Navantia has started testing the air-independent propulsion (AIP) system for Spain’s third S-80-class submarine.
Testing is underway at Navantia’s Cartagena shipyard inside a dedicated section of the Cosme García, where the AIP system is being evaluated before integration into the submarine’s pressure hull.
The process started with the first loading of liquid oxygen and bioethanol, which are used to generate hydrogen on demand. That hydrogen then powers fuel cells that produce electricity for propulsion while the submarine remains submerged.
Unlike earlier generations of AIP technology that relied on stored hydrogen, the S-80 system produces hydrogen as needed from liquid fuel.
This approach overcomes some of the limitations associated with previous AIP designs and allows submarines to remain underwater for a significantly longer period, according to Navantia.
Engineers are expected to evaluate the system under conditions designed to replicate real-world operations, including varying depths and speeds.
Spain’s S-80 Submarine Program
The S-80 program is Spain’s flagship submarine modernization effort set to replace the aging Galerna-class fleet operational since the 1980s.
The Navantia-led effort consists of four diesel-electric submarines designed for intelligence gathering, anti-surface and anti-submarine warfare, special operations support, and strategic deterrence missions.
The first submarine, the Isaac Peral, was delivered to the Spanish Navy in November 2023 after years of development and redesign work. The second submarine, the Narciso Monturiol, was launched in November 2025.
