US DARPA christens USV Defiant

August 13, 2025, by Fatima Bahtić

The US Defense Advanced Research Projects Agency (DARPA) has marked a traditional naval milestone with the christening of USX-1 Defiant, a ‘first-of-its-kind’ unmanned surface vessel (USV).

Defiant has 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 54.8-meter-long, 240-metric-ton lightship is completing final systems testing in preparation for an extended at-sea demonstration. The vessel was built as a demonstrator for the No Manning Required Ship (NOMARS) program.

The NOMARS program leapfrogs conventional thinking about unmanned ships, with a goal to minimize the need for “optionally manned” vessels, according to DARPA.

“Defiant is a tough little ship and defies the idea that we cannot make a ship that can operate in the challenging environment of the open ocean without people to operate her,” said NOMARS Program Manager Greg Avicola, during the ceremony.

“While relatively small, Defiant is designed for extended voyages in the open ocean, can handle operations in sea state 5 with no degradation and survive much higher seas, continuing operations once the storm passes. She’s no wider than she must be to fit the largest piece of hardware and we have no human passageways to worry about.”

“Defiant class vessels provide cost-effective, survivable, manufacturable, maintainable, long-range, autonomous, and distributed platforms, which will create future naval lethality, sensing, and logistics,” said DARPA Director Stephen Winchell.

“Defiant will protect and expand the capabilities of manned ships, multiply combat power at low cost, and unlock new American maritime industrial capacity.”

After completing the at-sea demonstration, Defiant will be turned over to the US Navy’s Unmanned Maritime Systems Program Office (PMS 406). DARPA is working closely with the US Navy to identify a pathway to ensure capabilities and technologies demonstrated throughout the NOMARS program are accessible for rapid transition and integration.

In the reconciliation bill, which passed in July of this year, the US Congress appropriated $2.1 billion “for development, procurement, and integration of purpose-built medium unmanned surface vessels.”

Upon transition to PMS 406, Defiant will be the US Navy’s first solely autonomous (vs. hybrid manned-unmanned) MUSV.

To remind, the vessel was launched in March this year, while the construction of the prototype was completed in February.