- Japan launched its latest Soryu-class diesel-electric attack sub this month, the Oryu.
- The sub was the first to feature lithium-ion batteries, which store about double the power as previous batteries.
- The new batteries may help Japan’s own defense industry and give Japan an edge in the increasingly crowded waters of the western Pacific.
With more Chinese submarines roaming the Pacific and the Trump administration pushing US-made hardware, Japan is putting into play a new piece of gear that may give its subs an edge at sea and keep its defense firms afloat.
On October 4 in the city of Kobe, Mitsubishi Heavy Industries launched the Soryu-class diesel-electric attack sub Oryu, the 11th sub in the class and the first to be equipped with lithium-ion batteries.
The Oryu has a number of upgrades over previous Soryu-class boats, which are the biggest diesel-electric subs in the world, but the biggest change is the batteries.
Diesel-electric subs use power from their diesel engines to charge their batteries, which they switch to during operations or in combat situations in order to run quietly and avoid detection.
The lithium-ion batteries in the Oryu – which store about double the power of the lead-acid batteries they replace – extend the range and time the sub can spend underwater considerably.
Mitsubishi turned to Kyoto-based firm GS Yuasa to produce the new batteries.
The latter company said in February 2017 that Japan would be the first country in the world to equip diesel-electric attack subs with lithium-ion batteries, putting them on the final two boats in the Soryu class: the Oryu, designated SS 511, and its successor, designated SS 512.
Previous Soryu-class subs used two Kawasaki diesel generators and two Kawasaki air-independent propulsion engines. (AIP allows nonnuclear subs to operate without access to atmospheric oxygen, replacing or augmenting diesel-electric systems.)
Both platforms have a top speed of 12 knots, or about 14 mph, on the surface and of 20 knots, or 23 mph, while submerged, according to Jane’s.
Soryu-class subs are outfitted with six tubes in their bow that can fire Japan’s Type 89 heavyweight torpedo. They can also fire UGM-84C Harpoon medium-range anti-ship missiles against targets on the surface.
Construction started on the 275-foot-long Oryu – which displaces 2,950 metric tons on the surface and 4,100 metric tons underwater – in March 2015. It’s expected to enter service with Japan’s Maritime Self-Defense Force in March 2020.
The Oryu’s launch comes as Japan’s military and defense industry face pressure from two vastly different sources.
The Trump administration has been pushing Japan to buy more US military hardware, which Trump sees as a way to cut the trade imbalance between the two countries.
Japan, which has tried hard to court Trump, has beefed up its purchases of US-made gear. Tokyo spent about $3.5 billion through the US’s Foreign Military Sales program in the most recent fiscal year, after never spending more than about $880 million a year through fiscal year 2011, according to Nikkei Asian Review.
Those acquisitions have helped Japan get sophisticated US hardware but have been of little benefit for Japan’s defense industry, which has struggled to export its own wares. Additional purchases from the US are likely to leave Japanese firms with fewer orders.
Facing pressure from US military imports and with Chinese and South Korean firms gaining an edge in commercial shipbuilding, subs are the only outlet left for Japanese heavy industry, which has specialized technology and strong shipbuilding infrastructure, according to Nikkei.
- Japanese Ministry of Defense
The Oryu also launches amid rising tensions in the East and South China Seas, where a number of countries have challenged Beijing’s expansive claims and aggressive behavior.
China has put “growing emphasis on the maritime domain,” the Pentagon said earlier this year. Beijing can now deploy 56 subs – 47 of which are believed to be diesel or diesel-electric attack boats. That force is only expected to grow.
While those subs need to surface periodically, they can still operate quietly and strike with long-range anti-ship missiles – capabilities that likely weigh on the minds of US and Japanese policymakers.
Of particular concern for Tokyo is Chinese submarine activity in the East China Sea, around the Senkaku/Diaoyu Islands, which Japan controls but China claims.
In January, a Chinese Shang-class nuclear-powered attack sub was detected in the contiguous zone around the islands – the first confirmed identification of a Chinese sub in that area. The presence of a concealed sub was seen by Japan as a much more serious threat than the presence of surface ships, and Tokyo lodged a protest with China.
Japan is using its own subs to challenge Beijing.
In September, JMSDF Oyashio-class attack sub Kuroshiro joined other Japanese warships for exercises in the South China Sea – the first time a Japanese sub had done drills there, the Defense Ministry said.
The drills, done away from islands that China has built military outposts on, involved the Japanese sub trying to evade detection.