Could We Build an Elevator to Space?

Is it possible for humans to get to space without blasting off on a rocket? After all, the transporter that beams people up on Star Trek doesn’t exist in real life and it’s not like we can just call an Uber to Saturn.  

A space elevator may be one possible option. It’s a theorized structure that functions very similarly to the same type of elevator you ride up and down a tall building, except that you can take it from the ground all the way to Earth’s orbit. Instead of flying to the moon, you’d ascend up a very long elevator cable. This would arguably be a safer and far less expensive way to move astronauts and cargo beyond Earth’s atmosphere.

But building a space elevator would be a daunting task for a multitude of reasons — in fact, it may be impossible. However, the idea has plenty of proponents, including some who are working to make it a reality.

How Does a Space Elevator Work?

The first question to answer is one of distance, but it’s also philosophical: Where does space begin? The most common answer is the Kármán line, an invisible boundary between 50 and 62 miles above Earth that marks the point where our atmosphere ends. To work, though, an elevator would need to have its counterweight much further out. 

Instead of the moon, let’s imagine we want an elevator that gets astronauts to the International Space Station (ISS). First, we’d have to move the station to geostationary orbit over the equator so that it “stays” in place — when you look up at the sky, it would always be in the same place. (Imagine taking a building’s elevator if the roof was always moving around, and you can see why the ISS needs to be geostationary.)

To remain geostationary, the ISS also needs to move much higher in the sky than it currently is. Today, it’s roughly 400 km above the surface, but the center of mass for a space elevator must be at least 35,786 km high to stay in sync with Earth’s rotation and its ground-level base. That means the cable running from the ground to the ISS would be more than 22,000 miles long. The cable would also need to run much, much further out from the ISS, with its end being the counterweight that allows elevators to function.

At this point, the ISS doesn’t need to use any boosters or rockets to move. It’s being pulled by the Earth by centripetal force. It’s not much different than quickly spinning a yo-yo like a lasso, with the yo-yo moving around your head at a fixed distance, rather than smacking you in the face. Once a taut cable connects the ground to the ISS, an elevator car can then move up and down it at will. 

If something else is used as the center of mass, the ISS can even be moved back down to 400 km and just hang off the cable. Instead of orbiting the Earth, it would be pulled along. After getting on at ground level (and pressing the “Up” button), astronauts could hop off on the ISS while others go all the way up — like coworkers in a really, really tall office building.

Can We Build a Space Elevator Right Now?

One downside to a space elevator, as opposed to a rocket, is that it would take a lot longer. If the elevator car moves at the velocity of a high-speed train, a journey to the ISS would take a few hours, but would take more than a week to get to the center-of-mass that’s at geostationary orbit. However, a bigger flaw in the space elevator idea is that we physically can’t build one — at least not yet.

Not only would the cable of a space elevator need to be thousands of miles long, but it also would need to be incredibly strong. However, it also needs to be lightweight. Stainless steel is strong, but it would collapse under its own weight if it’s used for a 22,000-mile cable.

Currently, there’s no material that we can make with the strength-to-density ratio needed for a space elevator. Graphene, carbon nanotubes, and diamond nano threads are among the low-density, high-strength materials that have been proposed as potential building blocks for the space elevator, but thus far they offer more promise than proof. A design for a space elevator recently won a prize, but even the designer admits the idea is “a bit fanciful” — for now.

Other potential issues involve clearing satellites and space debris from the path of the cable (airplanes would also need to fly around it). If the ground base of a space elevator were on a mobile ocean platform, it could theoretically shift just a little bit to dodge moving debris while still staying in sync with the top. There are also threats to the cable and base station, such as hurricanes and lightning strikes. You wouldn’t want a 22,000-mile cable snapping and falling back to Earth, even if much of it would burn up in the atmosphere.

Finally, anyone riding a space elevator would need to be shielded from radiation, which increases as you leave Earth’s atmosphere. Traveling on an airplane exposes you to cosmic radiation since the atmosphere is thinner and doesn’t block as much. Two cross-country flights expose you to as much radiation as a standard X-ray. Traveling by space elevator can take you much further from Earth’s natural shield and for longer periods of time, greatly increasing exposure.

So, even if we find the materials, money, and willpower to build an elevator to space, there will be plenty of other problems for us to solve before safely using it.