Sea Transportation: Robotic Subs Threatened By Somali Pirates

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July 21, 2011: The Somali pirates, who now prowl most of the Indian Ocean (west of India) have not only interfered with merchant shipping, but with oceanographic research as well. For example, an international effort to distribute and maintain 3,000 instruments into the world's oceans is now under attack off Somalia. The scientists use these 3,000 buoys and robotic mini-submarines to assist in predicting the weather and gaining a better understanding of the oceans in general. But the scientists can no longer travel into the western Indian Ocean, because of the risk. The small research ships have already had a few close calls with pirates. So the task of dropping off (and sometimes picking up) these robotic research devices will be carried out by some of the warships operating off Somalia, and points east.

This global use of robotic sensors has been growing more extensive and important, over the last decade. Much of the progress was made possible by the development of highly efficient AUVs (Autonomous Underwater Vehicle). The U.S. Navy developed one of these nearly a decade ago for monitoring the underwater "weather". This SeaGlider is a two meter (six foot) long, 52 kg (114 pound) device 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 lift, 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.

SeaGlider's 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 help it glide from place to place.

SeaGlider was not built to help with weather prediction, but to improve American anti-submarine capability. 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 was a cheap way to keep an eye on large chunks of the ocean. SeaGlider works because its onboard electronics draw very little power, as does its 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. 

Meanwhile, devices similar to SeaGlider are being used on an even larger scale to monitor a larger number of ocean characteristics. Apparently the Somali pirates have not captured and held for ransom one of these robotic subs, but they may have simply shot some to pieces as it surfaced near them (to transmit data). The scientists will continue to drop off and pick up their stationary and self-propelled sensors near pirate-infested waters. But in pirate territory, only warships will perform what is now a dangerous duty.

 


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