Space elevators have existed as a concept for more than a century, but without sufficient material technologies they have been relegated to the world of science fiction.

However, this could be set to change, as the idea is seeing renewed interest from commercial companies.

Simply put, a space elevator is system that runs from a point on the Earth’s equator right up past geostationary orbit to a counterweight located in space.

These two points are connected by a 100,000km long tether – a very thin ribbon-like material with enough strength to maintain the connection while supporting 20t of cargo.

Attached to the tether is some form of pulley system that would allow cargo – and humans – to move easily into space, without the need for rockets to escape the clutches of Earth’s gravity.

Such a system would be revolutionary, turning space travel into a relatively low-cost endeavour and greatly increasing the number of people who could leave Earth. Estimates by the International Academy of Astronautics (IAA) even suggest that the cost- per- kilogram of launching items into space could drop from the current rate of $20,000 to the bargain price of $500.

“It could take you from ground to orbit with a net of basically zero energy. It drives down the space-access costs, operationally, to being incredibly low,” explained Google X rapid evaluation team leader Richard DeVaul in an interview with Fast Company.

A Matter of materials

The biggest issue that is preventing the development of space elevators is the lack of a suitable material to function as a tether.

Earlier this year it emerged that Google X, the technology giant’s secretive research lab for extreme future technologies, had undertaken serious research to determine if development of space elevators was feasible.

Their conclusion was that the tether needed to be at least 100 times stronger than the best steel ever developed, and only one material fitted the bill: carbon nanotubes.

Unfortunately, material science is still working on making carbon nanotubes long enough; at present the most that has been achieved is 1m, a far cry from the 100,000,000m needed.

However, materials science is seeing something of a revolution at present, which is accelerating the development of a whole host of nanoscale materials.

Carbon nanotubes in particular have already been recognised as a key material for a slew of applications across electronics, medicine, energy generation and the military, so there is likely to be strong long-term support for research.

It is quite possible, perhaps even likely, that the generation of suitably long carbon nanotubes is just a matter of time.

Finding a timescale

How long it will be before space elevators are possible to build is a matter of considerable debate.

The International Academy of Astronautics IAA recently released a report outlining the value and challenges of space elevators, in which the organisation argued that the technology could be possible by 2035. For many, however, such an ambitious estimate is way off the mark.

Peter Debney, engineer for global construction firm Arup, believes the technology is on its way, but will take far longer to be realised.

“I believe that they could be built cost-effectively within a century, and pay for themselves within just a few years,” he said in a post on the company’s website.

“While we have not quite got all the technology in place, and there are still engineering challenges to be overcome, the space elevator has nearly arrived.”