Beautiful Swimmers
Little robots set out at a stately glide to explore the oceans
To Naomi Leonard, an engineer at Princeton University, Slocums, Sprays, and their kin have an almost living grace. "What beautiful creatures they are," she says. The day she launched several Slocum gliders into Monterey Bay to track a thermal front where warm and cold waters meet and predators gather to feed, it was easy to imagine that these robots are another species of sea life. As the gliders went in, about 200 dolphins cavorted around her boat.
Leonard wants to add to the resemblance. To enable AUVs to work together in groups without supervision, her team is developing cunning software for the onboard computers, inspired in part by the way schools of fish and flocks of birds move in concert. Gliders with a social sense could one day cooperate to follow giant eddies called gyres or move in formation along the edges of plankton and algae blooms.
As for the purloined Woods Hole glider No. 12, nobody called Fratantoni after its scoot to Santa Cruz, even though each of its wings bears a phone number for finders to dial. So he and Lund drove north on Highway 1. From the harbor parking lot in Santa Cruz, global positioning system satellite receivers led them to the office of the unsuspecting harbormaster, where they found it dumped by the back door. Its hull was split from a drop or a collision at sea. At last report, it will soon be repaired and back in the water.
SENTRIES OF THE DEEP
AUVs (autonomous underwater vehicles) offer scientists a powerful new probe of the oceans. Some have motors and propellers, but a clever new design simply glides through the ocean in leisurely climbs and dives. Oceanographers envision releasing fleets of these craft to survey temperature, currents, and other conditions over large areas of the ocean.
Run silent, run deep
In some ocean gliders, pumps and valves shift oil between an external balloon and an internal reservoir, changing the craft's buoyancy so it rises or sinks. Stubby wings convert vertical motion into a glide. Drawing on its batteries only for pumps, switches, and communication, a glider can stay at sea for months.
Phoning home
Each time a glider surfaces, it sends data and receives new instructions via a satellite link. It then sinks again to a depth of hundreds to thousands of feet, repeating this cycle thousands of times to roam the ocean.
Gaining range
Current gliders rely on battery-driven pumps. But models in development would gain extra endurance--up to five years--by harnessing the temperature difference between the warm surface and the chilly depths. A reservoir of wax would alternately melt and freeze, expanding and contracting to drive the buoyancy pumps.
(Drawing labels)
Antenna and rudder
External balloon
Oil flow
Bladder
Oil flow to internal bladder triggers drive
Thermal glider
40,000 km
1,500 meters
Battery driven glider
1,500 km
Sources: Monterey Bay Aquarium Research Institute, Webb Research Corporation, Woods Hole Oceanographic Institution
Rob Cady--USN&WR
advertisement
