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www.sea-technology.com July 2014 / st 49 T he ability to safely launch and re- cover an AUV is critical, especially for large-scale, deep-sea missions. Qianlong I is a 6,000-meter-rated Chi- nese AUV that performs near-bottom topography measurement, undersea photography and hydrological parameter measure- ment. 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 recon- struct the RV. The system allows operation in up to sea state 4 without small boat assistance, reduces cost and is adapt- able to other ships. Background 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 param- eters. 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 me- ters. 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 con- nected 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 low- ers the AUV into the wa- ter, 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 sig- nal 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 foat on the sea surface. The rope-capture device salvages the projectile head and rope from the sea surface, and it has two modes: manual and pneumatic. If the distance between the vessel and the rope is greater than 30 meters, the pneumatic mode is used; otherwise, the manual mode is used. When the projectile head and rope are thrown out of the AUV and onto the sea surface, the RV slowly steers toward the AUV, making sure the vessel's side is parallel with the rope, then the crew uses the rope-capture device to bring the projectile head and the Low-Cost Launch and Recovery System For Qianlong I AUV China Develops System to Aid Deep-Sea Manganese Nodule Detection By Jianguo Wu • Huixi Xu • Jian Liu (Top) The Qianlong I AUV. (Bottom) The us- age of the pin rod in AUV launch operations.