Science

US Navy's New Drone Hunts Mines Wherever They Hide

The US Navy is building a fleet of mine-hunting ships that investigators say aren’t all that hot at finding mines. So in the coming years, those ships are going to get drone supplements to dive deep below the sea to spot the underwater weapons. Think of ‘em as pairs of robotic glasses.

This is a scale model of the Navy’s newest drone sub, called the Knifefish. Manufactured by General Dynamics, the Navy unveiled it for the first time on Monday at its annual Sea Air Space convention just outside Washington DC.

The Knifefish — named after a real fish that emits an electric field — will be a 6m robot with a 21-inch (53cm) diameter that launches from a Littoral Combat Ship (LCS), the new US Navy ship built to fight close to shore. The robot is basically a solution to a chief LCS vulnerability discovered by the Pentagon’s top weapons tester: although one of its missions is hunting mines, its chief mine-spotting systems are “deficient” for exactly that task.

Enter the Knifefish. Starting in roughly 2015, according to General Dynamics, each LCS will be able to launch two Knifefish modules, with the primary task of finding mines buried in the sea floor. It’s an autonomous robot: sailors aboard an LCS will program the Knifefish’s navigation systems with instructions on where to swim ahead of launching it. It can swim for 16 hours at a time.

But the chief asset of the Knifefish’s autonomy isn’t navigation, it’s analysis. It uses a set of low-frequency wideband frequencies to spot a mine that gives off a resonance “very near” that of the particular mine it’s hunting, says Capt. Dwayne Ashton, the US Navy’s program manager for unmanned maritime systems. That “allows you to fingerprint the object being looked at”, instead of having a human sailor spending hours discovering and cataloging the types of mines he or she encounters — something Ashton calls a “significant game-changer”.

The Knifefish won’t neutralize mines that it finds, though — it just relays data back to the mothership about the mines’ location. That, at least, may take some of the pressure off the LCS’ other mine-spotting systems, the AN/AQS-20A Sonar Mine Detecting Set and the Airborne Laser Mine Detection System, neither of which have impressed Pentagon testers.

But the Knifefish won’t transmit that data in real time. It’ll store up to 12 terabytes of data collected by its acoustic sensor package. Data recovery will have to occur after the Knifefish swims back up to its LCS parent. Which might be a problem, since the LCS can’t survive a blast from any mines it doesn’t detect.

“We’re talking about a large amount of data, terabytes of data,” Ashton explains, adding that the Navy doesn’t believe it needs real-time data reporting right now, although it might reevaluate after the first Knifefish missions. The robots should arrive in the fleet not long after the first of two LCSes are permanently stationed in Singapore.

The Knifefish is also a step toward diversifying the Navy’s robotic portfolio. Successive Navy chiefs have been keen to build underwater robots that can swim across entire oceans, but the propulsion and fuel systems necessary aren’t technologically mature yet. The Knifefish is decidedly not a long-range robot sub, although General Dynamics and the Navy won’t say specifically how fast it can swim or how far it’s expected to patrol.

Still, the Navy has yet to fully explain what a vulnerable LCS is supposed to do while it waits for its mine-hunting robots to swim back to mama. How the Knifefish performs “will help determine the tactics, techniques and procedures” for the LCS, Ashton says. But if the Knifefish turns out not to be able to see very well, the Navy’s newest ship might be dead in the water.

Photo: Spencer Ackerman/Wired

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