The Japan Maritime Self-Defense Force (JMSDF) has commissioned the fourth of its Taigei-class diesel-electric attack submarines (SSK), which feature better detection and anti-detection capabilities than its older boats, Naval News reports.
Named JS Raigei (with pennant number SS 516), the new Taigei-class boat was inducted into the Submarine Division 1 of Submarine Flotilla 1, which is homeported at the Kure naval base in Hiroshima Prefecture, shortly after being handed over by shipbuilder Kawasaki Heavy Industries (KHI) at its facility in Kobe City on March 6.
According to the JMSDF, the new submarine has a crew complement of about 70, an overall length of 84 m, a beam of 9.1 m, a draught of 10.4 m, and a standard displacement of about 3,000 tonnes, meaning that it is slightly larger than the well-known previous Soryu-class SSKs, which are 84 m long, 9.1 m wide, 10.3 m depth, and have a standard displacement of 2,950 tonnes.
The Taigei-class for the first time has female-only compartments such as a living space for up to six women, according to the service.
Raigei means “thunder whale” in Japanese. The Taigei class submarines all incorporate “Gei” (whale) into their names, following the “Shio” (tide) and “Ryu” (dragon) series seen in previous JMSDF submarines. “Taigei” itself means “big whale.”
The new submarine, which cost about 70.2 billion yen ($470 million) to build, is powered by a diesel-electric engine generating 6,000 hp. It has a maximum speed underwater of 20 knots.
Submarine sonar
The Taigei-class sonar suite features the high-performance ZQQ-8, which has improved capabilities over the Soryu-class’ ZQQ-7.
New diesel engines
Until the third Taigei-class submarine Jingei, two Kawasaki 12V 25/25SB diesel engines were used as the main engines, but Raigei uses new Kawasaki 12V 25/31 diesel engines with a high output power for the first time. These new diesel engines are compatible with a new snorkel system with enhanced power generation efficiency.
Lithium-ion batteries
The JMSDF said that the Taigei-class boat is all equipped with lithium-ion batteries in place of lead-acid ones, just like the final two Soryu-class boats for the JMSDF: Oryu (SS 511) and Toryu (SS 512).
GS Yuasa, a Kyoto-based developer and manufacturer of battery systems, provided the lithium-ion batteries for those new submarines. So far Japan is the only country known to have fitted lithium-ion batteries into SSKs, with South Korea expected to be the next country to do so with the second batch of KSS-III (also known as Dosan Ahn Chang-ho)-class submarines sometime in the late 2020s.
New CMS and snorkel
The class also employs a new combat management system (CMS) combining advanced integrated sensors, command-and-control, and weapon engagement systems, the Japanese Ministry of Defense said.
In addition, it adopts an enhanced snorkel system to reduce signatures, and a new-generation sonar system based on fiber-optic array technology to enhance detection capability.
Additionally, the Taigei-class is the first being equipped with a new domestically produced non-penetrating periscope manufactured by Mitsubishi Electric.
Taigei-class SSK weapons
The Taigei-class employs the same torpedo counter-measures system that has been incorporated into the last four Soryu-class boats. It uses Japan’s newest torpedo, which is called the Type 18, succeeding the previous Type 89. The new torpedo features improvements in a number of areas, including propulsion, target detection, and processing.
The class is also capable of deploying the UGM-84L Harpoon Block II anti-ship missile against surface targets. This missile range is 248 km – enough to provide Japan with a “counterattack” capability.
Taigei-class submarine program so far
The lead submarine of the Taigei-class, named Taigei (SS 513), was commissioned in March 2022. The second of the class, named Hakugei (SS 514), entered service in March 2023. The third of the class, named Jingei (SS515), entered service in March 2024. The fifth submarine, Chogei, was launched in October 2024 and is currently being outfitted for commissioning in March 2026.
With China in mind
Chinese Navy’s third aircraft carrier, the Fujian, is expected to be commissioned within the year, forming a three-carrier task force with the Liaoning and the Shandong. As a result, it is expected that the Chinese Navy will pass through the so-called first island chain between Japan’s Kyushu and Philippines, which mainly consists of Japan’s southwest islands, and is most likely to operate more frequently in the Western Pacific Ocean around Japan. Japanese submarines, as the “ninjas of the sea,” are expected to check the assertive actions of the Chinese Navy.
