lithium-ion powered Taigei class gives Japan a massive submarine advantage against China

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Joseph P Chacko
Joseph P Chacko
Joseph P. Chacko is the publisher of Frontier India. He holds an M.B.A in International Business. Books: Author: Foxtrot to Arihant: The Story of Indian Navy's Submarine Arm; Co Author : Warring Navies - India and Pakistan. *views are Personal

Japan’s latest 29CC Taigei class diesel electric attack submarine is the first boat of its class to enter service on March 9. With a displacement of 3,000 tons, it sets the record for the largest tonnage of Japan’s conventional submarines. Compared with previous models, the new sub’s hull is designed in a shape that makes it more challenging to be detected by the opponent, and it is equipped with a lithium-ion battery to extend the diving time. The sub’s performance can be said to be world-leading.

The primary power of the boat comes from the two Kawasaki 12V 25 / 25SB diesel engines that are used as the main engine. 

A high-performance snorkel (intake and exhaust device) has increased the submerged time that is important for submarines. In addition, it is equipped with a new high-performance sonar system that uses optical fibre technology to improve detection capability.

It is also equipped with the submarine torpedo defense system (TCM) introduced from the Soryu-type 8th ship Sekiryu. 

In terms of armament, the boat is equipped with Type-18 torpedoes and “Harpoon” Block II anti-ship missiles with 248 kilometres range, so it has a strong anti-submarine anti-ship combat effectiveness.

Japan’s previous generation of AIP submarines is the 16SS “Soryu” class. It is also known as the world’s largest and most potent AIP attack submarine. It is said that the combat capability of Soryu class is similar to that of other countries’ nuclear submarines. 

Taigei’s length and width of 84 meters and 9.1 meters respectively are the same as the Soryu type, but the depth is 10.4 meters, which is 0.1 meters larger than the Soryu type. With a standard displacement of 3000 tons, it is 50 tons more than the Soryu type. As per the Maritime Staff Office’s Public Relations Office, Taigei costs 79.6 billion yen to build. The sub can accommodate 70 personnel. The shaft output is 6000 horsepower, and the speed is not yet announced.

Similar to the Taigei-class second ship, Hakugei, the next boat of the class, has a dedicated living area, shower room, and bedroom for female crew members.

The Taigei class has specific known advantages.

Li-ion batteries

The lithium-ion storage battery is developed by GS Yuasa. Although Germany and France have also tested and compared the advantages of lithium-ion batteries, they have not been applied to service submarines. 

There are references that the application of lithium-ion batteries has enabled the 29CC submarine to reduce the time taken for charging to less than 1 hour and increase the range to double. Reports also say that speed, high and low, performance has been dramatically enhanced.

“The aspect about the li-Ion battery; initial characteristics are claims. However, there is no denying that such batteries will reduce charging time to about an hour whilst at the same time giving much higher capacity. It gives much improved submerged endurance at higher speeds. How much? It is yet to be determined. Suffice to say that the Japanese have dispensed with the sterling AIP because of this arrangement. Interesting times ahead,” said Cmde Arun Kumar Retd), veteran submariner and author of the book S 71 INS Chakra – The Pioneer and Her Men. 

Optimised Hull

The specially optimised new hull significantly reduces the reflection intensity of the active sonar.

“The propellor of a submarine is crucial for radiated noise which comprises the self noise generated by its machinery, the noise created by the flow of water along the hull as the boat moves and thirdly the noise generated by the propellor due to cavitation. Self noise is reduced by construction techniques such as fundament dampeners, raft mounted machinery, and shock absorbing suspensions. Most modern boats employ raft mounted machinery. In this case, the vibrations of the equipment are not directly passed on to the hull but are dampened by the raft. The second type of noise is reduced by the hydrodynamic design of the hull. The third is reduced by the design of the propellor and the number of blades. The idea is to maximise the thrust with lesser propellor RPMs to delay the onset of cavitation, which is directly proportional to the RPMs. To obviate the cavitation of the propellor, the Pump-jet propulsor was invented for larger subs but is progressively being built into smaller boats with displacements from 2000 T and above. All these features have been incorporated into the design of the Taigei-class. It is reported that the forward planes may be shifted from the sail to the hull in the forward part ostensibly to reduce noise. I am not certain whether this will help at low speeds when the fore planes are used. At higher speeds with the planes turned in and housed in the forward casing, their noise will come down as will the drag friction, thereby giving higher speed for the same power,” says Cmde Arun.

Network Centric

A new type of bow conformable sonar array, the broadside sonar array and towed sonar array, and an advanced combat system make it capable of network-centric warfare.

Enhanced weapon system

The armament of the 29CC submarine has also been greatly improved. The most obvious is that the Type-18 torpedo and the “Harpoon” Block II anti-ship missile are onboard simultaneously. 

The Type-18 torpedo (development codenamed G-RX6) is Japan’s latest model and successor to the Type 89 torpedo. The torpedo tubes are located at the front of the bow. It can identify the decoy devices released by the enemy and can adapt to various coastal areas with complex sound environments and shallow water with poor terrain conditions and other environments, and finally launch a fatal blow.

Harpoon Block II is the most advanced ship-borne anti-ship missile in the United States. The missile has strong anti-electronic warfare capabilities. The weight of the warhead is about 140 kg, and the range is about 248 Kilometers. It can hit both ship and land targets.  

“In terms of armament, not much difference between Soryu and 29SS. The network centric and electronics to manage the Integrated PMS and Combat system will be a generation higher,” says Cmde Arun Kumar.

Role of Taigei class in Japanese Submarine mix

Putting Taigei class submarines into service is as per the plan of the Japan Maritime Self-Defense Force to equip itself with 22 submarines as stipulated in the Defense Guidelines in December 2018. Currently, the Japanese submarine composition includes 12 Soryu types, 9 Oyashio types and one Taigei type. 

Japan plans an unspecified number of boats of this type. The Taigei type will replace the older Oyashio boats after commissioning. So, we can expect nine boats of the type at the rate of one boat per year. The lead boat SS-513 is in service, SS-514 is in outfitting, and SS-515 is about to be launched. All three will be in service by March 2024.

Taigei will be deployed to the 4th Submarine of the 2nd Submarine Group at Yokosuka Base. Yokosuka base is an indispensable base for military operations against China. U.S. Navy’s aircraft carrier operations against China cannot be carried out without the Yokosuka base.


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