Spider Optics allow ROVs to ALMOST break free of the tether
By Ben Coxworth
December 13, 2010
Underwater Remote-Operated Vehicles, or ROVs, are used extensively in the oil and gas industry, in undersea engineering projects and, more glamorously, for doing things like exploring the wreck of the Titanic. These unmanned submersibles are linked to a surface support ship with a thick, cumbersome tether, which is used to pipe power down to the ROV as well as for communications. At the Future of Electric Vehicles conference, however, a new technology was presented that almost sets the ROVs free – the Spider Optics system.
“The problem is, dragging cable through water is an ineffective way to go fast and far,” said Jonathan Epstein, President and CEO of Hawkes Remotes. “These things are attached to power sources, they’re like building an electric car or an electric bike or electric plane with a large extension cord. And this is a large extension cord in a medium that is 850 times as dense as air, so it creates a huge amount of drag... and that creates a loss of range, of speed, and it makes it pretty difficult to maneuver. The result is that most ROVs can only free swim, from their point of tether origin, about 500 meters.”
Epstein discussed other possible methods of communicating with ROVs, each of which have their drawbacks – radio waves don’t propagate in water, acoustic signals can involve up to a seven-second delay, and light signals have a very short range. Even if one of those systems did work well, there’s still the small matter of getting power to the sub.
Epstein and his team looked at several other companies’ ROVs, including an expensive military model from Saab that could travel up to five kilometers, and the scientific Nereus ROV from Woods Hole Oceanographic Institution. At the time, Nereus was using a ten-thousandths-of-an-inch-thick fiber optic cable for communications. The ROV still had to be lowered into the depths on thick steel cables, however, and Epstein claimed that the optic cable repeatedly broke.
Spider Optic systemIn an effort to combine the range of the Saab with the fiber optic tether of Nereus, Hawkes Remotes created the Spider Optic system.
“Just like spiders deposit silk as they go, the key innovation is that the remotes have a thin and strong fiber optic cable inside the vehicle itself,” he explained. “So now you’re not pulling cable down from the top, you’re leaving cable behind in the water.”
The armored cable, which is only millimeters thick, comes in both reusable and thinner single-use versions – the company is working on making the single-use cable biodegradable. The compact ROVs designed for the system are powered by their own onboard 18 kW-h battery packs, and are reportedly much peppier than their heavily-tethered brethren, as their power isn’t subject to the resistance of a long copper cable.
“You don’t need the big ship anymore, you don’t need the big crane anymore,” Epstein stated. “You can use a small fishing boat to deploy this, and a pretty standard crane, and that saves millions of dollars a year, and arguably opens up sub-sea opportunities for a whole group of businesses and business models that right now just can’t afford to free up the resources.”