Nasa has announced two competitions aimed at developing the technologies needed for the future of space exploration.

The Centennial Challenges comprise the Tether Challenge to develop a super strong lightweight material that could be used in a space elevator, and the Beam Power Challenge to develop wireless technology that could power robots from a distance.

The initial prize is $50,000 for each challenge, and a second round worth $100,000 will be announced in 2006.

"This is an exciting start for the Centennial Challenges programme," said Brant Sponberg, programme manager for Centennial Challenges.

"The innovations from these competitions will help support advances in aerospace materials and structures, new approaches to robotic and human planetary surface operations, and even futuristic concepts like space elevators and solar power satellites."

The Tether Challenge will be settled by a simple strength test against a tether Nasa has developed itself, with the lines being stretched to breaking point.

Competitors in the Beam Power Challenge will have to power robotic climbers to lift the greatest possible weight to the top of a 50m cable in under three minutes.

About 15 teams, mostly from universities, have signed up to compete. Entrants will retain the intellectual property rights to the inventions used in the competitions.

Prizes have long been used to stimulate scientific discovery. Earlier this year Burt Rutan won the X Prize for successfully entering space twice in a private vehicle.

More information on the Nasa Centennial Challenges can be found here.