China completes testing on ‘deep-sea electro-hydrostatic actuator’ capable of slicing undersea cables as deep as 3.5 kilometers – new compact subsea vessel testing bridges the ‘last mile’ and could deploy in 2026

• China has successfully tested a new subsea cable cutting vessel
• The vessel uses a self-contained electro-hydrostatic actuator
• While designed for civilian purposes, the vessel has military application

China has completed the first successful test on a new deep-sea vessel that is capable of cutting subsea cables at a depth of 3,500 meters (11,483 feet).

A report from SCMP claims the new “Haiyang Dizhi 2” research vessel reportedly completed sea trials of a new 'deep-sea electro-hydrostatic actuator’.

The test “bridged the ‘last mile’ from deep-sea equipment development to engineering application,” the official China Science Daily reported.

Deep-sea cable cutter can slice through steel

Rather than relying on a connection with a surface vessel to provide the external oil piping used by hydraulic mechanisms, the deep-sea electro-hydrostatic actuator is a self-contained unit that houses the hydraulic system, electric motor and controls.

The vessel is touted as being designed for deep-sea engineering purposes. But like many technologies designed for civilian application, the vessel also has the potential to be used to sabotage subsea cables of nations that China views as hostile - such as the US.

Subsea cables are the arteries of modern digital life transporting over 95% of all international internet traffic - and with it much of the data our businesses and economies rely on. They are typically buried just beneath the sea floor at a depth of around 2,000 meters (6,561 feet), but can be laid deeper, particularly across large stretches of ocean.

Most subsea cables use a layered protective sheath of steel, rubber, and polymer, arranged to provide protection not only against the crushing pressures at the bottom of the ocean, but also against ship anchors, bottom trawling fishing vessels, and subsea vessels such as these.

This isn’t the first deep-sea cable cutter that China has revealed. The China Ship Scientific Research Centre (CSSRC) and the State Key Laboratory of Deep-sea Manned Vehicles has also developed a vessel that uses a diamond-coated grinding wheel to slice through sub-sea cables at depths of 4,000 meters (13,123 feet).

Subsea cables have become lucrative targets for espionage and disruption. In late 2024, two subsea cables in the Baltic sea were damaged, with Finnish authorities seizing a ship believed to belong to the Russian ‘shadow fleet’ as the responsible party. The UK government recently revealed that Russia launched undersea sabotage vessels in UK waters with the intention of targeting subsea cables in the North Sea.

Plans to lay cables in the Red Sea as part of projects such as Meta's 2Africa Pearls project have been delayed or cancelled due to hostilities between the US and Iran.

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