Japan's Soryu Class Submarine

The Sōryū-class   are diesel-electric (SSK) submarines that entered service with the Japanese Navy "Maritime Self-Defense Force" in 2009. Five have been built (since 2005) with all five operational in Japan's Navy. Four more await completion. The design is an evolution of Japan's Oyashio class submarine. Eleven Oyashios have been built since 1994 and all eleven are still operational.

The Sōryūs have a very large displacement for a diesel-electric sub (2,900 tonnes surfaced and 4,200 tonnes submerged). This compares to the Collins (3,050 tonnes surfaced and 3,350 tonnes submerged) http://en.wikipedia.org/wiki/Collins-class_submarine.

Significantly the Soryu carries a higher weapons payload than the Collins which is an important endurance-operational advantage. The Soryu carries 30 "reloads" (torpedos/Harpoon missiles) compared to 22 for the Collins.

The Soryus are fitted with air-independent propulsion (AIP) based on Kockums Stirling engines license-built by Kawasaki Heavy Industries, with AIP range (submerged of course) of 11,297 km at 12 km/h. Diesel-electric range appears to be classified but may be around 15,000 km. The Soryu is mainly heavier than the (2,750 tonnes surfaced and 4,000 tonnes submerged) Oyashios due to the addition of the AIP.

According to http://www.globalsecurity.org/military/world/japan/2900ton.htm: The Soryu features higher automation (particularly in combat systems) and computer-aided X control planes. The X rudder configuration was first developed by Kockums for the Gotland. The X rudder provides the submarine with greater manoeuvrability and also enables operation close to the seabed. The Soryu's hull is clad in anechoic coating (to reduce sonar and other forms of detection) and the interior features sound isolation of loud components. The hull is HY-80 alloy (the same as the USN's Los Angeles class SSN) steel. 

Japanese subs have a short service life averaging around 20 years compared to 30 years for most SSKs.

Pete's Comment

If Soryus wear out after 20 years that might be a major deficiency in the SEA 1000 selection process.

Japan's lack of experience in exporting submarines or other major weapons systems has many political, legal and technical support implications which Australia would need to resolve and feel confident about. Mission restrictions may well be a problem from choosing a Japanese sub design given Japan's complex peace or defence only orientation. Japan appear to change governments frequently with swings between nationalist-conservative  and pacifist-centrist governments. But then again the political, strategic, and repair-maintenance advantages of choosing a design from an Asia-Pacific ally like Japan (or for that matter the US) must be factored in. Such advantages would not be present if Australia purchased UK or European designs from Germany (HDW), Spain (Navantia),  Sweden (Kockums) or France (DCNS).

One confidence booster is that the main builders and presumably sellers of the Soryu are highly export and customer support orientated Mitsubishi and Kawasaki. Such confidence would assume that the corporate culture in Mitsubishi's and Kawasaki's defence product divisions are similar or the same as their civilian product divisions. 

As the Soryu combines many of the best European technological features and in a design near to SEA 1000's Asia-Pacific range-endurance requirements the Soryu Class looks a promising option.

Pete