The Japan Maritime Self-Defense Force (JMSDF) has officially commissioned its fourth Taigei-class diesel-electric attack submarine, JS Raigei (SS 516), which boasts advanced detection and anti-detection features. The new submarine was inducted into Submarine Division 1 of Submarine Flotilla 1, stationed at the Kure naval base in Hiroshima Prefecture, after being delivered by Kawasaki Heavy Industries (KHI) on March 6, 2025.
According to Naval News’ Kosuke Takahashi’s report; JS Raigei, the latest addition to the Taigei-class series, stands at 84 meters in length, with a beam of 9.1 meters and a draught of 10.4 meters. It displaces approximately 3,000 tons, slightly larger than the Soryu-class submarines. This new vessel also introduces female-only compartments, accommodating up to six women, a first for the JMSDF’s submarine fleet.
Named after the Japanese word for “thunder whale,” Raigei is powered by a diesel-electric engine generating 6,000 horsepower, allowing it to reach a maximum underwater speed of 20 knots. The submarine features a new sonar suite, the ZQQ-8, which offers enhanced performance compared to the Soryu-class’s ZQQ-7.
Raigei marks the first Taigei-class boat to be equipped with new Kawasaki 12V 25/31 diesel engines, providing a higher output and compatibility with a new snorkel system. Additionally, Raigei utilizes lithium-ion batteries instead of lead-acid batteries, further advancing Japan’s technological edge in underwater capabilities. GS Yuasa, based in Kyoto, supplied these cutting-edge lithium-ion batteries, making Japan the first country to fit them into SSKs.
The submarine also incorporates an upgraded combat management system (CMS), integrating advanced sensors, command-and-control, and weapon engagement systems. The Raigei is equipped with a new-generation sonar system based on fiber-optic array technology, a non-penetrating periscope, and a countermeasure system that includes Japan’s newest torpedo, the Type 18.
In terms of armament, Raigei is capable of launching Type 18 torpedoes, as well as the UGM-84L Harpoon Block II anti-ship missile, extending Japan’s reach with a missile range of 248 km. The commissioning of the Taigei-class submarines is seen as a strategic response to increasing Chinese naval activity, particularly with the anticipated commissioning of China’s third aircraft carrier, Fujian, which will likely increase Chinese operations in the Western Pacific.
JS Raigei joins the first three Taigei-class submarines: Taigei (SS 513), Hakugei (SS 514), and Jingei (SS 515). The fifth vessel, Chogei, was launched in October 2024 and is slated for commissioning in March 2026.
JS Raigei Picture by Taki Yoshihisa.