Science & Technology

A Space Elevator Could Make Space Travel Easier — If It Were Possible

It's really expensive to go to space. That's because it's really hard to escape Earth's gravity. The Saturn V rocket, for example, weighed in at 2.8 million kilograms (6.2 million pounds) and 85 percent of that was devoted to fuel alone, most of which was used to simply leave our planet. To borrow a line from an infomercial, there's got to be a better way! Well, there might be, but you have to promise not to laugh. We could just build an elevator: an elevator ... to space.

You Raise Me Up

If you think this idea is right out of science fiction, you're right: Arthur C. Clarke wrote a space elevator into his 1978 novel "Fountains of Paradise," although the idea was around for much longer than that. In essence, a space elevator would extend a (very) long cable from Earth's surface into space, placing its center of mass at geostationary orbit (GEO). That's 35,786 kilometers (22,236 miles) up, which is high enough for satellites to match Earth's rotation. Vehicles could travel along the cable to transport payloads and people between Earth and space — no rocket boosters required.

The cable would have to be tethered somewhere on the equator since hurricanes don't happen there and it lines up nicely with GEO. To keep it from falling back down to Earth, there would also need to be a counterbalance higher than GEO — some plans call for a captured asteroid to do the job. Below that would be transfer stations and perhaps a habitation structure; above that, the cable would keep on going to help slingshot spacecraft out of orbit with a fraction of the energy required on the planet's surface.

Nanotubes in the Sky, I Can Go Twice as High

Of course, it's easy to describe any science-fiction structure that strikes the imagination. That doesn't mean it's feasible. What would the cables be made of? What happens if it needs repair? And don't even get us started on suborbital elevator etiquette. Scientists have thought about these questions, and many have come up with answers. NASA conducted a workshop to come up with concepts for the structure in 1999 and Google was working on a space-elevator project as recently as 2014, but the project was later abandoned.

The latest attempt comes from a mathematician and a mechanical engineer from Johns Hopkins University. In a yet to be peer-reviewed paper posted on the pre-print site arXiv in April, Dan M. Popescu and Sean X. Sun say that it's perfectly possible to build a space elevator in the very near future. The key to their plan comes from biology. While the kinds of stress-to-strength ratios you'd use in the engineering of a skyscraper would make a space-elevator-sized cable impossible — it'd never withstand the stress — the researchers say that if the material were able to heal itself, like a bone or tendon can, you could use weaker materials that would still stand up to those punishing forces.

And the ability to use weaker materials is important since carbon nanotubes — the holy grail of super strong, super light materials, and the biggest hope for the space elevator — haven't been created to be any longer than a half meter at this point. If you mixed carbon nanotubes with other materials, stacked them in such a way that any one piece could fail without disrupting the others, and deployed autonomous repair robots to maintain the whole thing, you might be able to make a cable long and strong enough to hold up an entire space elevator with materials that are possible today. That's just the first baby step of many, but it appears that for space elevators, things are going up.

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Read the sci-fi novel that put space elevators in the spotlight: "Fountains of Paradise" by Arthur C. Clarke is available in paperback or for free on audiobook with a trial of Audible. We handpick reading recommendations we think you may like. If you choose to make a purchase, Curiosity will get a share of the sale.

Written by Ashley Hamer June 26, 2018

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