Japan Launches Fifth Taigei-Class Submarine for JMSDF

Japan Launches Fifth Taigei-Class Submarine for JMSDF
5th Taigei-Class Submarine "Chogei" (Credit: Kosuke Takahashi)
Japan’s Mitsubishi Heavy Industries (MHI) has launched the fifth Taigei-class diesel-electric attack submarine "Chogei" 「ちょうげい」 for the Japan Maritime Self-Defense Force (JMSDF).
Share

The new 3,000-tonne diesel-electric submarine (SSK), which has been named 「ちょうげい」 Chogei (with pennant number SS 517), entered the water on October 4 in a ceremony held at MHI’s shipyard in Kobe City. The newly launched SSK will use the new Kawasaki 12V 25/31 diesel engines with high output power, following the fourth Taigei-class submarine “Raigei”.

Chogei, which cost about 64.8 billion yen ($443 million) to build, is expected to enter service in March 2026. Chogei means “long whale” in Japanese. This is the third Japanese vessel to bear this name, following the first being the former Imperial Japanese Navy’s transport ship, the Chogei Maru (named after it was purchased from a ship built in the U.K.), and the second being the submarine tender, the Chogei.

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.”

According to the JMSDF, the new submarine has a crew complement of about 70, an overall length of 84 meters, a beam of 9.1 m, a draught of 10.4 m, and a standard displacement of about 3,000 tonnes. It is just slightly larger than the preceding Soryu-class SSKs, which have a standard displacement of 2,950 tonnes.

The Taigei-class features female-only compartments such as a living space for up to six women, according to the JMSDF. This is a first for a Japanese class of submarines.

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 started to use 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. It is unclear whether this will increase the shaft output of the Taigei-class, currently generating 6,000 horsepower, as well as a maximum speed underwater of 20 knots.

Lithium-ion batteries

The JMSDF said that the Taigei-class is 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 all 3 KSS-III Batch-II submarines,  also known as Dosan Ahn Chang-ho-class submarines. These vessels are scheduled to be commissioned from 2026.

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 MoD 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.

Taigei-class SSK weapons

Japan Launches Fifth Taigei-Class Submarine for JMSDF
The future JS Chogei at the launching ceremony (Credit: Kosuke Takahashi)

The Taigei-class employs the same torpedo counter-measures system that has been incorporated into the last four Soryu-class boats. It is expected to use Japan’s newest torpedo, which is called the Type 18, succeeding the previous Type 89. The new torpedo will feature improvements in a number of areas, including propulsion, target detection, and processing.

The Ministry of Defense in Tokyo is aiming to equip a new submarine succeeding the Taigei-class with a long-range standoff cruise missile, which can attack enemy ships from outside their missile range. The type of missile being considered for installation is an improved version of the Type 12 Surface-to-Ship Missile, based on the Japan Ground Self-Defense Force’s Type 12 Surface-to-Ship Missile, with an extended maximum range of about 1,500 km. Until now, Japanese submarines have been equipped with the UGM-84L Harpoon Block II anti-ship missile, but the new submarine-launched missile will be able to attack enemy land bases from long distances.

The MoD began developing this new submarine-launched missile in fiscal 2023, with MHI as the contractor. In the FY2025 budget request, the ministry has earmarked 3 billion yen($20.5 million) for the acquisition cost and will begin mass production in the same fiscal year. Development is scheduled to be completed in fiscal 2027.

With the next class, the MoD is also aiming to adopt a vertical launch system (VLS), in addition to the conventional torpedo tube launch method. The fiscal 2025 budget includes 30 billion yen for this research. Research and prototyping will be carried out from fiscal 2025 to fiscal 2029.

Since the construction costs of the ninth Taigei-class submarine has already been requested by the MoD in next year’s budget, it is expected that the new, larger submarines equipped with these new equipment systems will not actually appear until 2031 or later, after the tenth of the Taigei-class.

The Taigei-class is also equipped with Torpedo Counter Measures (TCM), which was introduced on the Sekiryu, the eighth Soryu-class ship ). This is a system that, when it detects a torpedo fired by an enemy submarine, launches a buoy or decoy that simulates the sound of the ship’s propeller, preventing the torpedo from heading towards the ship.

The Taigei-class is also the first to be equipped with a domestically produced non-penetrating periscope, made by Mitsubishi Electric.

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. Launched in April 2020, the third of the class, named Jingei (SS515), entered service in March 2024. The fourth ship, the Raigei (SS516), which was launched in October 2023, is currently undergoing outfitting and various tests in preparation for commissioning in March 2025.

Soaring submarine construction costs

Japan’s submarines are built alternately at MHI Kobe Shipyard and Kawasaki Heavy Industries(KHI) Kobe Plant every other year. Currently, the sixth Taigei-class submarine is under construction at KHI Kobe Plant, and the seventh at MHI Kobe Shipyard.

The construction cost of Taigei, the first of the Taigei-classs, was about 80 billion yen. Meanwhile, the budget request for fiscal 2025, announced at the end of August this year, included 116.1 billion yen for the construction cost of the ninth Taigei-class submarine. This is actually 1.45 times the original amount. This is a direct result of the rising prices of materials and other items and the weak yen year by year.

The Taigei-class is the third generation of cigar-shaped submarines

Until the Harushio-class, the hulls of JMSDF submarines were teardrop-shaped, but they changed from the Oyashio-class to a cigar-shaped one. The Taigei-class is the third generation of cigar-shaped submarines. In addition, the stern rudders of the Oyashio class and earlier were cross-shaped, but from the Soryu class onwards they were changed to an X-shape. The X-shape rudders have the advantage of excellent underwater maneuverability and less damage to the rudders even when they hit the bottom

Advertisement

Advertisement