China develops magnetic wake technology against submarine stealth

One more piece of the A2AD kill web falls in place

One of the key naval advantage the US enjoys is its stealth nuclear submarines. The Virginia and Seawolf Class submarines are the most potent and stealthiest attack subs in the world.

As China outnumbers US in naval surface ships and the US main traditional power projection tool, the aircraft carrier groups, are increasingly vulnerable to Chinese hypersonic missiles, its submarine fleet is considered as the tactical superiority over Chinese navy.

Despite its potency, subs that can be found can be easily destroyed as they move in very slow speed. Therefore, the single most important feature of a sub is its stealth, the ability to evade detection. The most advanced US subs deploy highly sophisticated sound-dampening coatings and silent propulsion systems that are extremely difficult to detect by traditional acoustic methods like sona.

One recent development in submarine detection technology, developed by the famed Northwestern Polytechnical University in Xi’an, is China’s answer to counter the US nuclear submarine stealth advantage.

Northwestern is one of the prestigious “seven sons of national defense” military-affiliated universities and is on the leading edge of China’s military aerospace and naval innovations. It is responsible for developing some of the most advanced hypersonic missiles and drones, for example.

The breakthrough involves a novel technique called Magnetic Anomaly Detection (MAD), which detects magnetic wakes left by even the stealthiest submarines.

A team led by Associate Professor Wang Honglei discovered that submarines leave magnetic wakes that can be detected using airborne magnetometers. The V-shaped disturbance, called the Kelvin Wake, is created when submarines slice through water. This wake, previously studied for radar-based imagery detection, generates a faint but detectable magnetic field when seawater ions, disturbed by motion, interact with the Earth’s geomagnetic field.

Using numerical simulations, the researchers have quantified how these magnetic signatures vary with a submarine’s speed, depth and size.

Traditional sonar systems face significant limitations in detecting the most advanced stealthy submarines, particularly in shallow waters like the Taiwan Strait. Low-frequency sonar loses effectiveness due to the lack of spherical sound spreading, causing energy to be absorbed by the seabed and surface reflections. This sound channelling limits the detection range and accuracy.

In addition, modern stealth subs evade traditional acoustic detection via sound-dampening coatings and pump-jet propulsion.

However, the magnetic wakes persist long after a submarine passes, essentially leaving footprints in the ocean’s magnetic fields. These magnetic wakes cannot be silenced, offering a persistent trace of a submarine’s path.

MAD solves the shortcoming of traditional sonar detection technologies, especially when combined with advancements in artificial intelligence and sensor technologies.

While no single technology guarantees submarine detection, China is weaving magnetic tracking into a multi-layered “kill web” that includes acoustic arrays, satellites, drones, seabed sensors, and AI algorithms to fuse data streams.

As China develops the capability to neutralize US stealth submarine advantage, the last piece of the puzzle to achieve full A2AD is falling in place.