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Are Space Elevators Possible or Still Science Fiction?

Innovation

Rockets are the best way we currently have to get humans and cargo into space, but they aren't necessarily the best way to do so, full stop. Space elevators could theoretically achieve the same goal without expensive, inefficient rockets—but just how theoretical are they? Are space elevators possible, or stuck firmly in the realm of science fiction?

What is a space elevator?

A space elevator isn't intended to function like a literal elevator. Instead, it would most likely be an object in geosynchronous orbit above the equator, leashed to an island at the equator with a kind of tether. This would serve as a counterweight to keep the tether taut. Vehicles powered by either solar or laser energy would climb this tether at a rate of up to 200 miles per hour, delivering people or cargo to low Earth orbit in as little as an hour, and to the end of the line in about two weeks. There would be no need for rockets or rocket fuel.

What problems would they solve?

Theoretically, a space elevator would be a way to transport people and objects into space without having to rely on a rocket. About twenty years ago, it cost roughly $27,000 per pound to send something up on the space shuttle. (For reference, an espresso machine cost nearly $2 million.) Today, the reusable Falcon 9 rocket from SpaceX has lowered that cost to $1,233 per pound. Experts think they can do even better with a space elevator, which would reduce costs to as little as $100 per pound.

In addition to cost, a space elevator would reduce the considerable environmental impact of space transport. If the vehicles that climb the tether are solar powered, they could operate with zero emissions. Since there are no rockets, there's no need for the building materials and fuel that go into producing them. Once the space elevator is built, it could be the cleanest method of delivering humans and cargo ever devised.

What challenges do builders and designers face?

The biggest issue is one of materials. A space elevator doesn't rely on a rigid elevator shaft, of course. The tether material must be incredibly strong—strong enough to withstand the force of the counterweight's pull, the weight of its payloads, collisions with space junk, and whatever weather it may be subjected to. The longer such a cable is, the stronger it needs to be. Experts estimate that this material would have to be thousands of times stronger than steel, and no such materials exist yet. (The current frontrunner is graphene, which is roughly 200 times stronger.) A secondary problem comes from space junk.

The area right around Earth is pretty polluted by derelict spacecraft, fragments of other mission debris, flecks of paint, particles of unspent fuel, and so forth. This even poses a threat for the International Space Station, one which it uses its thrusters to escape. A space elevator wouldn't be able to do so, however. Since it's tethered to a spot on Earth, whatever object is at the other end—a small space station, or even a captive asteroid—can't exactly get out of the way of a collision. A few startups are working on ways to reduce the amount of junk in space, but it's pretty slow going.

Who is currently working on one?

Right now, Shizuoka University in Japan, the Obayashi Corporation, and the China Academy of Launch Vehicle Technology are currently trying to find a way to build a space elevator. About two years ago, engineers from Shizuoka University created a scale model of one using two 10 cm (3.9 inch) satellites connected by a 10 meter (32.8 feet) long steel cable. A small, motorized container traveled along the cable, while cameras at either end tracked its progress.

The Obayashi Corporation plans to build a space elevator by 2050. This would involve a 400 meter diameter floating port on Earth, connected to a 12,500 ton counterweight in space by a carbon nanotube cable. Theoretically, they would initially deploy a 20 ton cable. This would be reinforced over and over again by lightweight climbing vehicles. While they acknowledge that there are still technological hurdles that keep production from going underway, they feel their plan is realistic enough to produce a viable space elevator.

The China Academy of Launch Vehicle Technology plans to have a functional space elevator by 2045. The Tsinghua University research team has developed a type of carbon nanotube fiber that they think may be the key to creating a tether. Chinese scientists have also carried out space tethering experiments, but haven't released details. A functioning space elevator would give mankind a way to escape Earth's gravity without the exorbitant monetary and environmental cost of sending rockets into space. With a counterweight that can withstand collisions and a material strong enough to tether it to Earth, it could revolutionize virtually every aspect of space transport.