A successor to the original Rutgers University “Scarlet Knight” autonomous underwater vehicle (AUV) has crossed the continental shelf of the U.S. and is well on its way along the Gulf Stream in its fourth week of an eight-month voyage across the Atlantic. Launched on 27 April from the New Jersey coast, the glider, somewhat more formally known by its model sequence designator — RU27 — is operated by a group of students at the Coastal Ocean Observation Laboratory (COOL) at Rutgers University. This is the second attempt at an underwater robot crossing of the Atlantic. The first Scarlet Knight was lost last fall somewhere near the Azores, tragically close to its destination, after a 160-day voyage covering some 5,700 km. MST recently spoke about the mission and the glider with principal investigator Scott Glenn, Rutgers professor of Marine and Coastal Sciences, and technical chief Dave Aragon, a Rutgers engineering graduate.
As of mid-afternoon today, the glider had traveled more than 2,074 kilometers during its first 22 days at sea. Crossing the continental shelf brings the glider to deeper, less busy ocean waters and relieves its controllers of some of the stress involved in transiting waters crowded with fishing vessels and gear, as well as dense commercial shipping lanes. So far, the Scarlet Knight’s controllers have encountered no serious problems with the glider and have managed to nearly perfectly track the Gulf Stream as it meanders generally eastward across the Atlantic. Team members report they have seen maximum current speeds of 193 cm/sec., which is quite high. According to reports on the team’s website, the goal is to take maximum advantage of the Gulf Stream currents while the glider has plenty of electrical power and is still physically “clean” — no biological fouling as of yet to hamper efficiency.
RU27 is a modified Slocum glider, designed by Teledyne Webb. The “Slocum” name comes from Joshua Slocum, who was the first man to sail around the world solo. For this mission it was lengthened to accommodate extra batteries, giving it an estimated endurance of about 300 days. Scarlet Knight is 93 inches in length, compared to 84 inches for most of the other Rutgers gliders. It was stuffed with 23.8 kilos of batteries, comprising almost 40% of the glider’s total weight of 60.6 kilos. With a volume of 59.1 liters (about 15 gallons), the glider has a density of 1.025 grams/liter, which is close to the average density of the North Atlantic Ocean where it flies. That means the glider can descend and ascend by using an internal pump to slightly change its density. Its wings translate the motion of ascent and descent to forward movement and a programmable autopilot steers the glider on course, using the tail fin to steer. Also in the tail is the glider’s satellite modem, which uses the Iridium network for communications.
Every six or eight hours, the glider surfaces to get a GPS location and send any data it has gathered, along with its position, back to the control room at Rutgers, using a satellite link. Typical gliders of this design fly at depths of 5 to 100 meters, but Scarlet Knight has a special new pump which allows it to dive to 200 meters (about 660 feet). A pressure sensor tells the glider how deep it is. While at the surface, the glider “checks its mailbox” to see if there are any new instructions for it. If so, it makes the adjustments — typically a course correction — and heads down on another flight cycle.
Writ large, the mission of Scarlet Knight is to cross the Atlantic ocean with an autonomous underwater vehicle. On a less macro scale, however, there are many accomplishments and goals to be achieved along the way. Scarlet Knight is pioneering extreme endurance autonomous flight and continue to build the experience base for navigation along the ocean’s many complicated currents. The students and their professors have created and polished several methods for tracking and strategically planning the flight route. They have learned to integrate Sea Surface Temperature (SST) maps with color (biological concentration) and altimetry maps in order to uncover small-scale eddies off the main currents in order to refine their flight routes. They have integrated the glider’s tracking data with Google Earth maps to help better visualize the vehicle’s progress and to more easily communicate it with wider audiences. You can download a Google Earth data file with the latest tracking data here.
Periodically, the flight controllers turn on Scarlet Knight’s scientific sensors and record a basic set of hydrographic data, including temperature, salinity and derived density. Over the course of its several month journey, Scarlet Knight will have built a nicely detailed plot of this data along its track.
You can follow the day-to-day operations and progress of the glider at a dedicated website of the Rutgers COOL here.
Copyright © 2009 by Marine Science Today, a publication of OceanLines LLC