4 ms·

Put 29 988 people spread out on the globe (slightly larger since we are further out in the radius, but lets ignore that). Do you still wonder? Probably you cou

Put 29 988 people spread out on the globe (slightly larger since we are further out in the radius, but lets ignore that). Do you still wonder? Probably you could put a few million up there before collision is a worry. Space debris and blocking observatories is a much larger problem.

ceejayoz 3y ago
> Put 29 988 people spread out on the globe... ... and then have them run at 17,000 miles per hour.
- bryanlarsen 3y ago
  ... on highly predictable and known paths.
  - swarnie 3y ago
    Where only a percentage of objects can change their path if needed. If a collision does happen 2 objects become 20,000 objects in an instance.
    - bryanlarsen 3y ago
      If a 300kg satellite at a 300 mile orbit becomes 20,000 pieces, those are pretty darn small pieces. Objects in space regularly get hit by <1cm micro-meteoroids. They may become disabled but they don't shatter. And by being so small their mass/area ratio becomes really small and they deorbit within 90 minutes from that altitude.
      - ceejayoz 3y ago
        The orbital tracks at https://en.wikipedia.org/wiki/2009_satellite_collision https://en.wikipedia.org/wiki/2009_satellite_collision clearly show how a high-speed collision can raise the orbits of the resulting debris, having imparted significant acceleration to them. (For example: <https://en.wikipedia.org/wiki/2009_satellite_collision#/media/File:Collision-50a.jpg https://en.wikipedia.org/wiki/2009_satellite_collision#/medi...>) That smash "created at least 1,000 pieces of debris larger than 10 cm (4 in)".
  - ceejayoz 3y ago
    https://en.wikipedia.org/wiki/Satellite_collision https://en.wikipedia.org/wiki/Satellite_collision lists six unintentional high-speed collisions involving satellites that have already occurred. That's with 2-8k or so in orbit at the time. https://en.wikipedia.org/wiki/2009_satellite_collision https://en.wikipedia.org/wiki/2009_satellite_collision alone made two thousand cataloguable fragments to track on new paths we didn't get to pick.
    - bryanlarsen 3y ago
      5 of those 6 were with debris. There is >500K pieces of debris in orbit bigger than 1cm in size, many of those in unknown orbits Adding 30K satellites in known orbits where debris cannot stay in orbit and required by law to have disposal plans before launch will not meaningfully change those odds.
      - ceejayoz 3y ago
        Iridium 33 was active and capable of avoidance maneuvers. Both orbits were known. Despite this, they collided. It is clearly possible for this to get fucked up, and with 30k satellites in a shell, adding thousands of pieces of debris to the mix is clearly a non-zero risk. The exact magnitude of that risk may be debatable, but its existence cannot be waved away. SpaceX's existing constellation (also in such a self-cleaning orbit) made 1,300 maneuvers in six months to avoid debris from a satellite explosion a year earlier. https://techcrunch.com/2023/07/10/starlink-satellites-are-dodging-objects-in-orbit-thousands-of-times-every-month/ https://techcrunch.com/2023/07/10/starlink-satellites-are-do...
        bryanlarsen 3y ago
        The risk of a collison is non-zero. The risk of Kessler from 30K satellites in a 300 mile orbit is zero.
        ceejayoz 3y ago
        Sorry, but that's simply false. https://en.wikipedia.org/wiki/ASM-135_ASAT#1985_test https://en.wikipedia.org/wiki/ASM-135_ASAT#1985_test destroyed a satellite at 345 miles. Debris from it persisted until 2004. The low orbit reduces the long-term impact of such a chain-reaction - we wouldn't be locked out of space for a thousand years - but it would still be a serious disaster.
flatline 3y ago
There have been several notable collisions in the last decade. I think a full blown Kessler scenario is unlikely but it will definitely be a problem for satellite operators. Let alone the impacts on terrestrial astronomy.
Keyframe 3y ago
are orbits (LEO, MEO, GEO) path-specific, like lanes, or it's willy-nilly where only altitude is mandatory-ish?

ceejayoz 3y ago

> Put 29 988 people spread out on the globe... ... and then have them run at 17,000 miles per hour.

bryanlarsen 3y ago
... on highly predictable and known paths.
- swarnie 3y ago
  Where only a percentage of objects can change their path if needed. If a collision does happen 2 objects become 20,000 objects in an instance.
  - bryanlarsen 3y ago
    If a 300kg satellite at a 300 mile orbit becomes 20,000 pieces, those are pretty darn small pieces. Objects in space regularly get hit by <1cm micro-meteoroids. They may become disabled but they don't shatter. And by being so small their mass/area ratio becomes really small and they deorbit within 90 minutes from that altitude.
    - ceejayoz 3y ago
      The orbital tracks at https://en.wikipedia.org/wiki/2009_satellite_collision https://en.wikipedia.org/wiki/2009_satellite_collision clearly show how a high-speed collision can raise the orbits of the resulting debris, having imparted significant acceleration to them. (For example: <https://en.wikipedia.org/wiki/2009_satellite_collision#/media/File:Collision-50a.jpg https://en.wikipedia.org/wiki/2009_satellite_collision#/medi...>) That smash "created at least 1,000 pieces of debris larger than 10 cm (4 in)".
- ceejayoz 3y ago
  https://en.wikipedia.org/wiki/Satellite_collision https://en.wikipedia.org/wiki/Satellite_collision lists six unintentional high-speed collisions involving satellites that have already occurred. That's with 2-8k or so in orbit at the time. https://en.wikipedia.org/wiki/2009_satellite_collision https://en.wikipedia.org/wiki/2009_satellite_collision alone made two thousand cataloguable fragments to track on new paths we didn't get to pick.
  - bryanlarsen 3y ago
    5 of those 6 were with debris. There is >500K pieces of debris in orbit bigger than 1cm in size, many of those in unknown orbits Adding 30K satellites in known orbits where debris cannot stay in orbit and required by law to have disposal plans before launch will not meaningfully change those odds.
    - ceejayoz 3y ago
      Iridium 33 was active and capable of avoidance maneuvers. Both orbits were known. Despite this, they collided. It is clearly possible for this to get fucked up, and with 30k satellites in a shell, adding thousands of pieces of debris to the mix is clearly a non-zero risk. The exact magnitude of that risk may be debatable, but its existence cannot be waved away. SpaceX's existing constellation (also in such a self-cleaning orbit) made 1,300 maneuvers in six months to avoid debris from a satellite explosion a year earlier. https://techcrunch.com/2023/07/10/starlink-satellites-are-dodging-objects-in-orbit-thousands-of-times-every-month/ https://techcrunch.com/2023/07/10/starlink-satellites-are-do...
      - bryanlarsen 3y ago
        The risk of a collison is non-zero. The risk of Kessler from 30K satellites in a 300 mile orbit is zero.
        ceejayoz 3y ago
        Sorry, but that's simply false. https://en.wikipedia.org/wiki/ASM-135_ASAT#1985_test https://en.wikipedia.org/wiki/ASM-135_ASAT#1985_test destroyed a satellite at 345 miles. Debris from it persisted until 2004. The low orbit reduces the long-term impact of such a chain-reaction - we wouldn't be locked out of space for a thousand years - but it would still be a serious disaster.

flatline 3y ago

There have been several notable collisions in the last decade. I think a full blown Kessler scenario is unlikely but it will definitely be a problem for satellite operators. Let alone the impacts on terrestrial astronomy.

Keyframe 3y ago

are orbits (LEO, MEO, GEO) path-specific, like lanes, or it's willy-nilly where only altitude is mandatory-ish?