Down To The Deep
CROSSBREEDING TO MAKE EXPLORING THE ABYSS ROUTINE
H umans have visited the very bottom of the ocean—the Marianas Trench in the western Pacific, nearly seven miles below the wavetops—only a few times. The first expedition took place in 1960, when Jacques Piccard set the U.S. Navy submersible Trieste down on the murky floor; the next occurred some 35 years later, when Japan’s Kaiko, a multimillion-dollar remotely operated vehicle (ROV), returned briefly to that black realm during several dives. The extreme depths and pressures of the earth’s least- explored territory have kept scientists from studying the ocean’s abyss up close. An innovative attempt may soon change that.
Engineers at Woods Hole Oceanographic Institution, Johns Hopkins University and the U.S. Navy have begun developing an undersea craft that is designed to do meaningful science at the lowest depths routinely and cost-effectively. The device, explains Woods Hole researcher Andy Bowen, will be a hybrid ROV; it will combine the capabilities of a fully autonomous undersea robot with those of a craft piloted from the surface via a thin optical-communications fiber, the same technology used to guide torpedoes. The one-ton machine and its support equipment are to fit into a pair of standard shipping containers. Thus, the system is intended to be sufficiently compact, lightweight and easily deployed from standard oceanographic vessels, thereby avoiding the need for a dedicated a mother ship. These features will make the machine flexible and cheap enough not only for deep diving but for other, traditional survey and sampling jobs. Managers expect that the $5.5-million project, which is being funded by the National Science Foundation, the Office of Naval Research and the National Oceanic and Atmospheric Administration, will be completed in four years.
The crossbreeding approach circumvents the limitations of other, conventional bathyscaphic and teleoperated technologies. Occupied suhmersibles end up being large and costly to ensure the safety of the people inside. Totally independent robots must be extremely intelligent” to carry out research activities—an expensive and technically difficult task. Meanwhile the lengthy cables used to tether craft to surface ships are simply too weak and unwieldy to support themselves plus a vehicle exploring broad swaths of the seafloor.
When operated as an autonomous device, the hybrid ROV will conduct wide-area surveys using sonar and other sensors. For detailed investigations, technicians will strap on an optical-fiber canister and a tool sled containing additional thrusters, extra flotation, batteries, an electromechanical arm and sampling equipment. After being winched below the treacherous currents on a steel cable, the craft will be released from a suspended depressor weight. An anchor will then pull the vehicle down to the seafloor, paying out optical fiber during the descent. Once the hybrid ROV arrives at the bottom, it will release the anchor and drive off to do its business, reeling out more microfiber from its stern. On completion of its work, the craft will cut the fiber link and then rendezvous and dock with the depressor weight, making it ready for retrieval by the ship.
If all goes well, the hybrid ROV will let scientists better understand fundamental processes occurring at the deep subduction zones along the continental margins where geochemical recycling of the earth’s crust takes place. Further, it will permit exploration of the unknown seas below the polar ice packs (a task that requires long horizontal transits) as well as rapid deployment to study any new undersea phenomenon that emerges unexpectedly.
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