4 Challenges for the Navy as More Unmanned Drones Go Underwater

• Navy
• warfare
• robotics
• UAV

1. Taking Off From the Water

Raytheon's newest unmanned aerial vehicle (UAV), tested successfully in September, takes off from the surface of the sea. The SOTHOC, or Submarine Over the Horizon Organic Capabilities, UAV is a considerably smaller vehicle than the company's KillerBee, Raytheon's Dave Bossert tells PM. "It's an aircraft in stowed configuration," he says—the UAV fits inside a tube about 39 in. long and 16 in. in diameter.

Getting the aircraft to the surface of the water from far beneath it is a problem Raytheon solved with an inflatable life preserver and some pressurized air, according to Jeff Zerbe, SOTHOC director and a 24-year veteran of Navy subs. Once the sub releases the UAV into the water, the pressurized tube carrying the UAV inflates buoys that raise it to the surface. The tube then turns vertically, and the pressurized gas inside blasts the UAV into the sky—the same principle behind the CO₂ cartridges that launch toy cars. Once airborne, the UAV unfolds and its own engine takes over.

"Once the UAV is launched," Zerbe says, "it doesn't have to be controlled by the sub." Officers back on land could fly the vehicle, he says, so when the UAV has completed its mission, a pilot could steer it back to shore or to base. He says the Navy is particularly interested in a UAV that a sub could deploy because it would drastically improve the vessel's vision, which is limited to about 20,000 yards through a periscope. In the future, once Raytheon's waterborne UAV has passed more tests, the Navy may want UAVs that the sub can retrieve, Zerbe says.

2. Retrieving an Unmanned Underwater Vehicle (UUV)

Blasting an unmanned vehicle from a sub's torpedo tube is pretty easy. Bringing that UUV back on board the ship is much harder. Yet if the Navy wants subs to carry unmanned vehicles, they will have to have the ability to retrieve the vehicles after their missions. Last year the USS Hartford attack submarine successfully launched Boeing's AN/BLQ-11 UUV, Doss says. And more importantly, the Hartford retrieved the unmanned vessel and brought it back on board.

Retrieving an unmanned vehicle in the water creates a different challenge than bringing it back on land, says Tom Jones, Boeing's director of marine systems. "Water is an incompressible fluid," he says, so displacement presents a huge obstacle to recovering an unmanned vehicle. A submarine displaces thousands of tons of water and creates a wake of turbulence all around it, Jones says. But the 20-ft-long UUV has to line up directly with the torpedo tube, so that a robotic arm can reach out, grab the vehicle and pull it back in through the tube. Despite the fact that a Navy sub has shown it can bring Boeing's UUV back on board, fluid dynamics remains a complex and elusive body of knowledge, Jones says. So while he and his team try to better understand the forces in turbulent water so they can steer and position a UUV, other engineers are working on another way to make it easier to bring unmanned vessels back on board—redesigning the ships themselves.

3. Overhauling Old Subs to Hold New Vehicles

Boeing designed a 21-in.-dia UUV so it could be launched through torpedo tubes. But you can only fit so much into a 21-in. UUV—moving into the modern age also required an upgrade for the Cold WarÐera subs, in order to allow them to use larger vehicles, and that upgrade might be on the way.

General Dynamics Electric Boat has already updated four old Ohio-class nuclear subs into modern SSGNs—Ship Submersibles with Guided Missiles and Nuclear Powered—carrying Tomahawk missiles and including modifications that allow them to carry special operations forces, spokesman Bob Hamilton says. But Electric Boat also proposed a new feature for the subs—the Universal Launch and Recovery Module, which would allow the sub to deploy larger unmanned vehicles than could fit through a torpedo tube. The module would work like an air lock, Hamilton says—when releasing a vehicle, sailors could put it into a lockout chamber, flood the chamber with water and then eject the vehicle out to sea. When retrieving the UUV, the robotic arm at the end of the module could grab the vehicle and bring it back on board.

According to Electric Boat's John Pavlos, the new subs could also hold many more UUVS in their cargo bays and deploy several at once for reconnaissance or mine-finding missions. "What it previously took several subs to do, you can now do with unmanned vehicles," he says. With the four Ohio-class submarines fully refitted and back in the fleet, Electric Boat is turning its attention to the newer Virginia-class attack subs, designed with modern warfare in mind. Pavlos, the project leader for the Virginia-class construction, claims the Navy has already commissioned five of the subs into service, and the company will turn out at least eight more in the next five years.

4. Building Autonomous Robots

Truly autonomous UAVS and UUVs aren't quite ready for duty, but they are a big part of the Navy's plan for the future. According to the Navy Unmanned Undersea Vehicle Master Plan of 2004, "While admittedly futuristic in vision, one can conceive of scenarios where UUVs sense, track, identify, target and destroy an enemy—all autonomously—and tie in with the full net-centric battlespace."

Engineers have achieved self-steering boats—PM covered MIT's autonomous research submarine in September. And Stephen Thaler of Imagination Engines, an expert in artificial intelligence for robots and drones, said that his company is right on the cusp of intelligent UAVs and UUVs. "It would be very spooky if you realized how close we are to total autonomy," he says. There's no way to preprogram a response to every possible situation the machine will encounter. But with creative intelligence systems able to analyze stimuli and decide how to act, Thaler says, autonomous AI is within our reach, and so is the capability for those robots to communicate with one another and create what he calls "Borg-like intelligence."

The Navy would like to see a drone's autonomous capability specifically tailored to its task. "The mission will drive how autonomy is employed by the UUV," Doss says. He tells PM he can't say more than that about specific kinds of missions, but he says it would mean specifying for contractors that build intelligent unmanned drones just how intelligent the Navy wants its robots to be. A drone on a long, complicated mission needs to be able to make more decisions for itself, but the Navy doesn't want to lose control of its unmanned vehicles either. Thaler says that he doesn't foresee unmanned vehicles being used for underwater attack in next decade, but not because the technology is unavailable. Rather, he says, when it comes to real warfare, it's hard for humans to turn over the decision-making to machines. "Admirals want somebody to court-martial when things go awry," he says.

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