January 30, 2007
Preventing Ice Before It Forms with NASA Technology
Icy airplane wings can be a serious safety hazard, especially during takeoff. It doesn't take much: a sheet of ice no thicker than a compact disc can reduce lift by 25 percent or more. But an anti-icing fluid developed by engineers at NASA's Ames Research Center helps stop ice from ever forming.
Airplane wings are typically cleared with a deicing solution that's applied after ice has already formed. The NASA-developed formula takes the "ounce of prevention" approach.When applied to a dry surface, the fluid prevents ice from bonding to the wing surface, saving time, money, and also excessive use of chemical solvents. But if "a pound of cure" is needed, the solution can also be applied to icy wings and perform like a traditional deicing formula.
It may seem counter-intuitive that spraying a liquid in freezing cold can prevent ice. The secret lies in a combination of propylene glycol, which has a very low freezing point, and a thickening agent.
The thickener, a pseudo-plastic, sprays on like a liquid (think lemonade), then becomes a gel (think lemon sherbet). Ice gathers on top of the formula and can be easily cleaned away. When wiped, the gel liquefies and then gels again when left to solidify. The sherbet-like consistency helps the formula cling to surfaces, especially those that are vertical or steeped.
The sherbet analogy isn't that far-fetched. When it was originally introduced, the solution was deemed "food grade" because its ingredients were approved by the U.S. Food and Drug Administration for use in ice cream.
This delicious difference also provides a safety advantage over deicing solutions that contain methyl alcohol and ethylene glycol. Both substances can have negative effects on people and animals, and widespread toxic effects in streams, rivers, or other bodies of water.
Closer to the ground, the deicing solution has also found other commercial uses. WorldSource, Inc., of Palm Desert, California offers Ice Free, a spray that helps prevent ice down to 20 °F.
Sprayed on before icy weather, it prevents ice or snow from bonding on a car's glass surfaces -- windshield, side or rear windows, and mirrors. Industrial suppliers have found that the product combines both deicing and lubricating benefits, and it may also have uses on railway switches and monorail electrical connections.
The deicing fluid is just the latest example of how NASA technology with roots in flight safety can benefit air and ground transportation safety. In the 1970s, NASA scientists found that cutting narrow grooves into the surface of runways allowed rainwater to flow off of the tarmac, decreasing slipping, hydroplaning, poor handling, and reduced braking times. Since then, this knowledge has aided airports around the world, and highway engineers have also realized its uses for improving slippery roadways.
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