David Axe China’s mysterious nuclear-battery submarine could hurt the US Navy badly in a Taiwan war Unique hybrid propulsion system offers a key advantage
China’s new nuclear-battery attack submarine – a unique hybrid boat running on batteries like a conventional sub but which recharges them using a tiny nuclear reactor – could be the ultimate near-shore defence sub, and a big problem for US and allied forces in the western Pacific.
The submarine first appeared in commercial satellite imagery of the Wuchang shipyard in Wuhan, China back in April. Five months later, the Type 041 boat reportedly suffered an accident at its moorings – and apparently sank.
While observers wait for signs Wuchang is repairing that first Type 041 or building new examples of the class, analysts are scrutinising its potential capabilities. Most notably the type seems to have a unique propulsion system – one that sidesteps longstanding engineering challenges in order to deliver a quiet attack submarine for near-shore operations, one that can stay submerged for long periods of time in order to preserve its stealth. The Type 041 is reportedly the first submarine with a tiny nuclear reactor that, while too small to power the entire boat, is big enough to charge the batteries for submerged operations.
This is a novel approach to the problem of powering a mostly or entirely non-nuclear submarine while it’s underwater. Conventional diesel-electric submarines recharge their batteries using old-fashioned diesel engines. For that, they have to surface or at the least put up a “snort” air intake mast at periscope depth – potentially exposing them to detection and attack. The main alternative is to use nuclear power for propulsion, which produces a very capable boat but is very expensive.
Some navies mitigate this vulnerability by installing so-called “air-independent propulsion” systems in their smaller submarines. There are many different types of AIP. Some burn liquid oxygen. Others draw power from fuel cells. The Japanese navy builds attack submarines powered by lithium ion batteries, which can hold much more energy than normal batteries but are regarded as too dangerous to use in subs by most designers.
All AIP systems are complex, delicate and – when badly made – dangerous.
“China is known to have struggled with developing a more advanced, fuel cell-based AIP system as is currently in use with the German, South Korean and Singaporean navies, among others,” Dr Sarah Kirchberger and retired US Navy captain Christopher Carlson noted in a recent essay for the Center for International Maritime Security. “Neither has China deployed lithium-ion batteries aboard its submarines, as pioneered by Japan.
“Here, Chinese analyses have stressed unresolved issues regarding the danger of thermal runaway, which poses heightened risks of a severe fire aboard a submerged submarine,” Kirchberger and Carlson explained.
Inasmuch as a tiny nuclear reactor is less prone to runaway heat, it might be a better solution to submerged power for a navy that hasn’t mastered other forms of AIP. With its nuclear-charged battery, a Type 041 might be able to remain submerged for 20 days straight, according to Kirchberger and Carlson. That’s a 10-fold improvement in underwater endurance compared to traditional diesel-electric submarines.
The Chinese navy’s older non-nuclear submarines – its Type 035s and 039s – have struggled to get past the first island chain stretching between Japan and The Philippines without having to surface and expose themselves to US and allied anti-submarine forces.
“Any AIP system would help to alleviate this predicament,” Kirchberger and Carlson wrote, “but the maximum submerged transit speed of a submarine utilising a conventional AIP system is still only four to six knots.”
By contrast, a nuclear-battery AIP system “could support submerged transit speeds of up to nine to 10 knots,” the analysts added. Type 041s would be able to move quickly and stealthily past Japan into the deeper waters on the eastern side of the islands, where they could lay in wait for US and allied ships.
If and when China attacks Taiwan and if the Americans intervene, a squadron of Type 041s , taking position days before the first shot was fired, could intercept US Navy battle groups steaming west to join the battle.
Given the disruptive potential of the type, there’s every reason to expect the Chinese navy won’t let the apparent sinking of the first Type 041 deter it from eventually fielding nuclear-battery attack subs. Unless and until Chinese engineers can master other forms of air-independent propulsion, the nuke battery might be the technological key to developing a near-shore submarine force that can inflict real harm on the US and allied fleets.
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