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SpaceX Starlink satellites had to make 25,000 collision-avoidance maneuvers

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Re: SpaceX Starlink satellites had to make 25,000 collision-avoidance maneuvers

#31

Post by dr_orpheus »

ineedasername wrote: post #11

>it [# of maneuvers] follows an exponential curve... it has gone up by a factor of 10 in just two years. Ridiculous. Per this chart, the # of satellites has also gone up by a factor of 10 in that same 2 year time period from ~400 to ~4000. Maneuvers-per-satellite does not appear to be increasing, given available data. https://en.wikipedia.org/wiki/List_of_Starlink_and_Starshiel...

Additionally, we have gotten better at tracking smaller objects in orbit as well, so we know of more things we need to maneuver around. Companies like ExoAnalytics have set up hundreds of sensors for finding and tracking objects in space. JSpOC has been increasing sensors has well. As we are able to track smaller things the number of things we are actually tracking can go up. If I remember correctly after the Space Fence came online in 2020 or 2021 the number of things being tracked by JSpOC went from like 25,000 to >100,000.

Re: SpaceX Starlink satellites had to make 25,000 collision-avoidance maneuvers

#32

Post by [deleted] »

wongarsu wrote: post #22
schiffern wrote: post #13

It's important to note that Starlink satellites will maneuver when they calculate a 1-in-100,000 probability of collision.[0] Most other satellite operators will only maneuver when they predict a 1-in-10,000 chance. The scaling isn't linear either. By setting the threshold 10x lower, SpaceX performs more than 10x as many maneuvers. Essentially they're complaining because SpaceX is too cautious . [0] https://www.space…

If you have 4000 satellites a 1-in-10,000 chance doesn't seem that unlikely anymore. The scale of their operation forces them to be more cautious

[deleted]

Re: SpaceX Starlink satellites had to make 25,000 collision-avoidance maneuvers

#33

Post by jacquesm »

FeepingCreature wrote: post #16
Lolaccount wrote: post #12

Humans are like satellites in orbit ... inert. It'll only take something like a starlink satellite punching a hole through the ISS for this to register or change anything ... c.f. light pollution

That would be difficult since Starlink orbits more than 100km higher than the ISS.

No, that actually makes it possible. If they were lower then it would be difficult (or even impossible). But the chances of a collision are really small given how tiny the relative cross sections of satellite and ISS are compared to the total surface area of the shell the ISS orbits in.

Re: SpaceX Starlink satellites had to make 25,000 collision-avoidance maneuvers

#34

Post by somenameforme »

Okay so the data they offer is that the satellites are, on average, making one orbital correction per month to avoid any possible trajectory with a greater than 1 in 100,000 chance of a collision. Those satellites are around LEO, which corresponds to a mean velocity of ~17,000 mph. So they're claiming that making one course adjustment per month, traveling at 17,000 mph, to avoid a 1 in 100,000 chance of a collision, is "Like swerving on a highway every 10 meters" in big bold font? I remember there's a reason I removed space.com from my space bookmarks.

Re: SpaceX Starlink satellites had to make 25,000 collision-avoidance maneuvers

#35

Post by foobarbecue »

Am I understanding correctly that they are mostly avoiding other Starlink satellites?

The article says there are 10,000 satellites in orbit, including dead ones. 4,000 of those are Starlink. I'm guessing that since they have similar altitudes, Starlink satellites are more likely to come near other Starlink satellites.

Re: SpaceX Starlink satellites had to make 25,000 collision-avoidance maneuvers

#36

Post by Roark66 »

nordsieck wrote: post #17
schiffern wrote: post #13

It's important to note that Starlink satellites will maneuver when they calculate a 1-in-100,000 probability of collision.[0] Most other satellite operators will only maneuver when they predict a 1-in-10,000 chance. The scaling isn't linear either. By setting the threshold 10x lower, SpaceX performs more than 10x as many maneuvers. Essentially they're complaining because SpaceX is too cautious . [0] https://www.space…

Another thing is that Starlink is low enough that space junk spontaneously de-orbits relatively quickly. I think within ~10 years, all of the junk SpaceX is maneuvering around shouldn't be a concern to them any more.

If there is no collision, yes you're right, but if there is one.... Stuff gets thrown into various orbits. Most of the debris will deorbit quickly, but a small percentage can get a substantial kick and go higher.

Re: SpaceX Starlink satellites had to make 25,000 collision-avoidance maneuvers

#37

Post by nordsieck »

Roark66 wrote: post #36
nordsieck wrote: post #17

Earlier quoted context omitted.

Another thing is that Starlink is low enough that space junk spontaneously de-orbits relatively quickly. I think within ~10 years, all of the junk SpaceX is maneuvering around shouldn't be a concern to them any more.

If there is no collision, yes you're right, but if there is one.... Stuff gets thrown into various orbits. Most of the debris will deorbit quickly, but a small percentage can get a substantial kick and go higher.

> If there is no collision, yes you're right, but if there is one.... Stuff gets thrown into various orbits. Most of the debris will deorbit quickly, but a small percentage can get a substantial kick and go higher.

That's a misleading description.

While a collision may increase an object's apogee, it will be in an elliptical orbit: it will always intersect the orbit where the collision happened.

This isn't just a collision thing either: all spacecraft do this[1] as a first step (move to an elliptical orbit), and then typically relight their engines at the apogee in order to circularize their orbit.

---

1. https://en.wikipedia.org/wiki/Hohmann_transfer_orbit

Re: SpaceX Starlink satellites had to make 25,000 collision-avoidance maneuvers

#38

Post by [deleted] »

Roark66 wrote: post #36
nordsieck wrote: post #17

Earlier quoted context omitted.

Another thing is that Starlink is low enough that space junk spontaneously de-orbits relatively quickly. I think within ~10 years, all of the junk SpaceX is maneuvering around shouldn't be a concern to them any more.

If there is no collision, yes you're right, but if there is one.... Stuff gets thrown into various orbits. Most of the debris will deorbit quickly, but a small percentage can get a substantial kick and go higher.

[deleted]

Re: SpaceX Starlink satellites had to make 25,000 collision-avoidance maneuvers

#39

Post by Buttons840 »

Roark66 wrote: post #36
nordsieck wrote: post #17

Earlier quoted context omitted.

Another thing is that Starlink is low enough that space junk spontaneously de-orbits relatively quickly. I think within ~10 years, all of the junk SpaceX is maneuvering around shouldn't be a concern to them any more.

If there is no collision, yes you're right, but if there is one.... Stuff gets thrown into various orbits. Most of the debris will deorbit quickly, but a small percentage can get a substantial kick and go higher.

Are you sure? My KSP intuition tells me this is wrong.

Orbits are circular and constant (accurate enough for my argument). An impact might cause some debris to go up, but when the debris that went up comes back around to the same spot in its orbit, it will again be going up. Well, extrapolate that backward a bit and you realize the debris that is going up was inside the atmosphere moments before.

In other words, if an instant impulse causes an orbit to have a higher apoapsis, it must also lower its periapsis. Which means the piece will go deeper into the atmosphere, and you don't come back from deep in the atmosphere.

Re: SpaceX Starlink satellites had to make 25,000 collision-avoidance maneuvers

#40

Post by Karellen »

Roark66 wrote: post #36
nordsieck wrote: post #17

Earlier quoted context omitted.

Another thing is that Starlink is low enough that space junk spontaneously de-orbits relatively quickly. I think within ~10 years, all of the junk SpaceX is maneuvering around shouldn't be a concern to them any more.

If there is no collision, yes you're right, but if there is one.... Stuff gets thrown into various orbits. Most of the debris will deorbit quickly, but a small percentage can get a substantial kick and go higher.

> Stuff gets thrown into various orbits. Most of the debris will deorbit quickly, but a small percentage can get a substantial kick and go higher.

Only at apoapsis. But, any item thrown into an orbit with a significantly higher apoapsis will very likely have a significantly lower periapsis. So even for high-energy fragments, each orbit should have a period of passing through a higher-drag part of its orbit, and lose energy relatively quickly.

Significantly, the periapsis can never be lower than the altitude that the collision occurred. The worst case, IIRC, is for fragments ejected in the direction of orbital travel at the time of collision. But even then, they'll still spend some time in whatever drag environment they were in beforehand.

That's not to say collisions are fine, but nothing is going to get thrown into random high low-eccentricity orbits where they hang around and pose a threat for decades or more.

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