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Low-Cost Launch and Recovery System For Qianlong I AUV
China Develops System to Aid Deep-Sea Manganese Nodule Detection

Jianguo Wu

Huixi Xu

Jian Liu

The Qianlong I AUV.

The ability to safely launch and recover an AUV is critical, especially for large-scale, deep-sea missions. Qianlong I is a 6,000-meter-rated Chinese AUV that performs near-bottom topography measurement, undersea photography and hydrological parameter measurement. When the AUV began development in 2011, a launch and recovery system was developed alongside as well.

Qianlong I operates from the RV Ocean VI, which is capable of dynamic positioning and has an A-frame located on the stern of the deck. The AUV's launch and recovery system was designed to use the A-frame to complete operations without having to reconstruct the RV. The system allows operation in up to sea state 4 without small boat assistance, reduces cost and is adaptable to other ships.

Qianlong I is a deep-sea exploration AUV developed by China that evolved from the CR01 and CR02 deep-sea underwater vehicles, mainly used for seabed manganese nodule detection up to 6,000 meters depth. Qianlong I is capable of autonomous navigation and obstacle avoidance in the complex underwater environment. It can travel for 24 hours at the speed of 2 knots and can carry a side scan sonar, underwater cameras, and sensors for CTD, dissolved oxygen, turbidity, Eh, pH and other environmental parameters. It is capable of acoustic communications and long baseline navigation. Qianlong I weighs 1,500 kilograms, with a length of 4.5 meters and diameter of 0.8 meters. It has two rings on the back, spaced 2.2 meters apart, for AUV recovery.

The height from RV Ocean VI's A-frame lifting points to the deck is 6.5 meters, and the maximum distance of the lifting point out to the stern is 7 meters. The A-frame has a dynamic lifting capacity of 16 tons. The distance from the recovery deck to the sea surface is approximately 2.7 meters. The operational area of the deck is approximately 5.2 by 6 meters, and there is a cable winch assembly on deck.

Launch Operations
Launch operations are relatively easy to complete. Two lifting belts are connected between the A-frame, and two cables are set on each lifting ring of the AUV. Meanwhile, the surface vessel sails at a low speed of about 3 knots. The A-frame lowers the AUV into the water, while a cable keeps the AUV from swinging. Once the AUV is in the water, a pin rod is pulled out of the lifting belts, which separates the AUV from the belts. The AUV then sails in the water, the surface vessel leaves the launching points, and the launch process is complete.

Recovery Operations
In addition to the A-frame and cable winch assembly on Ocean VI, the recovery process requires three other main elements: a rope-throwing device, a rope-capture device, and a lifting lock and lever.

The rope-throwing device throws a projectile head and pulls rope out of the AUV. When the AUV rises to the sea surface after a detection mission, the crew sends a rope-throwing command to the AUV, which triggers a current signal to launch the rope-throwing device. The projectile head is made of syntactic foam for buoyancy, and the rope is less dense than seawater, therefore the projectile head and rope can float on the sea surface. To continue this article please click here.

Jianguo Wu is an associate researcher at Shenyang Institute of Automation, Shenyang, China. He received a doctorate in mechanical engineering from Tianjin University in Tianjin, China, in 2010. His research interests include general AUV technology, underwater gliders and AUV docking technology. He has been involved in the development and production of various ocean vehicles since 2006. He is responsible for mechanical systems of the Qianlong I AUV.

Huixi Xu received a master's degree in mechanical engineering from Northeastern University in Shenyang, China. He is an associate researcher at Shenyang Institute of Automation, Shenyang, China. His research interests include AUV general technology, deep-sea AUVs and long-endurance AUVs. He has been involved in the development and production of various ocean vehicles since 2002 and is chief designer of the Qianlong I AUV.

Jian Liu was born in 1962 and received a master's degree from Dalian University of Technology in Dalian, China. He is a researcher of Shenyang Institute of Automation, Shenyang, China. His research interests include AUV general technology and AUV control. He is the chief designer of the Qianlong I AUV and CR02 AUV. He has 13 years of ocean experience with deap-sea AUV research and operations.

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