Reach for the skies: Space elevators

First published in the Lake Champlain Weekly
Written by Quentin Langley

At any given altitude above the surface of the Earth there is one speed for stable orbit. A satellite traveling faster than that speed will fly off into space and one traveling more slowly will fall to Earth. A low Earth orbit – around 100 miles above the surface – means a very fast speed and an orbital time of around 88 minutes. The most interesting orbit is just over 22,000 miles above the surface, when the orbital time is 24 hours. That means a satellite above the equator will remain above the same spot on the Earth’s surface. This is geostationary orbit. The satellite isn’t stationary, of course, it is just that its movement matches that of the Earth’s surface.

Let us imagine that you hang a cable from a satellite in geostationary orbit. If the cable is 22,000 miles long it will reach the surface. Indeed a cable that is 44,000 miles long can loop around a wheel and return to the satellite. This means that an elevator riding that cable can be powered partly by counterweights: if one elevator is going up and the other is going down they balance each other, at least insofar as their cargoes have equivalent mass. With such a system in place it would be possible to reach orbit relatively cheaply, without expending rocket fuel. Space craft could then be built in space, without the need for landing or take off.

This may seem odd, at first. Why would you want space craft that move from the orbit of one planet to the orbit of another, without ever landing? The answer is that the type of vehicle best suited to moving to and from the surface of a planet is not well suited to deep space travel. The type of vehicle that gets you to the airport is not suited to flying. It would be possible to design a craft which could fly the Atlantic and also pick you up and drop you off at home, but it would be hugely inefficient.

The cables for a space elevator would need to very light and very strong. Carbon nanotubes and diamond nanothreads may meet the specifications, in which case the necessary technology to build such an elevator will be in place within a few years. Actually building it, of course, is another matter. Someone would have to pay for it. It would be a project on such a scale that even the West Coast billionaires like Jeff Bezos and Elon Musk – who are both investing in space travel – might balk at the bill.

But now a new proposal from a New York firm of architects goes even further. What if you hang a skyscraper from a satellite? The firm, Clouds Architecture Office, is proposing a building that would be 20 miles high, some sixty times the height of One World Trade Center, and hang as part of a structure tens of thousands of miles high.

Buildings such as this are decades away. Indeed, the space elevator is probably a prerequisite, and it could open up space travel so much that such a skyscraper might be built on Mars first.

Quentin Langley lives in New York and London and teaches at the University of Bedfordshire Business School. He is the author of Brandjack: How your reputation is at risk from brand pirates and what to do about it

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