eli5 why is a higher amount of space junk a problem for us? Why can’t we shoot it away with missiles?
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Most space junk is small. This quote from National Geographic puts it in perspective –
“More than 23,000 known man-made fragments larger than about 4 inches, which is a little wider than two golf balls across, zip around our planet. But those are just the pieces large enough to track. An estimated 500,000 pieces between 0.4 inches and 4 inches across join those larger fragments.”
Almost all of those pieces are much too small to target (not to mention, you just blow them into more even smaller pieces), but even a half inch piece traveling at up to 22,300 mph can smash a hole in a satellite or manned spacecraft.
It really is a problem.
Because blowing up a piece of junk in orbit means you have turned one piece of junk into a hundred or more pieces of junk.
What do you think happens when a missile hits something?
It doesn’t vanish into the Shadow Dimension or anything like that. It just breaks up into smaller pieces, and it’s sent flying in all directions. But you’ve still got the same amount of *stuff*.
So if you try to blow up the space junk, you’re left with the same total amount of space junk, but spread across a larger number of smaller, faster-moving pieces. That only makes it harder to avoid and *more* dangerous
Most of the space junk is larger pieces, such as defunct satellites or discarded rocket stages. If you shoot at them with missiles you will not actually change their orbits at all but just turn them into thousands of small pieces of space junk. So now instead of having to worry about one large piece which can be easily tracked by radar and which can easily be avoided we have to worry about thousands of tiny pieces which does not show up on radar and which is spread over too large a field to avoid. The pieces are going 30 times the speed of a bullet so the smaller pieces is going to be just as destructive as a large piece.
In order to actually get rid of the space junk we have to change their orbits. You can not do this with a missile or a bullet because there is not enough energy in those. You need to somehow capture the junk and then slowly change its orbit using a rocket. We do not know how to do this effectively yet. Even worse the radars which are used to track the space junk was developed during the cold war to detect incoming ballistic missiles and are now being decommissioned due to their age and lack of funding. So not only do we not know how to clean up the orbits around Earth but we no longer have the radars to track the debris so they can be avoided.
Shooting debris with missiles just makes more debris. Things don’t just disappear. Explosions just make stuff into smaller pieces of stuff and add velocity to those pieces in all sorts of directions. The missile itself is composed of materials which, after an explosion, would become space debris.
The trouble is that, with anything in orbit, to truly get it out, you need to either slow it down enough that it falls to Earth or accelerate it a lot to get it to escape the draw of Earth’s gravity.
With the missile solution, some debris would likely be directed towards Earth, but the remnants of the missile and the unpredictability of where all the small bits of debris will be accelerated towards make it a larger problem in the long run.
Things in orbit are moving very, very fast. So even very small pieces of space junk can act like bullets when they hit satellites and spacecraft.
Missiles could turn large pieces of junk into many smaller pieces, but those small pieces would still be very dangerous. Additionally, there would then be more of them, and they would be much harder to track. Large pieces of space junk can be tracked using radar, and potentially avoided. Lots of smaller pieces can’t.
Space junk are old equipment that are big pieces of metal that are no longer used. They are still orbiting the earth and their paths can be predicted, so paths for new and currently in use equipment such as Starlink, GPS, and Space Telescopes, can be adjusted to avoid the big pieces.
Shooting space junk with missiles will break the big piece of metal into tiny pieces of metal, whose paths cannot be tacked after an explosion. And those tiny pieces will damage the valuable equipment that is impossible to fix once its up in space. The suggested strategy to deal with space junk is to slow them down so that they get out of orbit and fall back to earth to burn up like a meteor/shooting star (meteorites are the ones that land on earth).
If we shoot them away with out exploding them, like shooting them out of earths orbit and away from earth, they still exist out in space and will be a problem for future missions to send stuff further out.
Analogy: fill a balloon with confetti and inflate it. You can avoid an inflated balloon if it falls from above you. If you pop it, the confetti will pop out and fall, can you avoid the confetti?
Then, its better to clean up all the confetti and putting them in the trash can rather than pushing them under the couch and finding it later.
No one here has mentioned Kessler Syndrome.
In Space, there’s nothing to pull things together, so if something is hit by something else in space then likelihood is both or one object will break apart into many smaller fragments.
You may think that small debris would be less of a problem, unfortunately it’s actually a bigger problem because it’s harder to detect, at orbital speeds, these can be very destructive if they hit something. (ISS travels at about 7 kilometres per SECOND compared to us) Here’s what a speck of paint did to the cupola module on the ISS:
https://www.esa.int/ESA_Multimedia/Images/2016/05/Impact_chip
Kessler predicted that if things keep hitting each other in orbit eventually you’re left with a cloud of tiny debris orbiting the Earth at kilometres per second speeds, this has the unfortunate downside of shredding any spacecraft that tries to leave the planet to the point that we’re stuck here.
Shooting missiles at it will only accelerate the problem whilst putting more debris into orbit. That said, most satellites now have limited lifespans for this exact reason and they will de-orbit themselves due to atmospheric drag.
Another solution is to actively de-orbit the junk that’s already in space, though I’ve yet to see this happen in practice.
The main issue is we really need to keep on top of this through international cooperation to keep space open for all. De-orbiting spent boosters and obsolete satellites now is much easier then after they’ve collided, smashed into thousands of pieces, and drifted into many many different orbital paths. It’s one of the reasons Russia’s anti-satellite was condemned worldwide due to the unnecessary creation of lots of debris.
As others have explained, breaking up debris with missiles is a bad idea. But blasting it with *lasers* looks like a way to go.
> … The laser broom is intended to be used at high enough power to penetrate through the atmosphere with enough remaining power to ablate material from the target.[6] The ablating material imparts a small thrust that lowers its orbital perigee into the upper atmosphere, thereby increasing drag so that its remaining orbital life is short.[7] … The power levels of lasers in this concept are well below the power levels in concepts for more rapidly effective anti-satellite weapons.
https://en.wikipedia.org/wiki/Laser_broom
Because that would exponentially increase and disperse the amount of junk in orbit.
When something is hit with a missile, it doesn’t just *vanish*. It is exploded into many, many smaller pieces. The missile itself also fragments into smaller pieces. So overall you’re still adding mass to the amount of junk in orbit.
So now we’d have thousands and thousands more individual pieces of debris in orbit, and now they’d be less detectable due to their smaller size. But still just as deadly to a spacecraft.
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