- DARPA Confirms Completion of USX-1 Defiant.
- U.S. Navy’s Shift to Smaller, Scalable Uncrewed Ships.
- At-Sea Refueling Successfully Tested.
A streamlined, partially decked naval vessel seen recently in Washington state has been confirmed as the Defiant, a medium-sized unmanned surface vessel (USV). Created under the U.S. Defense Advanced Research Projects Agency’s (DARPA) No Manning Required Ship (NOMARS) program, Defiant is capable of being used without humans aboard. This ship may be a significant milestone toward the U.S. Navy’s ambition to deploy larger and more capable USVs within its fleet, reports TWZ.
Initial Sightings and Development History
DARPA has verified that Defiant’s construction, alternatively referred to as its hull number USX-1, was finished earlier this month. Its initial hints at the launch were by residents within Washington State who saw it towed by a tug through Saratoga Passage in Puget Sound, near Seattle to the north. It is near the U.S. Navy’s Naval Air Station (NAS) Whidbey Island.
Defiant, which is 180 feet long and 240 metric tons, is now to be subjected to rigorous in-water testing, both dockside and at sea. DARPA reports that it is to be subjected to a multi-month at-sea demonstration in spring 2025. The core contractor, Serco Inc., has been designing Defiant since 2020. The company has already reported that the main USV, excluding other mission systems, comes with an estimated price of $25 million.
Classification and Technical Design
The U.S. military categorizes uncrewed vessels like Defiant as medium USVs (MUSVs), which typically have lengths under 200 feet and displacements under 500 tons. Large USVs (LUSVs), in contrast, are classified as vessels up to 300 feet long with displacements reaching 2,000 tons.
Recent photos of Defiant in Puget Sound, and other photos published by DARPA, indicate the ship is still covered partially. Its hull shape and mast configuration, with several commercial navigation radars and antennas installed, are consistent with previous models and computer-generated images of the ship. A second smaller mast with additional radars and antennas is also visible on the bow.
NOMARS Program Requirements and Capabilities
DARPA’s NOMARS program set out to develop a vessel designed for long-duration open-ocean operations with the following core features:
- Distributed hybrid power generation
- Podded propulsors
- High-capacity batteries
- Enhanced hydrodynamic efficiency
The program emphasizes a concept called “graceful degradation”, ensuring that individual components can fail over time while still meeting system-level redundancy requirements. Even after one year at sea, the vessel is expected to operate at speeds of at least 15 knots despite potential component failures.
Payload and Mission Capabilities
Defiant has expansive open deck areas in front of and aft of its primary mast, which are intended to support modular mission systems. Serco has showcased mockups of Defiant with standard shipping containers, which could be utilized for a variety of payloads, such as military or cargo missions.
One of the possible armament choices for Defiant is the Adaptable Deck Launching System (ADL), which was created by BAE Systems. ADLs are modularly mounted angled launchers that can fire missiles from the same canisters as the Mk 41 Vertical Launch System (VLS). These systems can be used to launch:
- Surface-to-air missiles
- Anti-ship missiles
- Land-attack missiles
- Anti-submarine rockets
Defiant’s primary role
Despite its potential as an armed platform, Defiant’s primary role is as a testbed to validate the feasibility of a fully autonomous, human-free naval vessel. As DARPA states: “The NOMARS program aims to challenge the traditional naval architecture model, designing a sea frame from the ground up with no provision, allowance, or expectation for humans on board.” DARPA highlights the advantages of this approach, including:
- Smaller vessel size
- Lower costs
- Greater at-sea reliability
- Improved hydrodynamic efficiency
- Increased survivability against rough sea conditions and adversary actions
At-Sea Refueling and Operational Testing
DARPA and the U.S. Navy have already tested an at-sea refuelling system designed to support NOMARS vessels like Defiant. In a 2023 demonstration, two Navy USVs—Ranger and Mariner—were used to test the system. These vessels, converted offshore support ships, still can operate in crewed mode, but for this test, they simulated the autonomous refuelling process.
A DARPA press release emphasized the challenges of at-sea refuelling for USVs: “Fueling at sea (FAS) for USVs presents a problem that needs to be solved as current FAS solutions use personnel to handle lines and hoses on the platform being refuelled.” The test successfully demonstrated how Defiant’s future refuelling system could operate without human intervention.
Future Growth and Adoption by the Navy
Serco has positioned Defiant as a building block for future operational USVs, including uncrewed combat and logistics ships. The firm is in the process of developing a larger USV design, known as Dauntless, based on designs from the NOMARS program. Dauntless would have the capacity to carry four ADLs, among other mission-specific payloads.
One of the primary benefits of Defiant is that it is relatively easy to produce. In contrast to conventional warships, Serco has indicated that USVs such as Defiant might be produced outside normal shipyards, even at railworks facilities if need be. Such adaptability might assist in overcoming the U.S. Navy’s persistent challenges in building ships, which have been compounded by constrained domestic shipyard space.
The Navy’s Change in USV Acquisition Approach
Earlier this year, the U.S. Navy unveiled a change in its USV acquisition strategy, preferring smaller, less complex, and more interchangeable designs to larger, more complex ships.
Rear Adm. William Daly, head of the Navy’s surface warfare division (N96), explained this new direction at the Surface Navy Association’s annual symposium in January: “The designs already exist, and we must not over-spec this.”
He further emphasized the need for rapid deployment: “We’ve also had sufficient funding and experimentation to date to know what we need. Many of the payloads are ready and tested. [Concepts of operation] are coalescing. Let’s move faster. This is efficient, this is effective, and this is scalable.”
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Source: TWZ
