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Tethers tortured in $2 million contest

Three teams brought lengths of string to the Strong Tether Challenge today in hopes of winning as much as $2 million of NASA's money. But they all went away empty-handed ... except for the shreds of carbon nanotubes and glass fiber they had to pick up off the floor.

This year's challenge, organized by the California-based Spaceward Foundation, was conducted in conjunction with the 2010 Space Elevator Conference on the Microsoft campus in Redmond, Wash. (Microsoft and NBC Universal are partners in the msnbc.com joint venture.) The aim of the contest is to promote the development of lightweight materials that can outperform the strongest fibers available today.

Eventually, such materials could be used in the construction of space elevators, "railways" that reach tens of thousands of miles into the sky. But there are more immediate applications for ultra-strong, ultra-light materials: to make stronger ropes, better bulletproof vests and body armor, lighter and hence more fuel-efficient cars and airplanes, and hardier spacecraft.

NASA has been putting up the prize money for the Strong Tether Challenge since 2005. Five other NASA-backed Centennial Challenges - for prototype lunar landers, moondirt-digging robots, astronaut gloves, innovations in aviation and beam-power systems - have all produced winners. But no one in the tether contest has won a dime yet.

"This is probably the hardest challenge of all the challenges out there, because it's so fundamental to materials science," Spaceward's Ben Shelef, who has run the contest from its inception, told the 30 onlookers who assembled to watch the competition.

The Strong Tether Challenge is structured as a tug-of-war, matching lengths of experimental fiber against a heavier woven loop of Zylon fiber on what's known as a "tether torture rack," If the Zylon breaks first, then the challenging team wins a prize. But that's easier said than done. A single strand of Zylon looks like dental floss - but when I tried to wrench it apart with my hands, it ended up cutting my finger instead.

"If any one of these tethers beats this [Zylon] tether, we can pack up and go home, because we're starting to build a space elevator," Shelef said.

The standard to beat is quantified in terms of gigapascals per gram per cubic centimeter, or GPa/(g/cc), a measure that wraps the lightweight factor and the strength factor into one scale. This unit of measure, which is also equivalent to one N/Tex, is so useful when it comes to judging material strength that Shelef has proposed a new standard measure called the "yuri," in honor of space-elevator theorist Yuri Artsutanov. One GPa/(g/cc) or N/Tex is equal to a megayuri, and it takes 5 megayuris to win a prize.

The $2 million purse is structured with a sliding scale, based on the tether's length and mass. One of the teams entered in today's competition, the Tether Addicts from Florida (Gilberto Brambilla and Bruce Klappauf) theoretically could have won the whole shebang. The other two entrants, Bryan Laubscher and Christopher Cooper, could have won $300,000 to $600,000, depending on the combination of winning outcomes.

Calculating the potential permutations would have been an empty exercise, however, because none of the challengers came close to hitting the 5-megayuri mark. All of the fibers broke after just a few strokes of the hydraulic hand pump on the tether torture rack. The most spectacular sproing came during the final test, when pressure was put on the Tether Addicts' meter-long entry, woven from glass fibers that were coated with carbon nanotubes.

Brambilla told me that he and Klappauf had a length of fiber in their lab that could have won the prize - but that a cleaning crew accidentally threw that fiber in the trash. "It ended up in the vacuum cleaner," he said ruefully. The replacement fiber had to be made in a rush, and Brambilla wasn't all that happy with the result.

The Tether Addicts took time off from their day jobs at an optics lab to work on this year's entry, and Brambilla wasn't sure whether he could keep feeding the addiction. "You can't really justify working on this subject if you don't have the money," he told me. But Shelef was betting that at least one or two of this year's contestants would be back for the next tug-of-war in 2011.

"That wraps it up this year," Shelef declared after the last tether was torn. "Better luck next year."


For more about today's contest and the weekend schedule for the Space Elevator Conference, check out Ted Semon's Space Elevator Blog. Join the Cosmic Log corps by signing up as my Facebook friend or hooking up on Twitter with @b0yle. If you really want to be friendly, ask me about "The Case for Pluto."