian seas.”

In other words, yes, submarines now have a new weapon to fear — swarms of cheap drones both above and below the water (unmanned underwater vehicles, or UUVs).

Navies across the planet are pursuing new anti-submarine capabilities as a submarine arms race accelerates in the Pacific Ocean, according to a report by Sebastien Roblin at National Interest.

Developing technologies like quantum magnetometers and satellite-based optical sensors are leading to forecasts that submarines may be on the verge of losing their stealthy edge by the mid-twenty-first century.

Swarming drones are distinct from larger, higher capability (and more expensive) long-range autonomous unmanned vehicles like the Large-Diameter HSU-001 submarine, recently displayed by China, or the Extra-Large Displacement Orca being built for the US Navy.

Swarming systems, by contrast, are small, lightweight, cheap, numerous — and networked together to cooperate like bees from the same hive.

Essentially, a game changer in the making.

Larger UUVs, aircraft or warships could flood the ocean with hundreds of such cheap and expendable drone sensor platforms to form a long-endurance surveillance capability that could move based on new intelligence.

They could also be deployed by seemingly non-military commercial shipping, such as watercraft used by China’s vast maritime militias. This could make it virtually impossible to tell which ships are deploying and controlling the drones.

Submarine expert Coates points out that cheap and numerous underwater mini-drones could be strung across hundreds of miles in “nets” to detect and even follow submarines.

“The possibilities are endless, cheap and can occur in peacetime—no need for expensive naval assets. They can ‘cue’ naval assets to our [Australian] submarines, if and when conflict breaks out.”

Worse, as submarine-hunting drones mature they could theoretically acquire offensive kamikaze capabilities similar to existing Switchblade ground-attack mini-drones.

There are limitations, of course.

Small drones can’t carry much fuel or weaponry. That limits their range and speed, meaning they will likely require some sort of long-endurance mothership (or “motherplane”) to deploy from.

In an offensive role, the payload limitation of small drones means they couldn’t carry a large explosive with good odds of a crippling a sub.

A Mark 48 heavyweight torpedo has a 650-pound warhead.

By comparison, a swarming drone may be limited to 20 pounds or less, making them more likely to sabotage than deliver outright lethal attacks.

Maintaining underwater communication links is also difficult through the dense medium of water. Though autonomous drones can bypass this problem, it doesn’t obviate the need for a surveillance system to transmit back useful data.

Finally, small UUVs eek out endurance by traveling at very slow speeds. But those speeds would make it very difficult to pursue or intercept a submarine cruising at 6-12 knots or sprinting at up to 30.

Today’s swarming UUV designs are focused primarily on locating mines and submerged objects.

Navies could flood the ocean with hundreds of cheap and expendable drone sensor platforms to form a long-endurance surveillance capability. Credit: US Navy graphic.

One example is the 3.7-pound SwarmDiver drone developed by Aquabotix, which can be tossed over the side of a boat and remotely controlled by a human operator.

The current system already has an application for mine-countermeasure missions, recovery of unexploded ordnance on the seafloor, port security and port defense. 

A system that can detect underwater mines could potentially be evolved to track submarines as well.

Russia is also developing a system consisting of a swarm of underwater combat drones, Gazeta.Ru reported, citing a source.

The AI-controlled system, consisting of both surface and underwater vehicles with a total displacement of 500-1,000 tons, will be deployed in a range of missions, including against an enemy aircraft carrier, the Moscow-based news outlet explained.

“For example, the command post sets a common task — to destroy the enemy aircraft carrier strike group. Artificial intelligence, which will control the swarm of underwater drones, solves this problem in accordance with very specific and constantly changing circumstances,” the news outlet quoted the source as saying.

“All this will be done by artificial intelligence, which receives data on the situation from a wide variety of sources.”

Can underwater drone swarms be countered? Of course they can.

Submarines can’t expend their limited supply of expensive torpedoes to pick off underwater drones, and they lack close-defense weapons like those on surface warships.

However, they could themselves deploy interceptor drones from torpedo tubes. One could envision a higher-end recoverable drone designed to rove further ahead of the submarine and disable distant, less-agile drones or static surveillance systems.

According to the War Zone, the Navy has been working on a countermeasure system called the Netted Emulation of Multi-Element Signature against Integrated Sensors, or NEMESIS. 

NEMESIS employs distributed systems including decoys, jammers, acoustic countermeasures, and multiple-input/output radios (MIMOs) to create dozens of fake sensor returns so that opposing operators can’t tell which are real and which are fake.

US Navy anti-submarine drone projects:

  • The Navy is pursuing aerial swarming LOCUST drones (standing for Low-Cost UAV Swarming Technology) equipped with Magnetic Anomaly Detectors (MAD) to skim low over the ocean hunting subs. These could be dropped from patrol planes. The Navy has also developed cannon-like surface-based launch systems that can rapidly catapult multiple LOCUST drones into the sky.
  • In 2013, the Navy tested a drone developed by Bluefin Robotics called Submarine Hold-At-Risk, or SHARK — part of a larger DARPA program called Distributed Agile Submarine Hunting (DASH). In theory, a SHARK-type drone would be deployed after detecting a submarine using passive sensors. SHARK would then employ an active sonar to continuously track that submarine’s movements.

Sources: National Interest, The War Zone, Gazeta.ru, The Defense Post