Kawasaki Heavy Industries has officially launched Japan’s sixth Taigei-class submarine during a ceremony in Kobe. Named JS Sogei (SS 518), the new vessel incorporates state-of-the-art lithium-ion battery propulsion technology.
The ceremony, held at Kawasaki’s Kobe shipyard — a city recognized as the birthplace of Japan’s submarine shipbuilding — was attended by naval officials and representatives of the Japan Maritime Self-Defense Force (JMSDF).
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The name “Sogei” (そうげい) translates to “great and shining whale,” continuing the Taigei-class tradition of naming submarines after the sea and whales.
According to the JMSDF, JS Sogei is scheduled to be officially commissioned into the Japanese fleet in March 2027, strengthening the country’s submarine capabilities amid the ongoing modernization of naval forces across the Indo-Pacific.
Construction of the Sogei began on March 28, 2023. The submarine was designed to operate with a propulsion system based on lithium-ion batteries — a technology that replaces the traditional air-independent propulsion (AIP) system — allowing for greater submerged endurance, lower acoustic signature, and simplified maintenance.
With a standard displacement of 3,000 tons and a length of 84 meters, JS Sogei can reach speeds of up to 18 knots when submerged and 13 knots on the surface. Its main armament includes six 533 mm torpedo tubes compatible with Type 18 torpedoes and Harpoon anti-ship missiles.
The submarine will also be equipped with the new 12SSM-ER cruise missiles, recently introduced to extend the offensive reach of Japan’s naval forces.
The Taigei-class marks a technological milestone for Japan, being the world’s first submarine class specifically developed to operate with lithium-ion batteries. This innovation places Japan’s fleet among the most advanced globally in terms of silent propulsion and energy efficiency.
In March 2025, the JMSDF had already commissioned the fourth submarine of the same class, JS Raigei, currently based in Kure. Unlike earlier models, Raigei received upgraded Kawasaki 12V2531 diesel engines and the modern ZQQ-8 sonar system from Oki Electric Industries, showcasing the continuous evolution of the class.
Source and images: Japan Ministry of Defense – Maritime Self-Defense Force | @JMSDF_PAO_. This content was created with the assistance of AI and reviewed by the editorial team.
