Credit: Johns Hopkins

 

In the winter 2019 issue of the Johns Hopkins Whiting School of Engineering Magazine, how to make space elevators a reality is tackled.

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.

Explains Sean Sun, professor in the Department of Mechanical Engineering: “It’s mathematically possible to use steel. But the design parameters would require so much steel that there’s not enough material in the entire universe.”

Taking a different approach, Sun and graduate student Dan Popescu apply a bioengineering spin to this problem.

Autonomous robots

As Christen Brownlee explains in the magazine story, 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.

Good working order

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, explain the researchers.

Popescu and Sun recently reported their solution — Building the Space Elevator: Lessons from Biological Design – at Cornell University’s pre-print website, here:

https://arxiv.org/abs/1804.06453

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