Key Points and Summary on Taigei-Class Submarines – Japan’s new Taigei-class submarines are among the most advanced diesel-electric boats in the world, representing a significant threat to potential adversaries like China.
-Their key advantage lies in their revolutionary use of lithium-ion batteries, which provide greater underwater endurance and speed than traditional diesel-electric or even some Air-Independent Propulsion (AIP) systems.
-This technological edge is backed by Japan’s unique and robust shipbuilding strategy, which retires submarines after only 20 years of service, ensuring the fleet is always equipped with cutting-edge, domestically produced platforms without the need for costly and complex mid-life overhauls.
Taigei-Class Submarines Explained
The Taigei-class is Japan’s newest class of attack submarines, built by both Mitsubishi Heavy Industries and Kawasaki Heavy Industries, in service with the Japan Maritime Self-Defense Force.
The class’s name means “Big Whale” in Japanese, and compared to the Sōryū-class, which precedes the Taigei-class, it is somewhat larger. As of this summer, four of the submarines have been built.
Compared to the Sōryū-class, the Taigei-class features improved sonar, better hull coatings, and a reduced noise reduction. The submarine leverages lithium-ion batteries to operate for extended periods underwater, which also allows the submarine to operate at high underwater speeds, especially compared to diesel-electric submarines.
More Power
Compared to traditional lead-acid batteries, such as those used to supply electrical power to cars, lithium-ion batteries have several significant advantages.
“Lithium-ion advantages include increased battery-discharge rates, faster recharge times, and higher energy density. The results are enhanced silent operations, better speeds and sprints, longer underwater endurance, and significantly greater overall performance when compared with more conventional undersea submarines,” the United States Naval Institute explains. “The use of lithium-ion batteries also saves weight and complexity by making an air-independent propulsion (AIP) system unnecessary to extend the submarine’s underwater endurance.”
The advantages of lithium batteries have been well known for generations, and they are a common element in consumer technology. Their onboard use in submarines, however, remains extremely limited due to the inherent danger posed by hydrogen gas and the intense heat that the batteries can release in the event of malfunction and fire.
Although the advantages of lithium-ion batteries are well established, their use in products outside the computer market, and specifically in submarines, has been relatively limited, in part due to the fire risk posed by damaged or defective batteries and the inherent difficulty in extinguishing battery fires.
But, the U.S. Naval Institute explains, “the JMSDF and its defense industrial base have apparently learned to manage these challenges by pioneering battery technology and safety through an extensive research, design, and testing program dating back more than 20 years. Two submarines of the older Sōryū class, the Ōryū and Tōryū, were recently commissioned with lithium batteries and helped perfect this technology. These capabilities now have matured a step further with introduction of the Taigei class.”
As the Japan Maritime Self-Defense Force’s name implies, the Taigei-class is intended to defend Japan’s maritime and coastal zones, as well as disputed islands or other strategically important areas.
Especially considering China’s buildup of naval forces and increasingly bellicose rhetoric towards neighbors in the region. With that aim in mind, the Taigei-class’s X-shaped rudder and a hydrodynamic hull give the class good maneuverability in shallower waters.
The class is robustly armed. Sporting six 533mm torpedo tubes, the class can shoot both Type 89 heavyweight torpedoes as well as Harpoon anti-ship missiles. It is possible that the Taigei-class could also fire weaponry to attack targets on land too.
Service Life Management
Aside from basic statistics about the Taigei-class’ beam, complement, or armament, one of the real strengths of the Japan Maritime Self-Defense Force is the country’s submarine-building industrial base and approach to both designing and building new submarines, as well as sustaining those hulls.
In contrast to most navies, the JMSDF’s submarines often serve for just 20 years or so before retiring. This is roughly half the length of the submarines in service with the United States, France, the United Kingdom, or the navies of other countries.
One of the more unique factors inherent to Japan’s submarine industrial base is that the JMSDF eschews the midlife overhaul that the United States Navy and other navies typically undertake. “Ship repair officers report that overhauling older vessels can be unpredictable and lead to schedule slippage, and “cutting holes into tightly packed pressure hulls” is not the best use of time or resources,” the U.S. Naval Institute says.
“They admit that some midlife upgrades might save money, but the current system of prioritizing new construction and early retirement ensures more stability in the industrial base and the budget.”
Taigei-Class: One of the Best Subs On Earth
Although the Taigei-class pales in comparison to the capabilities of their nuclear-powered counterparts in the United States Navy, or arguably those of the French or British Navies, they are among the most capable diesel-electric submarines in Asia.
They could credibly rival the diesel-electric submarines of other navies as well.
And backed by Japan’s unique approach to submarine building, as well as the expertise of Mitsubishi Heavy Industries and Kawasaki Heavy Industries, the submarines are well-positioned to defend Japan’s home waters.
About the Author: Caleb Larson
Caleb Larson is an American multiformat journalist based in Berlin, Germany. His work covers the intersection of conflict and society, focusing on American foreign policy and European security. He has reported from Germany, Russia, and the United States. Most recently, he covered the war in Ukraine, reporting extensively on the war’s shifting battle lines from Donbas and writing on the war’s civilian and humanitarian toll. Previously, he worked as a Defense Reporter for POLITICO Europe. You can follow his latest work on X.
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