SHEER terror. Blind panic. Whatever you call it, it鈥檚 that gut-wrenching
feeling known to all newcomers to skiing and snowboarding as they hurtle
helplessly downhill. But help is at hand for beginners to the pistes. A new
generation of skis or snowboards will be fitted with built-in electronic brakes
that slow them down before things get too scary.
The new braking system is being developed by Victor Petrenko, an engineer at
Dartmouth College鈥檚 Ice Research Lab in New Hampshire. His idea involves running
a pair of wires the length of the board or ski鈥檚 underside, one at each edge.
The wires are connected to opposite terminals of a 3-volt battery, making one
wire positive and the other negative. Fingers branching off the wires every few
millimetres form an intersecting series of positive and negative electrodes
covering the entire underside of the snowboard or ski.
The braking effect arises from a useful property of ice: it is a 鈥渄ielectric鈥�
material that can hold a charge. When a positive electrode comes into contact
with compact snow, it induces a negative charge at the surface; in the same way,
the negative electrode induces a positive charge in the snow. Because opposite
charges attract, this pulls the board closer to the snow and increases
friction.
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And there鈥檚 another effect that can help slow you down on snow and ice
(see Graphic).
Looked at under a microscope, the surface of snow is covered with a
series of ultrafine icy ridges just a few micrometres high. When these ridges
come into contact with two opposite electrodes on one of Petrenko鈥檚 skis, a
small current passes through the ice and melts it. 鈥淭he contact points are tiny
and melt within a millisecond,鈥� says Petrenko. But once contact with the
electrodes is broken, the water refreezes and sticks to the ski. The force
required to break the bond between the ski and the ice helps to hold the skier
back.
The brakes worked well in tests, says Petrenko. 鈥淭he change in friction you
get is equivalent to going from being on ice to dry pavement.鈥�
He is now working with a snowboard manufacturer and hopes that snowboards
fitted with his brakes will be available next year. A sensor fitted to the
boards will monitor the board鈥檚 speed over the ice, and switch the brakes on if
it鈥檚 going too fast.
Petrenko expects his idea to find a ready market. Last year, 11,000 Britons
were injured skiing in France alone, and several died. And the French government
has rushed through measures allowing it to ban dangerous, macho skiers and
boarders.
Skis and snowboards aren鈥檛 the only surfaces that need to get a grip on snow.
Petrenko鈥檚 next aim is to build shoes and car tyres incorporating similar
electronic mechanisms.