Japan begins development of its next-gen attack submarines, the 29SS.

Apparently, Japan has commenced research, design and development for the successor to its Soryu-class attack submarines, which entered service in 2009. This new class, based on the Soryu-class is designated as 29SS submarine design.

A Soryu-class attack submarine of the JMSDF (Picture Source: JMSDF)

Japan’s Soryu-class is widely recognised as one of the world’s best submarines and often acknowledged to be the world’s most advanced, quietest, conventionally powered submarine. The diesel-electric vessels weigh in at approximately 4,000 long tonnes and are Japan’s largest post-war submarines, providing an important tactical and strategic edge over competitors.

Designed from the keel up to have an operation life of about 20 years, approximately half of comparable vessels operated by nations, including Australia, Japan’s planned fleet of 15 Soryu-class has recently been upgraded to include large banks of advanced lithium-ion batteries as a quiet source of power and is one of the major technological breakthroughs expected to be included in the nex generation of attack submarines.

Mitsubishi Heavy Industries (MHI), Japan’s leading submarine builder, has unveiled provisional designs for what is tentatively being designated as the 29SS submarine design, with the first submarine scheduled to be introduced in service in the late-2020s. The R&D phase will take place from 2025 to 2028, and the first ship of this class will probably be launched around 2031.

It is expected that while the 29SS submarine will retain the general hull form of the earlier Soryu-class vessels, the new vessels will incorporate a range of important design changes, including a substantially reduced sail, which is expected to be blended into the hull with the aim of reducing hydrodynamic drag, helping to lower the noise signature of the submarines, while the dive planes will be moved from the sail to the hull.

Additionally, it is expected that the 29SS will include a pumpjet as opposed to the traditional propeller for propulsion, in a similar fashion to what is expected to be introduced on Australia’s future Attack Class submarines.

29SS will likely retain the same armament as the Soryu boats, which consist of six bow-mounted 533-millimetre torpedo tubes. The submarine can carry up to 30 torpedo-launched weapons, a mixture of Type 89 heavyweight torpedo and the Sub Harpoon anti-ship missile. Although there is a general trend towards installing vertical launch silos behind a submarine’s sail, Japan does not have the missiles to fill them.