China’s Noisy Subs Get Busier — And Easier to Track*

The military’s latest secret assessment of China’s rapidly modernizing submarines has good news and bad news for the U.S. Navy. On one hand, the roughly 60 submarines in the People’s Liberation Army Navy (PLAN) fleet are spending more and more time on combat-ready patrols — signaling China’s increasing naval competence and growing seriousness about influencing the western Pacific Ocean.

On the other hand, the flurry of undersea activity gives American forces more opportunities to tail and examine Chinese subs. And U.S. analysts discovered a silver lining in the gathering strategic storm clouds. Chinese submarines are a hell of a lot noisier than anyone expected. The sound you hear is the Pacific balance of power tipping in Washington’s favor.

As recently as 2007, China’s diesel-powered subs and a handful of nuclear-propelled models managed just a few patrols per year, combined. Two years before that, none of Beijing’s undersea boats went on patrol. For years, the majority of PLAN submarines remained tied up at naval bases, sidelined by mechanical problems and a shortage of adequately trained crews.

As long as the PLAN’s submarines were idle, the U.S. Navy’s spy planes, surveillance ships and snooping subs had few opportunities to assess China’s undersea capabilities — and, most importantly, how much noise the Chinese generate while submerged and moving. Navies can use passive sonars to track submarines by the sounds they make. The louder a vessel, the easier it is to detect. And destroy.

With little information to go on, American intelligence officials had to guess. In cases like that, “you guess conservatively,” a respected U.S.-based naval analyst tells Danger Room on the condition of anonymity. The conservative estimates placed the latest PLAN subs roughly a decade behind the state-of-art for Russian submarines — and potentially 20 years behind U.S. undersea technology.

Now Chinese subs are patrolling more frequently. “Within the last year or two the Chinese have begun to deploy diesel boats more frequently into places like the Philippine Sea,” the analyst reveals. More and better data is flowing in from U.S. forces. With that data, the Navy conducted a fresh assessment of PLAN submarines. The unnamed analyst attended a classified briefing based on the assessment.

The assessment’s biggest surprise: Leaving aside the PLAN’s dozen imported Russian subs, new Chinese submarines can be detected at what’s known as the “first convergence zone,” a ring approximately 25 miles from an undersea vessel where outward-traveling sound waves pack close together.

During the Cold War, the U.S. Navy would arrange its own submarines in lines where each boat was 25 miles from the next, forming a sort of net to catch Soviet subs. With the introduction of the latest generation of quiet Russian diesel subs in the 1990s, the Americans thought that convergence-zone detection was no longer possible. But the Navy’s just discovered that China’s homemade subs are even louder than 20-year-old Russian boats. “Apparently they [U.S. subs] are making first convergence zone detections and holding them,” the analyst reports.

Assuming the Chinese stay with their current sub designs, American submarines should be capable of swiftly defeating Chinese boats in any potential future shooting war — helping clear the way for U.S. aircraft carriers to strike Chinese land targets. Combined with a slowdown in Chinese sub production, and the recent doubling of America’s submarine build-rate, the noise revelation could lead to a radical recalculation of the Pacific balance of power.

The U.S. Navy had a comfortable technological lead over the PLAN even before the increased Chinese sub activity fueled the recent intelligence coup. Now that lead has gotten even wider. And noisier.

* Article publicat al Danger Room de la revista Wired. El recomanem per poder conèixer l'equilibri de forces entre les flotes submarines dels Estats Units i la Xina al Pacífic.