27 September 2005

Arthur C Clarke on the space elevator

The Times Online guest contributors Opinion
Today's communications satellites demonstrate how an object can remain poised over a fixed spot on the Equator by matching its speed to the turning Earth, 22,300 miles (35,780 km) below. Now imagine a cable linking the satellite to the ground. Payloads could be hoisted up it by purely mechanical means, reaching orbit without any use of rocket power. The cost of launching payloads into orbit could be reduced to a tiny fraction of today's costs.

The space elevator was the central theme in my 1978 science-fiction novel The Fountains of Paradise (soon to be a Hollywood movie). When I wrote it, I considered it little more than a fascinating thought experiment. At that time, the only material from which it could be built – diamond – was not readily available in sufficient megaton quantities. This situation has now changed, with the discovery of the third form of carbon, C60, and its relatives, the Buckminsterfullerenes. If these can be mass-produced, building a space elevator would be a completely viable engineering proposition.

What makes the space elevator such an attractive idea is its cost-effectiveness. A ticket to orbit now costs tens of millions of dollars (as the millionaire space tourists have paid). But the actual energy required, if you purchased it from your friendly local utility, would add only about a hundred dollars to your electricity bill. And a round trip would cost only about one tenth of that, as most of the energy could be recovered on the way back.

Once built, the space elevator could be used to lift payloads, passengers, prefabricated components of spacecraft, as well as rocket fuel up to Earth orbit. In this way, more than 90 per cent of the energy needed for exploration of the solar system could be provided by Earth-based energy sources.
Looking even farther ahead, one could see the virtual elimination of the rocket except for minor orbit adjustments. By extending the elevator, it would act as a giant sling, and payloads could be shot off to anywhere in the solar system by releasing them at the correct moment. Of course, rockets would still be responsible for the journey back to Earth – at least until elevator/slings were constructed on the other planets. If this ever happens, the most expensive component of travel around the solar system would be for life support – and inflight movies.

As its most enthusiastic promoter, I am often asked when I think the first space elevator might be built. My answer has always been: about 50 years after everyone has stopped laughing. Maybe I should now revise it to 25 years.

Clarke (who predicted the communications satellite many years before the first one was launched) also speaks about the 1911-12 Antarctic expedition and the more than 40 years it took to return there and stay. I could think of much better things to do wth the NASA budget than another Apollo Program and a human-crewed Mars expedition. Building a space elevator is one of them.


Rich said...

I believe such a machine have basic issues with the laws of physics - which you canna change!

I leave the exact nature of these issues as an exercise for the reader. Hint: any object at the top of the "elevator" must be travelling at orbital velocity.

Alan said...

Every object is already travelling at 'orbital' velocity with respect to their distance from the planet's centre of gravity. An object moving at less or more would begin to zip across the landscape in an alarming manner.

Brian Dunbar said...

I believe such a machine have basic issues with the laws of physics - which you canna change!

You can believe what you like - a horde of techs, engineers, scientists and so forth are betting some serious cash that an SE 'works'. See our FAQ at www.liftport.com

Rich said...

Ok - I read the very comprehensive wikipedia article. I guess once you've solved the little problem of making huge amounts of carbon fibre nanotubes, currently costing $100 per gram, then making the space elevator will be a breeze. I notice the FAQ says that laboratory measurements of the strength of such nanotubes are very difficult to do - funny that making a 100,000km rope of them is gonna be easy...

Things on the earth's surface are *not* travelling at orbital velocity - that is why they fall when you pick them up.

Anyway, having built your wire to space, you would then need to wind things up it - this requires a very large amount of energy to be either carried or transferred to said things. Not hard I suppose, just built a simple particle beam or an easy to construct fusion reactor.

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