9 ms·

OneWeb, SpaceX satellites dodged a potential collision in orbit

61 points by advpetc 6y ago

mylons 6y ago
"Currently, there’s no national or global authority that would force satellite operators to take action on predicted collisions." Exciting.
- dylan604 6y ago
  "Space Force’s urgent alerts sent OneWeb engineers scrambling to email SpaceX’s Starlink team to coordinate maneuvers that would put the two satellites at safer distances from one another." This is exactly how it should work though.
  - Gwypaas 6y ago
    Not really. Coordination takes resources, doesn't scale and increases the risk of human error. A predefined set of rules making encounters predictable are way better. Like we have done for ships [0] and aircraft [1]. Any time you have to actively communicate with the other party you have not made your intentions clear enough. I.e. a transferring satellite gives way to an operational which gives way to a disabled. (Of course it's more involved than this, including predictable avoidance maneuvers, but that's would be the basic gist of it.) [0] https://en.wikipedia.org/wiki/International_Regulations_for_Preventing_Collisions_at_Sea https://en.wikipedia.org/wiki/International_Regulations_for_... [1] https://planefinder.net/about/visual-flight-rules-vfr-of-the-air/ https://planefinder.net/about/visual-flight-rules-vfr-of-the...
    - bryanlarsen 6y ago
      AFAICT NASA and SpaceX already have such an agreement, and is basically that the NASA satellite will hold steady and the SpaceX one will maneuver.
  - jagger27 6y ago
    These companies, NASA, the Space Force, and other space agencies need to have big scary red telephones on their desks for exactly this situation.
- JoeDaDude 6y ago
  I once met with Iridium [1] engineers not long after the collision of one of their satellites with a Russian weather satellite [2] in 2009. The meeting was for another purpose entirely, but since the collision was fresh news, it naturally came up in conversation. The Iridium folk told me that they would receive warnings from NORAD of imminent collisions, defined as two satellites coming with 500m. They were receiving warnings to the tune of 10 or 12 a day, so many that they basically started ignoring them. [1] https://www.iridium.com/ https://www.iridium.com/ [2] https://en.wikipedia.org/wiki/2009_satellite_collision https://en.wikipedia.org/wiki/2009_satellite_collision
intrepidhero 6y ago
Given that starlink is in LEO does that mean there is enough friction to deorbit fragments of a collision in a relatively short time frame? Does anyone know? Kessler syndrome is scary because it could render certain orbits unusable for a long time and starlink ups the risk by having a huge constellation but I've wondered how much of the risk is mitigated by being in LEO.
- wongarsu 6y ago
  If a Starlink satellite fails the drag alone will deorbit it within five years or so. (this actually happens, they used to have 5% failure rate) Of course a collision event is chaotic. The debris is catapulted in all directions, changing the orbit. But because of how orbital mechanics works their new orbit will still pass through their old orbit, so every piece of debris will deorbit eventually (unless it impacts something else first). Being so low reduces the risk considerably, and even with a couple thousand satellites more we are talking about mostly empty space.
- nabla9 6y ago
  Not all of them. Practically all space debris collisions in LEO will be hypervelocity collisions (the kinetic energy of the impact is greater than the explosive energy released by the same mass of TNT) When collision happens in LEO, some fragments gain more velocity than the colliding satellites. They may end up in higher orbits where they can stay for a very long time.
  - Gwypaas 6y ago
    That is not correct. To actually end up in an orbit with both higher apoapsis and periapsis another collision would need to happen higher upp, which then would raise the periapsis. Otherwise it would simply be an elliptic orbit still passing through the altitude which the collision happened at. An elliptic orbit may slow the decay though, but contrast this with the larger surface to weight ratio of smaller pieces and it should not really matter.
    - nabla9 6y ago
cesarb 6y ago
> SpaceX’s automated system for avoiding satellite collisions has sparked controversy, raising concerns from other satellite operators who say they have no way of knowing which way the system will move a Starlink satellite in the event of a close approach. For aircraft, we have TCAS RA, which tells each pilot in which direction they should move, with the knowledge that the other aircraft has been told to move in the opposite direction. It might be time to consider something like that for satellites.
- cptskippy 6y ago
  SpaceX has an automated system, that can be overridden to coordinate with others, which is exactly what they did in this case. I don't see why that's bad? If they refused to override and coordinate maneuvers, that's one thing, but they didn't. Having a system that can maneuver itself in the absence of outside intervention seems like a good thing when time to respond is measured in milliseconds under certain circumstances. This seems like collision avoidance systems in cars, easily overridden but functioning when the driver isn't paying attention.
- nickik 6y ago
  Yes, something like this should exist, but its very tricky to do as this is a global resource. There are few enough sats that it often still works as 'I know the guy who does operations at XY company or government and how to call them'. Unfortunately there is not even a global index of all sats with an easy way to reach the operator. Such a list exists but the phone numbers are often simply the public number of the space agency of that country. And getting from the China Space Agency to the person that can actually move the Sat it can be tricky. Not to mention that there are dead objects that simply can not be moved. The state of the art is moving forward slowly, both in monitoring and avoidance.
- mlindner 5y ago
  It turns out OneWeb as lying to to the press. https://twitter.com/joroulette/status/1384694830643679239 https://twitter.com/joroulette/status/1384694830643679239
tmarthal 6y ago
> collision probability of 1.3 percent, with the two satellites coming as close as 190 feet (50m) LEO orbits have speeds around 7.8 km/s (rounding up to ~8000m/s for quick calculations) - this avoidance detection is saying that the two satellites both traveling at 8000m/s would be in the same 50m box at the same second. A quick calculation shows that the collision avoidance is operating at least the millisecond level to predict this collision (50m/(8000m/s) ~.005 seconds. One thing someone once mentioned to me is that space is big and things travel fast. It's hard to believe that the two satellites (most likely each <1m in diameter) came "close" to colliding, when a half second later they would be 8000 meters apart.
- mhh__ 6y ago
  Starlink satellites are a bit bigger than that from what I can gather on google at least. > came "close" to colliding, when a half second later they would be 8000 meters apart. So is a bullet if it goes through you. Space is big but the orbits these satellites operate in aren't as big as space itself. Why does it matter if it's hard to believe anyway, they gave a figure of 1.3%, which is pretty low anyway, and they didn't do it on the back of a napkin.
  - satyanash 6y ago
    > they gave a figure of 1.3%, which is pretty low anyway, 1.3% chance of collision is _not_ low at all! Especially when you start considering the chaotic cascading effects that a collision can result in!
627467 6y ago
I saw this earlier: https://twitter.com/ProfHughLewis/status/1380647894705930242?s=19 https://twitter.com/ProfHughLewis/status/1380647894705930242...
- mlindner 5y ago
  Yeah that's a good thread.
mlindner 5y ago
This event was way overblasted in the news by OneWeb despite SpaceX helping them out and disabling their system for OneWeb. It's pretty clear that OneWeb is playing political football here and trying to make SpaceX out to be some kind of bad actor despite SpaceX going out of its way to help OneWeb. These articles are just pure clickbait and aren't helpful.

61 points by advpetc 6y ago

"Currently, there’s no national or global authority that would force satellite operators to take action on predicted collisions." Exciting.

dylan604 6y ago
"Space Force’s urgent alerts sent OneWeb engineers scrambling to email SpaceX’s Starlink team to coordinate maneuvers that would put the two satellites at safer distances from one another." This is exactly how it should work though.
- Gwypaas 6y ago
  Not really. Coordination takes resources, doesn't scale and increases the risk of human error. A predefined set of rules making encounters predictable are way better. Like we have done for ships [0] and aircraft [1]. Any time you have to actively communicate with the other party you have not made your intentions clear enough. I.e. a transferring satellite gives way to an operational which gives way to a disabled. (Of course it's more involved than this, including predictable avoidance maneuvers, but that's would be the basic gist of it.) [0] https://en.wikipedia.org/wiki/International_Regulations_for_Preventing_Collisions_at_Sea https://en.wikipedia.org/wiki/International_Regulations_for_... [1] https://planefinder.net/about/visual-flight-rules-vfr-of-the-air/ https://planefinder.net/about/visual-flight-rules-vfr-of-the...
  - bryanlarsen 6y ago
    AFAICT NASA and SpaceX already have such an agreement, and is basically that the NASA satellite will hold steady and the SpaceX one will maneuver.
- jagger27 6y ago
  These companies, NASA, the Space Force, and other space agencies need to have big scary red telephones on their desks for exactly this situation.
JoeDaDude 6y ago
I once met with Iridium [1] engineers not long after the collision of one of their satellites with a Russian weather satellite [2] in 2009. The meeting was for another purpose entirely, but since the collision was fresh news, it naturally came up in conversation. The Iridium folk told me that they would receive warnings from NORAD of imminent collisions, defined as two satellites coming with 500m. They were receiving warnings to the tune of 10 or 12 a day, so many that they basically started ignoring them. [1] https://www.iridium.com/ https://www.iridium.com/ [2] https://en.wikipedia.org/wiki/2009_satellite_collision https://en.wikipedia.org/wiki/2009_satellite_collision

intrepidhero 6y ago

Given that starlink is in LEO does that mean there is enough friction to deorbit fragments of a collision in a relatively short time frame? Does anyone know? Kessler syndrome is scary because it could render certain orbits unusable for a long time and starlink ups the risk by having a huge constellation but I've wondered how much of the risk is mitigated by being in LEO.

wongarsu 6y ago
If a Starlink satellite fails the drag alone will deorbit it within five years or so. (this actually happens, they used to have 5% failure rate) Of course a collision event is chaotic. The debris is catapulted in all directions, changing the orbit. But because of how orbital mechanics works their new orbit will still pass through their old orbit, so every piece of debris will deorbit eventually (unless it impacts something else first). Being so low reduces the risk considerably, and even with a couple thousand satellites more we are talking about mostly empty space.
nabla9 6y ago
Not all of them. Practically all space debris collisions in LEO will be hypervelocity collisions (the kinetic energy of the impact is greater than the explosive energy released by the same mass of TNT) When collision happens in LEO, some fragments gain more velocity than the colliding satellites. They may end up in higher orbits where they can stay for a very long time.
- Gwypaas 6y ago
  That is not correct. To actually end up in an orbit with both higher apoapsis and periapsis another collision would need to happen higher upp, which then would raise the periapsis. Otherwise it would simply be an elliptic orbit still passing through the altitude which the collision happened at. An elliptic orbit may slow the decay though, but contrast this with the larger surface to weight ratio of smaller pieces and it should not really matter.
  - nabla9 6y ago

cesarb 6y ago

> SpaceX’s automated system for avoiding satellite collisions has sparked controversy, raising concerns from other satellite operators who say they have no way of knowing which way the system will move a Starlink satellite in the event of a close approach. For aircraft, we have TCAS RA, which tells each pilot in which direction they should move, with the knowledge that the other aircraft has been told to move in the opposite direction. It might be time to consider something like that for satellites.

cptskippy 6y ago
SpaceX has an automated system, that can be overridden to coordinate with others, which is exactly what they did in this case. I don't see why that's bad? If they refused to override and coordinate maneuvers, that's one thing, but they didn't. Having a system that can maneuver itself in the absence of outside intervention seems like a good thing when time to respond is measured in milliseconds under certain circumstances. This seems like collision avoidance systems in cars, easily overridden but functioning when the driver isn't paying attention.
nickik 6y ago
Yes, something like this should exist, but its very tricky to do as this is a global resource. There are few enough sats that it often still works as 'I know the guy who does operations at XY company or government and how to call them'. Unfortunately there is not even a global index of all sats with an easy way to reach the operator. Such a list exists but the phone numbers are often simply the public number of the space agency of that country. And getting from the China Space Agency to the person that can actually move the Sat it can be tricky. Not to mention that there are dead objects that simply can not be moved. The state of the art is moving forward slowly, both in monitoring and avoidance.
mlindner 5y ago
It turns out OneWeb as lying to to the press. https://twitter.com/joroulette/status/1384694830643679239 https://twitter.com/joroulette/status/1384694830643679239

tmarthal 6y ago

> collision probability of 1.3 percent, with the two satellites coming as close as 190 feet (50m) LEO orbits have speeds around 7.8 km/s (rounding up to ~8000m/s for quick calculations) - this avoidance detection is saying that the two satellites both traveling at 8000m/s would be in the same 50m box at the same second. A quick calculation shows that the collision avoidance is operating at least the millisecond level to predict this collision (50m/(8000m/s) ~.005 seconds. One thing someone once mentioned to me is that space is big and things travel fast. It's hard to believe that the two satellites (most likely each <1m in diameter) came "close" to colliding, when a half second later they would be 8000 meters apart.

mhh__ 6y ago
Starlink satellites are a bit bigger than that from what I can gather on google at least. > came "close" to colliding, when a half second later they would be 8000 meters apart. So is a bullet if it goes through you. Space is big but the orbits these satellites operate in aren't as big as space itself. Why does it matter if it's hard to believe anyway, they gave a figure of 1.3%, which is pretty low anyway, and they didn't do it on the back of a napkin.
- satyanash 6y ago
  > they gave a figure of 1.3%, which is pretty low anyway, 1.3% chance of collision is _not_ low at all! Especially when you start considering the chaotic cascading effects that a collision can result in!

627467 6y ago

I saw this earlier: https://twitter.com/ProfHughLewis/status/1380647894705930242?s=19 https://twitter.com/ProfHughLewis/status/1380647894705930242...

mlindner 5y ago
Yeah that's a good thread.

mlindner 5y ago

This event was way overblasted in the news by OneWeb despite SpaceX helping them out and disabling their system for OneWeb. It's pretty clear that OneWeb is playing political football here and trying to make SpaceX out to be some kind of bad actor despite SpaceX going out of its way to help OneWeb. These articles are just pure clickbait and aren't helpful.