Engineers Develop Electronic Brakes for Skis

At age 3, Ian Hussey hasn't quite developed a healthy sense of fear on the slopes.

"He doesn't like to slow down, he doesn't like to turn, he just likes to go straight ahead — fast," said Dianne Hussey about their son.

When his parents take him skiing at Sugarloaf Mountain in Kingfield, Maine, they need to hold him back with a harness. As early as next year, they might have another option: built-in brakes.

Victor Petrenko, an ice engineer at Dartmouth College's Ice Research Lab in New Hampshire, has developed an electronic braking system that can keep skis and snowboards within a pre-set speed limit.

The system uses a network of wires that are embedded into the bottom of the ski and activate charges across the snow surface. Those charges interact with charges on the snow's surface to slow the skis.

"You can adjust the addition of resistance from nothing to very high," said Petrenko. "It's not like you turn on the power and the skis stop, it happens gradually by slowly increasing the charge."

Making Skis Stick

In the one-foot-long prototypes that Petrenko and his colleagues have tested on miniature indoor laboratory ski slopes, a sensor fitted to the boards monitors the skis speed over the ice. Once the skis accelerate beyond a pre-set speed, the brakes gently activate.

The idea works thanks to the ability of ice to hold a charge and to the fact that opposites attract in the realm of physics.

One set of wires on the skis triggers a negative electric charge, which clings to positive charges on the surface of the snow. Another set fire positive charges, which attract negative charges on the snow's surface.

Petrenko explains the actual contact between ski and snow occurs only on tiny microscopic ridges on the snow's surface. When a voltage is applied between the ice and ski, the electric current crosses these tiny bumps and melts them.

As the charged is released, the water refreezes against the ski's surface and the force required to break that bond helps hold the skier back.

Meanwhile, the attracting charges between the snow and ski further pull the ski closer to the snow's surface, which increases friction and slows the ski. A small battery, the size of a standard double A, powers the system from inside the ski.

When Slow May Not Mean Safe

"I often see parents skiing with their kids between their legs or in harnesses," said Petrenko. "With these brakes, I hope parents could just set a maximum speed and let their kids go."

Petrenko says Dartmouth College is now negotiating contracts with a few ski equipment companies including K2 and Karhu to incorporate the technology into new models.

In fact, statistics show most skiing-related injuries happen to adult skiers, not children. The National Ski Areas Association recently announced that 47 people died on U.S. slopes last year and 44 were seriously injured resulting in conditions like trauma to the head or loss of limbs. (That figure has dropped by half since the 1970s thanks to other improvements in equipment.)

Could ski brakes help curb accidents among adult skiers? Some are skeptical.

Jasper Shealy, an expert on skiing-related injuries at the Rochester Institute of Technology in New York, says the fatal moments of most skiing accidents happen long after skiers have fallen off their skis (in most fatal accidents the skiers strike trees). And he's concerned an automatic braking system might throw off a skier's control.

"The idea of having an external speed brake jump in could be an interesting experience and frankly, not one I think I'd be looking forward to," Shealy said.

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