A normal traction elevator uses a cable to winch a cabin up and down between floors inside a building. There’s a counterweight on the other end of the cable to make moving the cabin easier. You step into the cabin, press a button and are winched to the desired floor by an electric motor. As you go up, the counterweight goes down and vice versa.
A space elevator, as you might imagine, takes this idea a bit further. It relies on a cable that runs from space to Earth – thousands of metres of cable. Instead of needing a rocket to go into space, you run a cabin up the cable, which uses a fraction of the energy of a rocket launch and causes no pollution.
Sounds impossible, but people have been giving this some serious thought over the years. Amazingly the idea has been discussed since 1895, when Russian rocket scientist and pioneer of astronautics, Konstantin Tsiolkovsky, suggested a sky ladder.
The first problem is figuring out what to attach the cable to in space. Satellites in geostationary orbit are the answer. Geostationary orbit is the special distance from Earth where objects stay in one precise spot overhead instead of orbiting around us. This would put our space anchor point at around 36,000km (22,200 miles) above the equator.
Now a crazily long cable must be dropped down from the satellite. If the satellite boosts itself higher as the cable drops, it’ll counteract the weight of the cable and stay in the right place. (You can also add a large counterweight to the end in space to help.) Below geostationary orbit, gravity keeps the cable taut; above it, centrifugal effects do the same job.
The cable needs to be attached to the ground and anchored in some way. Some researchers suggest the anchor could be at the top of a mountain or a tower, to reduce the sheer length of cable needed. More recent concepts propose a mobile base on an ocean-going vessel or platform. It could be in international waters and could move to avoid storms (or falling space debris, should something go wrong at the top).
We now have our space elevator. It uses a ‘climber’ to pull a payload up the cable. But won’t climbing the payload into orbit pull the whole contraption down on our heads? Apparently not, the experts say. Calculations show that you can attach a payload of up to one per cent of the mass of the cable. And, with the cable likely to weigh hundreds of tonnes, that’s still a decent weight.
But there’s still the problem of the cable: it needs to be 50 times stronger than steel! Researchers have been trying to make cable of sufficient strength for years and all attempts have failed. But a recent report by the International Academy of Astronautics suggests that carbon nanotubes or graphene might have the right kind of strength. Watch this space (excuse the pun) because predictions suggest space elevators could become a reality in just a few years.
This article is an answer to the question (asked by Thomas Bletso) 'Could we really build a space elevator?'
To submit your questions, email us at questions@sciencefocus.com, or message our Facebook, X, or Instagram pages (don't forget to include your name and location).
Check out our ultimate fun facts page for more mind-blowing science.
Read more:
