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Submersible Glider Powered By Thermal Changes
An anonymous reader writes about a new robot submersible that uses temperature differences in the sea to power operation for more than twice as long as previous, battery-dependent vehicles. "The torpedo-shaped glider moves through the ocean by changing its buoyancy to dive and surface, unlike motorized, propeller-driven undersea vehicles. To power its propulsion, the submersible gathers thermal energy from the ocean. When it moves from cooler water to warmer areas, internal tubes of wax are heated up and expand, pushing out the gas in surrounding tanks and increasing its pressure. The compressed gas stores potential energy, like a squeezed spring, that can be used to power the vehicle. To rise, oil is pushed from inside the vehicle to external bladders, thus increasing the glider's volume without changing its mass, making it less dense. The oil can be shifted inside to increase the density and sink the vehicle."
Submarines don't use changes in depth to push them horizontally. This device is a bit like a sailplane.
http://michaelsmith.id.au
I know, I was shocked too, but the vaporware tag is wrong.
They have had one working that has traveled 1400 kms so far since launch in December. Better article here
http://www.cbc.ca/technology/story/2008/02/08/tech-glider-undersea.html
Last I checked submarines had air tanks for buoyancy control
The air tanks are used mainly used to switch between surface and submerged modes, for trimming (keeping the sub horizontal), and to compensate for changes in water density. Because the amount of lift generated by a body does not change much with its depth, the air tanks cannot provide fine control of your diving depth. Also, a naval sub prefers not to use the air tanks once submerged, because venting air leaves a trail on the surface.
For fine depth control, a sub uses its diveplanes: wing-like surfaces that provide lift (positive or negative) as long as the sub keeps its speed above a minimum.
In effect, this glider reverses the process: changes in buoyancy are used to generate an upwards/downwards force, which is converted by the wings into forward motion.
newer subs are not motorized, but nuclear-powered.
You mean some newer subs are nuclear-powered. Conventional-powered submarines are still being built today. Often, in addition to the traditional diesel engines, an air-independent propulsion system is installed, either a Stirling engine or a set of fuel cells.