July 23, 2025 • 29 mins
Going up! Can an elevator take you all the way to space (and beyond)? Jorge talks to two scientists trying to make this happen.
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Speaker 1 (00:01):
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.
(00:25):
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
(00:47):
we build an elevator to space?
Speaker 2 (00:56):
Hey?
Speaker 1 (00:56):
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,
(01:17):
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
(01:37):
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
(01:59):
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
(02:22):
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
(02:44):
the highest clouds go. Oh, and here joining us is
our first expert, Professor Matthew Pete, come in, doctor Pete,
thanks for joining us.
Speaker 2 (02:56):
Well, thank you for having me.
Speaker 1 (02:58):
Keith, Please tell us who you are and you do so.
Speaker 2 (03:00):
I'm a professor at Arizona State University and teach and
do research in orbital mechanics and controls and dynamical systems theory.
Speaker 1 (03:09):
Okay, so to thee on the program, we're answering the
question what is a space elevator? So where did this
idea come from?
Speaker 2 (03:16):
Well, you know, that's an interesting story.
Speaker 1 (03:18):
Arthur C.
Speaker 2 (03:19):
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
(03:40):
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.
Speaker 1 (04:00):
So he sort of invented rocket signs in a way.
Speaker 2 (04:03):
Yeah, I would give him credit for inventing rocket scignen.
Speaker 1 (04:06):
So the same person who came up with the rocket
equation came up with this idea of the space elevator
for the first time.
Speaker 3 (04:11):
Yeah.
Speaker 2 (04:11):
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.
Speaker 1 (04:25):
Like people would just come up with it and work
it out without knowing what somebody else had already done.
Speaker 2 (04:30):
Yeah, because it's an eminently logical and interesting idea.
Speaker 1 (04:34):
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,
(05:03):
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
(05:24):
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
(05:49):
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
(06:09):
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.
(06:31):
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?
Speaker 2 (06:40):
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,
(07:02):
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.
Speaker 1 (07:16):
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
(07:37):
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
(07:59):
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.
Speaker 2 (08:19):
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.
Speaker 1 (08:35):
Product, it's not good for the environment.
Speaker 2 (08:38):
Yeah, Okay.
Speaker 1 (08:40):
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.
Speaker 3 (09:02):
Welcome back.
Speaker 1 (09:03):
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,
(09:24):
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
(09:47):
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.
Speaker 3 (09:59):
Now.
Speaker 1 (10:00):
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,
(10:20):
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
(10:40):
is on Earth, so we feel a little lighter, but
you still definitely have your feet planet on the elevator floor.
Speaker 3 (10:47):
Now.
Speaker 1 (10:47):
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?
Speaker 3 (10:58):
No, I don't think so.
Speaker 1 (11:00):
Okay, I want to ask you how you got here.
But thanks for joining us.
Speaker 3 (11:03):
You're welcome, happy you could have me on.
Speaker 1 (11:05):
Can you please tell us who you are and what
do you do.
Speaker 3 (11:07):
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
(11:27):
who might be interested in investing in it and promoting
its construction.
Speaker 1 (11:32):
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
(11:53):
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.
Speaker 3 (12:05):
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.
Speaker 1 (12:24):
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.
Speaker 3 (12:36):
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.
Speaker 1 (12:54):
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
(13:18):
you build a space elevator?
Speaker 3 (13:21):
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.
Speaker 1 (13:31):
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
(13:54):
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
(14:16):
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?
Speaker 3 (14:31):
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.
Speaker 1 (14:54):
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
(15:16):
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
(15:40):
same spot on Earth. Okay, I think you know where
this is going. What happens next, doctor B.
Speaker 2 (15:48):
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.
Speaker 1 (16:10):
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
(16:33):
is the same, except instead of a balloon, you're putting
something in geosynchronous orbit.
Speaker 3 (16:40):
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.
Speaker 1 (16:57):
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
(17:18):
the elevator and build a whole city up there in space.
Speaker 3 (17:22):
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.
Speaker 1 (17:36):
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
(17:56):
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
(18:17):
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
(18:38):
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
(19:00):
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.
Speaker 2 (19:22):
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
(19:45):
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.
Speaker 1 (20:02):
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
(20:26):
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
(20:46):
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.
Speaker 3 (21:00):
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
(21:21):
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.
Speaker 2 (21:31):
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.
Speaker 1 (21:44):
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?
Speaker 3 (22:03):
All?
Speaker 1 (22:03):
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.
Speaker 2 (22:22):
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.
(22:46):
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
(23:08):
we'd get to that point.
Speaker 1 (23:09):
The day would get longer eventually if we launch enough things, the.
Speaker 2 (23:12):
Day would slightly longer eventually if we launch it enough.
Speaker 1 (23:14):
Stuff That doesn't sound good for the planet.
Speaker 2 (23:18):
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.
Speaker 1 (23:26):
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
(23:48):
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
(24:11):
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
(24:32):
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
(24:57):
that doesn't mean it's impossible. One postle idea is to
use carbon nanotubes.
Speaker 3 (25:06):
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
(25:26):
there's a third candidate called texagonal boron nitride.
Speaker 1 (25:30):
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.
Speaker 2 (25:51):
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.
Speaker 1 (26:06):
Cables because you just kind of like breed more cables
in as you go up.
Speaker 2 (26:10):
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.
Speaker 1 (26:28):
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?
Speaker 2 (26:34):
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.
Speaker 1 (26:49):
Okay, that sounds pretty good. What's the problem.
Speaker 2 (26:52):
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?
Speaker 1 (27:01):
Oh wow, yeah, So I mean it would be super
duper expensive. At the beginning, you're saying.
Speaker 2 (27:07):
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.
Speaker 1 (27:13):
That seems doable.
Speaker 2 (27:14):
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.
Speaker 1 (27:22):
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
(27:46):
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?
Speaker 3 (28:06):
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.
Speaker 1 (28:14):
Well, it sounds like this band would by definition be
space elevator music.
Speaker 3 (28:18):
That's what we were thinking. Yeah.
Speaker 2 (28:20):
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.
Speaker 1 (28:40):
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
(29:01):
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tell your friends we'll be back next Wednesday with another episode.
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.
(00:25):
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
(00:47):
we build an elevator to space?
Speaker 2 (00:56):
Hey?
Speaker 1 (00:56):
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,
(01:17):
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
(01:37):
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
(01:59):
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
(02:22):
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
(02:44):
the highest clouds go. Oh, and here joining us is
our first expert, Professor Matthew Pete, come in, doctor Pete,
thanks for joining us.
Speaker 2 (02:56):
Well, thank you for having me.
Speaker 1 (02:58):
Keith, Please tell us who you are and you do so.
Speaker 2 (03:00):
I'm a professor at Arizona State University and teach and
do research in orbital mechanics and controls and dynamical systems theory.
Speaker 1 (03:09):
Okay, so to thee on the program, we're answering the
question what is a space elevator? So where did this
idea come from?
Speaker 2 (03:16):
Well, you know, that's an interesting story.
Speaker 1 (03:18):
Arthur C.
Speaker 2 (03:19):
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
(03:40):
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.
Speaker 1 (04:00):
So he sort of invented rocket signs in a way.
Speaker 2 (04:03):
Yeah, I would give him credit for inventing rocket scignen.
Speaker 1 (04:06):
So the same person who came up with the rocket
equation came up with this idea of the space elevator
for the first time.
Speaker 3 (04:11):
Yeah.
Speaker 2 (04:11):
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.
Speaker 1 (04:25):
Like people would just come up with it and work
it out without knowing what somebody else had already done.
Speaker 2 (04:30):
Yeah, because it's an eminently logical and interesting idea.
Speaker 1 (04:34):
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,
(05:03):
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
(05:24):
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
(05:49):
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
(06:09):
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.
(06:31):
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?
Speaker 2 (06:40):
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,
(07:02):
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.
Speaker 1 (07:16):
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
(07:37):
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
(07:59):
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.
Speaker 2 (08:19):
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.
Speaker 1 (08:35):
Product, it's not good for the environment.
Speaker 2 (08:38):
Yeah, Okay.
Speaker 1 (08:40):
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.
Speaker 3 (09:02):
Welcome back.
Speaker 1 (09:03):
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,
(09:24):
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
(09:47):
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.
Speaker 3 (09:59):
Now.
Speaker 1 (10:00):
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,
(10:20):
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
(10:40):
is on Earth, so we feel a little lighter, but
you still definitely have your feet planet on the elevator floor.
Speaker 3 (10:47):
Now.
Speaker 1 (10:47):
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?
Speaker 3 (10:58):
No, I don't think so.
Speaker 1 (11:00):
Okay, I want to ask you how you got here.
But thanks for joining us.
Speaker 3 (11:03):
You're welcome, happy you could have me on.
Speaker 1 (11:05):
Can you please tell us who you are and what
do you do.
Speaker 3 (11:07):
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
(11:27):
who might be interested in investing in it and promoting
its construction.
Speaker 1 (11:32):
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
(11:53):
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.
Speaker 3 (12:05):
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.
Speaker 1 (12:24):
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.
Speaker 3 (12:36):
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.
Speaker 1 (12:54):
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
(13:18):
you build a space elevator?
Speaker 3 (13:21):
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.
Speaker 1 (13:31):
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
(13:54):
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
(14:16):
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?
Speaker 3 (14:31):
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.
Speaker 1 (14:54):
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
(15:16):
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
(15:40):
same spot on Earth. Okay, I think you know where
this is going. What happens next, doctor B.
Speaker 2 (15:48):
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.
Speaker 1 (16:10):
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
(16:33):
is the same, except instead of a balloon, you're putting
something in geosynchronous orbit.
Speaker 3 (16:40):
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.
Speaker 1 (16:57):
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
(17:18):
the elevator and build a whole city up there in space.
Speaker 3 (17:22):
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.
Speaker 1 (17:36):
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
(17:56):
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
(18:17):
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
(18:38):
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
(19:00):
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.
Speaker 2 (19:22):
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
(19:45):
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.
Speaker 1 (20:02):
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
(20:26):
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
(20:46):
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.
Speaker 3 (21:00):
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
(21:21):
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.
Speaker 2 (21:31):
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.
Speaker 1 (21:44):
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?
Speaker 3 (22:03):
All?
Speaker 1 (22:03):
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.
Speaker 2 (22:22):
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.
(22:46):
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
(23:08):
we'd get to that point.
Speaker 1 (23:09):
The day would get longer eventually if we launch enough things, the.
Speaker 2 (23:12):
Day would slightly longer eventually if we launch it enough.
Speaker 1 (23:14):
Stuff That doesn't sound good for the planet.
Speaker 2 (23:18):
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.
Speaker 1 (23:26):
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
(23:48):
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
(24:11):
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
(24:32):
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
(24:57):
that doesn't mean it's impossible. One postle idea is to
use carbon nanotubes.
Speaker 3 (25:06):
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
(25:26):
there's a third candidate called texagonal boron nitride.
Speaker 1 (25:30):
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.
Speaker 2 (25:51):
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.
Speaker 1 (26:06):
Cables because you just kind of like breed more cables
in as you go up.
Speaker 2 (26:10):
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.
Speaker 1 (26:28):
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?
Speaker 2 (26:34):
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.
Speaker 1 (26:49):
Okay, that sounds pretty good. What's the problem.
Speaker 2 (26:52):
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?
Speaker 1 (27:01):
Oh wow, yeah, So I mean it would be super
duper expensive. At the beginning, you're saying.
Speaker 2 (27:07):
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.
Speaker 1 (27:13):
That seems doable.
Speaker 2 (27:14):
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.
Speaker 1 (27:22):
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
(27:46):
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?
Speaker 3 (28:06):
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.
Speaker 1 (28:14):
Well, it sounds like this band would by definition be
space elevator music.
Speaker 3 (28:18):
That's what we were thinking. Yeah.
Speaker 2 (28:20):
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.
Speaker 1 (28:40):
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
(29:01):
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
PhD Comics and the name of your favorite platform. Be
sure to subscribe to Sign Stuff on the iHeartRadio app,
(29:22):
Apple Podcasts, or wherever you get your podcasts, and please
tell your friends we'll be back next Wednesday with another episode.
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My Favorite Murder with Karen Kilgariff and Georgia Hardstark
My Favorite Murder is a true crime comedy podcast hosted by Karen Kilgariff and Georgia Hardstark. Each week, Karen and Georgia share compelling true crimes and hometown stories from friends and listeners. Since MFM launched in January of 2016, Karen and Georgia have shared their lifelong interest in true crime and have covered stories of infamous serial killers like the Night Stalker, mysterious cold cases, captivating cults, incredible survivor stories and important events from history like the Tulsa race massacre of 1921. My Favorite Murder is part of the Exactly Right podcast network that provides a platform for bold, creative voices to bring to life provocative, entertaining and relatable stories for audiences everywhere. The Exactly Right roster of podcasts covers a variety of topics including historic true crime, comedic interviews and news, science, pop culture and more. Podcasts on the network include Buried Bones with Kate Winkler Dawson and Paul Holes, That's Messed Up: An SVU Podcast, This Podcast Will Kill You, Bananas and more.
The Joe Rogan Experience
The official podcast of comedian Joe Rogan.