Massachusetts based company "iRobot" has made a splash this week by announcing that it will build and sell the “Seaglider” underwater robot. The company which is well known for it's "Roomba" vacuum cleaner robots as well as for their "PackBot" military robot has licensed the technology for these man-sized autonomous submarines from the University of Washington in Seattle. The robots' ingenious design without moving external parts makes them extremely reliable and durable, with two of the robots autonomously travelling a record 3700km through the Labrador Sea over the course of seven months in 2004 and 2005.
The Seaglider's design is based on a hull which compresses as it sinks, matching the compressibility of seawater. Seagliders rise and sink by adjusting their volume to be either slightly smaller or larger than that of an equal mass of seawater. Simultaneously adjusting their attitude by moving mass within the vehicle allows them to glide through the water. The result of the changes in volume and attitude is a zig-zag motion from the surface to depths of 1000m and back up every 3 to 9 hours.
For more information on the Seaglider check out it's homepage at the Unversity of Washington: http://www.apl.washington.edu/projects/ ... mmary.html
For an even cooler design which uses changes in water temperature to stay autonomous for years rather than months check out Webb's thermally-driven robotic glider: http://blogs.spectrum.ieee.org/automato ... botic.html