The team of researchers, led by engineer Li Yuhang with the 713th Research Institute of China State Shipbuilding Corporation, used real-world environmental data collected by Chinese sensors in the South China Sea to look at water surface wake in a bid to “offer some suggestions for the safe navigation of Chinese submarines”. They detailed their research in a peer-reviewed paper published in the Chinese Journal of Theoretical and Applied Mechanics on May 27.
These fine ripples can give clues to important information such as the submarine’s position, speed, direction or even make. However, the formation and spread of these waves are greatly influenced by environmental factors like ocean currents, temperature and salinity, resulting in significant differences in signal strength and patterns across different sea areas.
Due to military sensitivity, publicly available research in the past has focused on theoretical models while avoiding real-world data.
“Currently, research on [submarine] water surface wake in the actual ocean is still relatively scarce,” Li and his colleagues wrote in their paper.
The novelty of Li’s work lies in the use of real data from the South China Sea for the first time. This has allowed scientists and engineers to conduct “systematic research on the characteristics of the water surface response wave field excited by submarines in the actual ocean”.
And they obtained some unexpected results.
When navigating in this area, the Chinese researchers found that submarines around 100 metres long (328 feet) and more than 10 metres in diameter – similar to the size of SSN-22 – may resonate with the surrounding water, causing unexpected disturbances.
When the submarine’s depth is 100 metres and the speed exceeds 20 knots, a large number of ripples with heights up to several centimetres can be generated on the ocean surface, according to their estimate.
The speed reading of the SSN-22 before the collision appeared in a footnote of the US military investigation report released in 2022. The investigators said the Connecticut was travelling at high speeds in the South China Sea as it headed towards Okinawa for a “humanitarian evacuation” when the mishap occurred.
While the Seawolf-class is the most advanced attack submarine of the US military, its design was completed 40 years ago when surface ripple detection mainly relied on visual observation. High-speed cruising has been considered safe even if it is close to the enemy’s coastline.
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This particular discovery could add another challenge to any potential submarine warfare in the South China Sea. Before launching a surprise attack on land or sea targets, submarines generally need to enter preset positions at speeds of two to eight knots and rise to a depth of less than 100 metres to release submarine-launched missiles, according to some military experts.
If a submarine’s position is exposed during this period, it could have disastrous consequences, they said.
Anti-submarine forces rely on different reconnaissance platforms to confirm a target, including traditional sonar, seabed sensor networks, air-based geomagnetic anomaly detectors, high-precision gravity detectors and lasers.
Significant progress and breakthroughs have been achieved by scientists and engineers in detection technology in these areas in recent years, posing serious challenges to the stealth combat capabilities of traditional submarines.