Chinese researchers claim to have discovered a new terahertz-based submarine detection technique, which, potentially coupled with advancements in sensor and drone technology, could pose a significant new challenge to US submarine operations and extended deterrence guarantees.
The South China Morning Post (SCMP) reported last month that China has tested the world’s first submarine-detecting terahertz device based on next-generation communication technology. Researchers from China’s National University of Defense Technology published their findings last month in the Chinese-language peer-reviewed Journal of Radars.
The device identified tiny surface vibrations, reportedly as tiny as 10 nanometers, produced by a low-frequency sound source in the open sea. These waves can help find submarines and gather critical intelligence, such as noise signatures that can be analyzed to identify a submarine’s model. According to the research team, the technology “will have significant application potential in underwater vessel detection and other areas.”
Terahertz is a frequency range between microwave and infrared radiation. It has been proposed as a potential solution for achieving high data transmission and low latency for upcoming 6G communication technology, which is predicted to provide theoretical maximum speeds up to 100 times faster than 5G.
Terahertz screening devices are currently already being used in some airports in China to detect illegal items that may be concealed under a passenger’s clothes.
The SCMP report says that generating powerful terahertz signals was a challenging task for the research team. However, due to increased investment in 6G technology, scientists in China and elsewhere have recently made significant breakthroughs in its mass application.
China has also recently made substantial advancements in submarine detection technology, with significant operational and strategic implications.
Last month, Asia Times reported that researchers from the Chinese Academy of Sciences Fujian Institute of Research on the Structure of Matter have developed a highly sensitive submarine detection system that can detect even the faintest traces of advanced submarines from significant distances.
The science team published their findings in the peer-reviewed Chinese Journal of Ship Research, run by the China Ship Scientific Research Center, noted for its history of being at the forefront of ship and ocean engineering developments.
The system uses computer modeling to determine the possibility of detecting the highly subtle bubbles produced by nuclear submarines, which are significantly stronger than the sensitivities of advanced magnetic anomaly detectors.
The electromagnetic emissions of cavitation bubbles vary over time and generate a unique signal in the extremely low frequency (ELF) range. This discovery could be a game-changer for anti-submarine warfare (ASW) operations, as modern ASW uses active and passive sonar with magnetic anomaly detection (MAD) to extract submarine signals from ocean noise.
These advanced technologies can expedite the integration of drones in ASW operations. Drones offer a viable solution to augment ASW missions due to their low cost, ability to operate remotely, endurance and stealth, significantly improving their effectiveness.
In an April 2023 article for TS2, Marcin Frąckiewicz notes that integrating drones in ASW operations has become a promising solution to counter growing underwater threats.
Frąckiewicz says drones offer several advantages, including their extended airborne endurance, persistent surveillance and reconnaissance capabilities and stealth. He mentions that they can be equipped with advanced sensors and payloads, such as synthetic aperture radar (SAR), electro-optical/infrared (EO/IR) cameras and MAD, all of which can further improve their detection capabilities.
Frąckiewicz mentions drones reduce the risk to human operators, allowing them to cover hostile areas without putting lives in danger. He says this feature is particularly beneficial in ASW operations, where the threat of enemy submarines is always present. He adds that the cost-effectiveness of drones allows military forces to deploy more of them, increasing their coverage and enhancing their overall ASW capabilities.
In line with that, Asia Times reported in September 2022 that China may plan to deploy its new large-scale unmanned submarines in the South China Sea. This move aligns with the latest sensor technology developments and the benefits of using drones in ASW operations.
Satellite imagery showed two of China’s extra-large uncrewed underwater vehicles (XLUUV) at Sanya Naval Base on Hainan Island, which geographically juts into the contested South China Sea. However, China’s intentions for the new subs are still unclear, sparking speculation on how it may use the platforms in future naval operations.
The first XLUUV is approximately 16 meters in length and two meters wide. It has a sleek front and two tail propellers placed next to each other. This suggests the vessel may be connected to the HSU-001 XLUUV introduced in 2019.
The HSU-001 can carry smaller UUVs, sensors and naval mines, and is mainly intended for intelligence, surveillance and reconnaissance (ISR) purposes. It may also perform anti-submarine operations by actively searching and tracking enemy submarines without endangering manned surface vessels or submarines.
These developments could create difficulties for the US to locate and track Chinese nuclear ballistic missile submarines (SSBN) that are patrolling the South China Sea. According to reports, American nuclear attack submarines (SSN) are already operational in the region. In November 2021, the USNI reported an incident where the USS Connecticut collided with an uncharted seamount in the contested waters.
Conversely, various commercial technologies such as satellite imagery, synthetic aperture radar and social media disseminated tracking have increased transparency of the world’s oceans. These technologies, alongside China’s advancements in ASW, may threaten the survivability of US SSBNs, which in turn would have significant implications for US strategic stability.
In a 2019 report for the Center for Strategic and International Studies (CSIS), Ari Kattan notes that US adversary advances in ASW can destabilize America’s extended deterrence commitments, which have been successful in establishing security guarantees with countries like Japan and South Korea and various NATO members since World War II.
Kattan notes these guarantees have discouraged many nations from acquiring nuclear weapons, leading to fewer nuclear weapons worldwide and thus lower risks for nuclear-armed states to go to war.
However, he notes that if the US had reduced confidence in its second-strike capabilities, it would feel less secure and less willing to engage in war-related behavior, potentially inducing US allies to develop their own nuclear weapons, leading to the degradation of the global nuclear nonproliferation regime and unpredictable consequences for international security.