Key Points and Summary – China leverages quiet, cost-effective Air-Independent Propulsion (AIP) submarines, primarily the Type 039A/C Yuan-class, to bolster its undersea fleet without relying solely on expensive nuclear boats.
-Produced rapidly, these Stirling AIP-powered subs offer enhanced stealth compared to older diesel-electrics, making them potent anti-ship platforms and threats within China’s near seas.
Type 093B Submarine from China. Image Credit: Screengrab.
-While lacking the endurance of nuclear submarines, their quietness, advanced features like angled sails, and ability to launch various missiles and torpedoes make them a formidable component of China’s naval strategy, especially concerning Taiwan and regional dominance.
The Yuan-Class Is China’s Big AIP Submarine Play
China does not have to worry about producing a massive fleet of expensive and difficult-to-produce nuclear-powered submarines.
It has two types of diesel-electric submarines that use the eerily quiet Stirling Air-Independent Propulsion (AIP).
The best of these models are the Type 039A and Type 039C Yuan-class subs.
There is also a technology demonstrator and trainer that employs AIP, called the Type 032 Qing-class, as well as a newfangled Type 041 Zhou-class that uses a hybrid nuclear/conventional powerplant, which is still in development.
The Yuan-class Leads the Way
The Yuan-class is one of the best, if not the best, Stirling AIPs in the world.
This could be the quietest conventional engine in use.
They are easier and cheaper to produce, and China has the shipyards to build them quickly.
The Chinese are making Yuan-class boats at a remarkable pace.
They can produce more than one at the same time, while the United States and allies struggle to keep up. Chinese shipyards in Wuhan and Shanghai are always busy pumping out conventional Stirling AIP boats in an impressive manner.
The Yuan-class can better “reflect” active sonar. They have angled profiles and sails for better stealthiness.
The Stirling AIP allows the Yuan-class to conduct missions covertly.
They do have to surface before they can sail outside the Second Island Chain, so that is a disadvantage that grants them less endurance than nuclear-powered boats.
There are at least 21 Yuan-class submarines on active duty, with the number increasing.
The SSK attack submarines can reach speeds of 20 knots while submerged. Not a bad speed, but slower than American Virginia-class boats.
The Yuan-class replaces the ancient and noisier Type 033 Romeo-class.
These Subs Have Better Tactical and Operational Mission Sets
The idea behind the Yuan-class, which first appeared in the media in 2006, was to create a weapon of death for surface ships.
Submarine-launched projectiles would take out enemy vessels when sneaking in close to launch anti-ship missiles.
The Yuan-class could also protect China in its massive coastline, in addition to the East China Sea, the Taiwan Strait, and the South China Sea.
It could defend against Chinese territorial claims and patrol around various islands and reefs that Beijing believes it rightfully owns.
Offensive Assets Could Bully Taiwan
There was once a belief that the Yuan-class was more for defensive purposes.
Still, as the belligerence against Taiwan and the United States grew, the People’s Liberation Army Navy realized that since the Yuan-class was so quiet, it could be used for more offensive operations and support a potential amphibious attack against Taiwan with land attack missiles.
Kilo-Class Submarine. Image Credit: Creative Commons.
Now the Yuan-class can take on more enemy submarines due to the Stirling AIP system and continue its primary function of removing adversarial warships from the sea.
Better Noise Reduction Compared to Older Diesel-Electrics
The Yuan-class has a tail design similar to the Type 39 Song-class. “The [Yuan-class is equipped] with upper and lower rudders and stern planes with a single propeller shaft. A pair of fairwater dive planes are positioned on the sail. The submarine is equipped with indigenously developed machinery rafts (shock absorbers) system that helped to reduce noise level by over 35 decibels. Additionally, the submarine is covered with rubber anti-sonar anechoic tiles to reduce the risk of acoustic detection. A new improved ‘C’ variant was also launched,” according to SeaForces.org.
Yuan-Class AIP Weapons
The Yuan-class has six 533mm torpedo tubes for Yu-6 torpedoes.
These boats can also fire YJ-18 land attack and d along with the YJ-8 projectile that can also destroy enemy vessels.
For combat operations, the Yuan-class used the Thales system for battle control that it imported from France in the 1980s and 1990s. Russia supplied many of its sonar systems early on in the program.
Could They Be Useful in a Taiwan Blockade?
The Yuan-class is also similar to the Russian Kilo-class.
Sails became more angular on the Yuan boats for improved stealth, featuring a new anechoic coating.
The Chinese have much confidence in the Yuan-class for its impressive design and quiet propulsion from the Stirling AIP. Since it is being built so rapidly, the U.S. Navy and its allies must be ready to defend against it. Taiwan could find itself surrounded by Yuan-class boats if the Chinese attempt to execute a blockade or quarantine on the island.
The Type 032 Qing-class, equipped with AIP, significantly influenced the Yuan-class and tested many of the new systems onboard.
These extensive submarine tests involved submarine-launched cruise missiles and new torpedoes.
Without the Qing-class, the Yuan-class would not have been produced in such significant numbers.
The Qings are experimental boats but are essential to the PLAN’s submarine force. Engineers and technicians know that they have a valuable asset for bringing new technologies on board the Yuan-class by utilizing the Qings for research and development.
The Type 041 Zhou-class is another experimental submarine in development that has endured a difficult start to its service life.
One sank in a shipyard in early 2024. The Zhou-class has an “X-shaped stern.” It’s around 279 feet long and displaces 3,600 tons. The Zhou-class is noteworthy for its diesel-electric propulsion combined with what may be a small nuclear reactor to charge the engine when more power is needed. The hybrid Zhou-class can remain submerged for longer periods and it is faster than the conventional AIP-powered Yuan-class.
China’s AIP Boats Look Like a Threat to the U.S. Navy or Any Navy
The best aspect of China’s AIP program is the lower cost and the manufacturing efficiencies. China pumps these boats out, and they have a significant advantage in cruise missile land attack and anti-ship missiles.
I see them as an asset to threaten Taiwan and to protect territorial claims. They have less endurance than nuclear-powered subs, but they are getting stealthier and are venturing out to seas beyond China’s coastal waters.
Keep an eye on these boats, they are only going to get better with the angled design and sonar-reflective materials. China has a hit on their hands with the AIP Yuan-class, and due to economies of scale in the shipyards, the Yuan-class is a worthy adversary that has a diverse skill set.
About the Author: Brent M. Eastwood
Brent M. Eastwood, PhD is the author of Don’t Turn Your Back On the World: a Conservative Foreign Policy and Humans, Machines, and Data: Future Trends in Warfare plus two other books. Brent was the founder and CEO of a tech firm that predicted world events using artificial intelligence. He served as a legislative fellow for US Senator Tim Scott and advised the senator on defense and foreign policy issues. He has taught at American University, George Washington University, and George Mason University. Brent is a former US Army Infantry officer. He can be followed on X @BMEastwood.
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