THE hunt for deep-sea volcanic vents, peculiar creatures of the abyss and the flight recorders of drowned aircraft could soon become much cheaper and easier thanks to spider-inspired submersibles.
Today鈥檚 remotely operated submersible vehicles (ROVs) are tethered to a support ship by cables about 2.5 centimetres thick which provide electrical power. But hauling several kilometres of thick cable through the watery depths creates debilitating drag which impedes the ROV: typical speeds are less than 2 kilometres per hour.
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It needn鈥檛 be that way, says submersible designer Graham Hawkes of San Francisco, who has previously built winged, carbon-fibre submarines. Battery technology is now reaching the point where ROVs could carry their own power, in the form of lightweight, high-capacity lithium batteries.
Without the need for a thick power cable, only a thin optical fibre need be used to relay control signals. 鈥淕o down to tether diameters of 2 to 4 millimetres and all of a sudden you have sharply reduced drag,鈥� says Jonathan Epstein, president of (HRI) 鈥� the company that Hawkes set up to build his ROVs 鈥� based in Richmond Point, California.
The fibre cable would be stored on the ROV itself. 鈥淟ike a spider making a web, we trail out a line of thin, strong cable behind the ROV as we go, slightly faster than the craft is moving, which reduces drag further.鈥�
Because of this, these so-called 鈥淪piderOptic鈥� ROVs should be able to travel at more than 10 kilometres per hour using much smaller, lighter motors than those used on conventional ROVs. And without the need for an on-deck cable winch and tether management system, a much smaller vessel can be used to deploy the new breed of ROVs, says Epstein.
HRI is designing three ROVs with this system. The U-11000 is a 3-metre-long vehicle designed for repair missions at up to 20 kilometres from a launch point 鈥� the kind of operations likely to be demanded more often in future in the wake of the blowout of the Deepwater Horizon oil well in the Gulf of Mexico, Epstein says. The 2.5-metre-tall upright T-6500 has skids for a seabed landing and is geared for science missions, with powerful gripper arms and two high-resolution cameras for peering into the murk; while the F-11000 is a sleek long-range observation craft which is able to dispense with the tether entirely and work autonomously if need be.
The new ROVs will cost between $800,000 and $1.2 million apiece, but Epstein estimates that their ability to launch from small boats without complicated tether-management systems could save operators up to $100,000 a day in ship and crew rental costs. He says that 鈥渁 major oceanography lab鈥� has pre-ordered three vehicles, one of each design.
Alan Whitfield, operations manager at , a UK-based ROV operator which recently converted a tourist submarine into an , agrees that HRI is addressing a key issue in reducing cable drag. 鈥淗awkes鈥檚 idea is an interesting concept and in principle it should work,鈥� he says.
