A growing number of scientists and space-technology enthusiasts are looking into ways to construct a huge elevator, either on Earth or the moon, that could transport cargo to and from space.
In a study published in September, which has not been peer reviewed, two graduate students proposed a version of a space elevator that would stretch from the moon to Earth's satellite-level orbit. They said the structure could be built with current technology.
"They're right, and we were right first, that the lunar elevator is feasible technology," Michael Laine, president of space-elevator development company LiftPort Group, told Business Insider.
Other advocates of space elevators have argued for years that building such a structure is feasible with current technology and could open up new frontiers of space exploration.
In 1895, Russian rocket scientist Konstantin Tsiolkovsky gazed at the Eiffel Tower and imagined it stretching into space.
Relative to rockets, space elevators would be a cheaper, faster way to get cargo and people off of Earth. That's because liftoff is one of the most expensive and difficult parts of space travel.
"The space elevator would essentially be an economic game-changer for the space industry," Tyler Harris, an engineer at the Pacific Northwest National Laboratory, told Business Insider.
The basic design of a space elevator would involve a cable, or "tether," that could stretch from an anchor on the ground to a counterweight in space.
The centrifugal force of the Earth's rotation would hold up the tether.
Experts say this type of structure could be built with current technology. Cost estimates range considerably, from $1 billion to nearly $90 billion.
The $90 billion cost estimate comes from the Obayashi Corporation, which is based in Japan. The company wants to build a space elevator by 2050.
Obayashi expects it to take 20 years to construct the cable from a 400-meter base that floats in water.
The Japan Aerospace Exploration Agency (JAXA) launched a miniature version of a space elevator in September 2018 to see how it reacted to the space environment.
The same Japanese research team is planning to launch a larger version of the device.
LiftPort, meanwhile has conducted space-elevator technology demonstrations on the ground. Climbers ascended cables as high as 1,000 feet.
The trickiest part of developing a space elevator is finding the right material for the tether.
Space-elevator advocates think carbon nanotubes could be the answer — the hollow tubes of carbon are just nanometers wide yet 100 times stronger than steel.
Another hurdle keeping space elevators in the realm of science fiction: space debris.
However, the moon doesn't contend with all that debris, and lower gravity there means that more materials could support their own weight. So some researchers think a lunar space elevator is a better place to start.
At LiftPort, Laine is also working on a lunar elevator concept. For the tether material, he has his eye on Dyneema, a polyethylene plastic fiber that's 15 times stronger than steel.
One analysis calculated that a lunar elevator could pay for itself after 53 uses, since it could cut at least two-thirds of the cost of landing on the moon and reduce the cost of sample-return missions at least nine-fold.
For now, though, any space elevator remains theoretical. “The big idea is still subject to a lot of details that we don’t have the answers to," Laine said.
But if a space elevator eventually becomes a reality, it could also help us access resources in space.
Once we figure out how to extract valuable resources in space, that may open up possibilities for further exploration.