DARPA and Serco Unveil USX Defiant: The First Fully Autonomous Warship

The future of naval warfare is taking shape as the Defense Advanced Research Projects Agency (DARPA) and Serco have completed the construction of the first No Manning Required Ship (NOMARS) prototype. This groundbreaking vessel, named USX Defiant, represents a major leap in autonomous naval technology, redefining how the US Navy envisions its fleet operations.

Designed as a medium-sized unmanned surface vessel, USX Defiant is built for transporting payloads without any crew, mission systems, or human intervention. Unlike traditional naval ships that require extensive onboard personnel, this vessel is engineered from the ground up for full autonomy, reducing operational costs, increasing efficiency, and enhancing survivability in contested environments.

With construction completed, USX Defiant is now set to undergo a rigorous series of dockside and open-water trials, testing its endurance, navigational capabilities, and adaptability in real-world maritime conditions. These tests will pave the way for future deployment scenarios, where autonomous vessels could operate independently in logistics, reconnaissance, or other mission-critical roles.

The journey toward an unmanned naval fleet has been years in the making. DARPA and Serco initiated the NOMARS program to challenge conventional shipbuilding norms. Their goal was to create a vessel optimized for autonomy—prioritizing factors such as increased hydrodynamic efficiency, stealth, and resilience against external threats.

A key milestone in this program was achieved in December 2024, when DARPA successfully conducted its first at-sea refueling test using drone ships Ranger and Mariner. These autonomous ships executed complex maneuvers, including probe connections and fuel transfer operations, demonstrating the feasibility of self-sustaining unmanned vessels.

The design process of USX Defiant was equally revolutionary. Serco utilized advanced software modeling to generate multiple hull configurations, ranging from 170 to 270 metric tonnes. The final build settled at 210 metric tonnes, incorporating hybrid power systems capable of achieving speeds of 15 knots (28 km/h).

According to DARPA, the NOMARS program aims to push the boundaries of naval architecture by eliminating crew-dependent design constraints. This approach not only reduces costs but also enhances the ship’s operational reliability and stealth characteristics, making it harder to detect or compromise in hostile environments.

As USX Defiant embarks on its testing phase, its success could mark the beginning of a new era in naval warfare—one where autonomous ships patrol the seas, execute missions with precision, and redefine the role of human sailors in modern maritime defense.