A “National Defense Key Laboratory of Autonomous Underwater Vehicle Technology” has been established at Harbin Engineering University. Published papers focus on sensing and navigation for autonomous underwater vehicles, and techniques for controlling fleets of them over a wide area.
“They're putting a lot of money, a lot of engineers into this field, “says Lyle Goldstein, strategic researcher at the U.S. Naval War College's China Maritime Studies Institute. “They're energized because they know there's a gap in underwater capability, and this is a chance to leapfrog ahead.”
Rather than having propellers or thrusters, a glider adjusts its buoyancy by pumping gas in or out of an external bladder, then glides a shallow path as it rises or falls. Average speed is typically just half a knot, but with the endurance to cross oceans. Since their development in the 1980s in association with the U.S. Navy, gliders have won acceptance. Three U.S. companies now offer different versions.
The Navy is the biggest user, with up to 150 vehicles on order over three years for the Littoral Battlespace Sensing-Glider program. Teledyne Webb is supplying the gliders, which will carry out a variety of missions including measuring underwater conditions affecting sonar and communications.
A U.S. Defense Security Service report claimed that in 2010 “East Asian and Pacific-affiliated collectors targeted underwater gliders specifically” for technology espionage, and China appears to be catching up in the glider race.
In 2011 China tested its first locally designed glider, the Sea Wing, developed at Shenyang Institute of Automation. This deep-water research vehicle reportedly carried out several successful missions in the Western Pacific, diving to 2,700 ft.
Many more designs are in the pipeline. The Petrel is a hybrid craft from Tianjin University, with a propeller as well as a buoyancy engine, using the propeller for rapid, short-range manoeuvring. Petrel is undergoing field trials at Fuxian Lake.
Other Tianjin projects are extending the gliders' endurance. The Dragon has a fuel cell rather than lithium batteries, with perhaps a mission duration measured in years. Another Tianjin glider will have a 'temperature difference engine.' This is similar to the prototype thermal glider pioneered by Teledyne Webb, which extracts energy from the temperature variation between sea water layers at different depths. It has the potential to power a glider indefinitely.
Researchers at Northwestern Polytechnic University at Xian are improving glider agility by giving them wings that can move independently. The researchers claim this design is faster and more efficient than fixed-wing gliders, as well as more maneuvrable.
A second Xian project takes the idea further, with flapping wings that act like a turtle's fins to provide extra propulsion. This model is now starting laboratory trials. China excels in the field of “robotic fish” with flapping fins. Gliders incorporating this technology could put on a burst of speed without compromising stealth, while retaining glider endurance for long missions.