U.S. Navy to Gain More Lionfish and REMUS Underwater Drones as HII Expands Production by 25%.

The U.S. Navy is set to gain greater production capacity for unmanned systems used in reconnaissance, mine warfare, and operations in contested waters after HII expanded its Pocasset, Massachusetts, facility by 25%, the company said. The additional capacity will support production of Lionfish small unmanned undersea vehicles, REMUS 620 UUVs and components for the ROMULUS unmanned surface vessel family as demand grows for missions that keep sailors out of high-risk areas.

The 10,000-square-foot expansion increases the site to 50,000 square feet and strengthens HII’s ability to manufacture multiple autonomous maritime platforms at scale. For the U.S. Navy and allied fleets, that means greater potential to field persistent, distributed unmanned assets for surveillance, seabed operations, and mine countermeasures while reducing crew exposure in increasingly contested maritime environments.

Related Topic: U.S. Navy Virginia-class submarine achieves first recovery of REMUS 620 unmanned undersea vehicle

The U.S. Naval Oceanography booth displays Remote Environmental Measuring Units (REMUS), unmanned underwater vehicles (UUVs), designed to support autonomous undersea missions, including oceanographic surveys, environmental data collection, reconnaissance, and mine countermeasures. (Picture source: U.S. Department of War/Defense)

Announced by HII on September 22, 2026, the expansion is particularly significant for Lionfish production, which is already underway for the U.S. Navy, and it also adds capacity for the longer-range REMUS 620 and for integrating Odyssey autonomy hardware into ROMULUS unmanned surface vessels. The additional manufacturing space could help HII scale several complementary surface and undersea systems as the U.S. Navy moves toward more distributed maritime operations.

Lionfish is derived from HII's REMUS 300 and serves as the U.S. Navy's next-generation small unmanned undersea vehicle. HII completed its 42nd Lionfish at the end of 2025 under the program's base-year production phase, while the broader five-year program could expand to as many as 200 vehicles with a potential value exceeding $347 million. HII said in July 2026 that the Navy exercised an option for continued production, giving the enlarged Pocasset facility a direct role in sustaining a growing operational inventory.

The military value of Lionfish lies in providing naval forces with a compact autonomous underwater system for missions where sending divers or crewed vessels would increase exposure to mines, surveillance, or hostile fire. The REMUS 300 design on which Lionfish is based offers modular battery sections that provide up to 30 hours of endurance and is intended for missions including mine countermeasures, hydrographic reconnaissance, and environmental assessment.

The Pocasset expansion will also support production of the REMUS 620, a medium-class unmanned underwater vehicle designed for missions requiring considerably greater reach. HII lists a maximum endurance of 110 hours, a range of up to 275 nautical miles, an operating depth of 600 meters, and speeds of up to 8 knots, allowing the vehicle to remain underwater for several days while conducting mine countermeasures, hydrographic survey, intelligence collection, surveillance, and electromagnetic warfare missions.

That endurance matters because it lets naval forces deploy an unmanned underwater vehicle farther from its launch point, survey larger maritime areas, and keep crewed submarines or surface ships farther from potentially mined or monitored waters. REMUS 620 also uses interchangeable payload sections and open-standard interfaces, allowing operators to adapt sensors and mission equipment without redesigning the entire vehicle.

The U.S. Navy has also tested ways to integrate REMUS 620 directly with its submarine force. In 2025, a Virginia-class submarine test arrangement successfully recovered a second-generation REMUS 620 through a torpedo-tube configuration, an important step toward allowing attack submarines to deploy autonomous sensors for reconnaissance, seabed surveillance, or mine-related missions while remaining submerged. The Pentagon later awarded HII work on submarine launch-and-recovery technology, further linking unmanned underwater vehicles with conventional submarine operations.

HII is expanding the same Pocasset site as its ROMULUS unmanned surface vessel program also moves toward initial production. The ROMULUS family is designed for speeds above 25 knots and sustained open-ocean missions, with roles including intelligence, surveillance and reconnaissance, targeting support, counter-unmanned aircraft defense, mine countermeasures, strike missions and the deployment or recovery of smaller unmanned systems. In April 2026, HII announced plans to place four additional ROMULUS 151 vessels into production alongside one already under construction.

ROMULUS and REMUS are designed to operate with HII's Odyssey autonomy software, which manages and coordinates missions across multiple autonomous systems. Expanding hardware integration and simulation capacity at Pocasset therefore addresses more than vehicle output: it supports an architecture in which unmanned surface vessels can carry sensors or effectors while deploying unmanned underwater vehicles farther forward, extending surveillance and mission reach without requiring a crewed warship to enter the same threat area.

The expansion also reflects the growing scale of HII's unmanned-undersea business. The company says it has delivered more than 750 REMUS vehicles to customers in over 30 countries, including 14 NATO members, and that more than 90% of systems delivered during the family's 25-year history are still in active service. Those figures are manufacturer-reported, but they illustrate an established international user base that can support common training, sustainment, and operational experience among allied navies.

For the U.S. Navy, the immediate effect of the Pocasset investment is additional industrial capacity behind systems that are moving from experimentation toward larger-scale production and closer integration with submarines and surface forces. The 25% facility expansion does not by itself establish how many additional vehicles HII will produce each year, but it increases the manufacturing and integration infrastructure available for Lionfish, REMUS 620, ROMULUS, and Odyssey as autonomous maritime systems assume a larger role in mine warfare, intelligence collection, and distributed naval operations.

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Written by Alain Servaes – Chief Editor, Army Recognition Group
Alain Servaes is a former infantry non-commissioned officer and the founder of Army Recognition. With over 20 years in defense journalism, he provides expert analysis on military equipment, NATO operations, and the global defense industry.