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question 47: when can we take the elevator to heaven?

Building an elevator to space has long been a dream among science-fiction authors. If this becomes possible one day it will be thanks to the incredibly strong and incredibly small nanotube – a structure that nano scientists foresee a revolutionising future for.

Text by Eva Krutmeijer

Carbon nanotubes are the strongest-known fibres under tension. They are 100 times stronger than steel with a sixth of the weight and they are as rigid as diamonds. They can stretch beyond 20% of their rest length and can be bent and tied in knots without any resulting defects.

What mightn't we be able to build with this fantastic material? Dent-resistant car bodies, suspension bridges spanning enormous distances and earthquake-resistant buildings... So far, though, we've really only developed materials that exploit nanotubes' extreme lightness and strength, for example in tennis rackets and golf clubs.

An even more intriguing example of their application would be to build a cable, not just any cable but one that would connect the Earth with an orbiting satellite. But is it really feasible?

Professor Eleanor Campbell, physicist and nano researcher in Göteborg knows:

"High-quality carbon nanotubes are the strongest individual fibres that can be made. In theory they have the properties we need to build a long cable to connect up to a counterweight, a satellite, in geostationary orbit round the Earth."

As the Earth spins, the satellite will stay in the same place relative to the Earth's surface - with the distance between it and the base station on Earth always the same.

But what use could such an ‘elevator' be put to?

"It would allow spacecraft to ride the cable into orbit. It would give us a much cheaper and environmentally-friendly way of launching spacecraft. Safer too."

Can it really be feasible?

"Oh yes, but we've still a long way to go. What's important is that it's now theoretically possible - which it wasn't before!"

To get an idea of the strength of nano fibres we can compare them with steel, which is pretty strong. Let's say we wanted to build a hawser of steel that could manage the thousands of kilometres out to a satellite. In practice this is actually impossible because the cable would have to carry its own weight. If we assume that the cable is one millimetre in diameter at the Earth's surface, the properties of steel mean that it would need to be 40 000 000 000 km thick up at the satellite end. You can compare that with the diameter of the Earth, which is only 13,000 km! A carbon cable, on the other hand wouldn't need to be more than a few metres thick.

No doubt about it, carbon nanotubes have a revolutionising potential that we're only just beginning to grasp...

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