Philippines investigates ‘acoustic glider’ recovered off Ilocos province

MANILA – The Philippines is investigating a suspected Chinese acoustic glider recovered by a fisherman floating at sea off the northern Filipino province of Ilocos Norte.

A fisherman has recovered this acoustic glider off the northern Philippine province of Ilocos Norte.

The winged torpedo-like submersible was handed over by local village officials to the police.

Security officials have not issued any statement about the recent find, but according to reports by The Maritime Executive magazine, Chinese underwater gliders operate throughout the Indo-Pacific, from the Bay of Bengal to the Bering Sea, from high seas to sovereign waters. These submersibles are being deployed in droves to collect information about the marine environment.

Gliders move up and down in the water column by adjusting their buoyancy while their “wings” enable them to move forward at an angle. As anti-submarine warfare platforms, gliders offer several advantages.

 

Due to their low power requirements, some gliders can operate at sea for months at a time. Because of the simplicity of their design, gliders are also comparatively cheap - an important attribute since they must be deployed in large numbers to be effective. Unlike fixed undersea sensors, gliders can move to where they are needed (albeit very slowly, at just about one knot).

 

The gliders can maintain regular communications with their operators by transmitting their location (and other information) and receiving new commands when they surface at the end of a dive.

 

Traveling underwater in a vertical sawtooth pattern, gliders use onboard sensors to measure characteristics of the ocean such as temperature, salinity, dissolved oxygen, and current speed at different depths to generate water column profiles. This data indirectly bolsters the capabilities of the People’s Liberation Army Navy (PLAN) by expanding its tactical understanding of the ocean environment, according to the reports.

 

The reports said scientists and engineers in China are also developing a new generation of gliders that could play a far more direct role in naval combat by detecting enemy submarines. Since 2014, experts at the PLAN Submarine Academy, working with colleagues at civilian institutions, have been equipping Chinese gliders with passive acoustic sensors. Chinese language records of their activities show a determined effort to adapt this technology for anti-submarine warfare, an enduring weakness for the PLAN - one that, if remedied, could shake U.S. conventional deterrence in the Western Pacific.

 

Chinese scientists also had to develop a vector sensor that could reliably operate in the high-pressure environment of the deep ocean. Since many countries prohibit the sale of acoustic sensors to China, researchers could not simply import a foreign product.

 

In 2019, researchers tested the new sensor in the South China Sea at depths of 800 meters and 1,200 meters with promising results. By early 2000s, experts at Harbin Engineering University have conducted path breaking research on vector sensors. The team at the Submarine Academy built off their work to develop a deep water vector sensor.

 

Since 2018, the Dolphin has undergone multiple tests in the South China Sea, in the deep water northwest of the Paracel Islands. To date, Chinese researchers have only tested the glider’s ability to detect surface ships, which are obviously much louder than submarines.

 

Two series of tests conducted in May and June of 2018 focused on reducing self-noise. Since then, the team has sought to refine the capabilities of the glider’s onboard systems. The most recent known tests conducted in January of 2020 offer a gauge of the Dolphin’s current capabilities. They also show the scale of the PLAN’s commitment to developing these platforms.

 

According to the PLAN researchers working on the project, they would be used to “complete tasks such as autonomous detection, tracking, attribute discrimination, and sending back information on moving targets in sensitive waters or areas of denial.”

 

The program director, Rear Admiral Da Lianglong, likened them to a front-door “security system.” One of his briefing slides from a 2019 presentation suggests that the PLAN intends to deploy them in the relatively quiet, deeper waters of the Philippine Sea and northern South China Sea, operationally-important areas where China lacks islands to build fixed undersea arrays.

 

The Dolphin Project

 

While the advantages of gliders seem obvious, there are also many technical challenges that must be overcome before they can be used in anti-submarine warfare. Since 2014, the PLAN Submarine Academy, working in conjunction with scientists and engineers from Tianjin University and the Qingdao Pilot National Lab for Marine Science and Technology have methodically surmounted many of these challenges and now possess a capable prototype glider, the “Dolphin,” which has already undergone several rounds of testing in the South China Sea.

 

The Dolphin is based on the Haiyan glider developed by researchers at Tianjin University. Like most sea gliders, the Haiyan is a tubular robot with wings and a visible antenna. However, it is somewhat unusual in that it is equipped with a small propeller, a useful feature if needed to surface quickly in the event of a potential submarine contact. Chinese oceanographers have already deployed Haiyan gliders within the first island chain and beyond. A specially designed Haiyan variant (Haiyan-X) is capable of diving to tremendous depths, including the bottom of the Mariana Trench. Another variant (Haiyan-L) has been built for greater endurance, purportedly up to five months of continuous operations.

 

The Dolphin looks like a typical Haiyan glider, except for a vector sensor protruding from its nose. Within the body of the glider, forward of the batteries, is its signal processor indicating that the platform is designed to autonomously detect, classify, and locate undersea targets, not merely to record and transmit raw data for interpretation elsewhere.

 

The Dolphin project is led by the Naval Undersea Warfare Environmental Research Institute at the PLAN Submarine Academy. It is overseen by the Institute’s Director, Rear Admiral Da Lianglong, perhaps the PLAN’s most accomplished expert on undersea science and technology. (Mindanao Examiner, The Maritime Executive)