Taigei-Class: Why Japan’s New Submarines Are Something Special

October 16, 2020 Topic: Security Region: Asia Blog Brand: The Buzz Tags: JapanJSDFJapanese NavySubmarinesChinaTaigei-classSōryū-class

Taigei-Class: Why Japan’s New Submarines Are Something Special

These new technologies will keep Japan’s submarines relevant for a long time to come.

Japan’s manufacturing heavyweight Mitsubishi Heavy Industries just launched the Japanese Navy’s first new diesel-electric attack submarine. The new class, known as the Taigei-class, is intended to supplant the older Sōryū-class as Japan’s premier attack submarines. Here’s what we know so far.

One of the more notable technologies that Japan’s new Taigei-class features is the use of lithium-ion batteries for electrical energy storage, rather than traditional lead-acid batteries. Like the large (and heavy) battery in your car, lead-acid batteries have powered submarines for quite a while. But, like the battery in your smartphone, lithium-ion batteries are more energy-dense, and can store more potential power than the equivalent volume of lead-acid batteries—of crucial importance on a submarine, where real estate is at a premium.

In addition to power output advantages, lithium-ion batteries can in some circumstances charge faster than their lead-acid counterparts. Faster charging is a boon to submarine crews, as it reduces the amount of time a submarine has to sit exposed on the surface, waiting for a full charge.

Although the Sōryū-class was the first in Japan to be equipped with lithium-ion batteries, the Taigei-class is expected to be equipped with upgraded, higher performance lithium-ion batteries, extending the range that the Taigei submarines will be capable of while underway.


Once introduced, Japan’s new class of submarine will augment their Navy in a big way. In addition to the propulsion advantages offered by a modern battery suite, the class is expected to be significantly quieter than its predecessors.

A buffer mechanism between the outer and inner hulls would in theory offer a greater degree of separation between the them, and help to shield the submarine from the vibration its own diesel engines would make.

One of the other significant steps taken to reduce the Taigei’s noise signature relates to fluid noise, or the sound created by ocean water flowing over the submarine’s surfaces. A smoother, sleeker design means less fluid noise, and therefore a quieter submarine.

In addition to submarine torpedoes, the class is likely capable of firing American-supplied Harpoon anti-ship missiles.

Eyes on the Prize

Japan’s military expansion (in terms of both capabilities and mandate) has, of course, been driven in large part by the increasingly assertive Beijing regime, though threats posed by a nuclear North Korea also certainly play a part in Japan’s defense calculus. Though the People’s Liberation Army Navy is now the larger than the United States Navy, the Japan Self-Defense Force’ new submarine class aims at evening the odds.

Ultimately, the first of the Taigei-class is intended to be a test platform for the multiple new technology designs it carries onboard. Though it will likely not fire any shots in anger, the information the submarine gleans will hone the capabilities of succeeding Taigei-class submarines.


There is still much to be learned about the Taigei-class, though independently-verifiable details are difficult to come by. Keep an eye on this class for more information in the future.

Caleb Larson is a defense writer for the National Interest. He holds a Master of Public Policy and covers U.S. and Russian security, European defense issues, and German politics and culture.

Image: Reuters