Why is space junk such a big problem?
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Hello, I'm Hannah Gelbart. Welcome to this episode of What in the World from the BBC World Service. At the end of December, a huge red-hot metal ring fell from the sky, landing on a small village in Kenya. The people there were like, what is this? Where's it come from? Is it an alien spacecraft? I suddenly heard a loud sound like a bomb. I was shocked.

I started looking around, also wondering if it was gunshots. I looked up in the sky to see if there was a smoke. Nothing. The truth was much less exciting. The Kenya Space Agency said it was a piece of space junk, one of millions of pieces of rubbish floating around in space. And the more satellites, probes and rockets we send up, the more waste we're leaving behind. So today you're going to hear why we've got so much space junk, what kind of problems it's causing and how some people are trying to get rid of it.

Five, four, three, two, one. To help us sift through all the debris, here in the studio with me is BBC Science presenter Caroline Steele. Hello. Hello. Thanks for having me on. Welcome back.

So Caroline, to start us off, what is space junk? So space junk is basically anything human-made that's orbiting Earth that isn't useful. So it's like retired satellites or bits of satellites left over from collisions. And in fact, I have two pieces of space junk here with me. Not going to lie, they kind of look like jacket potatoes wrapped in silver foil. OK, this one's an apple wrapped in silver foil. This one's a lime wrapped in silver foil. But if these were pieces of space junk...

Which one do you think is more common? I would imagine space junk to be like a pretty big piece of metal. So I'm going to go with the bigger potato. So there are bits of space junk this size. In fact, there are 30,000 pieces of space junk that are 10 centimetres across or larger. That sounds like a lot, right? But actually, the correct answer is secret piece number three,

This tiny speck, can you see it? It's a tiny bit of silver foil and it's like smaller than my baby fingernail. Yeah, so if you count the number of pieces of space junk that are less than a centimetre across, there are hundreds of millions of pieces this small. It's hard to know the exact number because we can't count them because they're so tiny, but the majority of pieces of space junk are smaller than a centimetre across. So we're talking about really, really tiny things, but because they're travelling so fast, they can still do a lot of damage.

And why is it that they're just hanging out there in outer space? Why don't they come down to Earth or, I don't know, why don't they get absorbed into some greater thing? So if we...

This is no longer a piece of space junk. This is a satellite. If you just throw a satellite up, right, from Earth, it comes back down because of gravity. If I threw it across the studio, what would happen then? It would go in a kind of arc shape, but it would still come back down to the floor. Yeah, exactly. So it would be kind of travelling forwards, but it would still hit the ground because the gravity from Earth is pulling it down to the ground, right? Okay. Now, I need the...

Earth, you've got hidden to your side there. I've got a nice big globe. All I want to do is just spin it around. You can do that at the same time. Make it even more chaotic. Okay, I'm going to spin the globe. So if I stood on top of a mountain and say, okay, now we need to stop it. Let's say, where am I? I'm in northern Canada. I'm on the top of a mountain in northern Canada. It's ten times higher than Everest. And I throw this with so much speed. I'm super strong. It's a super good throw. Okay.

This satellite will travel forwards with loads of speed. It will still be being pulled back down towards Earth, but because it's going so fast and it started so high, it never actually lands on Earth because of the curve of the Earth. It just kind of keeps falling in a circle. And actually, I would need to watch out because after one orbit, this satellite would hit me in the back of the head because it would end up in the same place. So that's why it doesn't

It doesn't fling off into space. And why is it a problem? So we've got, you said, 30,000 pieces that are smaller than 10 centimetres, but actually millions of bits of space junk just hanging out in outer space. What's wrong with that?

So the worry is collisions, because as well as all the space junk we have orbiting Earth, there are some really important satellites up there, right? So we have satellites that we use for GPS navigation. We have satellites we use for communication. Satellites we use for monitoring the Earth, predicting climate change, forecasting weather. You know, our lives are completely dependent on these satellites. And there is a risk of them colliding with bits of space junk. And you might think something as tiny as this can't really affect

spacecraft in like a concerning way. But these are travelling at thousands of kilometres an hour, some faster than a bullet. So that could cause serious damage. And talking of satellites, right, it used to be just governments that put out satellites, but now companies are doing it too, like SpaceX and Amazon. Is that making this problem worse? Yes, we're putting more and more satellites into orbits

Some estimates think that we might by 2030 have 60,000 satellites in orbit. That's at least 10 times more than we have now. And more satellites means more collisions, means more space junk, means more retired satellites, basically more things we need to be worrying about. This has kind of conjured up all these pictures of like plastic bags in the oceans, all of our landfill. You know, we have filled the earth with rubbish and now we're filling space with rubbish too. It's kind of...

It's sad, isn't it? It's really sad. Is there a tipping point? Will there be a time when there's just no more space in space for rubbish? Yeah. So there is sort of a theory that there is a point where there is so much space junk that a collision causes lots of debris and that goes on to collide with three more things and causes even more debris, which goes on to collide with ten more things and basically...

the whole of all of our satellites and end up involved in a collision. And that could be really problematic. That's called Kessler's syndrome. So there is a point where that would happen. We don't know exactly where that is or how close we are to that yet. But that's obviously something we need to avoid. As we heard, Caroline, this does actually happen, right? Bits of space junk that are big enough and made of the right material can actually come to Earth. That's what happened in Kenya. How common is this?

Not very common is basically the answer. So it does happen like it did in Kenya. You know, people heard what they thought was a gunshot, ran outside and there was this huge metal ring glowing red because it was so hot from entering the atmosphere. And that was two and a half metres wide and weighed half a ton. That's pretty big and had a pretty, you know, big effect on residents, even if just from the point of view of, oh, my gosh, that could have been my house. It does happen.

But not very often for a few reasons. One, because when space junk enters our atmosphere, mostly it burns up. If it doesn't burn up, it's most likely to land in the ocean because our oceans cover 70% of the globe. Even if it does land on land, humans actually only occupy still quite a small surface area of the land. So it's still unlikely to land in a human settlement, but it could.

And even if it does land in a human settlement, the odds of it not landing in a field but instead on someone's home or someone else is slim. Although with more space junk, it could be something we see more often, but it's probably not something I'm going to lose sleep over. What do you think is the worst case scenario here? So like if we fill space with stuff and not much of it is coming down, it's hanging out in orbit, as we've said,

Will space become unusable? Will we not be able to put more stuff up in space? Like, will that affect all of our satellites, our communications, internet, weather, everything else? Yeah, I mean, I guess the worst case scenario is Kessler syndrome, where we end up with one explosion that leads to more, that leads to more, that leads to more, and basically renders so much stuff useless. Then we would have to change our focus. We'd have to stop launching more satellites and instead actually address the problem and clean up space.

But hopefully we don't get as far as that and we sort it out sooner.

So how do we get rid of all this space junk? Here is Wanji Kuchibet-Kinjumba. She's a PhD student from Kenya studying aerospace engineering. I'm aware of some technologies that have been tested out and could be feasible in the near future. But one active project that I believe that's underway with the European Space Agency is the Clear Space One mission that's set to happen next year in 2026.

where they'll actively remove a piece of debris. I'm also aware of some technologies that are being tested out, robotic arms and nets, electrodynamic tethers and lasers to nudge the debris into like a different direction.

But, you know, those are still in the experimental stages as far as I'm aware. But I have some optimism that we will find a more very concrete steps on how to get rid of any space debris that's already out there and also prevent any new space debris from being created.

Caroline, when GQ mentioned lasers, how can they be used to get rid of space junk? So lasers might end up being really important for space junk that isn't big enough to be collected by a giant claw or by a giant net because it's too small. So if you had that tiny bit of space

space junk above you or below you so lasers could be used from earth or from space you can use a laser to sort of nudge it change the direction it's going so that it eventually spirals towards earth and burns up in our atmosphere but the difficult thing is legally you're not allowed to interfere with other people's space junk yet other people's satellites and therefore space junk so

There's a legal territorial battle going on over space junk. Yes, you're not allowed to say you use a laser on someone else's bit of satellite because it is ultimately a piece of a satellite. So that would need to be ironed out as well before we could use lasers. Are companies, governments, the people putting all of this stuff out into space, are they doing anything about it to try and get rid of it? Yes, there is a lot of research.

going on into different solutions. So there's one company that's looking at launching satellites with a giant claw, another company that's looking at launching satellites with a giant net, each to catch a big piece of space junk and bring it back down to Earth. But at the moment, there's no legal obligation to clear up after yourself.

There are sort of groups that are campaigning and encouraging companies and governments to think about not just the life of their satellite in orbit, but also about the death or end of life of their satellite. So one thing in the future that could feasibly happen is when you launch a satellite, you need a plan for how you're going to get it back out of space. So that might be having a bit of fuel on board so that at the end of its life, you can sort of blast it back down towards Earth so it burns up in the atmosphere.

That would kind of fix a problem if we sort of stopped launching rockets with satellites that just end up endlessly orbiting if we started being accountable and taking our junk down. Is it something to do with what these satellites are made of? Because it's got to be metal, right? It's got to be the most durable thing out there. I've been reading about these sustainable satellites. You know, would they be made of something else?

Yeah, so most satellites are made of metal at the moment for a couple of reasons. One, it's really lightweight, so it's kind of cheaper to launch. You don't need as much fuel and because it's really strong.

But it's not super sustainable in the sense that we can't replace it. You know, there is a limited amount of metal. And also when it comes back through the atmosphere, there is now evidence that as it sort of vaporises and burns up, it's leaving these tiny particles of metal in our atmosphere. And we don't know what that could cause, what that means for the future. So there is...

another option that Japanese scientists have been looking at. Last year, a wooden satellite was launched. So it's sort of a small box made of wood and that could be a sustainable option for the future because we can plant more trees. And also as it comes back through the atmosphere towards Earth, it can burn in a sort of clean way without releasing these tiny particles of metal.

But the question is, is it strong enough? Can it withstand the heat well enough? You know, how will it last in space? So at the moment, it's sort of being assessed for six months. We're in that six months now. So we'll soon know whether or not wood is a feasible material to make satellites out of in the future. It does sound like lots of people are trying innovative solutions. They're trying to solve this problem of space junk because...

I would hate to see what we've done on Earth be replicated in space and it just to be absolutely full of our rubbish. Yeah, I think there is a sort of a feeling of this is our problem. It's getting worse and we need to fix it. And there is more pressure on governments and companies to think about this kind of stuff. So I'm hoping that in 10 years, we both see more satellites that are useful for humans, but also less space junk. Caroline, thank you so much for joining me in the studio. Thanks for having me.

And thank you for watching, for listening, for joining us wherever you are. This is What In The World from the BBC World Service. I'm Hannah Gelbart and we'll be back with another episode soon. See you then.