The U.S. Department of Defense’s Defense Advanced Research Projects Agency (DARPA) has completed trials of the “Sea Hunter” – the world’s largest unmanned ship. The vessel demonstrator, which was tested as part of the agency’s Anti-Submarine Warfare (ASW) Continuous Trail Unmanned Vessel (ACTUV) program, has officially been transferred to the Office of Naval Research (ONR) for further development.
According to DARPA, the vessel could revolutionize U.S. maritime operations. ONR will continue developing the prototype vehicle—the first of what could ultimately become an entirely new class of ocean-going vessel able to traverse thousands of kilometers over open seas for months at a time, without a single crew member aboard—as the Medium Displacement Unmanned Surface Vehicle (MDUSV).
“ACTUV’s move from DARPA to ONR marks a significant milestone in developing large-scale USV technology and autonomy capabilities,” said Alexander Walan, a program manager in DARPA’s Tactical Technology Office (TTO). “Our collaboration with ONR has brought closer to reality a future fleet in which both manned warships and capable large unmanned vessels complement each other to accomplish diverse, evolving missions.”
While advanced software, hardware and three radar systems are key to the Sea Hunter’s navigation system, composites are the backbone of the vessel, allowing it to absorb high amounts of stress while remaining incredibly sturdy. In 2016, Scott Littlefield, the program manager of DARPA’s tactical technology office, told Composites Manufacturing that the agency looked at both aluminum and composite construction early in the development process. However, composites provided better overall performance and life-cycle costs.
The ship features a composite hull and foam core with GFRP skin. The main hull, deck, internal structures and outriggers are made from E-glass infused with a vinyl ester resin as well as a carbon fiber epoxy prepreg. The external shell features a linear styrene acrylonitrile (SAN) foam core, and the internal structure uses a PVC foam core. The prototype vessel was built using vacuum-assisted resin transfer molding (VARTM). The ship weighs 145 tons (with full-load displacement) and can travel approximately 10,000 nautical miles at 12 knots. The goal is to reach top speeds between 24 and 27 knots.
ONR plans to conduct additional at-sea tests to further develop ACTUV/MDUSV technologies, including automating payload and sensor data processing, rapidly developing new mission-specific autonomous behaviors, and exploring autonomous coordination among multiple USVs. Pending test results, MDUSV could transition to U.S. Navy operations by the end of 2018.