Redwing glider during test launch
Teledyne Marine
A small robot submarine is about to circumnavigate the world for the first time. Teledyne Marine and Rutgers University New Brunswick in New Jersey are launching an underwater glider called Redwing as part of their Sentinel mission from Martha's Vineyard in Massachusetts on October 11.
Researchers have been using underwater gliders since the 1990s. Instead of a propeller, gliders have a buoyancy engine – a gas-filled piston that slightly changes the overall buoyancy of the ship. An electric motor pushes a piston inward, making the glider heavier than water, so it slowly sinks down at a slight angle. Having reached the bottom of the dive at an altitude of about 1000 meters, the piston extends and the submarine, now floating, glides upward. The result is a slow and steady progression along a sawtooth path. Auxiliary propellers can be deployed if necessary, but the goal is to avoid this.
“The Redwing will ride with the current rather than fight it, traveling at an average speed of 0.75 knots,” or just under 1 mph, he says. Shea Quinn at Teledyne Marine, which is leading the Sentinel mission.
Redwing is 2.57 meters long, no bigger than a surfboard, but weighs 171 kilograms. Previous gliders have flown missions for months – the Redwing's fuselage is packed with batteries, giving it even greater endurance.
“The historic Sentinel mission plans to circumnavigate the world in approximately five years,” Brian Maguire at Teledyne Marine. Redwing will travel alone, monitored by engineers from Teledyne Webb Research and students from Rutgers University as it reaches the surface and communicates via satellite. Mission control will adjust the glider's course twice a day to keep it on its planned flight path. Maguire said he would likely need to replace the battery during the five-year trip.
Redwing will follow the route of explorer Ferdinand Magellan's circumnavigation of the world from 1519-1522, calling at Gran Canaria off northwest Africa, Cape Town in South Africa, Western Australia, New Zealand, the Falkland Islands in the South Atlantic and possibly Brazil before returning to Cape Cod, covering about 73,000 kilometers.
The gliders can carry out long-range, long-duration research missions without expensive support ships, and they have become vital for tracking data key to understanding climate change. Redwing will collect data about ocean currents And sea temperature in relatively unknown regions using a wide variety of tools.
“We believe this is the longest open ocean sampling effort ever undertaken,” says Maguire.
Previous glider missions crossed the Atlantic in 2009 and the Pacific in 2011 and traveled under Ross Ice Shelf and other hard-to-reach places. “Gliders are great tools for taking measurements in areas where it’s too risky to send a ship, such as in the middle of a storm or hurricane or in front of a calving glacier,” says Karen Haywood at the University of East Anglia in the UK. The main hazards to completing the mission are likely to be fishing nets and shipping lanes rather than weather conditions. “Gliders are actually surprisingly resilient and can withstand high winds and rough seas,” she says.
Alexander Phillips Britain's National Oceanographic Center says the glider will have to contend with other threats, including sharks and biofouling, where plants and algae accumulate on the ship's outer shell. “Biofouling can render a glider unusable due to marine growth on the outside of the glider. In some ocean areas, gliders have been lost to sharks. Shipping and fishing sometimes damage or cause the loss of gliders.”
The mission data will be shared with universities, schools and other institutions around the world, but the main goal is to highlight the gliders' capabilities and inspire future missions.
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