A New Hitch in the Plan for Building a Space Elevator

Carbon nanotubes may not be as strong as scientists once thought

space elevator
A concept design for a space elevator. NASA

Lightweight and incredibly strong, proponents have touted carbon nanotubes as the ultimate building material. These tiny cylinders of interlinked carbon molecules have been popping up everywhere, from racing bikes to biomedical devices. And many scientists have suggested using this material to take the long-held dream of a space elevator from fiction to reality. But a new study throws another hitch in the concept, showing that the arrangement of atoms in the tiny carbon structures could cause the whole system to collapse, George Dvorsky reports for Gizmodo.

A space elevator works exactly like its name suggests, lifting a car or enclosure from Earth’s surface into space.  The technology could revolutionize space travel by making it easier and cheaper than launching a spacecraft aboard enormous rocket engines.

The idea was first introduced into popular culture by Sir Arthur C. Clarke in his 1979 science fiction novel The Fountains of Paradise, Michelle Z. Donahue reports for Smithsonian.com. Scientists later hopped on the concept and have been inching towards the towering structure for decades.

Building a space elevator is no small task. The basic idea is that the space elevator would be anchored to a position on Earth, extending out to a terminal in space that moves in sync with Earth's orbit and rotation. But because the cable would have to stretch for tens of thousands of miles, the material would needs to be both strong and lightweight to work.

new study, however, has found that carbon nanotubes aren't the perfect solution. While a perfectly constructed carbon nanotube roughly the width of a thread could be strong enough to lift a car, misplacing a single atom cuts its tensile strength in half.

“Only [carbon nanotubes] with extreme quality are able to retain their ideal strength,” Feng Ding, a researcher at Hong Kong Polytechnic University and lead author of the study tells Jacob Aron for New Scientist. “Most mass-produced [carbon nanotubes] are highly defective, and high-quality [carbon nanotubes] are hard to produce in large quantity.”

Ding and his colleagues ran computer simulations testing how the the hexagonal grid structure of most carbon nanotubes would hold up if altered. They found that a single atom out of alignment causes a weakness that could essentially "unzip" the entire tube, like pulling a loose thread on a sweater, Aron reports.

Nanotube manufacturing is still in its infancy, making a few bad tubes inevitable. But this latest study shows that these few weak links could potentially cripple larger structures. Even the most optimistic proponents of space elevators have long known that making it a reality is a long way off. But this study suggests scientists have even more barriers to erecting the massive structure, Dvorsky writes.

“Unless great breakthroughs on [carbon nanotube] synthesis can be achieved, using [carbon nanotubes] to build a space elevator would be extremely challenging,” Ding tells Aron.

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