The US Navy’s nuclear-powered submarines are considered some of the world’s most stealthy war machines. However, with advancements in submarine-detection technology, Chinese scientists are claiming that they can now detect even the most-silent nuclear submarines.
Researchers from Northwestern Polytechnical University (NPU) in Xian claim they can now detect even the quietest submarines by harnessing the magnetic fields created by their wakes (complex, turbulent flow fields generated around the moving vessel). They reckon this novel technique can revolutionize naval combat, as reported by the Hong Kong-based South China Morning Post.
The team, led by associate professor Wang Honglei has reportedly modeled the Kelvin wake, a V-shaped surface disturbance produced by submarines as they cut through the water. The report says, “This wake, previously studied for radar-based imagery detection, generates a faint but detectable magnetic field when seawater ions – disturbed by the vessel’s motion – interact with the Earth’s geomagnetic field.”
The researchers measured the changes in these magnetic signatures with submarine size, depth, and speed using computer simulations.
“For example, increasing speed by 2.5 meters per second (8.2 feet per second) boosts magnetic intensity tenfold; reducing the depth by 20 meters (66 feet) doubles the field strength; and longer submarines produce weaker fields, while wider hulls amplify them.”
According to Wang and his colleagues, the wake’s magnetic field can reach 10⁻¹² tesla for a Seawolf-class submarine traveling at 24 knots (12.5 meters per second) and 30 meters (98 feet) depth. This is “well within the sensitivity range of existing airborne magnetometers.” Detailed in the peer-reviewed Journal of Harbin Engineering University on December 4, the team’s approach makes use of a crucial flaw: “Kelvin wakes cannot be silenced.”
The research paper singled out the Seawolf-class submarine for its study. Interestingly, the US Navy’s nuclear-powered fast-attack submarine, the USS Seawolf, was spotted in China’s backyard–in Yokosuka, Japan, last October.
The Seawolf-class subs have the reputation of being one of the most powerful, lethal, complicated, and expensive underwater combat platforms of the US Navy designed for high-end missions close to an adversary’s shore. Known as “silent killers” due to their capability to dive far and pursue targets for months, Seawolf-class submarines are equipped with a significant quantity of Tomahawk missiles and torpedoes that can seriously endanger China’s coastal infrastructure and the PLA Navy.
One of the Seawolf-class submarines—the USS Connecticut—crashed into an underwater seamount in the contentious South China Sea in October 2021. Since the submarine was on a classified mission, its whereabouts were not known. This triggered a fierce reaction from China, with the Chinese state-owned publication Global Times publishing a report criticizing the US for not releasing crucial information about the accident of a nuclear-powered submarine.
Wang said in his paper that until now, militaries have relied on sonars to detect acoustic signatures of submarines. However, in contrast to acoustic detection, which modern submarines evade via sound-dampening coatings and pump-jet propulsion, the magnetic wakes linger long after a submarine passes, creating “footprints in the ocean’s magnetic fabric.“Thus making submarine detection a lot easier.”
However, this is barely the first time that Chinese scientists and researchers have claimed to have developed a technology capable of detecting submarines. As tensions between China and the United States continue to mount and the threat of conflict looms large, Beijing is on a mission to build anti-submarine warfare capability. The first step, however, would be detection.
China Is Building Submarine Detection Capability
Unlike conventional submarines, which are typically diesel-electric powered, nuclear-powered submarines (SSNs) have many advantages. For instance, they can operate over greater distances, dive deeper, and move faster. Therefore, they are far more difficult to detect and eliminate than conventional submarines.
The United States, for one, only operates nuclear-powered submarines. With military bases located all over the world and two vast oceans separating it from the rest of the world, the United States needs nuclear-powered submarines for their extended range. Additionally, these submarines are routinely deployed to accompany American aircraft carrier battle groups across the world’s oceans.
This means that in a potential conflict between the US and China, US nuclear submarines will have a significant role to play. Loro Horta, an academic and author from Timor Leste, explained in a previous EurAsian Times op-ed: “In a possible conflict over Taiwan, the 14 SSNs the US currently operates, not all deployed in the region, would have to get closer to the Chinese coast to support their surface fleet and hunt for Chinese submarines.”
China has, therefore, focused its attention on building submarine detection capability. Last year, for instance, a team of scientists from Shanghai Jiao Tong University claimed they could locate and monitor undersea military targets by analyzing low-frequency emissions. They said they had developed a detector—the size of a truck—that was able to pick up weak electromagnetic waves from a rotating propeller at a distance of around 20 kilometers.
The scientists claimed that with a detection range around ten times longer than anything previously documented, the device could offer China a competitive edge in the escalating underwater arms race. The team said that the technique is to monitor the seabed to detect electromagnetic signals emitted by the submarines. The findings were published in the Chinese peer-reviewed Journal of Vibration and Shock.
Later, in 2024, another team of scientists claimed that they used high-energy microwave synthesis technology to create a radio-emitting source in the sky, which led to a breakthrough in submarine detection.
They stated that this virtual signal source, sometimes known as a ghost radar, is capable of continually emitting electromagnetic waves while moving at almost the speed of light. The findings were published in the Chinese academic journal Modern Radar on November 25.
Some analysts believe that anti-submarine warfare will become so sophisticated in the next 20 years that the submarine will become obsolete. Although this is debatable, it is undeniable that new technology is making submarine operations much riskier.
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