Servo - December 2013

— a compressive structure supported from the bottom up.

No known material, however, has the compressive strength to support a free-standing tower tall enough to reach geostationary orbit. Other scientists, however, picked up where Tsiolkovsky left off.

The modern proposal for a space elevator is to deploy a cable or tether (or ribbon, if you will), from a satellite down to Earth. A counterweight on the tether in space means that the structure is under tensile stress instead of compressive stress. Even though we’re talking about serious tensile stress, the tensile structure deals with forces much more manageable than a compressive structure about as tall as 110,000 Eiffel Towers.

Nowadays, we have a material that makes such a structure feasible: carbon nanotubes. With an achievable structure within reach, the space elevator has been the subject of a renewed research effort, and detailed proposals have emerged that fill in some of the important specifics about the project such as location, space debris avoidance, and other head scratchers.

One proposed space elevator would climb at what sounds like a speedy 200 km/h.

That means that the trip to geostationary orbit would only take a mere seven and a half days. That’s a long time to listen to

The Girl From Ipanema.

One way in which the space elevator has been pushed closer from the realm of science fiction into the realm of science fact is through competition. Much like the Ansari X-Prize, several organizations seek to spur innovation with a monetary incentive. One such organization was Elevator:2010, a partnership between the Spaceward Foundation and NASA Centennial Challenges.

Elevator:2010 sponsored competitions for five years beginning back in 2005, and presented two different challenges. One was to build the strongest tether possible. The other was to create a wirelessly powered climber capable of ascending a tether at a certain speed.

RoboGames also included a ribbon climbing challenge inspired by the space elevator. For their challenge, teams had to build a robot to ascend a tape ribbon up to six meters high, pause in the middle on command, and stop automatically at the top. Bonus points were awarded to teams who beamed power from the ground to their robot.

Ribbon Dancer

A challenge like ribbon climbing may be daunting to the uninitiated, but as with any challenge the key is to break it down into manageable steps. A key part of the ribbon climber that we were keen to tackle given our background was the climbing mechanism itself. Unlike some of the other challenges inherent in a ribbon climber, the climbing mechanism appears to be rather straightforward.