'RoboClam' Anchor Holds Ships Steady

Dec. 2, 2008 -- Ships have changed dramatically over the last few thousand years, but one piece of technology -- the heavy, metal anchor -- has remained largely untouched. But scientists have now created a light-weight, cigarette-sized anchor that burrows itself into the sea floor, anchoring anything from small unmanned submersible to maybe even huge oil platforms.

The new anchor is based on one of nature's faster diggers, the oblong-shaped razor clam, Ensis directus.

"It turns out that clams are actually very fast diggers," said Anette "Peko" Hosoi of the Massachusetts Institute of Technology. "One of my students, Amos Winter, actually calls the razor clams we looked at something like the Ferreri of the clam world."

The RoboClam, as the device is called, digs itself into the ground in two ways, similar to how a razor clam digs.

First, the RoboClam vibrates, changing the relatively solid seabed into a quicksand-like fluid that is easier to dig through. Then the two "shells" of the machine expand, locking the anchor in place, while a worm-like foot pushes down. Once the foot is embedded, the shells contract and the foot pulls the rest of the machine down.

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The team is still testing and refining the machine. For now, the RoboClam can push down with about 80 pounds of force, 36 times greater than a razor clam, and dig up to 15 inches deep. The researchers hope the RoboClam will eventually dig twice as far as a razor clam, which can reach depths of more than 28 inches at a rate of about 0.4 inches per second.

Once deep enough, the RoboClam is more than 10 times stronger and an order of magnitude more energetically efficient at burrowing than other vibration-based anchors. It is several orders of magnitude more efficient than traditional anchors, and, if necessary, can even dig itself out.