The Japan Maritime Self-Defense Force (JMSDF) commissioned a new submarine, Hakugei, the second ship of the new Taigei-class diesel-electric vessels, earlier this week, and is slated to deploy it to defend choke points in the East China Sea and Sea of Japan against Chinese maneuvers.
Manufactured by Kawasaki Heavy Industries (KHI), it is equipped with lithium-ion batteries (LIB) that enable longer underwater operations and is considered a leap over Air Independent Propulsion (AIP) systems.
The JS Hakugei replaces the Oyashio, the lead boat of the Oyashio-class, which was decommissioned earlier this month after 25 years of service.
The submarine is expected to defend chokepoints and ambush Chinese submarines in the East China Sea and Sea of Japan before they break out into the Pacific Ocean – as per a plan envisaged by US strategists, according to Nikkei Asia.
The third boat of the Taigei-class, the Jingei, was launched in October 2022 and is scheduled to be delivered to the JMSDF by early-2024.
But the development highlights Japan’s noted advancement in LI Battery technology, leaving a significant mark in naval underwater propulsion.
China, too has been reported to be seeking LIB capability for its submarines, according to the South China Morning Post (SCMP). China has been assessed to possibly build upon its status as the producer of three-quarters of the world’s electric car batteries, also powered by LIBs.
Nuclear Powered, Air Independent Propulsion & Lithium-Ion Batteries
The defining feature of LIBs in general, and the ones on the new Japanese submarine, is being able to generate a “burst speed.” This allows for a sudden and high flow of energy charge into the engine that increases speed, allowing the submarine to evade an incoming torpedo quickly.
“(It can also) speed quickly out of a position where the torpedo can lock on and start homing,” former US Navy submarine Tom Shugart quoted in the Asia Nikkei report. The stealth capability acquired because of the battery propulsion, “combined with Japan’s tradition of underwater-noise analysis, gives Japan an advantage over Chinese submarines,” the report added.
20 MAR, the Ship Commissioning Ceremony of JS #HAKUGEI was held at Kobe Works, KAWASAKI Heavy Industries, Ltd.
JS HAKUGEI is the 2nd TAIGEI class. Her name comes from the White Sperm Whale.#submarine #debut pic.twitter.com/C8LqDOIaGF
— Japan Maritime Self-Defense Force (@jmsdf_pao_eng) March 21, 2023
A diesel-electric submarine (or SSK) works like a hybrid vehicle, charging the battery while it runs on the diesel engine and switching to its lead-acid batteries once submerged during operations.
SSKs, however, periodically need to snorkel by sending up a mast above the water, which sucks in atmospheric oxygen and feeds it into its diesel engines. This, however, is dangerous and prone to detection by overhead anti-submarine warfare (ASW) aircraft. The submarine’s engine is virtually the quietest while running on its batteries.
Unlike nuclear-powered submarines, turbines make distinct sounds and are relatively easier to detect on sonar. However, modern coating and quieting technologies developed by the United States, France, and Russia have addressed this vulnerability.
They are, however, costlier and difficult to operate, besides requiring separate onshore atomic equipment and specialized training. But these have exponentially longer endurance, can spend many months underwater, dive deeper, and are faster than diesel electrics.
This is where AIP-powered submarines came in, serving as a viable midway between diesel electrics and nuclear submarines. Generating the oxygen required for the diesel engines internally, they are simpler to operate and can stay underwater for at least two weeks.
Future Of Conventional Submarine Propulsion
But Lithium-ion batteries, introduced to replace lead-acid batteries, hold much more energy and charge faster. Compared to traditional lead-acid batteries, LIBs have greater energy density for their volume and weight, can charge much faster, and discharge their energy with 80 to 90% efficiency, as against 60-70% for lead batteries.
JMSDF eventually became the first in March 2020 to install LI batteries in the last of its Soryu-class submarine, the JS Ouryo. Four Japanese submarines – two Taipei-class boats and another Soryu-class submarine – have lithium-ion batteries.
Interestingly, the Soryu was one of the initial contenders for the Project-75 India (P-75I) program, which required all Original Equipment Manufacturers (OEM) to have operational AIP engines on their vessels.
But the AIP also has its drawbacks, with a major one being increasing the length of the submarine to insert the module. “This makes the vessel heavier and markedly slower,” said an article on the Observers Research Foundation (ORF).
Lithium-Ion Batteries Aren’t Perfect, Either
LIBs are not without flaws, the primary one being a tendency to discharge too much power. A fire aboard a parked Boeing 787 Dreamliner at Boston’s Logan airport in 2013; Samsung Galaxy S7 tablets spontaneously combusting; a fire aboard a US Navy SEAL Delivery Vehicle mini-sub caught fire in Pearl Harbor in 2008 are some incidents which made navies wary of LIBs.
Retired Indian Navy submariner Commander Ashok Bijalwan, does not believe the hype around LIBs, especially in the absence of exhaustive test data. “There has to be empirical data on their usage aboard submarines to validate their claimed advantages,” Bijalwan said.
He also said a “burst speed” capability, that the Hakugei is claimed to have because of the LIB, is also dependent on the “hull form, motor capacity, propeller design and the inertia of the boat.” “So the battery singularly can not improve the burst speed exponentially,” Bijalwan added.
But Japan has, however, invested substantial money and time in research and development in refining LIB technology and improving its safety and reliability.
“(It has) improved battery-cell matrices with hardened dividers, stabilized chemicals and automatic fire extinguishers, and has reportedly tested the configuration rigorously to account for various high-stress scenarios such as exposure to seawater,” said an article in The National Interest.
However, China has a massive fleet of around 66 submarines, which would work in tandem with its enormous surface combatants, carrier and land-based aircraft (ASW, bombers, and fighters), and the world’s largest and diverse arsenal of combat drones, long-range anti-ship, and land attack missiles.
A singular Japanese advantage in the underwater arena would be far from having any strategic impact on China’s military capability or goals.