Science Friday - Are Space Elevators Really A Possibility?

Episode Date: August 21, 2024

The space elevator has been a staple of science fiction for decades, from The Fountains of Paradise by Arthur C. Clarke to the Apple TV show “Foundation.” But the work and theories to make it a reality have been in development since the late 19th century.It’s a simple concept: Imagine a long cable, stretching from the Earth’s surface to a satellite locked in orbit 22,000 miles high. It would work like elevators here on Earth, enabling us to send things—and people—up into space. And it would make the need for the expensive rockets we use today obsolete.Although it has never been considered feasible due to the exorbitant cost and the engineering challenges it poses, the idea refuses to go away.One of Japan’s biggest construction companies, the Obayashi Corporation, which built the Tokyo Sky Tree, had plans to build a space elevator in 2025 but has reportedly delayed that goal.So what are the hurdles that keep us from building it? And why does it seem that the space elevator is always 25 years away? Ira Flatow is joined by Dr. Dennis Wright, president of the International Space Elevator Consortium to talk about the feasibility of this megaproject.Transcripts for each segment will be available after the show airs on sciencefriday.com. Subscribe to this podcast. Plus, to stay updated on all things science, sign up for Science Friday's newsletters.

Space elevators could revolutionize the space industry. Far cheaper than rockets and also the tonnage that you could put into orbit on a very regular basis is much greater than rockets and also safer. But could the science fiction concept become a reality? It's Wednesday, August 21st, and this is Science Friday. I'm SciFri Radio Fellow Valeria Diaz. Imagine a long cable, stretching from the Earth's surface to a satellite docked in orbit 22,000 miles high. It will work like elevators here on Earth, sending things and people up into space. This would make the need for expensive rockets we use today obsolete.

It may sound impossible, but physicists have been thinking about the space elevator since the late 19th century. Today, some people believe that its construction could be closer than most people think. But it has never been considered a feasible project due to its supposed exorbitant cost and the engineering challenges it poses. So how close are we to making this concept a reality? Here is Cyphrice Ira Flato with more. Here to parse some of the problems is Dr. Dennis Wright, president of the International Space Elevator Consortium.

He joins us from Santa Fe, New Mexico. Welcome to Science Friday. Thank you. Thanks for having me. Tell us what the parts of a space elevator would be. There is the cable, as you mentioned, and it would extend from the surface of the Earth to actually well-pastynchronous orbit. The geosynchronous orbit or the geostationary orbit is the key thing here. It is that point in the sky, 22,000 miles up, which would maintain the same spot over the place on the equator where the cable is anchored.

And so that would be the place where you had a satellite and a cable would be sent down from the satellite and one also sent upwards. And gravity and centrifugal force would stretch it taught and make it a cable which could be climbed by various. craft. So the idea is that once you have a space elevator, it would be cheaper than rocketry to bring stuff into space, right? Far cheaper because you're taking advantage of the rotational energy of the Earth. So you get a free ride, most of the way, at least. You have to do an initial boost to get things going. Far cheaper than rockets and also the tonnage that you could put into orbit on a very regular basis is much greater than rockets and also safer. Ideally on Earth, on the the Earth side of it, where would you like to locate it?

A lot of places have been proposed, but first of all, the equator, somewhere on the equator, is almost essential. You could go plus or minus five degrees and still have good lifting capacity. But the equator, and then whether you put it on land or ocean, is a debatable point right now, but it seems like the ocean is best because in the event that you do have a collision or some kind of severance event in orbit. Part of the elevator may come down, and it would come down in the ocean. So that is the best place for it. And it also avoids local governments who might want to use the elevator only for their

purposes and other political aspects that would be avoided by putting it in the sea. So are you viewing this? Is this viewed as an enterprise sort of thing? We think it would probably have to be one of these multinational things. So it would hardly be private, and especially in the early going, where research funds are needed. So most likely some kind of international cooperation would be required, at least in terms of international law, because no matter where you put this, some international law would have to be dealt with. Space law, for example, is actually dealing with this issue right now and trying to figure out what issue you'd have to address. So let's talk about the challenges. What are some of the challenges that we are facing right now?

I think the first one is probably the one that most people know about who have looked into the issue before, and that is the material. So in the past, there just were no materials strong enough to build a space elevator. So up until about 1991 at the discovery of carbon nanotubes, there was nothing strong enough that could support itself, let alone support payloads. And since then, three materials have come in. We already had the carbon nanotubes to talk about, graphene and hexagonal boron nitride. And each of these are strong enough. They exist. They've been made in the laboratory.

They have strengths well beyond that of steel. And indeed, that was the impetus for a NASA advanced concept study in 2000, which really demonstrated the feasibility of a space elevator. But the challenge then is taking these materials from the laboratory and making them industrially, large amounts relatively quickly. But the material is strong enough, you're saying? About if you, for an equivalent mass of steel, the graphene, for example, is about 200 times stronger.

And that's more than enough to support the cable and substantial payloads going into space. So how do you make sure then it reaches for hundreds of miles? without losing its strength needed to hold this megastructure together? The key behind these materials is really the covalent bond. And so a lot of materials that we deal with on Earth are held together by Vandervalds forces, which are quite a bit weaker. But when we talk about graphene or carbon nanotubes or something like that, they are actually single molecules.

And these single molecules are held together with covalent bonds, which are very strong. In the real world, we never actually realize that strength because the materials are composed of grains and the grains are put into layers. But when you have many, many layers of graphene, each of which is a single molecule, you're taking full advantage of that strong covalent bond. And that never loses its strength. It doesn't decay or lose any strength due to hysteresis or something like that. All right. So how would you build the elevator itself? Would you build it down here on Earth and send it up in space, or do you build it in stages going up and up and up or in space and then lower it down? The best way we think is to transport roles of this

stuff into orbit at the geostationary spot or geostationary orbit and then pay out cables in opposite directions. So there would be one cable heading down toward Earth, another heading in the opposite direction. And you need that to make sure that. the center of gravity is still staying at geosynchronous orbit. And that'll vary from time to time as you do this, but that's the key. And so we think that's the best way. Send thin cables up and down. And then when they are in place, start laying laminants over those with more layers of graphene or what have you. If you're sending cables up, how do you keep them from falling back to Earth while you're building it. That's the key of keeping it in or near the geostationary spot.

Because if you lower cable from geostationary and then put cable up at the same time in the opposite direction, it will hold itself up. And so basically you have this thing called gravitational gradient stabilization. And that means that it naturally wants to be straight up and down. Even if you knock it about a little bit, it'll always come back to straight up and down. And if you've got the center of gravity near geostationary, then it'll hold itself up. And so what power is the climber? Is it wheels on the room itself moving up and down? Or how do you get power to move it up and down into space and back down? Two ways we've looked at. One is using wheels, so counter-rotating wheels that grip the tether

and pull itself up. The other is a maglev technology. There are maglev trains on Earth, which work very well and very fast horizontally. The problem is how do you get that to work vertically? And there may be some efficiency problems there, but people are still looking at magnetic levitation. And that's probably ideal because there's no actual contact with the tether and you're using electromagnetic forces. But right now we think maybe counter-rotating wheels is the best. Several of our people have actually designed a climber based on this concept, which could be built with materials that we have today. Would you be building just a building, just one elevator. I'm thinking of railroad tracks, right? You never build just one track

because you want to have things going in two directions at once. Would you do it that way or just build a single track up and down? There would be one track and the first thing you would do when you got that track is to build another one because you always want to have, A, a backup, and B, you're probably going to add many more after that in order to get significant amounts of mass into orbit. So I think the earliest implementation of this would be probably a set of six of them equidimidimely spaced around the Earth. The idea is that you always have enough backup that you can afford to lose one. Could you turn the space elevator into a tourist attraction? And I mean, not just going up into orbit, but possibly halfway up. You might have a rest stop or something

like that. Yes. There would be possibility for stations along the way. The tourist opportunity is certainly a great one and you wouldn't have to go all that high up. So that's the nice thing about it. It wouldn't take so long. And you could either pause the climber there and have them look around or you would otherwise have to attach something to the tether like a station and have people disembark there. And going further up, I mean, I think the real commercial possibilities are at geosynchronous orbit, because there you're far enough out of the gravity well that you can really go into the solar system. And how do we make sure the tether can resist damage from space debris, weather, radiation, stuff like that? Yeah, lots of good questions. And we're looking at those

challenges. One of the things about graphene is it's very tough. And experiments have been done, shooting bullets at it and it's very good at resisting bullets. It's a lot better than Kevlar, which of course is used in bulletproof vests. So I know that orbital debris is a lot faster than a bullet, but the graphene could absorb many of these impacts without significant damage. There may be holes, which could be repaired later. That's one of the aspects of it. The other is that, of course, We have a lot of space debris, and we've done a study based on the trackable material in space, and so we know all those orbits, and especially the bigger ones. If the orbit is known, then you can set up a vibration in the tether so that it misses the object,

let's say the space station, international space station, coming by, and you know what that orbit is. And so just vibrated out of the way, and then it'll come back, and you've made it. missed it. What do you mean vibrated out of the way? So the tether is a stretch taught, as I mentioned, but it is kind of like a rubber band in a sense. It's very tight, but it still will vibrate from side to side. So it'll have modes of oscillation like a violin string. And so there will be many different frequencies. Most of them will be very small. The amplitudes will be small. but you can set up a vibration that still maintains the space elevator in a stable configuration, and that will allow you to avoid a lot of the space, John.

You don't want to start creating a vibration like on the Tacoma Narrows Bridge. No, absolutely not. That's a very good example. And one of the things you have to worry about, as you mentioned, radiation, if you do get a large solar storm, like a coronal mass suggestion or something like that, That would be enough to set up vibrations in the tether if it is very highly conducting. And so you have to make sure that the tether is either not conducting or you know, have some warning that the storm is coming in advance and you can counteract it. Interesting.

How long would it take to get into orbit if you're on the elevator? You said it's, what, 200 kilometers an hour? That's probably the speed we're looking at. We think that's probably conservative. 300 might be more likely. At 200 kilometers per hour, it would be a week to get to geosynchronous, and then obviously much less to get to low Earth orbit. So you could go up and down in a day if you went to lower Earth orbit. And you mentioned that one of the reasons you would build it out in the ocean is because if it falls, no one would, on Earth at least, would be heard.

That's right. And the science fiction scenarios that you pointed out are rather dramatic, but probably not too realistic. So assuming the rare case that we do get a split or a severance in orbit, that is most likely going to happen at low-worth orbit. So that's about 500 miles up. If 500 miles of the tether came down, then it would fall in the ocean and you're far enough from land. That's fine. It would also likely break up as strong as the graphene or the other materials are, they might likely break up before they actually get to the Earth's surface. So that particular danger of it wrapping many times around the Earth is not going to happen. The break in the tether would then cause the remainder of it, that is the outbound part.

That would slowly drift out into space and slowly is the key because that could be rescued. You could actually tug that back into place once you got a repair mechanism in place. So I think the disaster scenario is not very likely, although there would be always the possibility of some kind of event that would bring part of it down. But we think it's rare based on our studies. You know, I mentioned in the introduction that fusion energy is always 30, 25, 30 years away. And, you know, it sounds like the space elevator is always 25, 30 years away. Yeah, it seems frustrating, although we hope that we are on the exponential curve. It's just the flat part of the curve right now.

From the discovery of these materials, so graphene was discovered in 2006, I believe, or I specifically identified. And since then, there's been a lot of progress. So, first of all, it was just a little grain that was taken off graphite with scotch tape. and then it was produced in the laboratories. And as time goes on, bigger and bigger samples of being produced. Now there's a piece of single crystal graphene, so a single molecule, about half a meter wide and half a meter long. So the length is increasing.

There are three companies, at least, that are manufacturing polycrystalline graphene, and these are in lengths of kilometers. So the lengths has been increasing quite a bit lately, and we think we might be on the increasing slope here. Is there enough international interest for a joint project to do this? That's a very interesting question, because we believe several countries are working on it, although some of them seem to have gone dark.

So we know that work has been done in China. That is, in fact, that a large piece of single crystal graphene, I mentioned, was produced in China. We haven't heard much from them lately. South Korea has been doing quite a bit on this. And you mentioned earlier, Obayashi Corporation. They're still quite interested. And yeah, so work is being done.

Well, we will keep watching this. And please come back when you've got something new to report, Dr. Wright. I'd love to. Thank you for taking time to be with us today. And thank you. Dr. Dennis Wright, president of the International Space Elevator Consortium, he was joining us from Santa Fe, New Mexico. That's all the time we have for today.

A lot of people help make this show happen, including Jordan Smudgett, Charles Burgquist, Jason Rosenberg, John Dancosky. Tomorrow, the conversation with the authors of the book, Forest Walking, discovering the trees and woodlands of North America, about how to engage with your local forests. I'm Cyfry Radio Fellow Valeri Diaz. See you soon.