> 12000 objects spread over an area larger than the surface of the earth isn't all that much
People keep saying this, but the only way to assure there is no collision is to have non-intersecting orbits, but that is not going to work: not enough space.
It's a tell that SpaceX is now lowering the orbits, even though their satellites mostly move in flocks that maintain a formation relative to each other: because the other ways are exhausted.
Of course if they do cause a (low orbit) Kessler syndrom, then they don't have a business any more, and SpaceX will have achieved the opposite of its stated goals.
The major reason to lower these orbits is likely the risk of a terrorist state turning these constellations into a weapon, by willingly causing the Kessler syndrome. SpaceX isn't going to tell you that, just as it doesn't tell you it's the USA's most important military asset.
> The major reason to lower these orbits is likely the risk of a terrorist state turning these constellations into a weapon, by willingly causing the Kessler syndrome.
Hard to see how the repositioning appreciably alters this risk, since there are still thousands of satellites in the original plane to get hit by shrapnel from intentionally caused collisions, and the satellites in the lower orbit aren't invulnerable to it either
Suspect there's a rather more practical calculation that the extra thruster firings needed to main position in a lower orbit with more atmospheric drag are offset by the smaller number of conjunction avoidance manoeuvres they need to undertake in less congested space (the cost of lowering the orbit is simply deducted from their original delta-v budget for end of life deorbiting). In simple terms they get lower accidental collision risk without operations in the lower orbit shortening satellite lifetime.
> Hard to see how the repositioning appreciably alters this risk, since there are still thousands of satellites in the same plane to get hit by shrapnel from intentionally caused collisions, and the satellites in the lower orbit aren't invulnerable to it either
Yes, but the lower the orbit, the faster atmospheric drag (which isn't zero, just low) cleans up a cascade.
Feel like I'm repeating myself here, but they're moving less than half of them, which is going to have a negligible impact on a state with sufficient ASAT weapons' ability to create a massive mess with the many thousands of Starlink satellites operating in their original plane. Not even like the satellites in the lowest orbit are insulated from the effects of debris cascades set off in higher reaches of LEO either
Plenty of operational reasons to want a large fraction of your constellation in a slightly lower orbit, none of them involve "terrorist states"
It is the difference between optimization and unacceptable risks. Unacceptable risks make you act, they create a leitmotiv, and you don't seem to get that. So you talk about other motives, while ignoring the potentially main one.
Space no longer is a friendly place, it is the battle field of the future. SpaceX is a major military power in ascent, Musk is richer than many nations already, and he'll be in the supervillain category soon, and alone in actual physical power. He sits between the nations as a different entity in nature. It's happening in front of your eyes but you don't see it. That's why you are repeating yourself, as if we didn't see what you see. You speak about a technical motive we all see, as if only you see it. We all see that, it's trivial given the subject, and I mentioned it. Maybe we're not as stupid as you think we are, "teacher".
If that's the only risk, sure. But there's modelling and observation that suggest the required number of ASAT weapons to cause a Kessler cascade is currently zero, i.e. we're already in the early stages of one.
Because physics of orbital dynamics is less dramatic than shown in film, lowering orbits of satelites is an effective way to mitigate this.
This paper is brought up elsewhere in this thread and responded to. TL; DR It raises interesting modelling strategies, and develops on cool numerical methods from Kessler (2001), but it's far off from "pretty good chance."
People keep saying this, but the only way to assure there is no collision is to have non-intersecting orbits, but that is not going to work: not enough space.
It's a tell that SpaceX is now lowering the orbits, even though their satellites mostly move in flocks that maintain a formation relative to each other: because the other ways are exhausted.
Of course if they do cause a (low orbit) Kessler syndrom, then they don't have a business any more, and SpaceX will have achieved the opposite of its stated goals.
The major reason to lower these orbits is likely the risk of a terrorist state turning these constellations into a weapon, by willingly causing the Kessler syndrome. SpaceX isn't going to tell you that, just as it doesn't tell you it's the USA's most important military asset.