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Spain has unveiled the S-81 Isaac Peral submarine, featuring advanced air-independent propulsion (AIP) that converts bioethanol into hydrogen for fuel cells, enabling submerged operations for weeks. This capability enhances stealth and operational reach while aligning with climate goals.

The S-81's design minimizes acoustic emissions, improving concealment and operational effectiveness. The prototype, with current diesel generators and an electric motor, is set for full AIP integration by 2029.

The program signifies Spain's sovereignty in maritime systems, with potential global interest from nations needing stealthy, long-endurance vessels. The technology can also benefit commercial applications, including research and environmental monitoring, potentially accelerating the adoption of fuel-cell systems in shipping.