China has developed a long-range underwater drone designed to extend the range of its activities in the South China Sea.
The autonomous underwater vehicle (AUV) Sea-Whale 2000 recently completed a non-stop 37-day test run in the South China Sea over a distance of 2,011km (1,250 miles), the Chinese Academy of Sciences said in a statement on Tuesday.
The mission path remained a secret, but with that range the drone could easily cover the Paracel and Spratly islands " claimed by China but also by its neighbours " and return to China's naval base in Sanya, Hainan.
The torpedo-shaped drone, which is about three metres long and weighs 200kg (441lbs), is equipped with artificial intelligence technology and a wide range of sensors to detect temperature, salinity, current, trace chemicals, underwater visibility and biological activity.
It can dive 2,000 metres below the surface and cruise at speeds of up to 1.2 metres per second.
"Sea-Whale 2000's development is to meet the long-term deep-sea mobile survey needs in the South China Sea," said an announcement by the programme team, led by Dr Huang Yan of the Chinese Academy of Sciences' robotics institute in the northeastern Liaoning province.
The drone is able to run "a long-endurance mission for weeks with one launch, and can accomplish multiple working mode missions", they said.
They declined to elaborate on why China is building the drone for the South China Sea.
Sea-Whale 2000 is not the world's longest-range AUV. For instance, Britain's Autosub Long Range, nicknamed Boaty McBoatface, is claimed to have a 6,000km range with endurance of up to six months.
But China is gearing up for a race in developing unmanned submarines and is among the first to have put the technology into service.
To extend the drone's range, Huang and colleagues came up with an unusual hybrid structure that would allow it to run in different modes to reduce energy consumption. It can cruise like a conventional submarine, glide up and down, or ride the tide like a drifting bottle.
The drone uses a low-power central processing unit from STMicroelectronics, a semiconductor company based in Europe, and communicates using a global satellite network run by Iridium Communications, an American firm.
China is not the only country concerned with its capabilities in the South China Sea. Over the decades, the United States and its allies have established extensive surveillance networks in the region, with military and scientific research vessels conducting regular patrols in disputed parts of the sea to gather intelligence.