It has been said that we know more about the surface of the moon than we do about the deep sea. The reason for this is that the deep layer of the ocean (roughly defined as any place greater than 1,000 fathoms – or a little over a mile - deep) is pitch black and pressure is so great that it limits traditional exploration methods. In order to learn more about these deep, dark regions, researchers have to take more innovative approaches.
One such approach was the invention of the Sentry, an autonomous underwater vehicle (AUV) designed to survey the deep sea. Created by scientists and engineers from the Woods Hole Oceanographic Institution (WHOI) and the University of Washington, the vehicle recently completed its first mission. The Sentry surveyed over 30 square miles of ocean floor by going back and forth over the area like a person would with a mower while cutting the lawn. The innovative AUV gathered the most precise maps to date of seafloor features known as Hydrate Ridge and Axial Volcano, around the edges of the Juan de Fuca tectonic plate off the coast of Oregon and Washington. Powered by more than 1,000 pressure-resistant lithium-ion batteries (similar to the batteries used in laptop computers), the Sentry was submerged for as long as 18 hours at a time.
The Sentry is capable of diving as deep as 3.1 miles below the ocean’s surface (descending at a rate of over 2 miles per hour), swimming like a fish or flying like a helicopter through the water. Similar in appearance to a vertically flattened submarine, the shape of the vehicle provides stability and balance while cruising through bottom currents. Airplane-like wings in the front and back of the Sentry are equipped with thrusters that allow the vehicle to gain lift, drag or directional momentum as needed - enabling it to start, stop and change directions. The state-of-the-art robot operates independently – with no cords or other connections to ships above – and, perhaps most impressively, can actually think for itself. Though the Sentry is pre-programmed with guidance for deep-water surveying, it also can make its own decisions about navigation while on the seafloor.
With its first mission successfully completed, Sentry will now join the National Deep Submergence Facility (NDSF), a federally funded center that operates, maintains, and coordinates the use of vital deep ocean vehicles for the U.S. oceanographic community. Along with the Sentry, the NDSF also houses human occupied vehicles (HOVs) and remotely operated vehicles (ROVs) that provide other means of exploring mysterious deep waters. The hope is that these innovative devices will help scientists and researchers gain greater insight into the dark world miles below the ocean surface. "This investment into emerging technologies is paying off in delivering state-of-the-art science support," said Julie Morris, Director of National Science Foundation’s Division of Ocean Sciences. "In the near future, Sentry will conduct high-resolution oceanographic surveys that would be otherwise impossible."