Comment by why_at
1 year ago
Random thought I just had: What are the odds of a rocket launch crossing through one of these laser links on its way to a higher orbit and disrupting traffic for a fraction of a second?
I know space is really big and so the odds of a rocket hitting a satellite on its way up are incredibly low, but now we're talking about lots of lines between each satellite rather than just the satellites themselves. Are the odds still tiny?
Not that it would be a big deal if it happened, just curiosity.
It's absolutely incredibly small, think of how large the surface area of a sphere of LEO and the surface area of these lasers linking the vertices of the 5,289 satellites. The gaps between them are probably hundreds of kilometres. I would imagine that each link has multiple routes so if there was a failure traffic can still be routed in the same way the Internet has many routes.
https://satellitemap.space is pretty amazing but a Starlink satellite looks massive on there, really at the scales we are talking they wouldn't even be a pixel. Do we know how many of the satellites are actually interlinked by lasers?
There’s no friction in space. So the question is not how wide the plume of a rocket engine gets, but how spread out does the vapor trail need to be before it stops being an optical impediment?
Volume is even larger than area…
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I think they are still tiny. Also don't networking systems routinely deal with temporary link disruption?
What does that have to do with the odds of rocket induced dropped packets?
Any rocket induced dropped packets will just be resent after the rocket has passed or will be routed over other links.
Lets not forget about clouds, birds, airplanes, hot hair balloons and tons of other things that separate the ground from space.
We have protocols and networks already designed today that deal with this exact problem.
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Interesting question. It used to be zero, before the satellites and before the rockets, but now is probably not zero.
I think you could take the time a rocket would be in the way and compare it to the time it would take any given satellite link pair to make an orbit to form an estimate of the chance of a single interference. Then multiply by rockets and satellite pairs to form an overall estimate.
I've done some research, I don't have a probability but from what I've found. A Falcon 9 shortly before stage 1 separation is around 50km altitude[0] doing ~2000 m/s. Preseperation the F9 is 70m tall, add 130m for plume[1] so 200m total. At 2000 m/s it'll cover it's own length and plume in 100ms. If the laser link is running at 100 Gbps that's 10Gb of data lost.
Which is actually a lot more then I estimated when I started this math, kinda puts into perspective more then 1 of the scales at play here.
Tl;dr Rockets are fast, data is apparently faster.
[0] Apparently on its longest distance link Starlink intersected 30km altitude
[1] Ref: my ass
> the odds of a rocket hitting a satellite on its way up are incredibly low
Aside, but it's not left to chance. They only launch when there's a gap in the space traffic.
Fair, but they don't compute and probably can't know the laser paths between Starlink nodes.
It doesn't matter what the odds are; loss of connectivity is going to happen. Packet loss is common across the internet, fortunately we have protocols that can deal with this.