Scientists with the Naval Information Warfare Center Atlantic's Unmanned Naval Innovation Team reached a historic milestone Sept. 9 when they recovered a Navy-sponsored unmanned surface vessel named the Lightfish in Troia, Portugal, following its harrowing — and completely solo — transatlantic crossing.
This fully autonomous vessel accomplished the journey in just over two months, nearly 12 days faster than the last known previous attempt.
UNIT engineers launched the Lightfish, a solar-powered, low-profile USV designed for long-endurance missions, on a blazing summer day from a community boat ramp in Sullivan's Island, South Carolina, at the end of June. After performing numerous systems checks and taking a moment to christen the vessel, Michael Grass, the team's lead scientist and program manager, waded into waist-deep seawater to send the unmanned vessel off on its long voyage across the Atlantic Ocean.
"With the launch of this small, unmanned surface vessel, we're pushing the boundaries for what we can do with maritime domain awareness," Grass said at the launch. "No one has been on the water for this long of a journey. So, it's a big proof of concept, not only for the reliance and durability for the platform itself but for testing the rigor of the data architecture."
These final moments of send-off would be the last time the USV would be touched by human hands for more than 60 days as it expertly and independently traversed the waters between the U.S. and Europe. It was headed 4,000 miles away to its final destination of Troia, Portugal, where it arrived safely to much excited fanfare in early September.
Although the UNIT crew was physically hands off while the vessel traversed the ocean, the mission was not out of sight. The journey was diligently monitored using onboard cameras, remote software and real-time telemetry by engineers and various fleet watch floors as they maintained distant command and control of the Lightfish.
"The objective is to prove that we can execute command and control of a USV across the Atlantic, where we are crossing not only the body of water, but also crossing areas of responsibility," Grass explained.
"We're able to demonstrate a follow-the-sun command and control approach," he continued. "At least twice per day, we would change command and control and oversight of this vessel between various Navy numbered fleets. Every morning and every evening, there was essentially a change of command, and ownership, and oversight of this particular vessel for the entirety of the duration."
The mission was supported by Commander, Task Force 66, U.S. 6th Fleet's premier all-domain task force established in 2024 to accelerate robotic and autonomous systems development, to assist in recovering the Lightfish during Robotic Experimentation and Prototyping using Maritime Uncrewed Systems, a Portuguese-led military exercise focused on maritime unmanned systems experimentation, capability development and interoperability.
Navy Lt. Alexander Varon, officer in charge for unmanned software development within CTF 66, was present for Lightfish's arrival in Portugal and agreed that the transit was a milestone achievement in USV enablement.
"I think people tend to underestimate just how manned unmanned operations are," Varon said. "Not only is there a large manned footprint when it comes to the deployment, the recovery and the care and feeding of these craft, as well as the actual operations, but there is a massive engineering support role, specifically that we're receiving from NIWC Atlantic over in Charleston, South Carolina, that is helping connect these different types of craft all into a single ecosystem of systems."
The careful monitoring and remote management of the trip enabled the Lightfish to make a scheduled arrival in Portugal in plenty of time for its participation in REPMUS, one of
NATO's premier annual experimentation events.
REPMUS brings together more than 30 nations, NATO centers of excellence, industry partners and academic institutions to test and demonstrate the latest advancements in unmanned systems. The exercise provides a venue for U.S. and allied forces to experiment with new capabilities, improve command and control architectures, and accelerate technology transition from prototype to fleet use.
"Being able to bring Lightfish directly into REPMUS following its transatlantic journey is a tremendous force multiplier," Grass said. "It allows our engineers to validate real-world endurance while immediately contributing to NATO's collaborative experimentation environment."
Despite being at sea for months, the Lightfish only required a bit of fuel to replenish the onboard generator, a few minor repairs and a good cleaning to be ready for the exercise. UNIT teammates and helpful military partners happily sacrificed their dry clothes to jump in and welcome the vessel back to shore.
Then it was all hands on deck to complete inspections and scrape off the dozens of barnacles that had collected on the underside of the Lightfish as it traveled and then loitered for several days off the coast while waiting for its port call.
"Lightfish's successful crossing highlighted not only its durability but also the Navy's progress in harnessing unmanned systems to enhance maritime domain awareness," said Eric Stephenson, UNIT lead systems engineer with NIWC Atlantic.
The USV journey marks a significant achievement for the Navy's ongoing efforts to integrate unmanned systems into its broader operational framework. It underscores the potential of a hybrid fleet that includes both manned and unmanned platforms, extending operational reach while reducing risks to sailors.
"Every nautical mile that Lightfish sailed autonomously and every data packet that was transmitted back helped push us closer to operationalizing a global unmanned fleet architecture," said David Bate, a NIWC Atlantic engineer with UNIT.
"As demonstrated here, USVs, and drones in general, are proving themselves to be quite an asymmetric threat," Varon said. "Unmanned assets are [lower cost options that are easier to replace] and we can put them into dangerous environments without risking human life — freeing up our national assets for more important mission tasking or giving them longer periods of time to work through their maintenance availabilities and stay up to speed."
USVs also don't require much in the way of rest. Following its boundary-breaking transatlantic adventure, NIWC Atlantic's Lightfish USV will spend even more time at sea as it travels to Africa to participate in another exercise and then will turn right back around to make the long crossing back to Charleston. NIWC Atlantic engineers will continue to study its progress — refining autonomy, endurance and data integration capabilities for future missions.
"Lightfish showed us, once again, what is possible in the unmanned realm," Grass said. "Now our job is to continue to build on that momentum — integrating lessons learned into the Navy's unmanned strategy and strengthening interoperability with our NATO partners."