A New Robot for the Deep Frontier
Hybrid vehicle will enable scientists to reach the deepest trenches
If the engineers of WHOI’s Deep Submergence Laboratory have their way, Americans will soon return to a remote environment they have not visited since the 1960s: the deepest trenches of the world’s oceans.
Associate Scientist Dana Yoerger and Research Specialist Andy Bowen, along with Johns Hopkins University Associate Professor Louis Whitcomb, are developing a “hybrid” remotely operated vehicle (HROV), a battery-powered robot that will take scientists as deep as 11,000 meters (nearly 7 miles) below the ocean’s surface. The National Science Foundation, U.S. Navy, and the National Oceanic and Atmospheric Administration recently awarded the team $5.5 million to build the novel vehicle, which will be part autonomous, free-swimming robot and part tethered ROV.
Though the oceans average two miles in depthwell within the range of several ROVs, including WHOI’s Jason IIthe deepest reaches such as the Mariana Trench in the Western Pacific can plunge almost 36,000 feet. These regions comprise just a few percent of the ocean floor, but they contain some of the most active earthquake zones.
Americans have visited the deepest seafloor only once, when Lieutenant Don Walsh and Jacques Piccard descended to the Challenger Deep in 1960 in the Navy bathyscaphe Trieste. The Japan Agency for Marine-Earth Science and Technology sent its ROV Kaiko to the bottom of that trench in 1995. But Kaiko was lost during a storm in 2003, so today there are no operational vehicles that can reach the deepest parts of the ocean.
“Having access to these very deep and remote areas will open up whole worlds to the scientific community,” said seafloor geologist Patty Fryer of the University of Hawaii. “We will be able to ask questions we never could ask before, and we will be able to go collect the evidence to answer them.”
Unlike other remotely operated vehicles,
the HROV can be reconfigured in the midst of a scientific expedition to operate
in different modes: a free-swimming vehicle for mapping and broad surveys, and
a tethered ROV for close-up sampling and imaging. By design, the HROV will be
compact enough (roughly 10 feet by 7 feet by
7 feet) for quick deployment from virtually any ship in the world, allowing rapid response to interesting geophysical events such as volcanic eruptions or earthquakes.
“We are going to investigate an environment that is essentially unexplored,” said Yoerger, head of the Deep Submergence Lab. “We often talk about surveying the seafloor with various tools in a methodical mannerwe call it ‘mowing the lawn.’ In this case, we will be mowing the lawn where the grass has never been cut. We don’t even know if there is grass!”
HROV will require several novel technologies to reach its goals. To overcome the tremendous pressure at extreme depths, the engineering team must work with special ceramic housings for their equipment. “In very simple terms, it’s strength versus weight,” said Bowen. Titanium has generally been used for pressure housings, but it would be about five times heavier than a ceramic housing. They must fend off 16,000 pounds per square inch of pressure without creating a vehicle that is too large to handle and too expensive to build.
The engineering team needs to not only reach the deepest seafloor, but maneuver when they get there. Traditional ROV cables and wincheswhich transmit both information and electricityare thick and heavy, and they are likely to become restrictive at such great depth. Instead, the HROV will draw power from special onboard batteries and will communicate with its operator through a fiber-optic cable less than 1/32 of an inch thick, about the width of fishing line. The microcable has been used by the U.S. Navy in torpedo guidance, but never in this kind of application.
“Fiber-optic tethers, ceramic pressure housings, 11,000 meter vehicles, and autonomous vehicles have each been developed and deployed previously,” said Whitcomb, a visiting investigator at WHOI. “ But the HROV will be the first vehicle to marry these technologies for access to extreme depths. The scientific need has existed for decades. We are taking advantage of recently developed technologies to provide a novel and cost-effective vehicle to meet this need.”
“The real challenge is to build a vehicle that is actually useful at 36,000 feet,” added Yoerger, who expects the project to take three to four years. “This is a combination of science and adventure, and we can’t use the same old methods. We need tools and sensors that match the scale of what we are trying to achieve, while allowing us the freedom to explore.”