Hey, welcome to Science Stuff, the production of iHeartRadio. I'm Moreham and today we are going to space. No, we're not going to strap ourselves to a giant rocket full of flammable fuel. Instead, we are going to take the elevator. It may seem like science fiction, but a space elevator is something serious scientists actually think is possible to build. And it's not just something that can take you to space.
It might actually help you get to other planets. To put on some relaxing music, step inside and ride with us as we go up to answer the question, can we build an elevator to space?
Hey?
Everyone, Okay, today we are tackling a pretty wild idea, which is to build an elevator that can take you to space. But I promise you that by the end you're going to be thinking, my gosh, that totally makes sense. Let's build one right now. Now. To get there, I need you to imagine that you're getting into an elevator, and at each floor we're going to be answering a different question about space elevators. So step inside, perfect now,
hit the button for the first floor, and we're going up. Okay, while we go up, I'll just tell you that the idea of a space elevator is that instead of taking a rocket to go to space, you just take an elevator. There would be a structure that is based here on Earth, and it would extend up past the tallest building we've ever built, past the clouds, past the atmosphere, and into space. And so if you want to go to space or take something into space, all you have to do is
get on, and then you'd be in space. And if you go up high enough, when you get off, you'll actually be in orbit around Earth, meaning you wouldn't fall back down to Earth. Oh, which has got to our first stop. Okay, Here, I imagine we are ten kilometers above the surface of the Earth. This is about twelve times higher than the Birch Khalifa, which is the highest building we've ever built. Here, at ten kilometers, we're at the top of the troposphere, which is the main layer
of our atmosphere. It's the lear where all the weather happens because it has most of the water that's in the atmosphere. And this is about as high as even the highest clouds go. Oh, and here joining us is our first expert, Professor Matthew Pete, come in, doctor Pete, thanks for joining us.
Well, thank you for having me.
Keith, Please tell us who you are and you do so.
I'm a professor at Arizona State University and teach and do research in orbital mechanics and controls and dynamical systems theory.
Okay, so to thee on the program, we're answering the question what is a space elevator? So where did this idea come from?
Well, you know, that's an interesting story.
Arthur C.
Clark had a great paper on this and he counted the number of times it had been reinvented, and I think he was at eleven. The first invention of the space elevator was by Konstancy Sokowsky. If you don't know who is you might be forgiven. But he was one of these very early rockets guys, and living in a cabin outside of Moscow back in eighteen ninety five. What he was doing inventing rockets and space elevators we could leave to our imagination. So who knows what he was
doing out in his cabin. But although famous for space elevators, he's of course far more famous for inventing the rocket equation. So he laid out the basic mathematical foundations for the use of rockets back in eighteen ninety.
So he sort of invented rocket signs in a way.
Yeah, I would give him credit for inventing rocket scignen.
So the same person who came up with the rocket equation came up with this idea of the space elevator for the first time.
Yeah.
He was inspired by the Eiffel Tower and how far it reached up, and he said, well, if you reach far enough, you could just drop things off the ever tower and it we'd be in orbit. So he laid out the basics and then it was invented a couple more times.
Like people would just come up with it and work it out without knowing what somebody else had already done.
Yeah, because it's an eminently logical and interesting idea.
So this idea of a space elevator that we're writing right now came up a long time ago, back before we even had rockets, And he keeps popping up over and over again over the last one hundred and thirty years because it kind of makes sense. If you want to get to space, why not just build something that can get you there directly. Oh, we're in our next up. Okay, Here we are one hundred kilometers above the surface of the Earth, meaning about one hundred and twenty times the
height of the bird khalifa. Oh, what's your step? You definitely don't want to fall from here. At one hundred kilometers, this is what's called the Carmen line. We're technically still in the atmosphere, but this is the point that people say separates being on Earth and being in space. It's a little bit of an arbitrary number, mostly chosen because
one hundred kilometers is a nice round number. But at around this level is where airplanes can no longer fly or stay flying, because there isn't enough air to keep them afloat. It's also around here that there isn't enough air to burn up meteorites, so if you see shooting stars,
they would be below you. It's also where the International Aeronautic Federation defines the beginning of space, which technically means you and I in this space elevator are now officially astronauts, although if you step outside right now, you would basically just fall straight down because the force of gravity is pretty much the same as on the surface of Earth. It's only three percent lower. Okay, let's keep going like the pet. Can you please press a button for the
next floor, of course. Okay, our next stop is going to be one thousand kilometers above the surface of Earth. It's going to take a little bit to get there. So in the meantime, dark the peed. Can you tell us why build this space elevator?
So the obvious reason is that if you're not using a space elevator, the alternative is a rocket, and rockets are dangerous and rather explosive. And there's this thing called the rocket equation, which tells you that the amount of propellant you need to get a certain amount of mass up into space grows very large the farther you go up, so that the fraction of mass to propellant would be maybe one thousand to one, right, a lot of propellant
for very little mass to get up there. If you want to put a city on space, for example, it would be very difficult with rockets.
Okay, what doctor P is saying is that rockets are just fundamentally inefficient, and that's because of something called the rocket equation. It tells you that the amount of fuel you need to put something in space using rockets grows exponentially the more mass you want to take to space. That's because in a rocket, you not only have to lift the thing you want to take to space, you also have to lift all the fuel you're going to need along the way, and that's going to make your
rocket heavier. So you need to bring more fuel, which makes your rocket even heavier, which means you need to bring more fuel, et cetera, et cetera. This is why when you look at a rocket, most of the long cylinder that you see are the tanks for the fuel. Only the small part of the bottom is the engine, and only the very tippy top is where the astronauts sit.
So if we're ever going to launch a large spaceship with food and people to other planets, it's going to take a lot of fuel, and that brings other problems, right like your beat.
Yes, so recent rockets tend to use slightly different fuels, using etholocks and cara locks, which are petroleum based. So there's an environmental question which says that if you're going to put lots of things in space, well maybe it's not a great idea to burn quite that much petroleum.
Product, it's not good for the environment.
Yeah, Okay.
When we come back, we're going to continue our elevator ride into space, and we're going to talk about the big question, which is how do you build a space elevator? So don't hop off, keep writing with us. We'll be right back.
Welcome back.
All right, we're writing an elevator to space, and you're probably wondering, how do you build an elevator to space. We'll get to that in a minute, but first we're going to make another stop right about now. Okay, right now, we are one thousand kilometers above the surface of the Earth, which is twelve hundred times higher than the tallest building
in the world, the Birch Khalifa. So you can imagine to get to where we are, you'd have to stag twelve hundred of the tallest building on Earth, one on top of the other. At this height, we are still technically in Earth's atmosphere, but we're in the last layer, which is the exosphere. Below us, you can see the northern lights and there's almost no air.
Now.
About five hundred kilometers below us, we passed the International Space Station and you might be wondering, or hey, why didn't you stop the elevator. You could have just hopped off and boarded the space station. Uh not really. That's because the International Space Station zip past us at seventeen thousand, four hundred miles per hour, which is about eight times faster than a rifle bullet. The International Space Station has to go that fast in order to stay in orbit.
If we were to step off this elevator right now, you'd still fall straight down. The force of gravity right now is still about seventy five percent of what it is on Earth, so we feel a little lighter, but you still definitely have your feet planet on the elevator floor.
Now.
The reason we stopped here was to pick up another passenger. Ope, here he is, Hey, doctor Wright, did you take an uber up here? Uh?
No, I don't think so.
Okay, I want to ask you how you got here. But thanks for joining us.
You're welcome, happy you could have me on.
Can you please tell us who you are and what do you do.
I'm currently serving as the president of the International Space Elevator Consortium, which is basically a group of people who want to advance the development of the space Elevator and hopefully get it built within our lifetimes. We talk to people who do calculations for the space elevator, we talk to people who develop materials for it, and basically anybody who might be interested in investing in it and promoting its construction.
Great, hold on, let me press the button for the next top, which is going to be thirty five thousand, seven hundred and eighty six kilometers from the surface of the Earth. We'll explain why we're going to that height
in a minute. But docked right, I want to ask you most people listening probably assume that to build a space elevator like the one we're writing right now, you have to build it from the ground up, like you start building a base on Earth, and you just keep building up higher and higher and higher.
Yeah, pretty much, the ground up way is impractical. So Konstantin Sarkowski he came up with the idea of building a tower. He was thinking that of a rigid structure fixed to the equator, and he figured, well, if you build it high enough, yeah, you can get something into orbit that way, and it would be very efficient.
Right, like basically building a super gigantic Eiffel tower, or like a Birch Khalifa. But on steroids. But that wouldn't work, right, Like, you can't build a tower that tall exactly.
He realized that would not be practical because he was thinking of a compressive structure, in other words, a tower based on Earth, and so calculating the strength of steel and the mass of such a long structure it would take I think he estimated the mass of all the steel in the Solar System.
Okay, what doctor Wright is saying here is that to build a space elevator you can't build it from the ground up. That's because at some point the weight of the tower is too much and the whole thing which just collapse. You'd have to build a structure that is so ginormous you would use up all the steel in the Solar System, which is impossible. So then how do you build a space elevator?
The way we like to think of deploying it is starting with something in orbit. In geosynchronis orbit sending a cable down until you have a cable that reaches the Earth.
In other words, the way to build a space elevator is from the top down. But how do you do that? And that brings us to our next stop. We are now thirty five thousand, seven hundred and eighty six kilometers from the surface of the Earth. In other words, we are standing on the equivalent of forty three thousand, one hundred and fifteen birds, which khaliphas stacked one on top of the other. At this point, we are about three earth diameters away from the surface of Earth and about
a tenth of the way to the Moon. If you look down, you'd see the whole Earth about the size of a basketball held at arm's length. Now, why do we make a stop here. The reason is that at this distance from Earth, you fall into a geosynchronous orbit. Look, you're right, Can you explain that for us?
So this is a particular kind of orbit in which the object in the orbit at that altitude seems to keep the same position over the Earth when you're at the equator. So essentially, the velocity at geosynchronous orbit is the same as the angular velocity at the Earth, and it would just look like it's staying there. In fact, it's really moving at a pretty significant clip.
Okay, Remember I told you that the International Space Station, which was in orbit about four hundred klumter from Earth, had to go at about seventeen thousand miles per hour to stay in orbit, otherwise it would just crash down to Earth. Well, as you go further away from Earth, that speed gets slower and slower, and at some point the speed you have to keep to stay in orbit it's the same speed as the rotation of the Earth, and that orbit at that altitude is called the geosynchronous orbit.
So the Earth is rotating and we're flying around the Earth, but it looks like we're just floating because the two speeds match each other, and so we're always above the same spot on Earth. Okay, I think you know where this is going. What happens next, doctor B.
And So the idea of a space elevator is if you put like a really big spool of cable right at that geosynchronous altitude and just sort of let it down very gradually and slowly, it would just come all the way down to the surface of the Earth, and you could just tie it down and have a very long cable which you can then run some mechanical device up to get things up into geosynchronous orbit.
It's like if you were trying to build an elevator to a cloud. One way to do it is to build a huge tower from the ground that reaches the cloud, or you could just fly a balloon up to the cloud and once you're there, lower a rope or a cable down to the ground and use that to climb up to the cloud. The idea for this space elevator is the same, except instead of a balloon, you're putting something in geosynchronous orbit.
And then you have this straight or mostly straight cable that goes from the surface of the Earth, so it's a big stationary cable. And on this cable you would put a climber or an elevator car or something which lifts your payload up to whatever altitude you want.
And at this distance from Earth, if you s depth outside the elevator, you would just float. You wouldn't fall back down because the gravity would be weaker, and it would exactly match this interpretal force you get from going in a circle around the Earth. And the idea is that at this point you could bring materials up to the elevator and build a whole city up there in space.
So there are a lot of things we can do. So that's a perfect place to build solar power satellites. Rather large habitats could be built there. Okay, colonies things like that, orbibal factories.
Okay, when we come back, we're going to talk about another really cool thing you can do with a space elevator, and we're going to answer the question you're probably thinking right now, which is why haven't we built them? If space elevators are so great, why are we still sending things to space using rockets? Well, answer that question after
the break. You're listening to science stuff and we're back. Okay, you and I are currently in space thirty five thousand, seven hundred and eighty six kilometers above the surface of the Earth. At this point, we are definitely outside Earth's atmosphere. We left that at ten thousand kilometers, but we're still under the influence of Earth's gravity barely. At this height and at this speed, we are logged in geosynchronous orbit, which means we're always above the same point on the
surface of Earth as it rotates. And I should mention this only works of our orbit goes around Earth's equator. Now, if we were to lower a cable down to the surface of Earth thirty five thousand, seven hundred and eighty six kilometers, we would create a link between us and Earth that we could use as an elevator. You could attach a platform that climbs up the cable to bring things to space without having to use expensive, dangerous and
polluting rockets. That's the idea of a space elevator. And what school is that you can use it not just to put things in space, but to fling them to other planets, right the repete.
Yeah, And the final argument that people put forward is that you know, there's this balance between centripetal and gravitational acceleration, and when you're in geosynchronous they're precisely balanced and you're precisely above the Earth. But everything beyond that centripetal acceleration
is actually larger than gravitational force. So if you run a cable beyond the space elevator, if you run some kind of structure beyond the space elevator, at some point, if you go an additional three thousand kilometers, that tip the apex of the space elevator is actually moving faster than the velocity you need to escape the Earth's gravitational influence, so you could go to other planets.
Okay, this is pretty cool. So where we are now in geosynchronous orbit, it's sort of perfectly balanced. But if I were to extend the space elevator further out, like if I were to not just drop a cable down to Earth, but also let loose a cable the other way away from Earth, you could use that cable to fling things out into space. So, for example, if I attach a dumbbell to that cable above us, we would see that dumbell start moving away from us because of
centripetal acceleration. That's the force that pushes you out when say you're going around a Narry go round, or the force that pulls your arms out if you spin in place. So we'd see the dumbbell move away from us, going faster and faster, and then if the cable ends, the dumbo would get flung out into space. And that's how you can use a space elevator to launch things to other planets.
Yeah, you could let it go off the end of the cable and that would have its maximum release velocity. So if you release at one hundred thousand kilometers, then you can reach the inner edge of the asteroid belt without any extra rocket thrust. If you want to go to Mars, you can release at that altitude or a lower one. But if you release at that altitude, then you can get to Mars in about sixty one days as oppose to you know, they're talking about one hundred and eighty days for a typical mission.
Exactly, you wouldn't need any rockets at all. Presumably once you got to Jupiter, you wouldn't want to like crash into one of the moons, so there'd have to be some aerobraking, or you might want to like have a rocket to slow down at some point.
Yeah, so this space elevator wouldn't just get you to space. If you want to, say, live in a space station in geosynchronous orbit, you could also sling you to other planets. Okay, you're probably thinking, now this sounds great, Jorge, but why haven't we built one? What's the catch?
All?
Right, there are two caveats. The first one comes if you think about where the energy is coming from in a space elevator. I mean, you get to put things in space and even fling them to other planets without needing rockets. It sounds too good to be true, doesn't it, doctor Pete.
Yeah, now that's a great insight. So there's no free launch, I guess, But weird things happen in space because it's an energy conserving field, So where is the energy coming from. It's interesting because once you get beyond geosynchronous, the acceleration to get to the velocity to get to Jupiter is coming from actually the rotational inertia of the Earth itself.
So the Earth is spinning and pulling the space Elevator along with it, and so that acceleration is transferred to the base of the space Elevator, and every launch would very slightly slow down the spin of the Earth. So presumably we wouldn't launch too much or people would have to adjust their atomic clocks eventually, but I don't think we'd get to that point.
The day would get longer eventually if we launch enough things, the.
Day would slightly longer eventually if we launch it enough.
Stuff That doesn't sound good for the planet.
Well, if you compared it to the amount of rocket fuel we would have to burn in order to do the same thing, I think we could make an environmental case for this.
So basically, if we use the space Elevator too much, we would slow down the earth rotation. Now, the Earth is huge and massive, so we would barely affect it and besides, who wouldn't mind having a few extra minutes of time each day? And the other caveat is a big one. You've probably been wondering why how would we build a space elevator, And the answer is that it's
really hard to make. Remember how we're thirty five seven hundred and eighty six kilometers above Earth, and to make a space elevator you have to lower a cable down to the surface thirty five seven hundred and eighty six kilometers below. That's a lot of cable. If you were to hang down a steel cable that long, at some point, the weight of the cable itself being pulled down by
the Earth would break the cable. And if you try to make the cable thicker to make it stronger, that would just make the cable heavier and it would still break. It's like imagine trying to hang a long, long strand of cook spaghetti off the side of a building. At some point, the amount of spaghetti hanging would weigh so much you would break the spaghetti at the top, which
is holding all the weight. Scientists have calculated that basically it's not really possible to make a single space elevator cable that would work for materials we currently have, but that doesn't mean it's impossible. One postle idea is to use carbon nanotubes.
In nineteen ninety one, the carbon nanotubes were discovered, and that was really the first material that was ever demonstrated to have the sufficiently high strength and blow a mass at the same time. Okay, that you could conceive of building a tether that would support itself. Since then, there have been other discoveries of materials. One is graphene, and there's a third candidate called texagonal boron nitride.
These materials could potentially work, except we still haven't figured out how to really make them. They're still very experimental. And the other possible solution is to use carbon fibers in the shape of a thirty five thousand, seven hundred and eighty six kilometer tall inverted Eiffel Tower.
I would use a carbon fiber because it's well understood and reliable, and then I would go from like one cable at kilometers to three cables, and then five cables, and then you know, just multiply the number of.
Cables because you just kind of like breed more cables in as you go up.
So you can think of it as a really big slag tight it's like very thick at the top and then tapers down because all of that force has to be structurally supported. So in practice, you'd have a very thick cable at the geosynchronous and a very thin cable at the surface of the Earth.
And the math works out like, he'll stay, I'll hold that would work. How thick would the cable need to be at the top?
I have not done the math on that one, but I would estimate that it would probably be on the order of one hundred meters still, which is not that big. I mean, we have some spy satellites up in space which have a radius of one hundred meters.
Okay, that sounds pretty good. What's the problem.
So creating a huge stalactite in space requires a great deal of material and how do you get it up there? And the answer is you have to strock it to get it up there?
Oh wow, yeah, So I mean it would be super duper expensive. At the beginning, you're saying.
Yeah, so there are people that study the economics of this, and I think they're talking like a trillion dollars or something like that.
That seems doable.
Oh, it's doable. Yeah. I mean the question is do you have an economic case for doing so? Right? That's yeah, that's a real question.
All right. I think that's the end of our elevator right today. To recap, a space elevator would be a more efficient and more environmentally friendly way to get to space and beyond if we can figure out how to hang a thirty five, seven hundred and eighty six kilometer long cable from geosynchronous orbit. So the next time you look up at this guy, try to imagine us in this elevator car dreaming of pushing a button and getting a lift into space. Okay, I just have one last
question for our experts. Last question is someone it's a space elevator, what kind of music would you put in it?
Believe it or not. There's a British band called Space Elevator and I don't know how you characterize their music, but it is something different.
Well, it sounds like this band would by definition be space elevator music.
That's what we were thinking. Yeah.
Well, Johannes Kepler, who discovered orbits and is sort of one of my heroes, was also a very mystical person and tried to design music based on the geometric relationships of the planets in the sun, what you called the music of the spheres. So it's not particularly good music, but then most elevator music isn't very good anyway.
So thanks for taking a ride with us. See you next time. Hey, if you like to join the movement to get space elevators made, doctor Wright would like you to visit the International Space Elevator Consortium website at ISEC you've been listening to Science Stuff the production of iHeartRadio, written and produced by me or Heycham, edited by Rose Seguda, executive producer Jerry Rowland, and audio engineer and mixer Kasey Peckram. You can follow me on social media just search for
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