VESSEL REVIEW | Defiant – Scalable proof-of-concept USV developed for US Navy

The US Defense Advanced Research Projects Agency (DARPA) has unveiled a new unmanned surface vehicle (USV) designed for maritime security applications.

Defiant was built jointly by Nichols Brothers Boat Builders of Freeland, Washington, and Washington, DC-based Serco North America as a demonstrator for DARPA's no manning required, ship (NOMARS) program.

Optimised for ease of manufacture, maintenance, and deployment in large numbers

DARPA said the craft boasts a simplified hull design to allow rapid production and maintenance in nearly any port facility or tier III shipyard that traditionally supports yacht, tug, and workboat customers.

The ability to be accommodated at a greater number of ports even with minimal need for additional specialised infrastructure means that the craft can spend less time in port for maintenance and be out at sea on operations more often. This then ensures increased coverage for security applications such as surveillance, reconnaissance, and patrols.

The 180-foot (55-metre), 240-tonne USV was designed to be different from some of the optionally manned autonomous surface vessels being developed by the US Navy.

According to DARPA, the NOMARS program aims to divert from the traditional naval architecture model by designing a seaframe (i.e., the ship without mission systems) from the ground up with no provision, allowance, or expectation for humans on board.

DARPA remarked that by removing the human element from all ship design considerations, the NOMARS program intends to demonstrate significant advantages, to include: size, cost, at-sea reliability, greater hydrodynamic efficiency, survivability to sea-state, and survivability to adversary actions through stealth considerations and tampering resistance.

Capable of extended endurance operations

As with the US Navy’s other medium USVs, Defiant is regarded as a long-range sensing platform that can extend the reach of larger manned combatants into contested or high-threat areas without risking the lives of crewmembers.

A fleet consisting of such smaller autonomous platforms is expected to increase total deployed capabilities while decreasing fleet cost and reducing risk to service members.

The medium-sized craft has also been configured to operate autonomously for up to a year if needed. Tests meanwhile showed that it is capable of sailing at 20 knots, executing high-speed turns, and automated docking/undocking and harbour entry/exit.

NOMARS Program Manager Greg Avicola said that despite being relatively small, Defiant is designed for extended voyages in the open ocean, can handle operations in Sea State five with no degradation, and survive much higher seas, typically with wave heights of up to 30 feet (nine metres).

DARPA Director Stephen Winchell meanwhile said that Defiant and other USVs in the same class will provide cost-effective, survivable, manufacturable, maintainable, long-range, autonomous, and distributed platforms. With these attributes, the craft enhance combat power without proportional increases in cost.

Defiant will soon be turned over to the US Navy's Unmanned Maritime Systems Program Office. Later testing will see the USV deployed at various global locations to assess its performance under real-world conditions.