Feature ArticleAUVs Survey The Canadian Arctic
By Dr. James McFarlane • Raymond F. Murphy
Explorer AUVs on ISE's RV Researcher in Nanoose Bay during sea trials, just prior to the 2010 missions in the Arctic. (Photo Credit: ISE Ltd.)
As a Canadian manufacturer involved in the development of subsea technology, the ice-covered Canadian Arctic became a natural priority for Port Coquitlam, Canada-based International Submarine Engineering Ltd. (ISE) and its AUV program. ISE has carried out numerous Arctic operations since the program began.
ISE's first AUV was built in 1983 and was named ARCS. It was originally intended to be used for a survey of the approaches to Bridport Inlet in Viscount Melville Sound as part of a Canadian government plan to establish an LNG port in the area. When this project was abandoned, ARCS was used as a test bed for technology that would be used in future under-ice missions.
Between 1985 and 1991, extensive testing of various batteries, control systems, acoustic modems, obstacle-avoidance strategies and payload modules was undertaken to support the design of future AUVs.
Later, ARCS was also used to develop the fiber-optic cable laying strategy that would be used on a larger AUV.
ISE's first large-diameter AUV, Theseus, was the first AUV to lay fiber-optic cable on the seabed. This was the first instance of cable laying with an AUV anywhere—in open water or under ice.
The AUV was named after the mythical founder-king of Athens, son of Aegeus and Poseidon (god of the sea). Theseus laid thread in the labyrinth built by Daedalus, enabling him to escape with Ariadne, the daughter of Minos, king of Crete, after slaying the Minotaur.
The Theseus program began at ISE in 1985 as part of a Canada-U.S. program to lay cable under Arctic ice. ISE and the Defence Research Establishment Pacific (DREP) of Canada's Department of National Defence worked together to develop a large AUV for laying cable from a site near the shore of Ellesmere Island in the Canadian Arctic to a scientific acoustic array in the Arctic Ocean about 200 kilometers from shore. Two under-ice cable-laying missions were conducted 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 fiber-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 final 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 fiber-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. To continue this article please click here.
Dr. James McFarlane is the president of ISE Ltd. He founded the company in 1974 to build ROVs. He has been a part of engineering teams that have built more than 400 robotic manipulators and more than 240 vehicles. He is an Officer of the Order of Canada and a member of the Canadian Academy of Engineering, Sigma Xi, Marine Technology Society, Institute of Electrical and Electronics Engineers, and the Mine Warfare Association.
Raymond F. Murphy is the marketing and business development manager of ISE Ltd. He spent nearly 30 years with the U.S. Navy as a specialist in anti-submarine warfare, and submerged vehicle performance and evaluation. He joined ISE in 2002 and has the task of connecting ISE to various navies for the purpose of enhancing their underwater equipment.