Sometimes when I am crossing a beach covered with boulders, my gaze is so firmly fixed on the next step or two that I lose my sense of direction. I need to stop occasionally and look up, to plan out the best route to my destination. Quite often, my new perspective will call for a change of direction - to the left maybe, to take in a stretch of sand for example, to make the going easier.
Recently, I have been so focussed on our need to reduce carbon emissions to limit climate change, and also to preserve dwindling resources, that I have not considered the longer term route for humanity. Or to put it another way, the pronouncements we hear about the need to do this or that to limit global warming by 2050 are all very well, but where is the human race headed in 2100? Or 2200? Or later again?
It seems clear to me that unless we expand into space over the coming centuries, humankind is going to be limited to one or two billion at most by our earth-bound resources. Such a population reduction from where we are now at nearly seven billion does not bear thinking about. But up there, resources are plentiful. Going into orbit by rocket uses a shocking amount of fuel and is hideously expensive; we need to find a cheaper way. So how can we expand into space?
In the 1890s, Konstantin Tsiolkovsky proposed a tower reaching from earth into space which could be used as a lift. This is not as daft as it sounds. In effect, it would be a satelite in geostationary orbit which is so long that its bottom would reach the surface of the earth, and its top reach another 22,000 miles further out towards the moon. The centre of gravity would be in the middle, at the point of orbit.
Such a structure would require enormous strength, beyond any of the materials that we have had until recently. However, it is now possible to make Carbon_nanotubes, thin threads of a new arrangement of the carbon molecule which are very strong. Such threads have been spun together to form a cord too thin to be visible, but strong enough to lift up a truck. Provided a long enough length can be created, this material could be used as the basis for a space elevator. Once it was in position, the difficulty of reaching orbit would be enormously reduced. In addition, for a spaceship to reach escape velocity, it would simply go on up to the top of the upward extending arm and let go.
is best understood by quoting a praragraph by Arthur C Clarke, who imagined a space elevator being built in 2030. He wrote, "Of course, the Elevator was just the beginning. The plans for the future were astonishing; with space opened up at last, asteroids would be mined for metals, minerals and even water, and solar power stations the size of Manhattan would be asembled in orbit. A new industrial revolution was about to begin, and with the free flow of energy up there in space the possibilities for the growth of civilisation were unbounded. But the heavy industries which had done so much harm in the past, mining and energy production among them, would now be transferred off the planet. This time the earth would be preserved for what it was good for: serving as the home of the most complex ecosystem known." (Arthur C Clarke and Stephen Baxter, Sunstorm, Gollancz, London, 2005, page 247).
Clarke's novel The Fountains of Paradise (1979) is a fun read and introduces the concept well. Recommended. There were copies on ebay last time I looked. Read about Bradley Edwards who wants to build one sooner rather than later, and see his report. Browse the space elevator blog and spaceward and watch the development of carbon nanotubes. Read Arthur C Clarke's essay. Other links : news item Jan 09 . . . again Jan 2009 . . . International Space Elevator Consortium . . . Liftport Group . . . Rotation system . . .
David Pennant, Woking, UK