Chinese scientists look to 6G to hunt submarines, testing device small enough to fit on drone​

• Defence researchers say sensors can identify extremely small surface vibrations produced by a low-frequency sound source in the open sea
• UAV-mounted platform could work in concert with other submarine detection methods such as a magnetic anomaly detector (MAD), microwave radar or laser

Published: 11:00pm, 29 Aug, 2023

An experimental Chinese terahertz device identified extremely small surface vibrations produced by a low-frequency sound source in the open sea. The developers said it would help pinpoint a submarine. Photo: Xinhua

China has tested the world’s first submarine-detecting device based on next-generation communication technology, according to researchers.

The terahertz device identified extremely small surface vibrations produced by a low-frequency sound source in the open sea, scientists involved in the experiment said.

These ripples were as tiny as 10 nanometres tall, well below the detection range of existing technology.

Tracking and analysing these waves can not only help find the submarine but also gather critical intelligence, such as noise signature or the submarine model, according to the researchers.

The technology “will have significant application potential in underwater vessel detection and other areas,” said the project team with the National University of Defence Technology. Their work was published on August 11 in the Journal of Radars, a Chinese-language peer-reviewed journal

Terahertz is a frequency range between microwave and infrared radiation. Terahertz technology has been proposed as a potential solution for achieving high data rates and low latency for the next generation of communication technology, or 6G.

Electromagnetic signals in this range not only carry a lot more information than existing communication methods but can collect information about the environment. Some airports in China, for instance, use terahertz screening devices to detect illegal items concealed under passenger’s clothes.

Generating powerful terahertz signals used to be difficult but thanks to an increasing investment in 6G in recent years, scientists in China and other countries have achieved breakthroughs that make mass application of the technology possible.

“A small unmanned aerial vehicle (UAV) platform has the advantage of good mobility, low cost and flexible deployment,” they said in the paper.

And it could work in concert with other submarine detection methods such as a magnetic anomaly detector (MAD), microwave radar or laser.

“As a supplement to existing detection methods, it can provide important information for the detection and identification of submarines,” they added.

The paper did not state when the experiment was conducted but said it was at an unspecified location off the northeastern city of Dalian in the Yellow Sea. At the time of the test, the weather was fair but breaking waves produced lots of bubbles, according to their paper.

The military scientists used an artificial sound source to simulate the noise emitted by a submarine. And to mimic drone flight, the submarine detector was carried by an extended arm of a research ship.

When a submarine is travelling at high speed, “it produces significant radiated noise that propagates to the water surface and excites surface vibration”, the researchers said.

But the disturbance is extremely weak by the time it reaches the surface. Separating it from the natural waves of the ocean was previously thought impossible.

In the test, the terahertz sensor picked up man-made ripples with amplitude ranging from 10 to 100 nanometres, depending on the sea conditions.

The team said the result was a miracle of both hardware and software.

The terahertz waves’ high frequency made it ultra-highly sensitive. The Chinese scientists say they have also developed the world’s first algorithm that can effectively identify nanometre-size ripples over the wobbling ocean.

The same technology could be used in submarine communication, they said.

A submarine sometimes needs to establish contact with friendly aircraft to coordinate their movements in a large-scale military operation. The captain could encode messages in surface vibrations too small to be detected by enemy forces.

“By detecting acoustically-induced surface vibration signals, it is possible to invert the information conveyed by underwater sound sources,” the team said.

The sea test results suggested the terahertz technology “has high signal resolution” for cross-medium communication, which remains a challenge to naval powers, they said.

The 6G technology has been used in separate close-range communication experiments between water and the air, which had also produced successful outcomes, they said.

China claims breakthrough in US nuke sub detection

https://asiatimes.com/2023/08/china-claims-breakthrough-in-us-nuke-sub-detection/

Chinese scientists claim existing tech allows for detection of the nearly imperceptible tiny bubbles nuclear submarines produce

By GABRIEL HONRADA

AUGUST 16, 2023

China may have landed on a way to better detect stealth nuclear submarines, a development that could jeopardize US operations in the contested South China Sea and more significantly undermine the survivability of its underwater nuclear deterrent. This month, South China Morning Post (SCMP) reported that researchers at the Chinese Academy of Sciences Fujian Institute of Research on the Structure of Matter discovered an ultra-sensitive submarine detector based on existing technologies that can detect traces of the most advanced submarine from great distances.

The science team, led by Zou Shengnan, published their findings in the peer-reviewed Chinese Journal of Ship Research, run by the China Ship Scientific Research Center and noted for its history of being at the forefront of ship and ocean engineering developments. SCMP notes that the Chinese science team used computer modeling to determine the possibility of detecting the near-imperceptible bubbles a nuclear submarine produces. It says that the extremely low frequency (ELF) signal generated by these bubbles could be many times stronger than the sensitivities of advanced magnetic anomaly detectors.

The bubbles form when a submarine cruises due to increased kinetic energy and a corresponding decrease in potential energy expressed as pressure. This happens because the system’s total energy remains constant but the balance between kinetic and potential energy shifts. The SCMP report notes that this creates turbulence and can lead to an electromagnetic signature through the magnetohydrodynamic (MHD) effect, with computer models showing that electric field signals could be detected around different parts of the hull. The researchers found that electromagnetic emissions produced by the cavitation bubbles fluctuate over time, generating a distinct signal in the ELF range from 49.94 Hz to 34.19 Hz.

Lead researcher Zou said that the findings could be used to provide a reference for selecting electromagnetic communication frequencies for high-speed submarines, as ELF signals can travel great distances, penetrate water and reach the ionosphere, which reflects them to the Earth’s surface. Some suggest the discovery could be a game-changer for anti-submarine warfare (ASW) operations. In an August 2020 article for The Strategist, Sebastian Brixey-Williams notes that modern ASW uses active and passive sonar with magnetic anomaly detection (MAD) to extract submarine signals from ocean noise, noting the methods are expected to remain crucial for the foreseeable future.

Submarines are significant metallic anomalies moving in the upper portion of the water column, producing sound and changing the water’s physical, chemical, and biological properties, disturbing Earth’s magnetic field and unavoidably emitting radiation in the case of nuclear submarines. Brixey-Williams notes that as sensor resolution, processing power and machine autonomy improve, the range of detectable signals will expand, making it possible to distinguish other previously indistinguishable signals.

He also notes that non-acoustic detection techniques have been known for decades but only recently became exploitable due to faster computer processors, noting that oceanographic models can run in real-time. Moreover, according to a March 2021 paper by the Nuclear Threat Initiative (NTI), the utilization of both commercial and open-source technologies such as commercial satellite imagery, synthetic aperture radar and social media disseminated tracking can enhance the identification of submarine fleets, track the development of submarines and submarine bases, and potentially gain insights into their patrol patterns and actions.

Given that, Roger Bradbury and other writers note in a March 2023 article that it’s very likely (90%) that oceans will become transparent by the 2050s, with at least a 75% chance in most modeled cases, with the software used in their analysis evaluating the estimates with a high certainty of above 70%. They stress that despite advancements in stealth technologies, submarines, including nuclear-powered ones, can still be detected in the world’s oceans due to parallel progress in science and technology.

Such developments may complicate US plans to hunt down and detect Chinese nuclear ballistic missile submarines (SSBN) patrolling the South China Sea. US nuclear attack submarines (SSN) are known to be operating in the South China Sea, with USNI reporting on November 2021 about the collision of the USS Connecticut against an uncharted seamount in the hotly-disputed semi-enclosed body of water.

USNI notes that the USS Connecticut is one of the US Navy’s three Seawolf-class SSNs, initially designed to take on Soviet submarines in the open ocean during the Cold War and since upgraded and modified to carry out some of the US Navy’s most sensitive missions, including shadowing China’s SSBNs. Asia Times reported in April 2023 that China now can mount round-the-clock SSBN patrols, keeping one of its six Type 094 SSBNs on patrol at all times. China’s JL-3 nuclear missile has a range of up to 10,000 kilometers, putting the US within closer range. Photo: Twitter / Handout

Those SSBNs are potentially armed with the new JL-3 submarine-launched ballistic missile (SLBM), which has a 10,000-kilometer range and allows China to hit the continental US from newly-developed and highly-protected bastions in the South China Sea. Although US SSBNs are considered highly survivable, the growing transparency of oceans and the possibility of China and Russia coming up with a breakthrough in submarine detection technology pose a rising threat to US dominance of the seas.

Despite those concerns, Matt Korda argues in a December 2020 article for Defense One that the US lead in submarine detection and stealth technology, favorable geographic position with no territorial chokepoints and the threat of US nuclear retaliation against an attack on its SSBNs ensures the continued relevance and survivability of US SSBNs as the country’s ultimate nuclear deterrent.

China deploys swarm of satellites to monitor military exercises in Australia Exclusive by defence correspondent Andrew Greene

https://www.abc.net.au/news/2023-08-18/china-deploys-swarm-of-satellites-to-monitor-military-australia/102742594

Hundreds of Chinese satellites are currently passing over Australia collecting intelligence on military training activities involving the United States and other regional partners. Commercial space data obtained by the ABC details the full scale of Beijing's surveillance on the recently completed "Exercise Talisman Sabre", as well as the "Exercise Malabar" naval drills now being held off Sydney. 

In July, Canberra-based defence company EOS Space Systems tracked three Chinese geostationary orbit satellites manoeuvring into position below the equator to monitor the Talisman Sabre war games across northern Australia.

China's Shiyan 12-01 satellite was detected drifting westerly over the northern Australia region, while the Shijian-17 and Shijian-23 satellites were tracked drifting easterly to observe multiple areas where exercises were being conducted. Since Exercise Malabar began on August 10, hundreds of much smaller low-orbit satellites (LEOs) have also been tracked completing thousands of flights at much lower altitudes over the Australian continent, focusing on the activity of warships around Sydney Harbour. 

"We've been collecting optical surveillance data on Earth observing Chinese satellites during the Talisman Sabre and Malabar exercises and what that's showing is quite a lot of activity surveying the ground during those events," James Bennett from EOS Space Systems said.

"We've seen over 300 satellites surveying ground-based activities and the number of overflights is over 3,000 since the start of the Malabar exercise centred around the Sydney Harbour bay area," Dr Bennett added.

Exercise Malabar involves joint naval exercises between Australia and warships from the United States, India and Japan. 

Space is considered an increasingly important domain for modern war-fighting operations across the globe, with Australia's recent Defence Strategic Review categorising it as a key element of a more integrated force. 

The data on China's recent space activity was collected using telescopes stationed outside Canberra and at Learmonth in Western Australia, which was then analysed by EOS staff to precisely identify the satellites and their flight paths.

Dr Bennett said the large number of geostationary and low-orbit Chinese satellites currently above Australia is providing Beijing with extremely detailed and "persistent observation" of what is occurring on the mainland and offshore.

"They can glean military intelligence on what the capabilities and equipment are, as well as processes of ground military activities; they can use this to drive a fair bit of intelligence on military operations in Australia."

The Defence Department has declined to give details on how it was monitoring and mitigating any risks posed by the substantial Chinese satellite activity over Australia during what it describes as "well-publicised, complex war-fighting exercises".

"The ADF takes prudent measures to safeguard the information security of Australian and participating forces," a defence spokesperson told the ABC.

"Defence tracks satellite movements as part of broader space domain awareness efforts." James Brown, the chief executive of the Space Industry Association of Australia, said the numbers of Chinese satellites dedicated to tracking the military exercises is in line with Beijing's growing presence in space.

"We've seen an extraordinary amount of Chinese intelligence surveillance and reconnaissance satellites being launched in recent years and Australia is a target for all that activity; space is becoming a critical domain for any future conflict and any potential conflict," he said. 

"They have hundreds of military and intelligence satellites which are not only collecting on Australia and its allies but in some cases dazzling Australian and allied satellites and manoeuvring closely to other satellites.

"Australia by contrast doesn't own any military satellites and certainly doesn't have any capability to collect the sort of imagery that China's been collecting over Sydney Harbour this week."

In June, Labor announced it would scrap a Morrison government program to develop new Australian satellites to gather data on natural disasters, agriculture and marine surveillance, as it searches for budget savings.

"The irony being that whilst China has had 300 satellites focused on collecting observation data Australia this week, our own government just cut the program that would've given us our first four able to do the same thing," Mr Brown said.