2. Japanese Sōryū Class
Among the most sophisticated conventional submarines ever built are those of Japan’s Sōryū class. These boats enable long underwater operations by combining Stirling-cycle AIP systems with conventional diesel-electric power. Their 4,200 tonnes of enormous displacement enable remarkable payload capacity and operational lifetime. Advanced warfare equipment including Hughes/Oki ZQQ-7 sonar suite and ZPS-6F surface/low-level search radar abound throughout the class. Highly efficient in both coastal and deep-water operations, the Sōryū’s automation systems lower crew needs while preserving ideal performance.