Making Space Elevators a Reality

Winter 2019

Space elevator

For nearly 150 years, researchers have contemplated the idea of a space elevator—an alternate way to shuttle people and goods to space that wouldn’t involve a shuttle at all. Rather than using energy-expensive rockets for this task, a space elevator would move items up and down a strong cable with one end anchored on Earth, and the other balanced by a counterweight in space, moving in a geosynchronous orbit.

The main sticking point to bringing this futuristic concept to fruition is the cable itself, explains Sean Sun, professor in the Department of Mechanical Engineering. No material yet exists that’s strong enough to withstand the tension caused by the pull of the counterweight, the force of the Earth rotating, and the gravitational weight of the cable itself without using so much of the material that it becomes unrealistic.

“It’s mathematically possible to use steel,” Sun explains. “But the design parameters would require so much steel that there’s not enough material in the entire universe.”

That’s why Sun and graduate student Dan Popescu are taking a different tack, applying a bioengineering spin to this problem.

While most engineered structures operate at a fraction of their material’s tensile strength—how far they can be pulled without breaking—most biological structures, such as tendons, operate near their max.  That’s because biological structures are constantly breaking themselves down and rebuilding, which allows for continual repair.

Space elevators won’t require such a strong cable if the cable also continually renews itself, Sun and Popescu reason. This feat could be achieved, they suggest, by developing a cable that’s constantly serviced by autonomous robots. Rather than waiting for breaks in the cable, these robots can dynamically break down and rebuild the cable to make sure it’s always in good working order. This cable would be segmented so that if a break occurred, it wouldn’t extend beyond a small site, note the researchers, who recently reported their solution on the pre-print website arXiv.

Researchers could test this concept on Earth by using it to design other megastructures, such as suspension bridges, with weaker but dynamic materials. “If these pan out and prove to be economically feasible,” Sun says, “a space elevator would be a natural next step.”