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The 6th Soryu-class SSK, SS-506 Kokuryu, (meaning Black Dragon) was commissioned into service with Japan Maritime Self-Defense Force (JMSDF) at the Kawasaki Heavy Industries shipyard in Kobe on March 9th.
The Soryu Class diesel-electric submarines are being built by Mitsubishi Heavy Industries and Kawasaki Shipbuilding Corporation for the Japan Maritime Self-Defense Force (JMSDF). Ten Soryu Class submarines are planned for the JMSDF. The class is an improved version of the Oyashio Class submarine.

The keel for the first submarine in the class, Soryu (SS-501), was laid down in March 2005. It was launched in December 2007 and commissioned in March 2009. Unryu (SS-502) was laid down in March 2006, launched in October 2008 and commissioned in March 2010. Hakuryu (SS-503) was laid down in February 2007 and launched in October 2009 for commissioning in March 2011. The fourth and fifth submarines under construction are scheduled to be commissioned in 2012 and 2013 respectively.

SS-506 Kokuryu was laid down 21 January 201, launched 31 October 2013 and commissioned 9 March 2015

Main characteristics (as provided by Kawasaki Heavy Industries):
Length 84.0m
Width 9.1m
Depth 10.3m
Draft 8.4m
Displacement 2,950 Tons
Engine:
- Kawasaki 12V 25 / 25SB type diesel engine 2 groups
- Kawasaki Kokkamusu V4-275R Stirling engine four
Propulsion motor: 1 groups
Number of axes: 1 axis
Speed 20 knots

TOKYO – Japan is proposing jointly building Australia's new submarines, instead of exporting a new fleet, a report said Monday, after concerns in Canberra over the effect on the domestic ship-building industry.

Under the proposal, Japan's defense ministry is to cooperate with Australia in developing special steel and other materials for its new submarines, while Tokyo will be in charge of assembling them, the Mainichi Shimbun said.

The Australian side has taken "a positive stance" on the proposal, the daily said, adding that the two countries may strike a deal by the end of 2015.

Australia needs to replace its fleet of diesel and electric-powered subs, which date from the 1990s, and Japan's high-tech ship-building industry is thought to be well-placed to win the contract.

But opposition politicians and industry groups in Australia protest that losing the contract could deal a potentially fatal blow to naval shipbuilding at home, with a knock-on effect for associated industries.

However, critics point out that Japan may be able to supply the fleet for as little as half of the cost of making it at home.

Japan is on a drive to promote its manufacturing industries abroad, with Prime Minister Shinzo Abe touring the world as salesman-in-chief.

Abe has argued that Japan must play a bigger role on the global stage and has pushed to loosen post-World War II restrictions on when its well-equipped armed forces can act.

He has also relaxed a self-imposed ban on weapons exports, paving the way for the possible deal with Australia.

Immediate confirmation of the report was not available.

TOKYO — Japan has decided to power its new batch of Soryu-class submarines with Lithium-ion batteries instead of air-independent propulsion (AIP) technology — a move that could raise eyebrows after similar types batteries were faulted for fires aboard the Boeing 787 Dreamliner.

However, experts brush aside those concerns and instead say this type of technological leap increases power and performance, while reducing maintenance. It also could make Japanese subs more marketable overseas.

Yasushi Kojima, a spokesman for the Maritime Self-Defense Force (MSDF), said the change would affect the next four remaining Soryu-class submarines in Japan’s 10-boat class.

Senior officials from Australia, which struck a landmark technology agreement with Japan in June, told Defense News that they are aware of the switch to the Li-ion batteries and that they are still interested in pursuing Japanese sub-building technology, perhaps even purchasing Soryu-class subs outright.

The existing Soryu-class diesel-electric submarines (16SS) use AIP technology based on Kockums Stirling engines license-built by Kawasaki Heavy Industries, allowing them to stay submerged for long periods. The engines power Sweden’s smaller Gotland-class submarines for up to two weeks at 5 knots.

The current Soryu-class submarines are propelled by a large electric motor that has three power sources: diesel engines, the AIP engines and main storage batteries. Diesel engines, which require oxygen for combustion, power the boats on the surface or while snorkeling. The boats can snorkel for extended periods to limit their detectability while transiting submerged (only the snorkel mast is above the water) or for short periods to quickly recharge their batteries after operating underwater. The AIP engines — which burn small quantities of diesel fuel and liquid oxygen — are used for long-range underwater cruising at low speed, and to keep the batteries topped off. The batteries are used for ultra-quiet operation as well as high-speed underwater operations, which quickly depletes them.

By shifting to Lithium-ion batteries, the new Soryus would retain their main propulsion diesels, but be equipped with more powerful and far lower maintenance batteries than lead-acid types widely in use.