U.S. Navy Eyes HII REMUS and ROMULUS Naval Drones for Contested Maritime Warfare.

HII used Combined Naval Event 2026 in the United Kingdom to showcase its REMUS unmanned underwater vehicles, ROMULUS unmanned surface vessels and Odyssey autonomy software as an integrated maritime warfare package designed to push sensors and mission systems into contested waters without risking crewed ships or submarines. Presented on May 20, 2026, the systems reflect growing naval demand for distributed operations that extend surveillance, deception and strike support beyond the first layer of enemy detection.

The company’s approach combines unmanned surface and underwater platforms with submarine launch-and-recovery capability and live-virtual-constructive training to support ISR, mine warfare, seabed reconnaissance and counter-drone defense missions. The integration of autonomous vessels and modular payloads highlights how Western navies are shifting toward networked, lower-risk maritime operations built around survivability, persistence and distributed combat power.

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HII showcased its REMUS unmanned underwater vehicles, ROMULUS unmanned surface vessels and Odyssey autonomy software at Combined Naval Event 2026, presenting an integrated maritime autonomy package for ISR, mine warfare, seabed reconnaissance, counter-drone defense and distributed naval operations (Picture source: HII).

The most important point for U.S. and allied planners is that HII is not offering ROMULUS as a single-purpose patrol craft. The company describes ROMULUS as a family of 25-knot-plus unmanned surface vessels, powered by Odyssey, designed for open-ocean endurance, rapid mission reconfiguration and repeatable production. The advertised mission set includes intelligence, surveillance and reconnaissance, targeting support, counter-unmanned aircraft defense, strike and fires, mine countermeasures, and the launch and recovery of unmanned underwater vehicles, unmanned aerial vehicles and smaller unmanned surface vessels. This matters because the value of an unmanned surface vessel is not only its speed or range, but its ability to carry a sensor, communications relay or weapon payload into a position where a destroyer, frigate or amphibious ship would be too valuable to risk.

The armament issue should be treated carefully. HII has not publicly identified a standard missile, gun, loitering munition or electronic attack payload for the ROMULUS configuration shown around CNE 2026. What has been disclosed is a modular weapons and mission-system approach: the vessel family is designed to detect, track and engage airborne threats with scalable effectors and to integrate current and future weapons for strike and fires missions. In practical terms, this suggests that ROMULUS is being built around payload volume, electrical power, data interfaces, fire-control integration and autonomy behaviors rather than around a fixed deck gun or a named missile canister. The operational question for the U.S. Navy and Marine Corps will therefore be less about whether ROMULUS can carry a weapon and more about how it receives target-quality data, how a human commander authorizes lethal action, how the vessel maintains emissions control, and how weapons are safed during autonomous transit in congested sea lanes.

ROMULUS-25 gives a concrete example of the lower end of the family. HII and MetalCraft Marine delivered and sea-tested two ROMULUS-25 autonomous vessels for the U.S. Marine Corps under a Defense Innovation Unit contract, with delivery in December 2025 and follow-on reporting in May 2026. The 27-foot high-speed interceptor vessel is designed to carry up to 1,000 pounds of payload and has a stated range of up to 1,000 nautical miles. For Marine littoral units, that size class could support reconnaissance of island approaches, autonomous escort of logistics craft, placement of passive sensors, decoy operations, or the carriage of mission-specific effectors without assigning Marines to a small boat inside an anti-ship missile or drone threat envelope.

At the larger end, HII is moving ROMULUS 151 vessels toward production at Breaux Brothers Enterprises in Louisiana. In April 2026, the company announced plans to add four ROMULUS 151 vessels to one already under construction, while also pointing to an expanded assembly facility and the High-Yield Production Robotics initiative for unmanned vessel manufacturing. This is not a minor industrial detail. The U.S. Navy’s unmanned vessel problem has often been less about concept papers than about building enough reliable craft, at predictable cost, to train sailors and Marines at scale. A five-vessel production base does not create mass by itself, but it begins to move the program from demonstration toward repeatable manufacturing, which is a prerequisite for operational experimentation with multiple vessels under fleet conditions.

The undersea side is more mature: REMUS has been in service for 25 years, with HII reporting more than 750 vehicles delivered to over 30 countries, including 14 NATO members, and more than 90 percent of delivered systems still operational after more than two decades. Those figures are relevant because mine countermeasures and seabed intelligence require reliability, trained operators and sustainment chains, not only new sensors. REMUS vehicles have been used for defense, commercial and scientific missions, but the current military emphasis is on using unmanned underwater vehicles to map minefields, inspect seabed infrastructure, collect hydrographic data, and operate in water that may be too shallow, mined or tactically exposed for a nuclear-powered submarine.

The REMUS 620 provides the clearest technical baseline for the medium-class vehicle. HII lists a 600-meter depth rating, up to 110 hours of mission duration, a 275-nautical-mile range, speeds up to 8 knots and a removable 8-terabyte hard drive. Its mission applications include mine countermeasures, hydrographic survey, intelligence collection, surveillance and electromagnetic warfare, supported by dry or wet payload modules, external bulkhead adapters and open-standard interfaces. These figures show why the vehicle is tactically useful: it can spend several days collecting sonar, environmental or electromagnetic data, then return with enough stored information to support mine clearance planning, submarine route preparation, amphibious operations or infrastructure inspection.

Submarine launch and recovery is the capability with the largest implications for U.S. undersea forces. USS Delaware, a Virginia-class attack submarine, completed Yellow Moray operations in the U.S. European Command area, using a REMUS 600-based unmanned underwater vehicle to conduct the first forward-deployed torpedo-tube launch and recovery of this type to accomplish a tactical objective. The Navy reported three sorties of roughly six to ten hours using the same vehicle and no divers for launch or recovery. The same report also noted earlier failed recovery attempts in a Norwegian fjord, component damage, return of the vehicle to the United States for repair, and later successful operations after redeployment to theater. That sequence is useful because it shows both the potential and the remaining engineering burden: this is an emerging submarine capability, not a frictionless routine.

HII’s July 2025 REMUS 620 torpedo-tube validation adds another data point. The company reported a dry end-to-end checkout with the Autonomous Underwater Vehicle/Shock and Fire Enclosure Capsule All-Up Round in a Virginia-class Cradle Payload Integration Facility and Mk71 torpedo tube. If subsequent in-water testing confirms repeatable launch and recovery, the operational effect would be significant: an attack submarine could deploy an unmanned underwater vehicle for mine detection, seabed mapping or intelligence collection while remaining outside areas where the submarine’s size, acoustic signature or navigational constraints create unnecessary risk. This would give combatant commanders another option for preparing a maritime battlespace before a carrier strike group, amphibious force or special operations element enters the area.

Odyssey is the integration layer tying these systems together. HII states that the autonomy suite has operated on more than 30 systems and accumulated more than 12,000 hours at sea, while the ROMULUS product data cites more than 6,000 operational hours on more than 35 unmanned surface vessels. The software uses open architecture standards including UMAA, ROS and DDS, and supports sensor fusion, COLREGS-compliant navigation, autonomous health monitoring and multi-agent control. For Congress and allied procurement officials, the key issue is not the marketing label “AI,” but whether Odyssey can reduce operator workload, maintain predictable navigation behavior around civilian traffic, operate under emissions restrictions, and accept new payloads without a lengthy software rewrite.

The combined package could bring U.S. forces and allies three measurable advantages: more persistent sensing, lower personnel exposure and faster coalition adoption. REMUS gives allied navies a known unmanned underwater vehicle family for mine warfare and seabed reconnaissance; ROMULUS offers a surface vessel that can move payloads, sensors or effectors forward; and Odyssey provides a common autonomy baseline for training and control. The limits are equally clear: weapon integration remains largely undisclosed, command-and-control resilience will be tested under jamming, and unmanned vessels still need maintenance, launch sites, data links and rules of engagement. The useful conclusion is therefore not that unmanned vessels replace destroyers, submarines or mine countermeasure ships, but that they can extend those forces’ reach and absorb some of the risk in waters where the first contact with mines, drones, missiles or seabed threats may determine the tempo of the wider naval campaign.

Written by Evan Lerouvillois, Defense Analyst.

Evan studied International Relations, and quickly specialized in defense and security. He is particularly interested in the influence of the defense sector on global geopolitics, and analyzes how technological innovations in defense, arms export contracts, and military strategies influence the international geopolitical scene.