U.S. Navy eyes roles for underwater drones launched from submarines

Richard R. Burgess, Seapower Magazine
1 June 2015

Later this year, a Virginia-class attack submarine will be deploying with a REMUS 600 unmanned underwater vehicle (UUV) onboard for unspecified missions. This could lead to routine UUV operations from submarines, in particular in littoral waters.
The Navy is not disclosing what sensors or other mission systems the UUV will be carrying, only that “this UUV has a wide variety of sensors ready for deployment,” said CAPT J. Carl Hartsfield, deputy executive director and Undersea Rapid Capabilities Initiative (URCI) program manager for commander, Submarine Forces, in written responses to Seapower.
The versatile REMUS 600 can operate to depths of 600 meters.
“The REMUS 600-based vehicle deploying with a Virginia-class submarine is modular in nature and can deploy
with a wide range of payloads,” Hartsfield said. “Many payloads for medium-sized commercial vehicles exist, and many more are in development. Sensors fitted on these types of vehicles have collected ocean data, mapped the sea floor and sensed the above-water environment for commercial industry, academia and the military.” Sensors that are known to have been deployed on the REMUS 600 include side-scan, synthetic-aperture and forward-looking sonars, and a camera.
The REMUS 600 being deployed already is owned by the Navy, said Tom Reynolds, business development manager for defense at Hydroid, a unit of Kongsberg, which builds the REMUS family of UUVs.
“It’s tailored for them,” Reynolds said.” There is REMUS 600, the Littoral Battle Space Sensing AUV [autonomous underwater vehicle] and the Mk18 Mod 2 [mine countermeasures UUV], and there are some other programs for the Office of Navy Research that use REMUS 600s. Essentially, the back half of it is almost always the same. The navigation system is almost always the same, with a few differences.
“But the payload and communications – the front part – of it is different. What the submarine force is using incorporates probably 70 percent of what all REMUS 600s incorporate. We have worked with the Navy as well as the Woods Hole [Oceanographic Institute in Massachusetts] and other folks to have a front end that meets what the submarine force needs,” he said.
“There is really no limit other than the imagination for what will fit on this vehicle,” Reynolds said. “It’s a modular AUV [autonomous underwater vehicle], not constrained to mine warfare or any other specific mission. It is whatever any university or sensor organization can make that will fit in that 12-3/4-inch form factor. It would have to account for trim and buoyancy and a few other things. It’s a modular vehicle and, software-wise, it is open architecture. The Navy and the submarine force envision this as another tool that can deliver multiple and a wide variety of sensors and payloads to an area far away from the submarine.”
This first deployment on an attack submarine may not be just an experiment.
“UUVs and other sensors in the undersea domain are developing so rapidly that the line blurs between experiments and operations,” Hartsfield said. “To put military capability on the edge of emerging technology, military leaders are working hard to put certain systems in the field with utility early and iteratively work toward perfection. Reaching that end result does come with a little more technical risk, but the conventional wisdom is that this approach provides capability faster with less overall cost.” The REMUS 600 will be launched from the SSN’s Dry Deck Shelter “with a high degree of autonomy,” Hartsfield said. “Launch and recovery of a UUV is an engineering challenge that has been solved in multiple ways over the past decade. In some ways, recovery via submarine is much simpler without turbulent seas on the ocean surface that cannot always be predicted at time of launch. Submarines can do recoveries well below the wave line no matter what the weather is on the surface.
“The submarine force has launched a wide variety of devices from our ocean interfaces,” he said. “The torpedo tubes are no different. The mid-sized UUV does fit inside any submarine torpedo tube. URCI has a program to allow torpedo tube launch of UUVs, as well as Dry Deck Shelter launch. We have a wide range of programs that use all submarine interfaces with the ocean to deliver capable payloads.”
Command and control connectivity is another challenge being overcome, Hartsfield said.
“UUVs have successfully transmitted data via antenna, acoustics and optics. They can communicate with manned platforms and each other. Networking systems is powerful in some cases, but not always necessary as UUVs continue to pass important autonomy milestones. Just like manned submarines, they will connect when needed and not at all if need be,” he said.
One of the main challenges in UUV operation is the need for powerful but safe battery technology.
“Lithium ion batteries are really considered a standard for what provides the most power per unit of weight,” Reynolds said, noting the November 2008 fire that damaged the Advanced SEAL Delivery System, believed to have been caused by lithium ion batteries, raising safety concerns. “That caused the Navy to go into a hold on lithium ion until they could better and more safely certify these batteries. Right now, the REMUS UUVs are going to be operating with the submarine force but will be using alkaline primary batteries,” which cannot be recharged.
“Primary batteries are used now,” Reynolds said. “They are safe, but once the mission has been conducted they need to be replaced. Secondaries [which are rechargeable] are where the future is, but there are safety concerns. Certifying secondaries for the fleet to use on any platform is a major Navy effort and Hydroid is supporting the Navy in this.”
The Navy has plenty of experience operating REMUS UUVs, which are certified for use from oceanographic survey ships – in the form of the Littoral Battle Space AUV – the USS Ponce afloat forward-staging base ship, patrol craft and 11-meter rigid-hull inflatable boats. The 8-inch-diameter REMUS 100, as the Mk18 Mod 1 UUV, and the REMUS 600, as the Mk18 Mod 2 UUV, have served in the mine-countermeasures role.
The REMUS 100 was used in the initial stages of Operation Iraqi Freedom in the Umm Qasr port-clearing role, where Reynolds, as a Navy explosive ordnance disposal officer, had first-hand experience with the UUV. The Mk18 Mod 2 currently is deployed with the U.S. Fifth Fleet and has achieved a 98-percent availability rate. The REMUS is the only UUV to reach full-rate production for the Navy so far.
Though the REMUS 600 is modular, it is “not like Legos,” Reynolds said. It requires a climate-controlled environment where technicians can swap out mission sensors without dust and sea air contaminating the sophisticated computers.
“The most important aspect of our vehicles is their reliability and I think REMUS vehicles have been key for the Navy to see that you can put more and more complex and expensive sensors on this vehicle,” he said.
Another UUV now available for launch from a submarine with an extended Dry Deck Shelter is the Proteus, a large, free-flooding mini-sub that is unique in that it can be operated as a swimmer-delivery vehicle manned vehicle or as a UUV. The battery-powered Proteus has 170 cubic feet of
interior space for cargo or can carry two pilots and six swimmers (eight in another configuration). The cargo bay has ventral doors that open like an aircraft’s bomb-bay doors for placement of sensors, mines or other objects on the sea floor. External rails on each side allow the Proteus to carry cargo externally.
The Proteus can transport a payload of 3,600 pounds of in-air weight and, when in the water, it has a variable ballast of 1,150 pounds. The vehicle is equipped with a sonar for navigation and a camera for close-in inspection. It also can be launched from a ship by crane or well-deck.
“In the manned mode, the maximum working depth is 150 feet,” said Ross Lindman, vice president of Undersea Solutions, a subsidiary of Huntington Ingalls Industries, in which he is a director. “In the unmanned mode, it will go to 200 feet. It’s not a deep vehicle. This is a big undersea truck or a bus.
“One of the unique things about it is that, in one mission, you can run different parts of it manned and, in some parts of it, unmanned,” Lindman said. “As a UUV, it has a whole portfolio of mission-specific behaviors built into the autonomy.”
In manned mode, while the pilot navigates the Proteus, the co-pilot “is watching the sonar for obstacle avoidance, handles communications, changes in ballast while the pilot is focused on the navigation and flying,” he said. “It’s a lot like flying an airplane because you’re in 3D space. The pilot has at his disposal a whole set of autopilots that he can engage at any time. One of those is a hovering mode that this vehicle, because it has thrusters – fore and aft, both horizontal and vertical – it is able to hover and that is very useful for payload delivery for a number of different missions.”
Partnered with Undersea Solutions is Battelle, which provides the batteries, and Bluefin, Battelle’s subsidiary, which provides the navigation and autonomy systems that were adapted from the company’s Bluefin-21 UUV.
Battelle’s batteries are made with lithium polymer, which, unlike lithium ion types, are not flammable. With these batteries, the Proteus can cover more than 350 miles or, if more batteries are added in the cargo space, out to 900 miles. The Proteus, as currently configured, must be out of the water to charge the batteries, but could be modified to be charged underwater.
Retired RADM Fred Byus, general manager of Battelle’s Maritime Systems unit, called the battery system for Proteus a “technology leap.”
“Where, before, we were talking about battery forms that are about 1-1/2 kilowatt hours per cell,” Byus said. “For the Proteus, we put the battery into a form of 7-1/2 kilowatt hours per cell, so about five times the size in terms of a cell-by-cell basis. And then we have to put the battery management system in to where it’s now controlling 20 cells instead of five cells. We put an awful lot into the development of the large-form battery with an expectation that larger vehicles will require the power, the endurance and the reliability of a larger form battery in the future.”
Only one Proteus, in operation since September 2012, so far has been built, using only internal funds at the Undersea Solutions facility in Panama City, Fla., and has completed developmental testing.
“We now lease it to the Navy as a test bed supporting different programs for development of sensors, undersea technologies, undersea weapons systems, development of concepts of operations,” Lindman said. “As an aside, this has the ability as a training target. Because it has a big sonar signature on active sonar, it can be a stand-in for a diesel electric submarine in training [anti-submarine warfare] forces. With its range and payload capability, it is able to provide a near-term solution for urgent needs now.”
The Navy also has been considering modifying its Mk48 submarine torpedo into a UUV for other missions. “U.S. Navy heavyweight torpedoes have always been very capable,” Hartsfield said. “Torpedoes are really just highly specialized UUVs. With that in mind, it makes sense that torpedoes could be even more effective if they could have the endurance, navigational accuracy and communications capabilities of advanced UUVs. The submarine force and the Navy are actively pursuing advancements in these areas.
“The submarine force expects to host a wide variety of UUVs and UAVs [unmanned aerial systems], since we can provide covert ocean access,” he said. “Unmanned underwater vehicles and unmanned air systems have already launched from the Dry Deck Shelter, the torpedo tubes, the signal launcher and even the trash disposal unit. Submarines will continue to be a critical node that can deliver, recover and interface with a wide family of sea and air systems.”