By Kathryn Tomiello, Staff Editor
In the 2005 and 2006 Space Elevator Games, teams participated in tether-testing competitions before spectator crowds of more than 20,000 people, but neither event produced a tether that could withstand the increasing forces the challenges demanded.
NASA’s space elevator may eventually replace propulsion based systems people and cargo into space.
The tethers are part of NASA?s conceptual space elevator, a device that transports material from the Earth?s surface into space using the traversal of a fixed structure and a climbing mechanism. It is meant as an alternative to rocket propulsion. Theoretically, the space elevator could deliver cargo and people into orbit at a fraction of the cost of traditional launching methods.
Today, the technology to complete a space elevator is in its infancy. The SpaceForward Foundation, a non-profit organization dedicated to furthering space science and host of the Space Elevator Games, hopes the competition will stimulate the development of new technologies to make the structure a reality.
The space elevator is comprised of a thin ribbon, or tether, with a cross-section area roughly half that of a pencil, extending from a ship-borne anchor to a counterweight well beyond geo-synchronous orbit. The rotation of the earth and the earth?s counterweight keep the ribbon taught. At its lowest point, it pulls at the anchor with a force of about 20 tons. Electric vehicles, called climbers, ascend the ribbon using electricity from solar panels and a ground-based booster light beam. The elevator can also release payloads directly into lunar-injection or earth-escape trajectories.
The baseline system, including the counterweight, weighs approximately 1,500 tons and can carry up to 15-ton payloads at a rate of, easily, one per day. The ribbon is 62,000 miles long, about 3 ft wide, and is thinner than a sheet of paper. It is made out of a carbon nanotube composite material.
The climbers travel at a steady 200 km/hr (120 mph), do not undergo accelerations and vibrations, can carry large and fragile payloads, and have no propellant stored onboard. The anchor ship can be moved to avoid orbital debris and the ribbon itself is resilient to local space debris damage. The elevator has unlimited capacity. To expand, it carries additional ribbon pieces and sets them into place. 
Solar Panels and a ground-based light beam power NASA’s space elevator.
During the inception of the Space Elevator Games, NASA?s Centennial Challenges program announced its partnership with the Spaceward Foundation to hold prize contests in support of the event.
Aerospace engineer and co-founder and leader of the executive crew of the Spaceward Foundation, Ben Shelef, and his team made a tug-of-war machine for a head-to-head strength competition. Each tether is connected to the pull machine end-to-end and then stretched using a hydraulic piston until the tether breaks from increasing force.
The tether pull machine measuers tensile of the proposed elevator tethers and reference band.
The machine is made out of extruded aluminum structural framing supplied by Bosch Rexroth. The tether machine comprises a rectangular box structure about 12 ft long and 18 in. high on each side. It uses bolt-together connectors for quick assembly. The machine can also be extended beyond a simple frame and base to a complete multi-functional structure. Every aluminum structural framing component is reusable, which makes it simple to change the machine as design needs shift.
The purpose of the tether challenge is to develop an appropriate tether material for use in various structural applications. The competition requires a 50 percent improvement in breaking force from year-to-year. At the 2007 Space Elevator Games a total prize of $1 million will be awarded to the winning team.
NASA
www.nasa.gov
Bosch Rexroth
www.boschrexroth-us.com
Filed Under: Aerospace + defense