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This scares me a bit. The idea of having LEO internet is great and all, but the idea of quadrupling the number of functioning satellites, all operating in diffe

This scares me a bit. The idea of having LEO internet is great and all, but the idea of quadrupling the number of functioning satellites, all operating in different orbits but at a similar altitude seems incredibly dangerous to me. The article mentions the movie Gravity, which is a bit unrealistic as it portrays multiple large bodies in orbit all being at about the same altitude (which isn't the case in reality). That is not the case with this web of satellites. If a chain reaction of collisions does occur, it would cause a field of tiny, fast, deadly debris all orbiting on a similar orbital "plane". It would pretty much blanket the planet. Wouldn't this cause a large issue for anything attempting to reach orbit? What am I missing here? EDIT: A lot of replies here mentioning the fact that LEO spacecraft decay more quickly than higher orbits. Please note that not all LEO orbits are low enough to guarantee a quick decay without powered retrograde thrust. Stuff can hang up there in LEO a long, long time depending on the actual altitude.

wufufufu 8y ago
This is a well informed answer to your question: https://www.quora.com/Why-dont-satellites-crash-into-each-other https://www.quora.com/Why-dont-satellites-crash-into-each-ot...
- Rooster61 8y ago
  Thank you for the article, but it really doesn't answer my question. That thread's answers assume that we are talking about the current situation we have around the Earth. We have no precedent for this many satellites orbiting at the same altitude, but at different latitudes/longitudes (which negates the safeguard that they are moving at the same speed, it doesn't matter if they can intersect). The satellites would all need to be moving at both the same speed AND the same direction to not have a risk of collisions (which would of course be a circle, useless to this application).
  - ubercore 8y ago
    First, check out the video explaining the orbits: https://www.youtube.com/watch?feature=youtu.be&v=AdKNCBrkZQ4&app=desktop https://www.youtube.com/watch?feature=youtu.be&v=AdKNCBrkZQ4... Doing some quick math, the shell in which they'll be orbiting has a surface area of 373,367,808km. With ~7000 satellites, an even distribution would leave them 533,382 km between satellites. All the satellites have station keeping thrusters to keep them in LEO with drag. Keeping them from running into each other is probably pretty simple, in comparison to the other challenges they'll need to solve.
    - Rooster61 8y ago
      Sure, but this assumes nothing ever collides with one and causes debris to be introduced to the web. The web itself will clearly be ok as long as it remains intact, but if something does cause one of these to RUD catastrophically, we now have debris following a similar, but just different enough orbit to be dangerous.
      - throwahey 8y ago
        You won't find an answer to your question because you don't seem willing to drop your alarmist attitude. There is just far too much space for 100k objects, let alone 10k to ever run the risk of collission. These satellites are all meant to be in line-of-sight. They will communicate with optics as opposed or in conjunction to radio. You fear unforseen space particles destroying one and causing a chain reaction. Why don't you hold that same fear for existing satelittes which typically operate at an orbit with far lower decay rate? The orbit for StarLink is very low, small particles would not sustain their energy long enough to be a risk factor. The StarLink sats maintain orbit with fuel, everything else without fuel in that orbit will fall. The chance that a particle will end up in the same orbit, on the same plane, at the same time is astronomically low. Your comments just echo the same type of delusions of people who think in their brillance they've found problems others have not foreseen. SpaceX is really just full of amateurs you ought to submit your findings.
        Rooster61 8y ago
pkaye 8y ago
I'm guessing LEO satellites has a much shorter orbital decay so more likely to burn up in the atmosphere is something goes wrong.
ukulele 8y ago
These types of satellites typically sag out of orbit and burn up after a few years
biaachmonkie 8y ago
Well since it's in LEO and since the sats will have been destroyed or damaged they won't be able to maintain their orbits, so the debris orbit will be decaying from the moment of the incident and should re-enter in a matter of a few months. The scenario I'm sure will be simulated by numerous people/orgs by the time this project is in full swing.
- dr_orpheus 8y ago
  This is not true of the orbit that the SpaceX satellites are going in to. LEO is a bit of a general term that covers altitudes anywhere from 100 km to 2000 km. While it is true that something at 400 km altitude will deorbit in a few months, they will be orbiting at an altitude of 1100-1300 km. At that altitude it will take hundreds of years from them to deorbit. The drag goes down exponentially as you get in to higher orbits. The FCC filing says that the SpaceX satellites will have enough fuel remaining in order to deorbit the satellite after the satellite has reached its usable mission life. This was a big concern for NASA though. Their typical guidelines were that commercial satellites have to have >90% reliability to deorbit the satellite. But they want to increase this for the SpaceX satellites because if 10% (~400) of the satellites end up failing then they are effectively up there forever.
  - Rooster61 8y ago
    Not to mention a struck satellite (probably) no longer has the capability to deorbit, at least not in a controlled manner.
    - astrodust 8y ago
      Little pieces of smashed satellites are not obligated by the rules of physics to decay. An example of how long shit can stay in space: A Saturn V booster rocket is still out there, slowly orbiting the planet: https://en.wikipedia.org/wiki/J002E3 https://en.wikipedia.org/wiki/J002E3
  - tsuraan 8y ago
    I believe you're thinking about their initial application. They've updated it [0] to an altitude of 550km, so atmospheric drag should still de-orbit broken satellites fairly promptly. [0] - <https://fcc.report/IBFS/SAT-MOD-20181108-00083> https://fcc.report/IBFS/SAT-MOD-20181108-00083>
zackbloom 8y ago
Think how big the Earth is. How hard it would be to find a Xerox machine in the Amazon or the middle of the Atlantic if someone stuck it there. Space is much, much, bigger.
- Rooster61 8y ago
  I'm no stranger to the vast physical space at play here (amateur astronomer, here). I'm aware there is a LOT of room for this stuff to move around, but there is still a threshold, however high, to where the amount of debris would become dangerously numerous.
  - soared 8y ago
    And you think that we can only fit <10k objects in an area larger than the surface of the earth?
    - hwillis 8y ago
      At any one time there are usually <10k airplanes in the sky,and they still hit each other sometimes despite going 23x slower than satellites
      - Rooster61 8y ago
        To be fair, a lot of that is because of the fact that planes follow paths that are designed to keep collisions from happening, but aren't always adhered to.
      - JshWright 8y ago
        The vast majority of those collisions occur in areas where planes are forced to congregate (around airports, etc).
        cartoonfoxes 8y ago
        Isn't there high traffic where polar intersect? See: https://en.wikipedia.org/wiki/2009_satellite_collision https://en.wikipedia.org/wiki/2009_satellite_collision.
anvandare 8y ago
SpaceX gave their proposals for this (very valid) concern here: https://licensing.fcc.gov/myibfs/download.do?attachment_key=1210294 https://licensing.fcc.gov/myibfs/download.do?attachment_key=...
nickik 8y ago
I think this issue is over played a bit sometimes. 1. Satellites can kill themselves by dropping back into the atmosphere by their own propulsion system 2. Even if they fail, most of these are low enough that the time until they fall is reasonable short. 3. The objects are known and tracked so even if they are out of control, the others will avoid them. 4. We are moving into a world with cheap access to space and lots of satellites we need service satellites anyway and multiple are in development. This could be a legal requirement but even without it will develop because SpaceX doesn't want to have debris flying around on 'their' plane.
gpm 8y ago
This is known as Kessler syndrome. It could make orbital planes unusable, but is generally thought not to pose a substantial problem for launching through them, so worst case we just have to start putting satellites a bit higher.

wufufufu 8y ago

This is a well informed answer to your question: https://www.quora.com/Why-dont-satellites-crash-into-each-other https://www.quora.com/Why-dont-satellites-crash-into-each-ot...

Rooster61 8y ago
Thank you for the article, but it really doesn't answer my question. That thread's answers assume that we are talking about the current situation we have around the Earth. We have no precedent for this many satellites orbiting at the same altitude, but at different latitudes/longitudes (which negates the safeguard that they are moving at the same speed, it doesn't matter if they can intersect). The satellites would all need to be moving at both the same speed AND the same direction to not have a risk of collisions (which would of course be a circle, useless to this application).
- ubercore 8y ago
  First, check out the video explaining the orbits: https://www.youtube.com/watch?feature=youtu.be&v=AdKNCBrkZQ4&app=desktop https://www.youtube.com/watch?feature=youtu.be&v=AdKNCBrkZQ4... Doing some quick math, the shell in which they'll be orbiting has a surface area of 373,367,808km. With ~7000 satellites, an even distribution would leave them 533,382 km between satellites. All the satellites have station keeping thrusters to keep them in LEO with drag. Keeping them from running into each other is probably pretty simple, in comparison to the other challenges they'll need to solve.
  - Rooster61 8y ago
    Sure, but this assumes nothing ever collides with one and causes debris to be introduced to the web. The web itself will clearly be ok as long as it remains intact, but if something does cause one of these to RUD catastrophically, we now have debris following a similar, but just different enough orbit to be dangerous.
    - throwahey 8y ago
      You won't find an answer to your question because you don't seem willing to drop your alarmist attitude. There is just far too much space for 100k objects, let alone 10k to ever run the risk of collission. These satellites are all meant to be in line-of-sight. They will communicate with optics as opposed or in conjunction to radio. You fear unforseen space particles destroying one and causing a chain reaction. Why don't you hold that same fear for existing satelittes which typically operate at an orbit with far lower decay rate? The orbit for StarLink is very low, small particles would not sustain their energy long enough to be a risk factor. The StarLink sats maintain orbit with fuel, everything else without fuel in that orbit will fall. The chance that a particle will end up in the same orbit, on the same plane, at the same time is astronomically low. Your comments just echo the same type of delusions of people who think in their brillance they've found problems others have not foreseen. SpaceX is really just full of amateurs you ought to submit your findings.
      - Rooster61 8y ago

pkaye 8y ago

I'm guessing LEO satellites has a much shorter orbital decay so more likely to burn up in the atmosphere is something goes wrong.

ukulele 8y ago

These types of satellites typically sag out of orbit and burn up after a few years

biaachmonkie 8y ago

Well since it's in LEO and since the sats will have been destroyed or damaged they won't be able to maintain their orbits, so the debris orbit will be decaying from the moment of the incident and should re-enter in a matter of a few months. The scenario I'm sure will be simulated by numerous people/orgs by the time this project is in full swing.

dr_orpheus 8y ago
This is not true of the orbit that the SpaceX satellites are going in to. LEO is a bit of a general term that covers altitudes anywhere from 100 km to 2000 km. While it is true that something at 400 km altitude will deorbit in a few months, they will be orbiting at an altitude of 1100-1300 km. At that altitude it will take hundreds of years from them to deorbit. The drag goes down exponentially as you get in to higher orbits. The FCC filing says that the SpaceX satellites will have enough fuel remaining in order to deorbit the satellite after the satellite has reached its usable mission life. This was a big concern for NASA though. Their typical guidelines were that commercial satellites have to have >90% reliability to deorbit the satellite. But they want to increase this for the SpaceX satellites because if 10% (~400) of the satellites end up failing then they are effectively up there forever.
- Rooster61 8y ago
  Not to mention a struck satellite (probably) no longer has the capability to deorbit, at least not in a controlled manner.
  - astrodust 8y ago
    Little pieces of smashed satellites are not obligated by the rules of physics to decay. An example of how long shit can stay in space: A Saturn V booster rocket is still out there, slowly orbiting the planet: https://en.wikipedia.org/wiki/J002E3 https://en.wikipedia.org/wiki/J002E3
- tsuraan 8y ago
  I believe you're thinking about their initial application. They've updated it [0] to an altitude of 550km, so atmospheric drag should still de-orbit broken satellites fairly promptly. [0] - <https://fcc.report/IBFS/SAT-MOD-20181108-00083> https://fcc.report/IBFS/SAT-MOD-20181108-00083>

zackbloom 8y ago

Think how big the Earth is. How hard it would be to find a Xerox machine in the Amazon or the middle of the Atlantic if someone stuck it there. Space is much, much, bigger.

Rooster61 8y ago
I'm no stranger to the vast physical space at play here (amateur astronomer, here). I'm aware there is a LOT of room for this stuff to move around, but there is still a threshold, however high, to where the amount of debris would become dangerously numerous.
- soared 8y ago
  And you think that we can only fit <10k objects in an area larger than the surface of the earth?
  - hwillis 8y ago
    At any one time there are usually <10k airplanes in the sky,and they still hit each other sometimes despite going 23x slower than satellites
    - Rooster61 8y ago
      To be fair, a lot of that is because of the fact that planes follow paths that are designed to keep collisions from happening, but aren't always adhered to.
    - JshWright 8y ago
      The vast majority of those collisions occur in areas where planes are forced to congregate (around airports, etc).
      - cartoonfoxes 8y ago
        Isn't there high traffic where polar intersect? See: https://en.wikipedia.org/wiki/2009_satellite_collision https://en.wikipedia.org/wiki/2009_satellite_collision.

anvandare 8y ago

SpaceX gave their proposals for this (very valid) concern here: https://licensing.fcc.gov/myibfs/download.do?attachment_key=1210294 https://licensing.fcc.gov/myibfs/download.do?attachment_key=...

nickik 8y ago

I think this issue is over played a bit sometimes. 1. Satellites can kill themselves by dropping back into the atmosphere by their own propulsion system 2. Even if they fail, most of these are low enough that the time until they fall is reasonable short. 3. The objects are known and tracked so even if they are out of control, the others will avoid them. 4. We are moving into a world with cheap access to space and lots of satellites we need service satellites anyway and multiple are in development. This could be a legal requirement but even without it will develop because SpaceX doesn't want to have debris flying around on 'their' plane.

gpm 8y ago

This is known as Kessler syndrome. It could make orbital planes unusable, but is generally thought not to pose a substantial problem for launching through them, so worst case we just have to start putting satellites a bit higher.