Speaker 1: Hey, welcome to Science Stuff, the production of iHeartRadio. I'm
Speaker 1: Moreham and today we are going to space. No, we're
Speaker 1: not going to strap ourselves to a giant rocket full
Speaker 1: of flammable fuel. Instead, we are going to take the elevator.
Speaker 1: It may seem like science fiction, but a space elevator
Speaker 1: is something serious scientists actually think is possible to build.
Speaker 1: And it's not just something that can take you to space.
Speaker 1: It might actually help you get to other planets. To
Speaker 1: put on some relaxing music, step inside and ride with
Speaker 1: us as we go up to answer the question, can
Speaker 1: we build an elevator to space?
Speaker 2: Hey?
Speaker 1: Everyone, Okay, today we are tackling a pretty wild idea,
Speaker 1: which is to build an elevator that can take you
Speaker 1: to space. But I promise you that by the end
Speaker 1: you're going to be thinking, my gosh, that totally makes sense.
Speaker 1: Let's build one right now. Now. To get there, I
Speaker 1: need you to imagine that you're getting into an elevator,
Speaker 1: and at each floor we're going to be answering a
Speaker 1: different question about space elevators. So step inside, perfect now,
Speaker 1: hit the button for the first floor, and we're going up. Okay,
Speaker 1: while we go up, I'll just tell you that the
Speaker 1: idea of a space elevator is that instead of taking
Speaker 1: a rocket to go to space, you just take an elevator.
Speaker 1: There would be a structure that is based here on Earth,
Speaker 1: and it would extend up past the tallest building we've
Speaker 1: ever built, past the clouds, past the atmosphere, and into space.
Speaker 1: And so if you want to go to space or
Speaker 1: take something into space, all you have to do is
Speaker 1: get on, and then you'd be in space. And if
Speaker 1: you go up high enough, when you get off, you'll
Speaker 1: actually be in orbit around Earth, meaning you wouldn't fall
Speaker 1: back down to Earth. Oh, which has got to our
Speaker 1: first stop. Okay, Here, I imagine we are ten kilometers
Speaker 1: above the surface of the Earth. This is about twelve
Speaker 1: times higher than the Birch Khalifa, which is the highest
Speaker 1: building we've ever built. Here, at ten kilometers, we're at
Speaker 1: the top of the troposphere, which is the main layer
Speaker 1: of our atmosphere. It's the lear where all the weather
Speaker 1: happens because it has most of the water that's in
Speaker 1: the atmosphere. And this is about as high as even
Speaker 1: the highest clouds go. Oh, and here joining us is
Speaker 1: our first expert, Professor Matthew Pete, come in, doctor Pete,
Speaker 1: thanks for joining us.
Speaker 2: Well, thank you for having me.
Speaker 1: Keith, Please tell us who you are and you do so.
Speaker 2: I'm a professor at Arizona State University and teach and
Speaker 2: do research in orbital mechanics and controls and dynamical systems theory.
Speaker 1: Okay, so to thee on the program, we're answering the
Speaker 1: question what is a space elevator? So where did this
Speaker 1: idea come from?
Speaker 2: Well, you know, that's an interesting story.
Speaker 1: Arthur C.
Speaker 2: Clark had a great paper on this and he counted
Speaker 2: the number of times it had been reinvented, and I
Speaker 2: think he was at eleven. The first invention of the
Speaker 2: space elevator was by Konstancy Sokowsky. If you don't know
Speaker 2: who is you might be forgiven. But he was one
Speaker 2: of these very early rockets guys, and living in a
Speaker 2: cabin outside of Moscow back in eighteen ninety five. What
Speaker 2: he was doing inventing rockets and space elevators we could
Speaker 2: leave to our imagination. So who knows what he was
Speaker 2: doing out in his cabin. But although famous for space elevators,
Speaker 2: he's of course far more famous for inventing the rocket equation.
Speaker 2: So he laid out the basic mathematical foundations for the
Speaker 2: use of rockets back in eighteen ninety.
Speaker 1: So he sort of invented rocket signs in a way.
Speaker 2: Yeah, I would give him credit for inventing rocket scignen.
Speaker 1: So the same person who came up with the rocket
Speaker 1: equation came up with this idea of the space elevator
Speaker 1: for the first time.
Speaker 3: Yeah.
Speaker 2: He was inspired by the Eiffel Tower and how far
Speaker 2: it reached up, and he said, well, if you reach
Speaker 2: far enough, you could just drop things off the ever
Speaker 2: tower and it we'd be in orbit. So he laid
Speaker 2: out the basics and then it was invented a couple
Speaker 2: more times.
Speaker 1: Like people would just come up with it and work
Speaker 1: it out without knowing what somebody else had already done.
Speaker 2: Yeah, because it's an eminently logical and interesting idea.
Speaker 1: So this idea of a space elevator that we're writing
Speaker 1: right now came up a long time ago, back before
Speaker 1: we even had rockets, And he keeps popping up over
Speaker 1: and over again over the last one hundred and thirty
Speaker 1: years because it kind of makes sense. If you want
Speaker 1: to get to space, why not just build something that
Speaker 1: can get you there directly. Oh, we're in our next up. Okay,
Speaker 1: Here we are one hundred kilometers above the surface of
Speaker 1: the Earth, meaning about one hundred and twenty times the
Speaker 1: height of the bird khalifa. Oh, what's your step? You
Speaker 1: definitely don't want to fall from here. At one hundred kilometers,
Speaker 1: this is what's called the Carmen line. We're technically still
Speaker 1: in the atmosphere, but this is the point that people
Speaker 1: say separates being on Earth and being in space. It's
Speaker 1: a little bit of an arbitrary number, mostly chosen because
Speaker 1: one hundred kilometers is a nice round number. But at
Speaker 1: around this level is where airplanes can no longer fly
Speaker 1: or stay flying, because there isn't enough air to keep
Speaker 1: them afloat. It's also around here that there isn't enough
Speaker 1: air to burn up meteorites, so if you see shooting stars,
Speaker 1: they would be below you. It's also where the International
Speaker 1: Aeronautic Federation defines the beginning of space, which technically means
Speaker 1: you and I in this space elevator are now officially astronauts,
Speaker 1: although if you step outside right now, you would basically
Speaker 1: just fall straight down because the force of gravity is
Speaker 1: pretty much the same as on the surface of Earth.
Speaker 1: It's only three percent lower. Okay, let's keep going like
Speaker 1: the pet. Can you please press a button for the
Speaker 1: next floor, of course. Okay, our next stop is going
Speaker 1: to be one thousand kilometers above the surface of Earth.
Speaker 1: It's going to take a little bit to get there.
Speaker 1: So in the meantime, dark the peed. Can you tell
Speaker 1: us why build this space elevator?
Speaker 2: So the obvious reason is that if you're not using
Speaker 2: a space elevator, the alternative is a rocket, and rockets
Speaker 2: are dangerous and rather explosive. And there's this thing called
Speaker 2: the rocket equation, which tells you that the amount of
Speaker 2: propellant you need to get a certain amount of mass
Speaker 2: up into space grows very large the farther you go up,
Speaker 2: so that the fraction of mass to propellant would be
Speaker 2: maybe one thousand to one, right, a lot of propellant
Speaker 2: for very little mass to get up there. If you
Speaker 2: want to put a city on space, for example, it
Speaker 2: would be very difficult with rockets.
Speaker 1: Okay, what doctor P is saying is that rockets are
Speaker 1: just fundamentally inefficient, and that's because of something called the
Speaker 1: rocket equation. It tells you that the amount of fuel
Speaker 1: you need to put something in space using rockets grows
Speaker 1: exponentially the more mass you want to take to space.
Speaker 1: That's because in a rocket, you not only have to
Speaker 1: lift the thing you want to take to space, you
Speaker 1: also have to lift all the fuel you're going to
Speaker 1: need along the way, and that's going to make your
Speaker 1: rocket heavier. So you need to bring more fuel, which
Speaker 1: makes your rocket even heavier, which means you need to
Speaker 1: bring more fuel, et cetera, et cetera. This is why
Speaker 1: when you look at a rocket, most of the long
Speaker 1: cylinder that you see are the tanks for the fuel.
Speaker 1: Only the small part of the bottom is the engine,
Speaker 1: and only the very tippy top is where the astronauts sit.
Speaker 1: So if we're ever going to launch a large spaceship
Speaker 1: with food and people to other planets, it's going to
Speaker 1: take a lot of fuel, and that brings other problems,
Speaker 1: right like your beat.
Speaker 2: Yes, so recent rockets tend to use slightly different fuels,
Speaker 2: using etholocks and cara locks, which are petroleum based. So
Speaker 2: there's an environmental question which says that if you're going
Speaker 2: to put lots of things in space, well maybe it's
Speaker 2: not a great idea to burn quite that much petroleum.
Speaker 1: Product, it's not good for the environment.
Speaker 2: Yeah, Okay.
Speaker 1: When we come back, we're going to continue our elevator
Speaker 1: ride into space, and we're going to talk about the
Speaker 1: big question, which is how do you build a space elevator?
Speaker 1: So don't hop off, keep writing with us. We'll be
Speaker 1: right back.
Speaker 3: Welcome back.
Speaker 1: All right, we're writing an elevator to space, and you're
Speaker 1: probably wondering, how do you build an elevator to space.
Speaker 1: We'll get to that in a minute, but first we're
Speaker 1: going to make another stop right about now. Okay, right now,
Speaker 1: we are one thousand kilometers above the surface of the Earth,
Speaker 1: which is twelve hundred times higher than the tallest building
Speaker 1: in the world, the Birch Khalifa. So you can imagine
Speaker 1: to get to where we are, you'd have to stag
Speaker 1: twelve hundred of the tallest building on Earth, one on
Speaker 1: top of the other. At this height, we are still
Speaker 1: technically in Earth's atmosphere, but we're in the last layer,
Speaker 1: which is the exosphere. Below us, you can see the
Speaker 1: northern lights and there's almost no air.
Speaker 3: Now.
Speaker 1: About five hundred kilometers below us, we passed the International
Speaker 1: Space Station and you might be wondering, or hey, why
Speaker 1: didn't you stop the elevator. You could have just hopped
Speaker 1: off and boarded the space station. Uh not really. That's
Speaker 1: because the International Space Station zip past us at seventeen thousand,
Speaker 1: four hundred miles per hour, which is about eight times
Speaker 1: faster than a rifle bullet. The International Space Station has
Speaker 1: to go that fast in order to stay in orbit.
Speaker 1: If we were to step off this elevator right now,
Speaker 1: you'd still fall straight down. The force of gravity right
Speaker 1: now is still about seventy five percent of what it
Speaker 1: is on Earth, so we feel a little lighter, but
Speaker 1: you still definitely have your feet planet on the elevator floor.
Speaker 3: Now.
Speaker 1: The reason we stopped here was to pick up another passenger. Ope,
Speaker 1: here he is, Hey, doctor Wright, did you take an
Speaker 1: uber up here? Uh?
Speaker 3: No, I don't think so.
Speaker 1: Okay, I want to ask you how you got here.
Speaker 1: But thanks for joining us.
Speaker 3: You're welcome, happy you could have me on.
Speaker 1: Can you please tell us who you are and what
Speaker 1: do you do.
Speaker 3: I'm currently serving as the president of the International Space
Speaker 3: Elevator Consortium, which is basically a group of people who
Speaker 3: want to advance the development of the space Elevator and
Speaker 3: hopefully get it built within our lifetimes. We talk to
Speaker 3: people who do calculations for the space elevator, we talk
Speaker 3: to people who develop materials for it, and basically anybody
Speaker 3: who might be interested in investing in it and promoting
Speaker 3: its construction.
Speaker 1: Great, hold on, let me press the button for the
Speaker 1: next top, which is going to be thirty five thousand,
Speaker 1: seven hundred and eighty six kilometers from the surface of
Speaker 1: the Earth. We'll explain why we're going to that height
Speaker 1: in a minute. But docked right, I want to ask
Speaker 1: you most people listening probably assume that to build a
Speaker 1: space elevator like the one we're writing right now, you
Speaker 1: have to build it from the ground up, like you
Speaker 1: start building a base on Earth, and you just keep
Speaker 1: building up higher and higher and higher.
Speaker 3: Yeah, pretty much, the ground up way is impractical. So
Speaker 3: Konstantin Sarkowski he came up with the idea of building
Speaker 3: a tower. He was thinking that of a rigid structure
Speaker 3: fixed to the equator, and he figured, well, if you
Speaker 3: build it high enough, yeah, you can get something into
Speaker 3: orbit that way, and it would be very efficient.
Speaker 1: Right, like basically building a super gigantic Eiffel tower, or
Speaker 1: like a Birch Khalifa. But on steroids. But that wouldn't work, right, Like,
Speaker 1: you can't build a tower that tall exactly.
Speaker 3: He realized that would not be practical because he was
Speaker 3: thinking of a compressive structure, in other words, a tower
Speaker 3: based on Earth, and so calculating the strength of steel
Speaker 3: and the mass of such a long structure it would
Speaker 3: take I think he estimated the mass of all the
Speaker 3: steel in the Solar System.
Speaker 1: Okay, what doctor Wright is saying here is that to
Speaker 1: build a space elevator you can't build it from the
Speaker 1: ground up. That's because at some point the weight of
Speaker 1: the tower is too much and the whole thing which
Speaker 1: just collapse. You'd have to build a structure that is
Speaker 1: so ginormous you would use up all the steel in
Speaker 1: the Solar System, which is impossible. So then how do
Speaker 1: you build a space elevator?
Speaker 3: The way we like to think of deploying it is
Speaker 3: starting with something in orbit. In geosynchronis orbit sending a
Speaker 3: cable down until you have a cable that reaches the Earth.
Speaker 1: In other words, the way to build a space elevator
Speaker 1: is from the top down. But how do you do that?
Speaker 1: And that brings us to our next stop. We are
Speaker 1: now thirty five thousand, seven hundred and eighty six kilometers
Speaker 1: from the surface of the Earth. In other words, we
Speaker 1: are standing on the equivalent of forty three thousand, one
Speaker 1: hundred and fifteen birds, which khaliphas stacked one on top
Speaker 1: of the other. At this point, we are about three
Speaker 1: earth diameters away from the surface of Earth and about
Speaker 1: a tenth of the way to the Moon. If you
Speaker 1: look down, you'd see the whole Earth about the size
Speaker 1: of a basketball held at arm's length. Now, why do
Speaker 1: we make a stop here. The reason is that at
Speaker 1: this distance from Earth, you fall into a geosynchronous orbit. Look,
Speaker 1: you're right, Can you explain that for us?
Speaker 3: So this is a particular kind of orbit in which
Speaker 3: the object in the orbit at that altitude seems to
Speaker 3: keep the same position over the Earth when you're at
Speaker 3: the equator. So essentially, the velocity at geosynchronous orbit is
Speaker 3: the same as the angular velocity at the Earth, and
Speaker 3: it would just look like it's staying there. In fact,
Speaker 3: it's really moving at a pretty significant clip.
Speaker 1: Okay, Remember I told you that the International Space Station,
Speaker 1: which was in orbit about four hundred klumter from Earth,
Speaker 1: had to go at about seventeen thousand miles per hour
Speaker 1: to stay in orbit, otherwise it would just crash down
Speaker 1: to Earth. Well, as you go further away from Earth,
Speaker 1: that speed gets slower and slower, and at some point
Speaker 1: the speed you have to keep to stay in orbit
Speaker 1: it's the same speed as the rotation of the Earth,
Speaker 1: and that orbit at that altitude is called the geosynchronous orbit.
Speaker 1: So the Earth is rotating and we're flying around the Earth,
Speaker 1: but it looks like we're just floating because the two
Speaker 1: speeds match each other, and so we're always above the
Speaker 1: same spot on Earth. Okay, I think you know where
Speaker 1: this is going. What happens next, doctor B.
Speaker 2: And So the idea of a space elevator is if
Speaker 2: you put like a really big spool of cable right
Speaker 2: at that geosynchronous altitude and just sort of let it
Speaker 2: down very gradually and slowly, it would just come all
Speaker 2: the way down to the surface of the Earth, and
Speaker 2: you could just tie it down and have a very
Speaker 2: long cable which you can then run some mechanical device
Speaker 2: up to get things up into geosynchronous orbit.
Speaker 1: It's like if you were trying to build an elevator
Speaker 1: to a cloud. One way to do it is to
Speaker 1: build a huge tower from the ground that reaches the cloud,
Speaker 1: or you could just fly a balloon up to the
Speaker 1: cloud and once you're there, lower a rope or a
Speaker 1: cable down to the ground and use that to climb
Speaker 1: up to the cloud. The idea for this space elevator
Speaker 1: is the same, except instead of a balloon, you're putting
Speaker 1: something in geosynchronous orbit.
Speaker 3: And then you have this straight or mostly straight cable
Speaker 3: that goes from the surface of the Earth, so it's
Speaker 3: a big stationary cable. And on this cable you would
Speaker 3: put a climber or an elevator car or something which
Speaker 3: lifts your payload up to whatever altitude you want.
Speaker 1: And at this distance from Earth, if you s depth
Speaker 1: outside the elevator, you would just float. You wouldn't fall
Speaker 1: back down because the gravity would be weaker, and it
Speaker 1: would exactly match this interpretal force you get from going
Speaker 1: in a circle around the Earth. And the idea is
Speaker 1: that at this point you could bring materials up to
Speaker 1: the elevator and build a whole city up there in space.
Speaker 3: So there are a lot of things we can do.
Speaker 3: So that's a perfect place to build solar power satellites.
Speaker 3: Rather large habitats could be built there. Okay, colonies things
Speaker 3: like that, orbibal factories.
Speaker 1: Okay, when we come back, we're going to talk about
Speaker 1: another really cool thing you can do with a space elevator,
Speaker 1: and we're going to answer the question you're probably thinking
Speaker 1: right now, which is why haven't we built them? If
Speaker 1: space elevators are so great, why are we still sending
Speaker 1: things to space using rockets? Well, answer that question after
Speaker 1: the break. You're listening to science stuff and we're back. Okay,
Speaker 1: you and I are currently in space thirty five thousand,
Speaker 1: seven hundred and eighty six kilometers above the surface of
Speaker 1: the Earth. At this point, we are definitely outside Earth's atmosphere.
Speaker 1: We left that at ten thousand kilometers, but we're still
Speaker 1: under the influence of Earth's gravity barely. At this height
Speaker 1: and at this speed, we are logged in geosynchronous orbit,
Speaker 1: which means we're always above the same point on the
Speaker 1: surface of Earth as it rotates. And I should mention
Speaker 1: this only works of our orbit goes around Earth's equator. Now,
Speaker 1: if we were to lower a cable down to the
Speaker 1: surface of Earth thirty five thousand, seven hundred and eighty
Speaker 1: six kilometers, we would create a link between us and
Speaker 1: Earth that we could use as an elevator. You could
Speaker 1: attach a platform that climbs up the cable to bring
Speaker 1: things to space without having to use expensive, dangerous and
Speaker 1: polluting rockets. That's the idea of a space elevator. And
Speaker 1: what school is that you can use it not just
Speaker 1: to put things in space, but to fling them to
Speaker 1: other planets, right the repete.
Speaker 2: Yeah, And the final argument that people put forward is
Speaker 2: that you know, there's this balance between centripetal and gravitational acceleration,
Speaker 2: and when you're in geosynchronous they're precisely balanced and you're
Speaker 2: precisely above the Earth. But everything beyond that centripetal acceleration
Speaker 2: is actually larger than gravitational force. So if you run
Speaker 2: a cable beyond the space elevator, if you run some
Speaker 2: kind of structure beyond the space elevator, at some point,
Speaker 2: if you go an additional three thousand kilometers, that tip
Speaker 2: the apex of the space elevator is actually moving faster
Speaker 2: than the velocity you need to escape the Earth's gravitational influence,
Speaker 2: so you could go to other planets.
Speaker 1: Okay, this is pretty cool. So where we are now
Speaker 1: in geosynchronous orbit, it's sort of perfectly balanced. But if
Speaker 1: I were to extend the space elevator further out, like
Speaker 1: if I were to not just drop a cable down
Speaker 1: to Earth, but also let loose a cable the other
Speaker 1: way away from Earth, you could use that cable to
Speaker 1: fling things out into space. So, for example, if I
Speaker 1: attach a dumbbell to that cable above us, we would
Speaker 1: see that dumbell start moving away from us because of
Speaker 1: centripetal acceleration. That's the force that pushes you out when
Speaker 1: say you're going around a Narry go round, or the
Speaker 1: force that pulls your arms out if you spin in place.
Speaker 1: So we'd see the dumbbell move away from us, going
Speaker 1: faster and faster, and then if the cable ends, the
Speaker 1: dumbo would get flung out into space. And that's how
Speaker 1: you can use a space elevator to launch things to
Speaker 1: other planets.
Speaker 3: Yeah, you could let it go off the end of
Speaker 3: the cable and that would have its maximum release velocity.
Speaker 3: So if you release at one hundred thousand kilometers, then
Speaker 3: you can reach the inner edge of the asteroid belt
Speaker 3: without any extra rocket thrust. If you want to go
Speaker 3: to Mars, you can release at that altitude or a
Speaker 3: lower one. But if you release at that altitude, then
Speaker 3: you can get to Mars in about sixty one days
Speaker 3: as oppose to you know, they're talking about one hundred
Speaker 3: and eighty days for a typical mission.
Speaker 2: Exactly, you wouldn't need any rockets at all. Presumably once
Speaker 2: you got to Jupiter, you wouldn't want to like crash
Speaker 2: into one of the moons, so there'd have to be
Speaker 2: some aerobraking, or you might want to like have a
Speaker 2: rocket to slow down at some point.
Speaker 1: Yeah, so this space elevator wouldn't just get you to space.
Speaker 1: If you want to, say, live in a space station
Speaker 1: in geosynchronous orbit, you could also sling you to other planets. Okay,
Speaker 1: you're probably thinking, now this sounds great, Jorge, but why
Speaker 1: haven't we built one? What's the catch?
Speaker 3: All?
Speaker 1: Right, there are two caveats. The first one comes if
Speaker 1: you think about where the energy is coming from in
Speaker 1: a space elevator. I mean, you get to put things
Speaker 1: in space and even fling them to other planets without
Speaker 1: needing rockets. It sounds too good to be true, doesn't it,
Speaker 1: doctor Pete.
Speaker 2: Yeah, now that's a great insight. So there's no free launch,
Speaker 2: I guess, But weird things happen in space because it's
Speaker 2: an energy conserving field, So where is the energy coming from.
Speaker 2: It's interesting because once you get beyond geosynchronous, the acceleration
Speaker 2: to get to the velocity to get to Jupiter is
Speaker 2: coming from actually the rotational inertia of the Earth itself.
Speaker 2: So the Earth is spinning and pulling the space Elevator
Speaker 2: along with it, and so that acceleration is transferred to
Speaker 2: the base of the space Elevator, and every launch would
Speaker 2: very slightly slow down the spin of the Earth. So
Speaker 2: presumably we wouldn't launch too much or people would have
Speaker 2: to adjust their atomic clocks eventually, but I don't think
Speaker 2: we'd get to that point.
Speaker 1: The day would get longer eventually if we launch enough things, the.
Speaker 2: Day would slightly longer eventually if we launch it enough.
Speaker 1: Stuff That doesn't sound good for the planet.
Speaker 2: Well, if you compared it to the amount of rocket
Speaker 2: fuel we would have to burn in order to do
Speaker 2: the same thing, I think we could make an environmental
Speaker 2: case for this.
Speaker 1: So basically, if we use the space Elevator too much,
Speaker 1: we would slow down the earth rotation. Now, the Earth
Speaker 1: is huge and massive, so we would barely affect it
Speaker 1: and besides, who wouldn't mind having a few extra minutes
Speaker 1: of time each day? And the other caveat is a
Speaker 1: big one. You've probably been wondering why how would we
Speaker 1: build a space elevator, And the answer is that it's
Speaker 1: really hard to make. Remember how we're thirty five seven
Speaker 1: hundred and eighty six kilometers above Earth, and to make
Speaker 1: a space elevator you have to lower a cable down
Speaker 1: to the surface thirty five seven hundred and eighty six
Speaker 1: kilometers below. That's a lot of cable. If you were
Speaker 1: to hang down a steel cable that long, at some point,
Speaker 1: the weight of the cable itself being pulled down by
Speaker 1: the Earth would break the cable. And if you try
Speaker 1: to make the cable thicker to make it stronger, that
Speaker 1: would just make the cable heavier and it would still break.
Speaker 1: It's like imagine trying to hang a long, long strand
Speaker 1: of cook spaghetti off the side of a building. At
Speaker 1: some point, the amount of spaghetti hanging would weigh so
Speaker 1: much you would break the spaghetti at the top, which
Speaker 1: is holding all the weight. Scientists have calculated that basically
Speaker 1: it's not really possible to make a single space elevator
Speaker 1: cable that would work for materials we currently have, but
Speaker 1: that doesn't mean it's impossible. One postle idea is to
Speaker 1: use carbon nanotubes.
Speaker 3: In nineteen ninety one, the carbon nanotubes were discovered, and
Speaker 3: that was really the first material that was ever demonstrated
Speaker 3: to have the sufficiently high strength and blow a mass
Speaker 3: at the same time. Okay, that you could conceive of
Speaker 3: building a tether that would support itself. Since then, there
Speaker 3: have been other discoveries of materials. One is graphene, and
Speaker 3: there's a third candidate called texagonal boron nitride.
Speaker 1: These materials could potentially work, except we still haven't figured
Speaker 1: out how to really make them. They're still very experimental.
Speaker 1: And the other possible solution is to use carbon fibers
Speaker 1: in the shape of a thirty five thousand, seven hundred
Speaker 1: and eighty six kilometer tall inverted Eiffel Tower.
Speaker 2: I would use a carbon fiber because it's well understood
Speaker 2: and reliable, and then I would go from like one
Speaker 2: cable at kilometers to three cables, and then five cables,
Speaker 2: and then you know, just multiply the number of.
Speaker 1: Cables because you just kind of like breed more cables
Speaker 1: in as you go up.
Speaker 2: So you can think of it as a really big
Speaker 2: slag tight it's like very thick at the top and
Speaker 2: then tapers down because all of that force has to
Speaker 2: be structurally supported. So in practice, you'd have a very
Speaker 2: thick cable at the geosynchronous and a very thin cable
Speaker 2: at the surface of the Earth.
Speaker 1: And the math works out like, he'll stay, I'll hold
Speaker 1: that would work. How thick would the cable need to
Speaker 1: be at the top?
Speaker 2: I have not done the math on that one, but
Speaker 2: I would estimate that it would probably be on the
Speaker 2: order of one hundred meters still, which is not that big.
Speaker 2: I mean, we have some spy satellites up in space
Speaker 2: which have a radius of one hundred meters.
Speaker 1: Okay, that sounds pretty good. What's the problem.
Speaker 2: So creating a huge stalactite in space requires a great
Speaker 2: deal of material and how do you get it up there?
Speaker 2: And the answer is you have to strock it to
Speaker 2: get it up there?
Speaker 1: Oh wow, yeah, So I mean it would be super
Speaker 1: duper expensive. At the beginning, you're saying.
Speaker 2: Yeah, so there are people that study the economics of this,
Speaker 2: and I think they're talking like a trillion dollars or
Speaker 2: something like that.
Speaker 1: That seems doable.
Speaker 2: Oh, it's doable. Yeah. I mean the question is do
Speaker 2: you have an economic case for doing so? Right? That's yeah,
Speaker 2: that's a real question.
Speaker 1: All right. I think that's the end of our elevator
Speaker 1: right today. To recap, a space elevator would be a
Speaker 1: more efficient and more environmentally friendly way to get to
Speaker 1: space and beyond if we can figure out how to
Speaker 1: hang a thirty five, seven hundred and eighty six kilometer
Speaker 1: long cable from geosynchronous orbit. So the next time you
Speaker 1: look up at this guy, try to imagine us in
Speaker 1: this elevator car dreaming of pushing a button and getting
Speaker 1: a lift into space. Okay, I just have one last
Speaker 1: question for our experts. Last question is someone it's a
Speaker 1: space elevator, what kind of music would you put in it?
Speaker 3: Believe it or not. There's a British band called Space
Speaker 3: Elevator and I don't know how you characterize their music,
Speaker 3: but it is something different.
Speaker 1: Well, it sounds like this band would by definition be
Speaker 1: space elevator music.
Speaker 3: That's what we were thinking. Yeah.
Speaker 2: Well, Johannes Kepler, who discovered orbits and is sort of
Speaker 2: one of my heroes, was also a very mystical person
Speaker 2: and tried to design music based on the geometric relationships
Speaker 2: of the planets in the sun, what you called the
Speaker 2: music of the spheres. So it's not particularly good music,
Speaker 2: but then most elevator music isn't very good anyway.
Speaker 1: So thanks for taking a ride with us. See you
Speaker 1: next time. Hey, if you like to join the movement
Speaker 1: to get space elevators made, doctor Wright would like you
Speaker 1: to visit the International Space Elevator Consortium website at ISEC
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