TCS Daily


It's a Buoy!

By Noah Shachtman - October 23, 2002 12:00 AM

To most people, weathermen seem famously clueless about the skies. But to the people that study the ocean's depths, Al Roker and company look practically omniscient.

Every day, thousands of weather balloons are launched from airports around the globe to track the atmosphere's comings and goings. In contrast, examining undersea currents and temperature has traditionally required one of a few, specially-outfitted, $20,000-per-day ships to take the readings.

So the Navy, the National Science Foundation (NSF), and the National Oceanic and Atmospheric Administration (NOAA) are all backing programs to provide a clearer picture of what's going on down below.

The coolest of these efforts: robotic, underwater gliders, powered only by their own buoyancy. Developed by researchers at the University of Washington, the 110 pound, six foot long Seaglider doesn't have a traditional engine. Instead, it moves by inflating and deflating a sac about a third the size of a beer can, according to Washington oceanography professor Charles Eriksen. That changes the robot's volume, causing it to sink or rise. This up-and-down motion is then turned into horizontal actions by the glider's wings.

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The Navy wants to use the gliders' sensors to pick up the brine's density and temperature, which effect how SONAR works. Right now, when subs or minetrackers enter an area, they have little information about these conditions. It's a little like having a pilot fly into an area without a weather report.

The ultra-quiet gliders could be put into a watery warzone weeks before an attack, "so that when mine-hunting starts, we'll have a good picture of what the ocean looks like," said Dr. Tom Swean, a program manager at the Office of Naval Research.

Using on-board acoustic modems, the gliders could also receive information from underwater sensors and subs, then break the ocean surface to communicate the information back to headquarters. The gliders are guided by GPS, and receive orders from their handlers through the Iridium satellite system.

But the robots won't outrun anyone if they're found. The Seaglider ambles along at a lethargic, half-knot per hour gait. This drains just a half-watt of power from its lithium ion batteries to nudge the craft along - which means the robot can stay afloat for months at a time.

"In theory, it should be able to make it all the way across the Pacific," said Alex Isern, an NSF Ocean Technology program director.

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The robots are cheap enough - the prototypes run from $50,000 to $75,000 - that the Navy hopes to one day have them stationed across the globe, giving a complete, near real-time picture of the temperature, current, oxygen count, and salinity of the seas. Right now, however, the Navy only has a half-dozen of the Seagliders, and 15-20 Slocum Gliders - robots powered by the water's changing temperature, developed by Webb Research.

NOAA is in the midst of a somewhat similar effort, a multi-year project known as Argo, which aims to plunk three thousand buoys across the oceans to transmit some of this information. So far, 535 of these "floats" have been placed.

But the buoys are "free-floating, at the whim of the currents," Isern said. "The gliders have an ability to adjust to events - something we really haven't had before."

The military's not the only potential beneficiary of the robots, noted Clayton Jones, an engineer with Webb Research. Fisherman could, one day, use the robots' ability to detect algae and plankton to find better places to cast their nets. Rutgers University researchers are developing undersea robots that can track the growth of the toxic "red tide" algae that can wipe out shellfish populations.

Ironically, gliders may also find a place predicting the weather. Since above-ground storms can begin in the depths, ocean-going robots will likely be used to one day give Al Roker and his sky-watching pals a hand.
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