Senior Adam Huxtable explains some of the various modifications done to the Seagliders sensors in the applied physics lab.
Production engineer Mike Johnson works on several rails that allow the battery to be moved inside the sea glider. The shifting weight serves as a ballast that controls angle and pitch.
Navies of the world take heed: Submarines lurking below the waves will have a harder time hiding from the U.S. Navy once UW-produced technology is deployed at sea.
The device is called a Seaglider and was created by UW professors to study the ocean for scientific purposes. Incidentally, the Navy also developed an interest in the type of data the Seagliders are capable of gathering.
The Navy anticipates placing an order worth about $15 million and plans to use Seagliders for anti-submarine warfare. Each Seaglider manufactured by the fabrication center is sold at an average price of $100,000 per glider and the Navy ordered 150.
Sensor instruments attached to the Seaglider collect detailed information about how sound travels through seawater.
“One of the early things that was discovered by the navies of the world was that when there are sharp changes in the water density, you can hide your submarine underneath that because sound from the surface ships will bounce off the change in density before it penetrates and bounces off your submarine,” said Fritz Stahr, a scientist at the School of Oceanography. The Navy uses Seagliders and other oceanographic instruments to examine the water column for discontinuities in how sound travels through the water. The data gathered then can be used to aid the Navy in finding out where enemy submarines might be hiding.
Conversely, the same information can help submariners.
“If they know they’re going to be working in a certain part of the ocean, they want to know everything they can about it so they can hide subs,” said Mike Johnson, an engineer at the Seaglider Fabrication Center.
The Navy uses sonar, which sends a sound wave through the water, and having an intimate knowledge of how the water column can affect sound waves helps the Navy better interpret sonar data. By using the sensor data provided by instruments like the Seaglider, the Navy can selectively pinpoint where its ships should be scanning for submarines or discover good locations for its own submarines to avoid detection.
Johnson estimates that the Navy will probably use about 30 of the Seagliders at a time. Another portion of Seagliders will be in reserve while the rest will be on dry land being cleaned up from weeks at sea.
“That’s sort of the mindset of the Navy: If you need one, you buy three,” Johnson said.
One of the benefits the Navy gets from using the Seaglider is the relative ease with which the Seaglider is deployed. UW students and staff regularly test all of the gliders they manufacture by using a small, two-person boat to launch the Seaglider from.
“One of their operational modes is to go throw these things in the water for only a month or two and then take them someplace else and throw them in the water there,” Stahr said.
The growth of the project led to the formation of a fabrication center dedicated to producing Seagliders in 2005.
“Basically internal folks could order a glider and this other group would just build the gliders,” Stahr said. “It had a side benefit of being a group which could be set up within the University to also sell gliders to the outside parties.”
The Navy’s large order, however, will be licensed to an outside company whose manufacturing capabilities are greater than the UW Seaglider Fabrication Center.
The fabrication center, which employs two full-time engineers and two students, builds an average of 1.3 gliders per month. The Navy’s order of 150 gliders is thus too large for the fabrication center to handle on its own.
Most of the time, the fabrication center manufactures batches of about four or five Seagliders at a time. Right now, the fabrication center is building gliders for a group in Australia that hopes to regularly monitor the continent’s coastline.
“One of the great things about this as a robot is it will do that and not complain about it like people on a ship would,” Stahr said.
The employees at the fabrication center build the gliders and also test them out for a night at Port Susan, which is north of Seattle near Marysville.
“I’ll have to go out in the field and go to a series of dives overnight,” said Jennie Mowitt, a junior oceanography student. “I’m really surprised nobody’s fallen in yet.”
Sensors and other scientific instruments are added to the Seagliders after the fabrication center has manufactured them.
“What the Fab Center does is build the physical Seaglider and we change just about everything,” said Adam Huxtable, a senior who works on Seagliders in the Applied Physics Lab. “We do a lot of modifications.”
Huxtable and his co-workers add a variety of sensors to individual Seagliders in order to fulfill the requests of scientists who use the gliders for a variety of scientific purposes. For example, some scientists need instruments that can measure chlorophyll in the water while others are more interested in physical properties of the water like temperature, conductivity and depth.
Seagliders are in operation all over the world. This year, Seagliders have been deployed to Norway, Greenland, Taiwan, the Philippines and Iceland.
Two other U.S. institutions manufacture undersea gliders: the Scripps Institute of Oceanography and The Woods Hole Oceanographic Institution.
Huxtable, however, believes that the Seaglider is the best.
“I guess we just use it a lot more places and for a lot more applications than everyone else,” he said. “We definitely think ours is … the most efficient by far.”
The gliders run on batteries, but the battery life is extended by Seaglider’s energy efficiency.
“The whole thing is so energy efficient it literally shuts everything down between observations even if you’re taking observations every five seconds,” Stahr said.
Once Huxtable has finished adding the necessary sensors to each Seaglider, they are tested once again and then delivered to their buyers.
“I usually go and launch those. … Last summer I was in Taiwan and the Philippines,” Huxtable said.
As a finishing touch, the Seagliders are usually painted a bright color to distinguish them from the color of the ocean. The UW School of Oceanography has pink gliders whereas the Oregon State University received theirs in orange; one of their school colors.
The Seaglider project includes many departments around campus and about 50 UW staff members and students are involved with the Seaglider project. An electrical engineering professor helped developed the data transmission antenna and several labs are either devoted to or help supplement the production of Seagliders on campus. UW faculty members own about 25 gliders.
The Seaglider weighs about 100 pounds and travels at 2.5cm/sec, or the equivalent speed of a slow walk. It can stay at sea for up to seven months, although it transmits data via satellite at various intervals during its operation. The regular transmission of data is beneficial to scientists because researchers will still have at least a portion of data if the Seaglider goes missing at sea.
The Seaglider can dive to a depth of 1,000 meters and operates without moving parts by relying upon pitch and ballast to control the glider.
[Reach reporter Andrew Doughman firstname.lastname@example.org.]
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