Sunday, September 03, 2006

Wired News: Underwater Bot Roams the Seas

Wired News: Underwater Bot Roams the Seas:

"Oceangoing underwater robots are the new fish in the sea scientists are using to explore Earth's final frontier. The water bots are gathering data that could provide valuable insights into climate change and other environmental concerns.

Spray, one of these new autonomous underwater vehicles, or AUVs, left Bermuda in late March. It will head to New England to explore the Gulf Stream in the North Atlantic before returning to Bermuda sometime in July. The voyage will be the first long-distance round-trip mission undertaken by the 6-foot-long craft.

Looking like an orange torpedo with stubby wings, Spray contains no moving parts. It can run silently at 3,300 feet underwater taking temperature, salinity and biomass measurements.

'It's an underwater glider that moves up and down the water column,' said Breck Owens, a senior scientist at the Woods Hole Oceanographic Institution. Last year Spray was the first AUV to cross the Gulf Stream from Bermuda to New England, a one-way trip.

[...]

To control Spray's pitch, or angle of ascent or descent, the 26-pound lithium battery pack, the craft's sole energy source, shifts to tilt the weight within the vehicle.

"It operates like a hang glider, with the battery pack taking the place of a person," Owens said.

Spray uses very little energy as it leisurely descends to 3,300 feet and ascends to the surface three times a day, covering roughly 12 miles. It stays on the surface for 15 minutes to take a GPS reading and to phone home through the Iridium satellite phone network to relay its location and the data collected.

While on the surface, Spray also receives e-mail messages from Owens for course adjustments to avoid rip currents or other obstacles. Storms pose little problem underwater, but strong currents are a major challenge for the 112-pound glider.

"It's like swimming in a rip current. You have (to) swim perpendicular to the current," Owens said.

Spray is smart enough to calculate its location and direction when pushed along by currents underwater using dead reckoning, according to Owens.

However, fishing nets can pose a problem. And surface vessels have created difficulties. Last year another Spray -- there are several versions in use -- operated by Scripps was run over by a boat when it surfaced off the coast. According to Owens, the half-inch aluminum hull was split and a wing was torn off.

Five years from now, Owens expects there will be hundreds if not thousands of similar underwater robots going where no one has gone before. One reason is that Spray is relatively low-cost at $70,000. And Spray can travel up to 3,500 miles on its batteries, enough for a voyage next year that Owens' research team is planning which will take the craft from Greenland to Spain.

"Oceanographers are starved for data," Owens said. "We're trying to build Model Ts here, not space shuttles." "

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