China has continued developing deep-diving "underwater gliders" despite a decades-old U.S. ban on exports of these vehicles to China out of concern China will put the torpedo-shaped gliders to military use.

Chinese media recently revealed a Chinese underwater glider named Haiyi-7000 that plunged 5,751 meters into the Mariana Trench, the world's deepest ocean trench, had aroused the interest of the People's Liberation Army (PLA), China's armed forces.

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That depth was about 250 meters shy of the world record for underwater gliding of 6,000 meters set in 2009 by a Seaglider developed by researchers at the University of Washington. Another UW Seaglider also holds the world's endurance record, operating for nine months and five days in the Pacific Ocean.

An underwater glider is an autonomous underwater vehicle (AUV) that uses small changes in its buoyancy to convert vertical motion to horizontal, thereby propelling itself forward with very low power consumption.

Underwater gliders, which are motorless and have wings, trace an up-and-down sawtooth motion through the water. This method of propulsion allows gliders to travel farther than AUVs powered by electric motor-driven propellers. The United States is the world leader in this technology while the U.S. Navy is one of its biggest backers.

A huge advantage of military underwater gliders is they can cruise noiselessly and autonomously beneath the surface without human intervention for days, months or even an entire year. All the while, the gliders keeps collecting military data or monitoring activity over a vast ocean area.

An underwater glider armed with an explosive warhead can also be programmed to attack underwater targets such as enemy submarines. But, like wolves, armed gliders can be unleashed in packs of up to 100 vehicles to deny enemy submarines access to specific areas.

The Haiyi-7000 is one of a number developed by a team from the Shenyang Institute of Automation, Chinese Academy of Sciences led by Prof. Yu Jiancheng.

It was launched from Tansuo-1, the academy's new 94 meter research ship, which is part of the government's rapidly expanding scientific research fleet.

A video of how underwater gliders work can be viewed here.

Tagsunderwater gliders, china, United States, Haiyi-7000, Mariana Trench, Seaglider, University of Washington, U.S. Navy, Tansuo-1