Unmanned undersea vehicles are "embracing nature" and evolving quickly

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April 10, 2017

By drawing design inspiration from nature, unmanned undersea vehicles (UUVs) are evolving to become downright innovative and stealthy and, in many cases, capable of carrying payloads that can be customized for a wide variety of military missions.

One of the most well-known UUVs is Lockheed Martin’s Marlin, which is capable of fully independent operation. The U.S. Navy can use Marlin “for a variety of undersea applications such as below water intelligence, surveillance, reconnaissance, and small payload deliveries,” says Tim Fuhr, director of autonomous maritime systems for Lockheed Martin. “Marlin can go where submarines and manned vessels can’t or don’t want to go, and use its sensors, communication, and data reduction capabilities.”

Sea mines are one of the most formidable challenges the Navy faces, and finding and mapping them “is good usage of UUVs,” Fuhr says. “UUVs like Marlin can be outfitted to be a single-sortie detect-to-engage chain, coupled with the right sensors, target recognition software, and an expendable mine neutralizer.”

Another well-known UUV is “Knifefish,” which was created by Bluefin Robotics Corp. and has since become part of General Dynamics Mission Systems. Its standard model uses a wide variety of sensors to conduct its operations, including inertial navigation systems, Doppler velocity logger, compasses, and sound-velocity sensors. Knifefish’s payload is a low-frequency broadband synthetic aperture sonar to detect buried mines.

“Knifefish provides search, detection, classification, and identification of buried, bottom, and volume mines in high-clutter environments in a single pass – with minimal intervention by human operators and reduced overall mine countermeasures mission timeline,” says Matt Graziano, a director of the Maritime and Strategic Systems line of business within General Dynamics Mission Systems. “The proliferation of relatively low-cost and easily deployed underwater mines poses a unique threat to naval operations and maritime security.” (Figure 1.)

 

UUV payloads

As far as payloads being carried by UUVs, the ability to customize for specific missions is highly desirable. “We have multiple Marlin vehicles, and each is outfitted slightly differently with COTS [commercial off-the-shelf] parts, custom sensors, and communications electronics,” Fuhr notes. “It’s straightforward to customize the vehicles for a particular application as long as the electronics are compatible with Marlin’s size, weight, and power (SWaP) requirements.”

“Autonomy, data-processing capabilities, energy systems, and underwater communication systems are the main areas of development and challenge,” in UUV development today, according to Fuhr. “Energy-storage systems define the size of UUVs because the vehicle must carry its own energy source, which has to last for the duration of an intended mission. A UUV like Marlin wants to maximize mission range, minimize detectability, and have the capacity to be a data and communications node – in both single-asset and multiple-asset mission scenarios.”

Where is UUV technology heading next? Lockheed Martin is focusing on “coordinated development of extra-large UUVs for large payload capabilities; large-diameter systems for submarine-related operations; small UUVs for mine countermeasures and missions where expendability is desired; and cooperative behaviors between UUVs, unmanned surface vehicles (USVs), and unmanned aerial vehicles (UAVs),” Fuhr says. “Another key element is interoperability with other assets, and the ability to enable and participate in multidomain operations.”

Emerging innovations

Other defense prime contractors, government laboratories, and university teams are exploring innovations in the UUV realm. There are too many to note them all, but here are a few exceptional ones.

• Release the CRACUNS!

Seemingly something straight out of science fiction, researchers at Johns Hopkins University’s Applied Physics Laboratory recently developed the Corrosion Resistant Aerial Covert Unmanned Nautical System, dubbed the CRACUNS, which is an unmanned aerial vehicle (UAV) that can stay on station hidden below water, and then launch into the air to perform a variety of missions. (Figure 2.)

 

Figure 2: CRACUNS can be launched from a fixed position underwater or from an unmanned undersea vehicle. Image courtesy of Johns Hopkins Applied Physics Laboratory.

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The ability to “Release the CRACUNS” is ushering in new capabilities not previously possible with UAV or UUV platforms. Its ability to operate within the harsh littoral environment, as well as its payload flexibility, means that CRACUNS can be used for a wide array of missions. Its low cost is a bonus that makes it expendable, allowing for use of large numbers of vehicles for high-risk scenarios.

The most innovative feature of CRACUNS? The researchers say that it can remain at and launch from a significant depth or from a UUV without needing structural metal parts or machined surfaces. To do this, the designers fabricated a lightweight, submersible, composite airframe capable of withstanding water pressure while submerged. Sensitive components are protected from a corrosive saltwater environment by being sealed within a dry pressure vessel, while motors receive protective coatings.

• Undersea navigation

Another key advance currently underway is focused on undersea navigation. BAE Systems is working to develop an undersea navigation system for the U.S. Defense Advanced Research Projects Agency (DARPA) to provide precise global positioning throughout the ocean basins. (Figure 3.)

 

Figure 3: BAE Systems is developing an undersea navigation system, called POSYDON, for DARPA, with the goal of allowing undersea vehicles to navigate below the ocean’s surface. Image courtesy of BAE Systems.

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The Positioning System for Deep Ocean Navigation (POSYDON) program’s goal is to enable underwater vehicles to accurately navigate while remaining below the ocean’s surface. Intriguingly, POSYDON will tap some hardcore physics to create a positioning, navigation, and timing system designed specifically to permit vehicles to remain underwater by using multiple, integrated, long-range acoustic sources at fixed locations around the oceans.

BAE Systems has more than 40 years of experience developing underwater active and passive acoustic systems: “We’ll use this same technology to revolutionize undersea navigation for POSYDON by selecting and demonstrating acoustic underwater GPS sources and corresponding small-form-factor receivers,” says Joshua Niedzwiecki, director of Sensor Processing and Exploitation for BAE Systems.

The vehicle instrumentation that will be needed to capture and process acoustic signals will also be developed as part of the program. BAE Systems plans to use its capabilities in the areas of signal processing, acoustic communications, interference cancellation, and antijam/antispoof technologies. The company is collaborating with researchers from the University of Washington, Massachusetts Institute of Technology (MIT), and the University of Texas at Austin for the POSYDON program.

 

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