As I understand it, these constellations are all low enough in orbit that stuff deorbits from atmospheric drag relatively quickly. I think you get a few years at most for these sorts of satellites.
The "Kessler syndrome" worst case scenario - I'm just recalling stuff from Scott Manley videos here - I think is a 'really bad decade' where a cascade of collisions makes launching in to LEO impossible until everything settles down in 10ish years. Bad, yeah, terrible even, but possibly worth it in some sense? I mean, it makes about as much sense to me as growing subsidized corn for ethanol gas, I suppose. I'm sure someone is making money.
No. The problem is their development has been super slow and expensive (compared to Starlink) and also they picked fairly expensive launch providers compared to their main competitor (SpaceX).
Space junk is not in the top 5 reasons, and with better tracking and using low altitudes (like Starlink does, where debris deorbits very quickly), we can probably fit a factor of 100 times more satellites in LEO safely.
(People underestimate how much of a difference better tracking makes to this issue. Space is huge, and the real isn’t actual conjunctions, but the fact that the uncertainty range for objects is so large that you end up getting hundreds of times more false alarms and probably-unneeded avoidance maneuvers than you’d have if you had much better tracking.)
Space junk is real but much less of an issue at the low altitudes at which these newer constellations usually operate (very low in low Earth orbit). Without expending propellant to boost orbits, atmospheric drag causes them to naturally deorbit in months or a few years at most. Space junk and orbital debris are much bigger issues for higher altitudes where atmospheric drag is much weaker, but none of these satellites are that high.
Yeah, the debris removes itself with time. But there is still some uncertainty around how deorbiting harms the atmosphere [1]. Immediate effects of a single deorbit seem to be quite low but having such deorbiting scenarios at a higher frequency could have some negative effects.
> Indeed, even in the worst-case scenario, the average annual global mean ozone loss is found to be between 0.17×10–4 % and 8×10–4 %, while the Antarctic local ozone concentration change can reach about 0.05%. Those impacts are negligible when compared to the impact of anthropogenic activities, in particular emissions of industrial halogen-containing substances such as CFCs, that caused a global ozone loss of 3-4% (since 1970).
If it is like Starlink then it is not really a problem because the orbit is so low that it de-orbits quickly should they become inactive and vaporizes in the atmosphere. It's preferrable for them to put them in very low orbits because they are cheaper to get to and the reduced altitude improves latency.
