Finnish technology company Kelluu announced that its autonomous hydrogen-powered airship will take part in NATO’s upcoming REPMUS 25 exercise, one of the alliance’s largest and most demanding defense trials focused on unmanned systems.
Kelluu described its platform as a 12-meter-long autonomous aerostat combining artificial intelligence and modern sensor technology with the century-old concept of lighter-than-air flight. Quiet, environmentally clean, and powered by hydrogen, the airship is designed to provide persistent surveillance and intelligence below the cloud layer.
“For the next weeks our airships will be in the middle of one of the most demanding defense exercises in the world,” Kelluu said in a statement.
REPMUS — short for Robotic Experimentation and Prototyping with Maritime Unmanned Systems — is NATO’s flagship exercise for integrating unmanned technologies into joint operations. In 2024, it brought together more than 2,000 participants from 30 nations, operating more than 100 unmanned systems in over 700 mission serials. This year’s edition, REPMUS 25, builds on that scale, with participants expected to push unmanned platforms to their limits in maritime and aerial environments.
According to Kelluu, its hydrogen airship fills a critical intelligence gap between satellites and drones.
“Persistent surveillance below the clouds adds a continuous layer of accurate intelligence, extends the reach of sensors, radars and cameras, and keeps working even in GNSS-denied environments,” the company explained.
The airship serves as a flexible sensor platform capable of providing uninterrupted intelligence, surveillance, and reconnaissance (ISR) on a large scale. Unlike traditional drones, which are limited by flight endurance, Kelluu’s hydrogen-powered system is designed for extended missions, complementing existing NATO assets.
The company framed its participation as part of a broader effort to contribute to European security.
“We are here to support a smart and secure Europe,” Kelluu stated.
The use of hydrogen airships in a modern defense context reflects an unusual convergence of emerging technologies with concepts rooted in early aviation. By integrating artificial intelligence, lightweight materials, and clean energy, Kelluu aims to modernize the airship for persistent ISR roles in contested environments.
As unmanned technologies become increasingly central to NATO operations, platforms such as Kelluu’s airship may offer allies new options for surveillance and resilience. The company’s participation in REPMUS 25 underlines how smaller European firms are contributing to the alliance’s evolving defense ecosystem.