Sea Technology

MAY 2013

The industry's recognized authority for design, engineering and application of equipment and services in the global ocean community

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ducted from Ellesmere Island in 1996 in water depths that varied from 50 meters at the launch site to about 600 meters at the array site. Theseus is 10.8 meters long, has a diameter of 1.28 meters and a depth rating of 2,000 meters. Its large size is driven by the volume and buoyancy requirements of the fber-optic cable payload. With the full payload of 220 kilometers of cable, the weight of the vehicle is 8,600 kilograms. Theseus is powered by silver-zinc batteries and can reach speeds of 7 knots. At its designed cruising speed of 3.7 knots, the range is 920 kilometers. An endurance of at least 450 kilometers was required to lay the cable, allowing a return to the launch site and providing some reasonable margin for contingencies. A navigational accuracy of 1 percent of distance traveled, combined with a terminal homing range of 3 kilometers was needed to navigate the vehicle as it laid a 200-meter-long cable. On the Arctic deployment, Theseus completed two long under-ice missions, one of which was 460 kilometers in length—a record that still holds today. Navigational accuracy of the vehicle on average was 0.4 percent of the distance traveled. The Arctic operating environment is harsh. In 1996, the area of the ocean in which Theseus operated was completely ice covered, mostly by multiyear ice 3.5 to 10 meters thick, with ice keels extended to depths of 50 meters, water currents up to 25 centimeters per second and air temperatures of -40° C. Water temperature varied from -1° C at the launch site to 4° C near the bottom at the terminus. Theseus was transported to the Arctic in modular sections, which were delivered by helicopter to the fnal assembly point on the ice. It was reassembled in a large hut on the ice pack and then lowered through 3-meter-thick ice. Programmed to lay fber-optic cable along a preplanned route, Theseus proceeded with its mission, following the sea bottom at an altitude of 20 to 50 meters. While a full duplex communications link existed through the cable on the outbound leg, the vehicle was autonomous on the return leg. The total mission times were 63 and 52 hours, during which a total of 398 kilometers of cable was laid. Explorer Following market research and further study in the late 1990s, ISE determined that there was a need for smaller AUVs in the range of 4 to 6 meters long. Production was begun on the Explorer-class AUVs in 2003. The frst of these vehicles was delivered to France's ocean research institute, Ifremer, followed with a similar vehicle for Memorial University of Newfoundland, and another for the University of Southern Mississippi for scientifc research in the Gulf of Mexico. The experience with these AUVs provided confdence to build deeper-diving, longer-range AUVs. In 2008, ISE began production of the Arctic Explorerclass of AUVs. These vehicles were used in 2010 and 2011 for missions in the Canadian Arctic. Their specifc task was to obtain data that supported Canada's submission to the In- (Top) An Explorer under-ice AUV at work in the Arctic in 2010. (Photo Credit: Defence Research and Development Canada) Explorer AUVs at ISE headquarters in Canada. (Photo Credit: ISE Ltd.) 42 st / May 2013 www.sea-technology.com

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