A team of MIT scientists is testing its newest autonomous underwater vehicle (AUV) beneath the ice at Lake Winnipesaukee. The operation, begun on February 9, is in preparation for Odyssey II's expedition to the Arctic later this month, where the vehicle will be used to study the formation of ice cracks.
This testing is the prelude to a mission to understand sea-ice mechanics. This AUV provides a unique capability to responding to transient events in the ice. The vehicle will be deployed through a hole in the ice and will navigate to the site of ice cracking, where it will survey and videotape the under-ice canopy. The vehicle will then return to its site for recovery.
Introduction of small AUVs is expected to vastly extend the ability of oceanographers to study the underwater world. AUVs can go where humans can't, or can't afford to-such as under ice in the Arctic or over hydrothermal vents in the deep sea. The success of the flagship Odyssey paves the way for Odyssey II to gather data heretofore inaccessible beneath the Arctic ice cap. Odyssey and Odyssey II were developed by researchers at the MIT Sea Grant Underwater Vehicles Laboratory.
Like other AUVs, and unlike the better known remotely operated vehicles (ROVs) such as the Woods Hole Oceanographic Institution's Jason, the Odyssey II has no tether. All power and all instructions-in the form of computer programs-are stored aboard. This means that Odyssey II will not run into the often disabling problems caused by miles of cable pushed around by oceanic forces.
Odyssey II follows on the heels of its namesake, Odyssey, a powerful oceanographic research tool that is cheap enough, adaptable enough and small enough to run oceanographic missions on real-life, nonmilitary research budgets. The 165-kilogram (360-pound) Odyssey has a range of 270 kilometers (170 miles), a depth rating of 6,000 meters (20,000 feet) and a component cost of under $50,000, with one-sixth the weight, twice the range and a fraction of the cost of any previous deep-diving AUV in the world.
Odyssey successfully completed its first deployment in January 1993, in an Antarctic operation led by the Underwater Vehicle Laboratory's manager, James G. Bellingham, and postdoctoral fellow Donald Atwood. In that mission, Odyssey employed sonar and a video camera to perform a computer-programmed mission in Antarctic seas.
Lessons learned from Odyssey's voyage have been incorporated into the design of Odyssey II. The second-generation vehicle includes many modifications, with the original polyethylene and fiberglass structure replaced by a vacuum-formed polyethylene structure. Odyssey II is neutrally buoyant, allowing it to submerge and rise to the surface more easily than its predecessor. The new AUV also is more rugged, is more visible when surfacing, and can be produced more quickly and at significantly less cost than the original fiberglass structure. New navigational and communications systems also are key components to Odyssey II.
With camp set up on Lake Winnipesaukee, Drs. Bellingham, Atwood and colleagues have cut through the ice and set Odyssey II on its first underwater outing. Sensors placed on top of the vehicle will allow it to collect information about the ice surface. Testing the vehicle's sonar navigation and communication systems are of particular importance, assuring that it can be guided in whatever direction desired, then report its location and sightings and return to its point of entry.
A version of this article appeared in the March 2, 1994 issue of MIT Tech Talk (Volume 38, Number 24).
