Whilst science professionals harbour yearnings for all manner of inventions to make it into the real world, from cold fusion to Helium 3 harvesters, domestic serving units or driverless cars, for myself I hope to live to see a space elevator become reality. A lift that takes you up into space? Pretty cool. A launching pad to the planets? I’ll take that. A smart way to get asteroid elements down to earth and convert the kinetic energy at the same time? That’s a triple-win. Unfortunately, there remain several practical difficulties to overcome.
It is agreed that the elevator will take counterweight suspension form – a massy object in orbit will tether the top of the elevator with centrifugal force providing tension, and the Earth’s gravity performing the same function down below. So there’s the first problem. A massy object in orbit. This would require a large space station, or towing a suitable asteroid to the correct position and then (probably) lowering down a cable. Neither of these options are currently on the cards, so let’s skip to a couple of the smaller obstacles.
What possible cable could be used to tether a space station to the earth? The most likely candidate we have so far is perhaps graphene, the new wonder material. The physics says that the cable material must have a tensile strength of 130 Gigapascals and graphene hits that mark. What that means is that the material chosen should be able to support 5,000 km of its own weight at sea level (the asteroid/space station takes the rest of the load) and graphene is expected to be able to support nearly 6,000 km. So we have a material that will work. Possibly.
The elevator itself will likely need to be a ‘climber’ – the cable will need to be dramatically thicker at the geosynchronous orbit level than on the ground due to the stresses involved, so that would seem to rule out moving cables pulling the box up. To reach geosynchronous orbit (say 22,000 miles up) at a speed of 200 mph would take around 4.5 days. Even getting the lift up to 1,000 mph means it would still take a day and we would need a whole new generation of elevators to conjure up that spectacle. I’m not mentioning their power supply either.
So it seems that for the moment space elevators are just another fantasy, but at least they are a fantasy with a solution, however far off that may be.
Andy Malcolm is a science geek with an interest in future tech and inventions. He wrote this piece after being asked to consider lift installation by www.pickeringslifts.co.uk .