Underwater Robots for Deep Ocean Exploration
Most of the world’s sea floor has never been observed by human eyes. At present, according to Professor Louis Whitcomb, the surface of the moon has been mapped and photographed more thoroughly than the submerged portions of the Earth’s surface. Only a few percent of the world’s seafloor is shallow enough for direct examination by human scuba divers. The problem is hydrostatic pressure. Every 10 meters of depth adds another atmosphere of pressure. In consequence, even mixed-gas scuba divers can descend to only about 100 meters. Until recently, the only way for a scientist to directly examine the benthic floor was to descend in a specially designed deep-diving submarine. The deepest diving U.S. inhabited submarine, the DSRV Alvin, can descend to 4,500 meters depth, yet this is less than half-way to the ocean’s deepest depth of 11,000 meters. By comparison, Mount Everest is only 8,848 meters in height. To reach these great depths, Prof. Whitcomb and researchers around the world have developed underwater robotic vehicles that enable scientists to explore, by remote control, these deepest and most inaccessible parts of the ocean.
Whitcomb and his students have conducted original research on the navigation and control systems for these underwater “Remotely Operated Vehicles” (ROVs) for over a decade. They collaborate closely with researchers at the Woods Hole Oceanographic Institution (WHOI), where most of the U.S. deep-submergence oceanographic vehicles are developed and operated. Whitcomb is co-developer of the navigation and control system for the Jason ROV, the deepest diving U.S. ROV presently in operation. He and his students participate frequently in deep-ocean deployments to experimentally evaluate their newly developed systems. In June 1999, for example, Whitcomb and his Ph.D. student David Smallwood tested out a new Doppler-based sonar navigation system with their WHOI collaborators in the Mediterranean Sea between Malta and Israel. This expedition was led by leading geologist and oceanographic explorer Dr. Robert Ballard, and Harvard University archaeologist Dr. Lawrence Stager. On this expedition, equipped with video and still cameras, sonar devices, and a robotic arm, Jason photographed and explored the topography of several pre-Roman shipwrecks, sending the data to a ship on the surface via a fiber-optic cable. The artifacts documented and recovered for the archaeologists by the Jason team dated from about 750 BC, and they reveal clues about trading routes, economic and political alliances, and lifestyles in ancient cultures. Before the development of vehicles like Jason, it was infeasible to explore shipwrecks deeper than the scuba divers’ limit. An invaluable museum of human history lies waiting on the 97% of the ocean floor that remains unexplored.
Back at Hopkins Prof. Whitcomb and his PhD students built and, in August 2000, launched their own ROV, the JHU ROV. They have tested it in the United States Naval Academy’s 380-foot test basin. Whitcomb and his students use data they gather during these tests to develop accurate mathematical models of the vehicle’s dynamics, which in turn allows them to design improved control systems. They also use this ROV to field-test new designs. Once these designs are validated by field-testing, Prof. Whitcomb’s group can quickly transition them for use on other vehicles.
In June 2001, Prof. Whitcomb and his student James Kinsey again went to sea to test their newly developed sonar navigation system called DVL NAV aboard the new WHOI vehicle DSL120A. Whitcomb and his students developed the new navigation system on the JHU ROV, and have successfully deployed it on the new DSL120A vehicle and the inhabited submersible Alvin.
Whitcomb and his students are now collaborating with WHOI to help develop JASON II, a new vehicle designed to succeed Jason. It is “bigger, stronger, faster,” according to Prof. Whitcomb, and will have more sophisticated systems on board, including the navigation systems now being tested. Jason II can help unveil the mysteries of unique life forms, hydrothermal vents, and other natural phenomena of the deep. Prof. Whitcomb, by designing Jason II’s “brains,” has an important role to play in this exciting future of deep sea exploration.