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There are so many satellites in orbit that there is a pretty good chance that if even one was to be hit by something and explode in many pieces, it would crash

There are so many satellites in orbit that there is a pretty good chance that if even one was to be hit by something and explode in many pieces, it would crash another one and then another one until there is nothing left. The nasa is pretty scared of it, so is SpaceX.

fireflymetavrse 9mo ago
There is huge increase of orbital launches in recent years [1] done mostly by SpaceX and China is also planning to double its numbers in the coming years. The risks will be even higher. [1] https://spacestatsonline.com/launches/country https://spacestatsonline.com/launches/country
goku12 9mo ago
That's the Kessler Syndrome. But it's better if it happens in a lower orbit, irrespective of what assets are present there. Space will be free for exploration again in a few years since all the debris there would eventually decay and deorbit. The article mentions a few months at 480 km. I'm a little skeptical about this figure though, because the last tracked piece from an NRO satellite that was shot down at ~250 km by SM-3 missile in operation burnt frost, lasted 20 months in space before reentry. SpaceX is probably using a statistical cutoff percentage of fragments to calculate the time. But all the pieces are dangerous uncontrolled hypervelocity projectiles. Spain lost a military communications satellite a few days ago from a collision with a tiny undetermined space debris.
- _factor 9mo ago
  Two objects colliding can send debris into different orbits. Combined kinetic energy and mass differences can send debris to many different orbits. A golf ball hitting a bowling ball or basketball, both traveling at 30 units of speed can produce quite a fast golf ball. Not all of the debris will safely burn up.
  - tlb 9mo ago
    At the speeds we're familiar with, basketballs and golf balls have elastic collisions. At orbital speeds, satellites are nearly inelastic. So fragment exit velocities lie between the two initial velocities, kv1 + (1-k)v2 for some k that depends on where each fragment came from. If they're colliding, the velocities must be somewhat different, so the weighted average speed has to be lower than orbital speed. So fragments usually don't survive many orbits.
    - WithinReason 9mo ago
      That's what I was thinking, Kessler syndrome should be impossible for objects in LEO since all debris orbits decay rapidly (probably 99.9% enter the atmosphere and burn up in minutes, the rest in hours)
    - perilunar 9mo ago
      I guess if a collision ruptures a pressurised tank, or causes an actual explosion then you could end up with a higher-than-orbit speed?
      - indoordin0saur 9mo ago
        Possibly. But more likely the thrust from escaping gas will push it in a direction to either slow the orbit down or make it more eccentric and unstable.
        tlb 9mo ago
        Right, if there's something like a small hole in a pressure tank, it's very unlikely to be aligned exactly with the CG, so the tank will spin around and the net thrust will be near zero. If a pressure tank splits in half, both halves will fly away but that's a very inefficient way of using the energy in the gas, so the added velocity will be a small fraction of the speed of sound in the gas, which is 1/6 of orbital speed for hydrogen, less for any other gas. You can't really get much of a chemical explosion because the fuel and oxidizer both disperse very quickly in space.
- Cthulhu_ 9mo ago
  It's one reason why space should be regulated (but globally / internationally), the systems in place are kinda loose and more of a gentleman's agreement insofar as I understand it. A plan for decomissioning / de-orbiting stuff should definitely be mandatory. I know there's an area for geostationary sattelites to park themselves after their lifespan, for example. But the LEO ones like Starlink will see their orbit decay in about five years (if I'm reading things correctly) even if they run out of fuel / can no longer be controlled, according to e.g. https://space.stackexchange.com/a/59560 https://space.stackexchange.com/a/59560. But it's exponential, at 600 km it takes 10 years, at 700 25 years, at 800 100 years, etc. Between 500-600 km seems to be ideal for things to naturally decay in case of issues. But also, it won't be a hard and fast "we are confined to the earth now"; the simplest model is a "the risk of being hit by debris is now x%", more advanced is "there are debris clouds in these altitudes / inclinations so best to avoid those at these times of day".
  - vermilingua 9mo ago
    Given that the previous world police are presently treating international law as toilet paper, how do you propose global regulation of space would work or be enforced?
deleted 9mo ago
[deleted]
wongarsu 9mo ago
There are tentative signs that this is happening right now. As in: each collision causes debris that on average causes more than one additional collision, causing collision rates to go up exponentially. But so far it's not anything like in Hollywood movies, it's just a graph slowly going up. There are about 12000 satellites orbiting earth. That looks like a lot on a map, but 12000 objects spread over an area larger than the surface of the earth isn't all that much Like all exponential processes it will become a major issue if we don't address it, but this is one that starts pretty slow and is well monitored
- spiritplumber 9mo ago
  Yep. That's the things about exponential curves, it's a graph slowly going up until it's no longer "slowly". https://www.thefrogdoctrine.com/p/the-29th-day https://www.thefrogdoctrine.com/p/the-29th-day
  - indoordin0saur 9mo ago
    This can't go up forever. There is only so much mass up there in orbit, and much of it is in low earth orbit so will fall back into the atmosphere quickly as it's trajectory gets knocked off course.
- childintime 9mo ago
  > 12000 objects spread over an area larger than the surface of the earth isn't all that much People keep saying this, but the only way to assure there is no collision is to have non-intersecting orbits, but that is not going to work: not enough space. It's a tell that SpaceX is now lowering the orbits, even though their satellites mostly move in flocks that maintain a formation relative to each other: because the other ways are exhausted. Of course if they do cause a (low orbit) Kessler syndrom, then they don't have a business any more, and SpaceX will have achieved the opposite of its stated goals. The major reason to lower these orbits is likely the risk of a terrorist state turning these constellations into a weapon, by willingly causing the Kessler syndrome. SpaceX isn't going to tell you that, just as it doesn't tell you it's the USA's most important military asset.
tonyhart7 9mo ago
small price to pay for global internet
- ben_w 9mo ago
  When it happens, it no longer provides global internet.
  - tonyhart7 9mo ago
    interstellar internet ???
    - ben_w 9mo ago
      If you smash up your router, your router does not magically get better, it simply fails to provide any internet. The same happens with orbiting routers, e.g. Starlink satellites.
      - tonyhart7 9mo ago
        and we would fix that shit, you acting like its impossible problem
        ben_w 9mo ago
        A Kessler cascade necessarily requires the density of shrapnel destroys basically everything in that orbit. Below the density where this happens, it isn't a Kessler cascade in the first place. You would be forced by (currently around) 2000 tons worth of bullet-mass shrapnel to wait for that shrapnel to de-orbit. Depending on the orbit, this takes months to millenia, because it's determined by atmospheric drag. The lower the orbit, the better. Starlink's orbits got lowered, this is better vs. that particular issue.
inglor_cz 9mo ago
I think the maths is counterintuitive here and that 10-20-40 thousand objects, give or take, isn't that much. The volume of space around our planet is HUGE. Let us say that you had 10 thousand people running around on Earth, including all the oceans and Antarctica, and that collision of any two would release a hail of small deadly darts into the troposphere lasting, for, at 2 years or so. Which is approximately how long debris will last on LEO, though the actual values vary. You still wouldn't expect all those 10 thousand people to obliterate themselves like that, as the Earth's surface is pretty darn big. The volume of the LEO-relevant space is much bigger than the volume of the entire troposphere on Earth, because a) it is further away from the Earth's center than the troposphere, b) it is much deeper. Now, 10 million objects, that would be a different story. So would be some specific peculiar orbit which is overcrowded. But tens of thousands of objects spread all over the entire planet isn't that much. That would be like 2-5 people in total roaming the entire Czechia, how often would they come into contact? Not very often.
NetMageSCW 9mo ago
There is no chance at all of that happening, and especially not at the orbital height of Starlink.
laughing_man 9mo ago
At that altitude the pieces will deorbit in less than a few months.
JumpCrisscross 9mo ago
> there is a pretty good chance No;, there is not, particularly in LEO.

fireflymetavrse 9mo ago

There is huge increase of orbital launches in recent years [1] done mostly by SpaceX and China is also planning to double its numbers in the coming years. The risks will be even higher. [1] https://spacestatsonline.com/launches/country https://spacestatsonline.com/launches/country

goku12 9mo ago

That's the Kessler Syndrome. But it's better if it happens in a lower orbit, irrespective of what assets are present there. Space will be free for exploration again in a few years since all the debris there would eventually decay and deorbit. The article mentions a few months at 480 km. I'm a little skeptical about this figure though, because the last tracked piece from an NRO satellite that was shot down at ~250 km by SM-3 missile in operation burnt frost, lasted 20 months in space before reentry. SpaceX is probably using a statistical cutoff percentage of fragments to calculate the time. But all the pieces are dangerous uncontrolled hypervelocity projectiles. Spain lost a military communications satellite a few days ago from a collision with a tiny undetermined space debris.

_factor 9mo ago
Two objects colliding can send debris into different orbits. Combined kinetic energy and mass differences can send debris to many different orbits. A golf ball hitting a bowling ball or basketball, both traveling at 30 units of speed can produce quite a fast golf ball. Not all of the debris will safely burn up.
- tlb 9mo ago
  At the speeds we're familiar with, basketballs and golf balls have elastic collisions. At orbital speeds, satellites are nearly inelastic. So fragment exit velocities lie between the two initial velocities, kv1 + (1-k)v2 for some k that depends on where each fragment came from. If they're colliding, the velocities must be somewhat different, so the weighted average speed has to be lower than orbital speed. So fragments usually don't survive many orbits.
  - WithinReason 9mo ago
    That's what I was thinking, Kessler syndrome should be impossible for objects in LEO since all debris orbits decay rapidly (probably 99.9% enter the atmosphere and burn up in minutes, the rest in hours)
  - perilunar 9mo ago
    I guess if a collision ruptures a pressurised tank, or causes an actual explosion then you could end up with a higher-than-orbit speed?
    - indoordin0saur 9mo ago
      Possibly. But more likely the thrust from escaping gas will push it in a direction to either slow the orbit down or make it more eccentric and unstable.
      - tlb 9mo ago
        Right, if there's something like a small hole in a pressure tank, it's very unlikely to be aligned exactly with the CG, so the tank will spin around and the net thrust will be near zero. If a pressure tank splits in half, both halves will fly away but that's a very inefficient way of using the energy in the gas, so the added velocity will be a small fraction of the speed of sound in the gas, which is 1/6 of orbital speed for hydrogen, less for any other gas. You can't really get much of a chemical explosion because the fuel and oxidizer both disperse very quickly in space.
Cthulhu_ 9mo ago
It's one reason why space should be regulated (but globally / internationally), the systems in place are kinda loose and more of a gentleman's agreement insofar as I understand it. A plan for decomissioning / de-orbiting stuff should definitely be mandatory. I know there's an area for geostationary sattelites to park themselves after their lifespan, for example. But the LEO ones like Starlink will see their orbit decay in about five years (if I'm reading things correctly) even if they run out of fuel / can no longer be controlled, according to e.g. https://space.stackexchange.com/a/59560 https://space.stackexchange.com/a/59560. But it's exponential, at 600 km it takes 10 years, at 700 25 years, at 800 100 years, etc. Between 500-600 km seems to be ideal for things to naturally decay in case of issues. But also, it won't be a hard and fast "we are confined to the earth now"; the simplest model is a "the risk of being hit by debris is now x%", more advanced is "there are debris clouds in these altitudes / inclinations so best to avoid those at these times of day".
- vermilingua 9mo ago
  Given that the previous world police are presently treating international law as toilet paper, how do you propose global regulation of space would work or be enforced?

deleted 9mo ago

[deleted]

wongarsu 9mo ago

There are tentative signs that this is happening right now. As in: each collision causes debris that on average causes more than one additional collision, causing collision rates to go up exponentially. But so far it's not anything like in Hollywood movies, it's just a graph slowly going up. There are about 12000 satellites orbiting earth. That looks like a lot on a map, but 12000 objects spread over an area larger than the surface of the earth isn't all that much Like all exponential processes it will become a major issue if we don't address it, but this is one that starts pretty slow and is well monitored

spiritplumber 9mo ago
Yep. That's the things about exponential curves, it's a graph slowly going up until it's no longer "slowly". https://www.thefrogdoctrine.com/p/the-29th-day https://www.thefrogdoctrine.com/p/the-29th-day
- indoordin0saur 9mo ago
  This can't go up forever. There is only so much mass up there in orbit, and much of it is in low earth orbit so will fall back into the atmosphere quickly as it's trajectory gets knocked off course.
childintime 9mo ago
> 12000 objects spread over an area larger than the surface of the earth isn't all that much People keep saying this, but the only way to assure there is no collision is to have non-intersecting orbits, but that is not going to work: not enough space. It's a tell that SpaceX is now lowering the orbits, even though their satellites mostly move in flocks that maintain a formation relative to each other: because the other ways are exhausted. Of course if they do cause a (low orbit) Kessler syndrom, then they don't have a business any more, and SpaceX will have achieved the opposite of its stated goals. The major reason to lower these orbits is likely the risk of a terrorist state turning these constellations into a weapon, by willingly causing the Kessler syndrome. SpaceX isn't going to tell you that, just as it doesn't tell you it's the USA's most important military asset.

tonyhart7 9mo ago

small price to pay for global internet

ben_w 9mo ago
When it happens, it no longer provides global internet.
- tonyhart7 9mo ago
  interstellar internet ???
  - ben_w 9mo ago
    If you smash up your router, your router does not magically get better, it simply fails to provide any internet. The same happens with orbiting routers, e.g. Starlink satellites.
    - tonyhart7 9mo ago
      and we would fix that shit, you acting like its impossible problem
      - ben_w 9mo ago
        A Kessler cascade necessarily requires the density of shrapnel destroys basically everything in that orbit. Below the density where this happens, it isn't a Kessler cascade in the first place. You would be forced by (currently around) 2000 tons worth of bullet-mass shrapnel to wait for that shrapnel to de-orbit. Depending on the orbit, this takes months to millenia, because it's determined by atmospheric drag. The lower the orbit, the better. Starlink's orbits got lowered, this is better vs. that particular issue.

inglor_cz 9mo ago

I think the maths is counterintuitive here and that 10-20-40 thousand objects, give or take, isn't that much. The volume of space around our planet is HUGE. Let us say that you had 10 thousand people running around on Earth, including all the oceans and Antarctica, and that collision of any two would release a hail of small deadly darts into the troposphere lasting, for, at 2 years or so. Which is approximately how long debris will last on LEO, though the actual values vary. You still wouldn't expect all those 10 thousand people to obliterate themselves like that, as the Earth's surface is pretty darn big. The volume of the LEO-relevant space is much bigger than the volume of the entire troposphere on Earth, because a) it is further away from the Earth's center than the troposphere, b) it is much deeper. Now, 10 million objects, that would be a different story. So would be some specific peculiar orbit which is overcrowded. But tens of thousands of objects spread all over the entire planet isn't that much. That would be like 2-5 people in total roaming the entire Czechia, how often would they come into contact? Not very often.

NetMageSCW 9mo ago

There is no chance at all of that happening, and especially not at the orbital height of Starlink.

laughing_man 9mo ago

At that altitude the pieces will deorbit in less than a few months.

JumpCrisscross 9mo ago

> there is a pretty good chance No;, there is not, particularly in LEO.