4 ms·

There is a limit how much satellites LEO/GEO can hold unless every satellite has perfect dodging system. Called as Kessler syndrome [1], and one estimate is aro

by nicce 1y ago

There is a limit how much satellites LEO/GEO can hold unless every satellite has perfect dodging system. Called as Kessler syndrome [1], and one estimate is around 70k satellites. So it is a race who can get the most satellites orbiting, because after a certain point, there is no "space" anymore, and anyone who tries to launch after that point, will be blamed for destroying the satellites of the others. Winner takes all. [1]: https://en.wikipedia.org/wiki/Kessler_syndrome https://en.wikipedia.org/wiki/Kessler_syndrome

dgs_sgd 1y ago
I’m just a layman, but why can’t they increase the orbital radius to solve this problem? Like, if the current “layer” is too full, have the new satellites orbit further out?
- nemomarx 1y ago
  Low orbit is how star link is able to achieve their connections, isn't it? I think of they moved to normal telecom orbit the performance would be like normal satellite internet too
  - peterfirefly 1y ago
    They originally planned to be about 1100km up. They are currently about 550km up. Plenty of possible layers in between... Another 500 km won't affect latency much. It'll be around 3 more ms per round trip.
    - nemomarx 1y ago
      That's not a bad latency addition, you're right. Good note
- parl_match 1y ago
  very simple explanation but there's a few issues radio bandwidth: higher frequencies travel a shorter distance and provide more bandwidth. so you get frequency contention and also you need your sats to be physically closer latency: the further a sat is, the higher the latency. not an issue for text messages. a huge issue for phone calls and general internet tasks. the further you "push" your sat "back", the worst the user experience is there's other issues too, like geostationary vs geosynchronous and coverage and exposure.
- 01HNNWZ0MV43FF 1y ago
  WP says Low Earth Orbit is popular because it's cheap to get stuff there, the latency is low (speed of light starts to matter when you're a couple Earth diameters up) and bandwidth to the ground is high (I assume it's harder to send a signal a longer distance, even through vacuum) https://en.wikipedia.org/wiki/Low_Earth_orbit https://en.wikipedia.org/wiki/Low_Earth_orbit see "Use"
- 4rt 1y ago
  The reason starlink are so low in the first place is its cheaper to launch to that altitude, you need way less signal strength for devices to connect to them and the round-trip latency is vastly improved. They're intended to be essentially disposable, they're going for shorter lifetime and iterating on hardware improvements faster. The further out you get, there's less atmospheric drag and each satellite is in view of the ground stations for longer but the cost of launch is higher and latency becomes a big issue. People expect 50ms latency for internet access not 500ms.
- michaelmior 1y ago
  Not with a geostationary orbit. That must have a fixed radius. The problem is that satellites have to move to counteract the force of gravity to avoid falling out of orbit. But if they move too much or too little, then the satellite moves with respect to the earth and the orbit is no longer geostationary. (Caveat: Not an expert by any means, just someone who had a similar question and did some reading, so my answer may well be incomplete or not fully correct.)
  - zwily 1y ago
    Starlink satellites aren't geostationary.
    - michaelmior 1y ago
      The parent comment wasn't specifically addressing Starlink.
  - tejtm 1y ago
    This has already been addressed as LEO is not geostationary but to point as to why. Consider the earths equator rotates at a particular velocity so there is a particular orbital radius where the two cancel and NO energy is needed to fall around the equator at the same rate the equator is moving. That is a geostationary orbit. LEO maxes out ~ 1,200 miles radius, geostationary is at little over over 22,000 miles radius.
- JumpCrisscross 1y ago
  > why can’t they increase the orbital radius to solve this problem? Because there isn't a problem. LEO contains more than 200x the volume of commercial airspace. We run out of spectrum and launch capacity well before Kessler cascades become a problem.
- tejtm 1y ago
  Automatic EOL (end of life) deorbiting is a feature not a bug. I will again note that if Saber Tooth tigers had put things in the orbits we have, it would still be our problem.
01HNNWZ0MV43FF 1y ago
A land grab. That might explain the desire to put anything in space, even something useless like mirrors to reflect sunlight
ricardobeat 1y ago
That’s one single estimate, and the problem is much more nuanced. For example, Starlink satellites orbit so low, that even if every single one of them collides and becomes dust, it will all decay and burn up in a matter of months, a couple years at most. The debris cannot physically move to higher orbits to affect other “normal” satellites, though it might impair launches. Conversely, collisions at much higher geosynchronous orbits can’t possibly create a dense debris field as the total area is immense, deorbit will take millions of years, and everything is usually moving at the same speed (the synchronous part).
- nicce 1y ago
  > For example, Starlink satellites orbit so low, that even if every single one of them collides and becomes dust, it will all decay and burn up in a matter of months, a couple years at most. That is way too long. The threshold we are speaking of cannot allow any fragments, because they start chain reaction and destroy more satellites. And there is always one which is on the highest level. What if that gets destroyed?
  - bryanlarsen 1y ago
    No it's not. Kessler simulations show those chain reactions happening over multiple decades.
    - nicce 1y ago
      It purely depends of the density of objects. The whole definition of the Kessler syndrome is about the estimation when the density is too much to handle.
      - zevon 1y ago
        Maybe this is helpful: https://aerospaceamerica.aiaa.org/features/understanding-the-misunderstood-kessler-syndrome/ https://aerospaceamerica.aiaa.org/features/understanding-the...
  - 1y ago
peterfirefly 1y ago
Starlink's orbits are so low that everything deorbits automatically. The satellites need to actively work to stay up. That means no Kessler syndrome there. How many you can fit depends on the available technology. It should eventually be a lot more than 70K just in those low orbits... and still leave plenty of space for rocket launches and returns to thread their way in between them.
- nicce 1y ago
  > Starlink's orbits are so low that everything deorbits automatically. It is enough if it goes one round around. They can make a cascading effect which can destroy tens of satellites at once, and few fragments are enough. And closer to earth you are, less space there is. They can't all orbit on exactly the same level. There is always one which is on slightly higher level.
  - JumpCrisscross 1y ago
    > closer to earth you are, less space there is Humans are bad at intuiting exponents. There is roughly 200x more volume in LEO than there is between the ground and cruising altitude. Plane changes, moreover, take a lot of energy--you aren't going to get enough energy out of a collision to pollute nearby orbits.
    - nicce 1y ago
      > going to get enough energy out of a collision to pollute nearby orbits. There is no infinite space. The problem is exactly defining the number objects when that "small" amount of energy is actually enough to cause problems.
      - JumpCrisscross 1y ago
        > There is no infinite space Straw man. > problem is exactly defining the number objects when that "small" amount of energy is actually enough to cause problems The exercise, maybe. The problem? No. In LEO, which is where Starlink orbits, there is no known solution for causing a Kessler cascade that causes more than a few billion in damage. Space isn't infinite, but it's really big. Again, a few hundred thousand planes land every day [1]. They operate in a volume less than 1% that of LEO. To approach the object densities where we start controlling an airspace, you'd need tens of millions of objects in LEO alone. We simply do not have--not have any roadmap to having--the sort of launch capacity required to keep 30 million objects in LEO at a time. There are real problems with more Starlinks in space. Kessler cascades are not one of them. [1] https://www.travelandleisure.com/airlines-airports/number-of-planes-in-air#:~:text=There%20are,has%20rebounded%2C https://www.travelandleisure.com/airlines-airports/number-of...

by nicce 1y ago

dgs_sgd 1y ago

I’m just a layman, but why can’t they increase the orbital radius to solve this problem? Like, if the current “layer” is too full, have the new satellites orbit further out?

nemomarx 1y ago
Low orbit is how star link is able to achieve their connections, isn't it? I think of they moved to normal telecom orbit the performance would be like normal satellite internet too
- peterfirefly 1y ago
  They originally planned to be about 1100km up. They are currently about 550km up. Plenty of possible layers in between... Another 500 km won't affect latency much. It'll be around 3 more ms per round trip.
  - nemomarx 1y ago
    That's not a bad latency addition, you're right. Good note
parl_match 1y ago
very simple explanation but there's a few issues radio bandwidth: higher frequencies travel a shorter distance and provide more bandwidth. so you get frequency contention and also you need your sats to be physically closer latency: the further a sat is, the higher the latency. not an issue for text messages. a huge issue for phone calls and general internet tasks. the further you "push" your sat "back", the worst the user experience is there's other issues too, like geostationary vs geosynchronous and coverage and exposure.
01HNNWZ0MV43FF 1y ago
WP says Low Earth Orbit is popular because it's cheap to get stuff there, the latency is low (speed of light starts to matter when you're a couple Earth diameters up) and bandwidth to the ground is high (I assume it's harder to send a signal a longer distance, even through vacuum) https://en.wikipedia.org/wiki/Low_Earth_orbit https://en.wikipedia.org/wiki/Low_Earth_orbit see "Use"
4rt 1y ago
The reason starlink are so low in the first place is its cheaper to launch to that altitude, you need way less signal strength for devices to connect to them and the round-trip latency is vastly improved. They're intended to be essentially disposable, they're going for shorter lifetime and iterating on hardware improvements faster. The further out you get, there's less atmospheric drag and each satellite is in view of the ground stations for longer but the cost of launch is higher and latency becomes a big issue. People expect 50ms latency for internet access not 500ms.
michaelmior 1y ago
Not with a geostationary orbit. That must have a fixed radius. The problem is that satellites have to move to counteract the force of gravity to avoid falling out of orbit. But if they move too much or too little, then the satellite moves with respect to the earth and the orbit is no longer geostationary. (Caveat: Not an expert by any means, just someone who had a similar question and did some reading, so my answer may well be incomplete or not fully correct.)
- zwily 1y ago
  Starlink satellites aren't geostationary.
  - michaelmior 1y ago
    The parent comment wasn't specifically addressing Starlink.
- tejtm 1y ago
  This has already been addressed as LEO is not geostationary but to point as to why. Consider the earths equator rotates at a particular velocity so there is a particular orbital radius where the two cancel and NO energy is needed to fall around the equator at the same rate the equator is moving. That is a geostationary orbit. LEO maxes out ~ 1,200 miles radius, geostationary is at little over over 22,000 miles radius.
JumpCrisscross 1y ago
> why can’t they increase the orbital radius to solve this problem? Because there isn't a problem. LEO contains more than 200x the volume of commercial airspace. We run out of spectrum and launch capacity well before Kessler cascades become a problem.
tejtm 1y ago
Automatic EOL (end of life) deorbiting is a feature not a bug. I will again note that if Saber Tooth tigers had put things in the orbits we have, it would still be our problem.

01HNNWZ0MV43FF 1y ago

A land grab. That might explain the desire to put anything in space, even something useless like mirrors to reflect sunlight

ricardobeat 1y ago

That’s one single estimate, and the problem is much more nuanced. For example, Starlink satellites orbit so low, that even if every single one of them collides and becomes dust, it will all decay and burn up in a matter of months, a couple years at most. The debris cannot physically move to higher orbits to affect other “normal” satellites, though it might impair launches. Conversely, collisions at much higher geosynchronous orbits can’t possibly create a dense debris field as the total area is immense, deorbit will take millions of years, and everything is usually moving at the same speed (the synchronous part).

nicce 1y ago
> For example, Starlink satellites orbit so low, that even if every single one of them collides and becomes dust, it will all decay and burn up in a matter of months, a couple years at most. That is way too long. The threshold we are speaking of cannot allow any fragments, because they start chain reaction and destroy more satellites. And there is always one which is on the highest level. What if that gets destroyed?
- bryanlarsen 1y ago
  No it's not. Kessler simulations show those chain reactions happening over multiple decades.
  - nicce 1y ago
    It purely depends of the density of objects. The whole definition of the Kessler syndrome is about the estimation when the density is too much to handle.
    - zevon 1y ago
      Maybe this is helpful: https://aerospaceamerica.aiaa.org/features/understanding-the-misunderstood-kessler-syndrome/ https://aerospaceamerica.aiaa.org/features/understanding-the...
- 1y ago

peterfirefly 1y ago

Starlink's orbits are so low that everything deorbits automatically. The satellites need to actively work to stay up. That means no Kessler syndrome there. How many you can fit depends on the available technology. It should eventually be a lot more than 70K just in those low orbits... and still leave plenty of space for rocket launches and returns to thread their way in between them.

nicce 1y ago
> Starlink's orbits are so low that everything deorbits automatically. It is enough if it goes one round around. They can make a cascading effect which can destroy tens of satellites at once, and few fragments are enough. And closer to earth you are, less space there is. They can't all orbit on exactly the same level. There is always one which is on slightly higher level.
- JumpCrisscross 1y ago
  > closer to earth you are, less space there is Humans are bad at intuiting exponents. There is roughly 200x more volume in LEO than there is between the ground and cruising altitude. Plane changes, moreover, take a lot of energy--you aren't going to get enough energy out of a collision to pollute nearby orbits.
  - nicce 1y ago
    > going to get enough energy out of a collision to pollute nearby orbits. There is no infinite space. The problem is exactly defining the number objects when that "small" amount of energy is actually enough to cause problems.
    - JumpCrisscross 1y ago
      > There is no infinite space Straw man. > problem is exactly defining the number objects when that "small" amount of energy is actually enough to cause problems The exercise, maybe. The problem? No. In LEO, which is where Starlink orbits, there is no known solution for causing a Kessler cascade that causes more than a few billion in damage. Space isn't infinite, but it's really big. Again, a few hundred thousand planes land every day [1]. They operate in a volume less than 1% that of LEO. To approach the object densities where we start controlling an airspace, you'd need tens of millions of objects in LEO alone. We simply do not have--not have any roadmap to having--the sort of launch capacity required to keep 30 million objects in LEO at a time. There are real problems with more Starlinks in space. Kessler cascades are not one of them. [1] https://www.travelandleisure.com/airlines-airports/number-of-planes-in-air#:~:text=There%20are,has%20rebounded%2C https://www.travelandleisure.com/airlines-airports/number-of...