Japan Launches Seventh Taigei-Class Submarine ‘Shogei’ With Improved Detection Capabilities

Japan launched its new Taigei-class submarine, Shogei, at Mitsubishi Heavy Industries’ shipyard in Kobe, Hyogo Prefecture, on October 8. Around 300 officials and guests attended the launch ceremony.

The 3,000-tonne diesel-electric submarine is expected to be delivered to the Japan Maritime Self-Defense Force (JMSDF) in March 2028.

Japan is also working on plans for submarines that can launch long-range missiles from vertical launching systems. The country is looking at ways to improve submarine speed and endurance as Chinese naval activity in the Western Pacific grows.

Japan has not decided whether its future submarines will use nuclear power. However, Defence Minister Shinjiro Koizumi said on September 11, 2026, that the country would keep the option open while reviewing its three national security documents ahead of the end of the year.

The Shogei, which carries the pennant number SS-519, is 84 metres long and 9.1 metres wide. It has a standard displacement of about 3,000 tonnes and can carry around 70 crew members.

Building the submarine cost approximately 80.5 billion yen ($509 million).

Its name, written as 翔鯨, means “Soaring Whale”. This is the first time the JMSDF has used the name. The former Imperial Japanese Navy did not have a vessel with the same name.

Shogei will use Kawasaki 12V 25/31 diesel engines, which provide higher output than earlier engines. The same engines are used in the fourth Taigei-class submarine, Raigei, and the later Chogei and Sogei.

The submarine also has improvements designed to reduce noise from its machinery and crew activities. Less noise can help its sensors pick up underwater sounds while making it harder for other submarines and surface ships to detect it.

The submarine will undergo further outfitting and testing before its planned delivery in March 2028.

Taigei-Class Submarines

Taigei-class submarines use large-capacity lithium-ion batteries to stay underwater for longer periods. However, their batteries need to be recharged using diesel engines. This requires the submarines to approach the surface and use a snorkel to draw in air and release exhaust gases, which can make them easier to detect.

The batteries also run down faster when the submarines travel at high speeds for long periods. This limits how long they can maintain high speeds while staying underwater.

The Taigei class uses the same torpedo countermeasures system fitted to the last four Soryu-class submarines. Its weapons include Japan’s Type 18 torpedo, which replaces the Type 89. The newer torpedo has improvements in propulsion, target detection and processing.

The submarines can also fire UGM-84L Harpoon Block II anti-ship missiles at surface targets. The missile has a reported range of 248 km.

Japan is working towards developing and eventually acquiring submarines fitted with vertical launching systems under three national security documents adopted in December 2022.

On July 6, 2026, Japan’s Acquisition, Technology & Logistics Agency awarded Mitsubishi Heavy Industries a 3.9 billion yen ($24.6 million) contract to study the overall design of a next-generation submarine fitted with a vertical launching system.

The research will run from fiscal 2026 through fiscal 2029.

Adding a vertical launching system could require a larger hull and other changes to the submarine. More advanced sonar equipment and unmanned underwater vehicles could also increase its power requirements.

This could create problems for conventional submarines, which rely on batteries while operating underwater.

In September 2025, a panel of experts advising Japan’s Ministry of Defense recommended further research into submarines fitted with vertical launching systems. It also called for a study of what it described as “next-generation propulsion”.

The panel did not specifically recommend nuclear propulsion.

References: newsonjapan, navalnews