The Centennial Challenges and the Space Elevator

Less than two weeks from now the Centennial Challenge-sponsored power beaming and tether events will be held at the X-Prize Cups. These events, which have also been called the elevator games and climber challenge for the power beaming event, have been mentioned before on this site and will be covered in detail after they occur. The interest in these events is because they directly relate to the construction of a real space elevator.

The tether challenge focuses on the primary hurdle for the space elevator – macroscopic material with the strength sufficient to build the space elevator ribbon. Plenty of places now produce carbon nanotubes in bulk but no commercial entity is producing any threads, fibers or bulk material that can be used for structures. The distinction is critical and so is the progress on this front. The initial competition with a $50k prize was not sufficient to spur development but the recently announced increase in the prizes for the two challenges to $4M over the next few years should help increase interest.

The climber challenge directly relates to perhaps the second most critical component of the space elevator – the climbers. The challenge is to build a climber that can ascend a ribbon at 1m/s using only power beaming and to do this carrying a payload. This is about 2 miles per hour, not blazing fast but a good start. Design considerations show that a climber ascending at this speed with a mass of 25 kg should be able to do it and carry a couple times its mass as its payload. This challenge demonstrates the viability of complete power beaming system but only on a small scale, the overall control and drive
systems and the performance capabilities.

In the best design with off-the-shelf parts a climber at the competition could win the challenge and carrying 100 kg up the ribbon at 1m/s. How does this relate to a real climber? The climbers laid out as the baseline travel at about 20 miles per hour deep in Earth’s gravity well, weigh in at 7 tons and carry a payload of 13 tons. Obviously there is scaling up to be done but let’s assume that we simply use more of the same motors, arrays and components. Based on this and adjusting for the difference in payloads we get a full-size climber that can do 4 mph. This is just scaling the expected performance for a climber built for the competition – potentially this year. If we imagine the competition becoming more aggressive in the coming years with composite frames, customized motors, lightweight arrays, higher power lasers, etc. and going to much longer ribbons suspended from a large aerostat (balloon). I think we will see this competition produce climbers that will meet the basic operating requirements of the real space elevator. The short falls of the climber competition in addressing the climber come in terms of operation in a vacuum, high-speed operation out of the gravity well, and the operating life requirements of the real climbers. These will require additional tests.

The upcoming climber and tether competitions are great platforms for everyone to get involved and work to develop the technology required for the space elevator.

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