third lithium submarine in operation, new frigate and additional aircraft carrier

In recent weeks, the Japanese Navy reached several new milestones in its operational deployability in the foreseeable future. For example, there was the news that the helicopter ship Kaga (Izumo class) will be transformed into an aircraft carrier. Another milestone was the arrival of the submarine Taigei in its home port, enabling Japan to reach its operational target of 22 active submarines. In addition, the first frigate of the Mogami class was taken into use. The operational milestones must be seen in a larger context, namely the advance of the Chinese navy and the vulnerability of the Japanese economy with its overseas trade routes.

JS Taigei, the first of the Taigei class, consisting of seven submarines. This first boat has been designated as a test platform. The boats in the Taigei class are 84 meters long, have a displacement of 3,000 tons and a crew of 70 people. These boats do not have AIP. (Photo: Japanese Navy)

First-class lithium submarines
On April 6, the submarine Taigei, the first of its class on seven boats, arrived at its home port of Yokosuka. Taigei was commissioned on March 9 and arrived at her home base on April 6. Japan’s goal of having a submarine service with 22 operational boats has therefore almost been reached. Not quite, for the Taigei has been classified as a test and training submarine. Usually this honor belongs to old submarines, but the Japanese navy has chosen it because this submarine has the latest technology that the submarine personnel of the future will have to work with.

Taigei offers, among other things, the most modern technology in Japanese submarines, such as a new bow sonar and improved flank array (sonar on the sides), in addition to a towed sonar. The information from these sensors is combined in the command center.

Like the Soryu-class Oryu and Toryu, the Taigei also has lithium-ion batteries. A new technology in submarines. This allows the boat to stay submerged for longer or reach higher speeds than diesel-electric submarines that still use the old lead-acid batteries or outdoor air-independent propulsion (AIP). Japan previously used Stirling engines from Saab, but has switched from AIP to a modern battery type with new boats.

The AIP types currently in use are mainly suitable for low speeds. Unlike the previous submarine classes, which were mainly aimed at defending coastal waters, both the Taigei and Soryu class represent an offensive capacity of the Japanese fleet aimed at longer patrols at a distance and increased tactical deployability at speed.

More about AIP and lithium in the podcast with Douwe Stapersma and Carel Prins

Japan plans to build seven Taigei-class submarines. Every year in March, a new submarine comes into use.

JS Kaga, Izumo class. (Photo: Japanese Navy)

Modernization of Kaga for an aircraft carrier
Like her sister ship Izumo, the Kaga will undergo the transformation from a helicopter ship to a (light) aircraft carrier. The conversion will take two years and includes reinforcement of the deck with heat-resistant material and adaptation of the front deck to a trapezoidal shape to create more space. Additional power plants will also be installed on board the ship to generate the power needed to operate aircraft.

The hangar itself will not be altered because it was already designed to accommodate 28 fighter jets. Thanks to the large hangar, the ships in the Izumo class can be used multifunctionally. In addition to planes and helicopters, the hangar can also be used to transport 400 military personnel and 50 3.5-ton vehicles.

Like her sister ship Izumo, the Kaga will operate the US F-35B fighter jet. The B variant of the F-35 is specially designed to operate on aircraft carriers and, like the Harrier jet, can take off and land vertically. Japan plans to buy a total of 42 F-35Bs from the United States. This would equate to 21 F-35Bs per. Izumo-class aircraft carrier, although in reality there are always a number of aircraft on hand for training and reserve.

Confrontation with the Chinese navy
Building more offensively oriented warships does not just happen. The eyes of the Japanese navy are focused on the expansion and improved deployability of the Chinese navy. As an island nation, Japan is heavily dependent on overseas trade, and most of its trade routes run along China’s coastline. The advance of the Chinese navy therefore poses a real threat to the Japanese navy. In addition, Japan and China are involved in a territorial dispute over the Senkaku Islands’ property north of Taiwan. These islands are now under Japanese control, but are claimed by China as the Diaoyu Islands.

The islands are too rocky to build military bases and airports. This means that in a maritime conflict, the deployment of aircraft carriers is necessary to achieve air superiority over these islands. The Chinese navy currently owns two aircraft carriers, Liaoning and Shandong, with a third under construction. Liaoning can carry up to 26 Shenyang J-15 fighter jets, while Shandong has room for 35 fighter jets. Both Chinese aircraft carriers are capable of carrying more aircraft than both Izumo-class aircraft carriers.

On the one hand, Japan reckons with the technological superiority of the F-35B over the J-15. The F-35B is also easier to deploy from an aircraft carrier thanks to its vertical take-off and landing capability, a procedure that is faster to learn and less dangerous than conventional aircraft cargo landing. In addition, the Japanese Navy also trains a lot with the U.S. Navy. Over the past fall, Izumo operated alongside the Nimitz-class aircraft carrier USS Carl Vinson and US Marine Corps F-35B aircraft practiced landing and taking off from Izumo.

In mid-December, Izumo was sent to the Philippine Sea to observe the movements of the Chinese aircraft carrier Liaoning. Liaoning was at that time with one practice in the western Pacific. Both ships remained in close proximity to each other during December 19th and 20th close

JS Kumano. The Mogami is the first ship in the class, but that construction did not go as smoothly as the Kumano’s. Mogami will be taken into use at the end of this year. (Photo: Japanese Navy)

22 new frigates
A third often forgotten aspect of the Japanese navy is the large amount of frigates and destroyers it uses. The country has 36 destroyers and 10 frigates. Last month, a first frigate of the Mogami class, the Kumano, was commissioned. 21 more of these frigates follow. These ships are modern but fairly standard frigates. They have a displacement of 5,500 tons, a length of 133 meters and a launch vehicle with 16 cells.

Impact force
Looking at the impact force, the Japanese Navy now has 1,304 vertical launch cells. However, the majority of these, 744 firing cells, can be found on the eight ships of the Maya, Atago and Congo class. By comparison, the Chinese Navy has ‘barely’ 880 firing cells spread across its surface fleet since our last count in early February.

Going forward, it is uncertain whether the Japanese fleet will sustain these trends given internal economic challenges. The country is expected to try to keep pace with the Chinese navy and try to keep the current balance of power stable, as a strong navy is a guarantee of security on Japan’s maritime trade routes. That does not change the fact that a number of ships are currently nearing the end of their service life and that the construction of new ships will now only serve to compensate for the loss of efficiency.

The emergence of larger Chinese ships such as Type 055 cruisers, also known as the Renhai class, each with its 112 launch cells, threatens to break this balance of power and potentially lead to an increase in Japanese operational targets and deployability.

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