The U.S. Navy has created a highly efficient AUV (Autonomous Underwater Vehicle) for monitoring the underwater �weather.� SeaGlider is a six foot long, 114 pound AUV that looks like a torpedo with wings. It can stay at sea for up to six months (before needing a battery recharge) and �glides� through the water at up to 20-25 kilometers a day. The AUV is propelled by a system of shifting weights (the battery pack) an air tank that is emptied and filled to adjust depth, and a pair of wings that provide life, as wings do for an aircraft in the air. The SeaGlider moves forward by diving, and comes back up in a forward glide as well, collecting data all the way.
SeaGliders main mission is to measure of the water, and use its built in satellite phone, every four hours or so, to send the information to anyone in the navy that needs it. SeaGlider also uses the satellite phone to get new orders, and has a built in GPS and other navigation sensors to enable it to find its way to areas it has been ordered to monitor. SeaGlider also collects information on currents, and uses that to glide from place to place.
The composition (temperature, salinity, oxygen content, quantities of biomatter, and so on) of the water in oceans changes slowly. Those characteristics influence the effectiveness of sonars (both active and passive.) If you can monitor the water composition more accurately, your sonars will be more accurate. SeaGlider can be dropped by aircraft or helicopter and spend days, weeks, or months collecting water information (at depths of up to 3,000 feet) before friendly subs show up for action.
At $100,000 each, SeaGlider is a cheap way to keep an eye on large chunks of the ocean. SeaGlider works because it�s onboard electronics draw very little power, as does it�s movement mechanism. SeaGlider isn�t fast, but it has that most prized UAV/AUV characteristic; persistence. SeaGlider can hang around for a long time, waiting for the enemy to show up. This was a mission submarines were originally designed for. But manned subs were too expensive to put enough of them out there to cover large areas of the ocean. SeaGlider is cheap, efficient, patient and never has to worry about crew morale. What the navy is not discussing is a future version of SeaGlider that wanders around an area looking for hostile submarines as well.