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- For decades the prospect
of interplanetary travel
has been restricted by fuel.
But one organization is working
to use light from the sun
to travel to the stars.
- [Technician] Three, two, one, zero.
- The Planetary Society recently began
the first orbital test of
their LightSail 2 spacecraft
and it's already started
sending back images.
If solar sailing proves to be
a viable means of propulsion
it could one day be used
to explore the galaxy.
To learn more we brought in
the Planetary Society's CEO, Bill Nye.
Hi Bill, so congratulations
on the successful mission
how's the light sailing going?
- Sailing is going very well.
So we have a small
spacecraft, it's in orbit
and it's getting a push
from the Sun every orbit.
It's very exciting, you know,
I was in astronomy class in 1977
and Carl Sagan was talking
about a solar sail mission.
How long ago was that 42 years ago?
And now we finally pulled it off.
We are sailing on sunlight.
- So can you tell us a little bit
about how the light sail works?
- I happen to have a model right here.
So this is 1/10 size of LightSail 2.
So this is the Three Unit
CubeSat here in the middle.
And so its 30 centimeters
by 10 centimeters
by 10 centimeters to give you perspective.
That's almost, but not quite as big
as a conventional loaf of bread.
And then this is 32 square meter sail.
So it's about the size of a boxing ring.
And even if you've never
been to a boxing ring,
you've seen one the TV.
So sunlight hits these solar panels
here on the spacecraft,
by a long tradition
the main part of a
spacecraft is called the bus.
The sails comes [zipping] out of the bus,
out of the main cube and they get to be
relatively this big.
And this is the real material,
feel it, Daniel, it's crazy thin isn't?
- Yeah.
- Get in from
the edge we have reinforced the edge
to make it more durable for carrying.
But feel how thin that is?
- It's like
hardly there.
- Much thinner
than human hair, and you can see
the rip-stop feature in the sail material.
So sunlight hits it and gives it a push.
It's just out of your everyday experience
that light can push something.
And so we found that the sails
do billow a little but, just like
sails on a sailboat.
And we found that because
here on these panels,
we have cameras, two cameras.
And they're gorgeous, you see the shots
of the Earth below with
the sail in the foreground.
And so it'll fly and we twist 90 degrees
with every orbit because in here is,
what nowadays people
call a momentum wheel,
but you might of used to, you might used
to have called it a gyroscope,
a spinning wheel can produce torque
to twist the spacecraft in space.
It's just amazing, and this has been
a human dream so you could put this,
a spacecraft like this, in an orbit
closer to the Sun than the Earth is,
now the closer you are to the Sun,
the faster you go around.
Mercury goes around faster than Venus,
which goes around faster than the Earth.
The Earth goes around
faster than Mars and so on.
But what you could do, is be as close
to the Sun as Venus, but
because solar pressure
is hitting your sail,
you could keep in line
or keep station with the Earth.
And the practical application for that
is monitoring what we call solar weather.
If there's a coronal mass discharge
of particles from the
Sun going at the Earth,
you could get five or six hours warning
which could be priceless.
In 2012, there was a solar,
coronal mass ejection
of particles that just missed the Earth,
crossed the Earth's orbit about two weeks
behind us, as Earthlings.
If that were to hit our
communications satellites
and ground based systems, it would be
a catastrophic catastrophe.
The other thing is from
that position in orbit,
around the Sun, you could
watch for asteroids.
As the saying goes,
"Looking for an asteroid
"is like looking for a charcoal
briquette in the dark."
Very difficult to see
at optical wavelengths.
But in the infrared, in the just a little
above Absolute Zero in
heat, you could find 'em.
And there are 100s of 1,000s of asteroids
that cross the Earth's orbit.
Some fraction of those would
be the end of the world.
So we wanna find those.
- Worth looking out for.
- That's right, the
preventable natural disaster.
Very low probability,
very high consequence.
- And so when this spacecraft is launched,
it's about the size of loaf of bread,
right?
- It's actually
smaller than a loaf of
bread by a little bit.
- [Daniel] But it unfurls
to the size of boxing ring?
- Right.
- Can you
kinda walk me through the process
of how that's done?
- A standard has emerged
in spacecraft called a
CubeSat, cubical satellite,
and this happened because universities
wanted to build these things,
the Air Force is involved in this
and so you can go online and buy parts
for cubical satellites and the standard is
10 centimeters by 10 centimeters
by 10 centimeters, X, Y, Z, a cube.
Well then the standards emerged
so we have a 10 centimeters
by 10 centimeters by 30,
so it's what you call
a Three Unit, or Three U Cube Sat.
And in there is a little,
literally Swiss motor,
like a Swiss watch, this
very, very small motor
on this crazy small, very
precisely made gear train
the booms are very much
like tape measures,
they're thin, steel ribbons
and they wind up into
this very small volume.
They get very, almost flat.
And so we have a motor that pushes them
to get them started and then it holds them
back so they don't go [zipping]
out too fast and tear the sail.
And this was something, this
is classic engineering problem.
You think, you might think,
if you wound up these springs
they would just deploy,
just un-spool on their own.
But they don't because
the material is curved,
and when you flatten it, the curve changes
and the stresses change.
We have software that commands
the motor to un-spool
the, to deploy the booms.
Then the sails are attached to the end
with little springs 'cause the heating
and cooling as you go around the Sun is,
makes the booms change
length by a little bit,
and so figured that out too.
And the crazy thing is the sails are made
of this Mylar material that's 20 microns.
This is crazy, and so you can pack
this huge, shiny silver sail
into these very small volumes.
It's origami.
- So this is
a CubeSat, and you've managed
to raise the orbit of this CubeSat.
Is this, looking to the future,
is this something that could ever be used
to one day bring humans to other planets
or even other stars?
- Humans,
almost certainly not, the
problem with humans is
they're heavy and we are not electronic.
We need to drink and recover
the water that we get rid of.
And it's very, very, it's a massive system
to support a human, but
going to another star system,
a solar sail is really the only technology
anybody can think of right
now that would enable that.
And what you would do, you'd build
something like LightSail 2.
And you'd put it in orbit,
and then you'd hit it, or
push it with laser beams.
Then you would create
laser beams here on Earth
with an enormous amount of electricity
and shoot 'em at the spacecraft
and push it to another star system.
And keep in mind, if you were to do that,
even a spacecraft the
size of a postage stamp
would show up in the Proxima Cenaturi,
Alpha Cenaturi solar system,
four light years away,
it would show up there with the energy
comparable to a small nuclear weapon,
like a Hiroshima-style bomb.
And so if it were to hit something,
well okay, we're from Earth, cool.
[explosion]
I sent you this bullet
that's enough to you know,
- it's a great way
to say hello.
- Destroy a city, yeah.
So I'm not saying it would, it just,
don't get carried away everybody.
It's like, not a solved problem.
The other thing that everybody's
really enchanted about
is exploring nearby space.
And by nearby we mean the Kuiper Belt
where all these icy objects
are orbiting the Sun
with a solar sail that got out there
because it could get up a
100 kilometers a second.
So what you would do is have a solar sail
that might have the same shape
as LightSail 2, but the materials
it would be made of would be able to
hold their shape, their
integrity, close to the Sun.
So you'd send the
spacecraft in nearer the Sun
and you'd have so many
photons hitting it so strongly
that it would push it
out at a 100 kilometers
and you could get out to, way out,
in the solar system relatively fast.
That technology doesn't exist right now.
The materials don't exist right now.
But the longest journey
starts with but a single step.
So we like to think of LightSail 1 and 2
as part of the overall mission
of advancing space,
science and exploration.
That's what we do at
the Planetary Society,
citizen funded flight by light.
- Well congratulations on taking
that first step and thanks so much
for joining us Bill.
- Thank you Daniel.
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