Japanese company Kawasaki Heavy Industries (KHI) has launched the fourth Taigei-class diesel-electric attack submarine “Raigei” for the Japan Maritime Self-Defense Force (JMSDF).

The new 3,000-ton diesel-electric submarine (SSK), named Raigei (with insignia number SS 516), entered the water on October 17 at a ceremony held at the KHI facility in Kobe city. The newly launched SSK will use the new high-power Kawasaki 12V 25/31 diesel engines for the first time.

The Raigei, which has cost about 70.2 billion yen ($470 million) to build, is expected to enter service in March 2025. Raigei means “thunder whale” in Japanese. All Taigei-class submarines incorporate “Gei” (whale) in their names, following the “Shio” (tide) and “Ryu” (dragon) series seen on previous JMSDF submarines. “Taigei” itself means “great whale.”

According to the JMSDF, the new submarine has a crew of about 70, an overall length of 84 meters, a beam of 9.1 m, a draft of 10.4 m and a standard displacement of about 3,000 tons. It is slightly larger than the Soryu-class SSKs, with a standard displacement of 2,950 tons.

The Taigei class features dedicated women’s compartments, including living space for up to six women, according to the JMSDF. This is a first for Japanese submarines.

New diesel engines

Taigei-class submarineLaunching of the Taigei class submarine, Raigei SS-516

Until the third Taigei-class submarine, the Jingei, two Kawasaki 12V 25/25SB diesel engines were used as main engines, but the Raigei will use new high-power Kawasaki 12V 25/31 diesel engines for the first time. These new diesel engines are compatible with a new snorkel system with higher power generation efficiency. It is unclear whether this will increase the shaft power of the Taigei class, which currently generates 6,000 horsepower, as well as a maximum underwater speed of 20 knots.

Lithium-ion batteries

The JMSDF stated that the Taigei class is equipped with lithium-ion batteries instead of lead-acid ones, as are the latest two Soryu-class ships for the JMSDF: Oryu (SS 511) and Toryu (SS 512).

GS Yuasa, a Kyoto-based battery systems developer and manufacturer, supplied the lithium-ion batteries for those new submarines. To date, Japan is the only country known to have installed lithium-ion batteries in SSKs. South Korea is expected to be the next country to do so with the second batch of KSS-III class submarines (also known as Dosan Ahn Chang-ho).

New CMS and snorkel

The class also employs a new combat management system (CMS) that combines advanced integrated sensors, command and control, and weapon docking systems, the Japanese Defense Ministry said.

Furthermore, it adopts an improved snorkel system to reduce signatures and a new generation sonar system based on fiber optic array technology to improve detection ability.

Armament of Taigei-class SSKs

The Taigei class employs the same anti-torpedo countermeasures system that the last four Soryu class ships have incorporated. She is expected to use Japan’s newest torpedo, called the Type 18, which succeeds the older Type 89. The new torpedo will incorporate improvements in several areas, such as propulsion, target detection and processing.

The class is also capable of deploying the UGM-84L Harpoon Block II anti-ship missile against surface targets. The range of this missile is 248 km, enough to provide Japan with a “counter-strike” capability.

The Taigei-class submarine program to date

The main Taigei class submarine, named Taigei (SS 513), entered service in March 2022. The second in the class, named Hakugei (SS 514), entered service in March 2023. The third in the class, Jingei (SS515), launched in April 2020, will enter service in March 2024.

Kosuke Takahashi