The Tether Challenge is one of NASA's Centennial Challenges, administered by the Spaceward Foundation. The challenge is to construct super-strong tethers. Tethers are foundation elements to space system efforts such as space elevators and rotovators. 
2005 Tether Challenge
The award for the first contest in 2005 would have been US$50,000, if the challenge had been met. The requirements of the challenge was that the winning team would construct the strongest tether. The key to the challenge was that the tether would have to beat the house tether. This house tether could outweigh the challenging team's tether by 50%. In 2005 no team was able to beat the baseline house tether.
2006 Tether Challenge
In 2006 the challenge requirement was that the winner outperform the previous year's winning tether by 50%, and beat the other challengers. The prize for the 2006 Tether Challenge was increased to $200,000.