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[♪ INTRO]
Since the 1950’s, humanity has gotten really good at putting stuff up into space.
But we haven’t had as much success at bringing in back down again.
What goes up doesn’t always come down as fast as we want it to,
and we’re now facing the growing problem of space junk cluttering the skies.
But finally, in a long overdue effort to clean up after ourselves,
space researchers are considering a nifty little accessory
called a drag sail that could transform the life cycles of orbiting stuff.
Ever since Sputnik, thousands of rocket launches have put satellites,
space stations, rocket parts, and other assorted junk into the skies above our planet.
NASA reports that there are about 23,000 chunks of space junk larger than a softball, half a
million pieces larger than a marble, and 100 million fragments one millimeter or more across.
All of them are traveling at up to 28,000 kilometers per hour,
so they have a lot of potential to do serious damage to anything that might get in their way.
In fact, with so much going on up there, scientists have warned of a catastrophic
chain reaction of collisions known as Kessler Syndrome.
In this scenario, one space junk collision generates more, smaller pieces of space junk.
They may be smaller, but they’re still fast and capable of destruction.
So more pieces lead to more space junk collisions, to more space junk, and so on.
Eventually, low Earth orbit becomes inhospitable to the stuff we want there,
from communications satellites to the ISS.
Basically, we drown those orbits in space garbage.
A UN report in 2013 projected that catastrophic space junk collisions might occur at least
every nine years, and as we put more stuff into space, that chance only gets higher.
And it’s not a problem that will resolve itself easily.
Some dead satellites and rocket parts do drop down low enough to experience
atmospheric drag, slow down, and burn up.
In fact, eventually all of our space junk will meet this fate.
Even in orbit, there’s always some drag from the very top of the atmosphere.
But eventually isn’t good enough.
Stuff will come down, but in many cases it’ll take decades, or even longer.
Typical humanity, right?.
Pollute space first, think about it later!
Well, we’re in the second part now because more and more engineers
are looking for solutions to the space junk problem.
Many proposals have suggested ways to deal with the junk that’s already there,
like firing lasers from Earth to change the trajectory of pieces,
or sending up trash collection missions to scoop up as much as possible.
These are all… a bit of a challenge to pull off.
Whether it’s costs, or risks, or some other reason,
no one has come to a decision about the best way to dustbust the skies.
But there is a potential solution that would help avoid making any more space junk,
by providing spacecraft with a way to deorbit much faster.
Ironically, these new accessories were first developed to help spacecraft
to fly farther into space, rather than to bring them home.
Solar sails offer an economical alternative to traditional fuel
when it comes to long-term missions and deep space exploration.
By spreading out huge thin sheets, they allow spacecraft to fly like a glider,
pushed along by the pressure of photons radiating from the sun.
The push is very small, but the force acting constantly on the solar sail
could help it accelerate gradually up to very high speeds, with no fuel necessary.
It’s a technology that’s already been proven too.
Lightsail2 is a spacecraft about the size of a can of tennis balls,
but it’s fitted with a paper-thin solar sail about 32 meters square.
Using nothing but the light from the sun,
it’s been cruising around in low Earth orbit, maintaining its altitude since 2019.
Lightsail2 has been the inspiration for other solar sails on future space missions,
but the technology has also inspired an approach to Earth’s space junk problem.
Because while huge sheet-like sails are good at catching light,
they’re also not picky about what else they scoop.
When these sails, with their massive surface areas, encounter even the thinnest air
at the very top of Earth’s atmosphere, they’ll experience a huge force of drag
opposing their flight, relatively speaking, anyway.
In theory, a sail would be enough to rapidly slow down a spacecraft or satellite, so that it can
drop out of orbit quickly and not spend any more time as space junk than necessary.
So, engineers are looking to incorporate these drag sails into future satellite flights.
Made of a foil that’s just one tenth the thickness of a human hair, they can vary in size
depending on the size of the object they’re meant to bring down to Earth.
The smallest are about three and a half square meters, and can deploy in just 0.8 seconds,
while the largest are about 100 meters square and take 45 minutes to extend fully.
The bigger the sail, the more drag, and the faster the descent.
The developers believe that this technology could bring down satellites
weighing up to 1500 kilograms!
The idea is that the sail would be stowed throughout an orbiter's mission,
but when the mission concluded they would be released and would unfurl.
After deployment, they’d be completely passive,
and wouldn’t need any extra guidance or control.
They’d exploit simple aerodynamics to do their job of bringing the spacecraft home
in a blaze of glory!
Drag sails have already been tested successfully on several missions in the last few years,
and the European Space Agency are looking to incorporate the technology into more flights.
Even if we can’t rid ourselves of smothering junk,
we may finally have a way of at least slowing its growth.
Who’d have thought that the way to slow stuff down and bring it home
was to use technology we’d developed for speeding it up and keeping it in space!
Both in orbit, and on the ground, we’re learning more
about how to make the future more sustainable.
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So, you can find that link in the description, and thank you for supporting SciShow.
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