They are not manually maneuvered but there's still unpredictable inteplay of solar wind and tenuous atmosphere to correct. And some sats will fail, the environment is harsh. So I believe some safety separation will be a must, used 1 second as a rule of thumb and the orbital speed is 7.8 km/s at the altitude.

I suspect more safety time will be required. Say a micrometeoroid impact happens causing one satellite to go off track. Now the controller computer needs some time to recompute whole swarm trajectories to minimize debris impacts. Even sats that are currently on the other side of planet might need to start thrusters immediately, as it takes only 10 minutes on average to cover the distance.

Let’s do some math and see. If we assume the earth is a sphere (I know it isn’t, but it’s mostly close), and using 4(pi)r^2, it’s about 511 million km2 in area on the surface (counting oceans, etc). Double checking, it’s actually about 507 million km2, so decently close.

4 * 3.1459 * (6378^2)

Starlink is orbiting at 550km altitude (approx). At that altitude, we’re looking at…

4 * 3.1459 * (6928^2) = 603,977,365 km2

The thing to keep in mind about orbits is the defining factor is your eccentricity and velocity. Faster velocity == higher orbit, assuming it’s a round/circular orbit, that velocity will also be consistent.

As long as everyone is going in the same direction and trying to maintain a circular orbit, you can stack orbits ‘on top’ of each other or put satellites quite close to each other just like planes do with flight levels. So even that number is misleading, as you could 10x that if you had decent traffic control.

Even without that, you’re talking a density of 1 satellite per 600 square kilometers of space with a million satellites for a given ‘flight level’.

The velocity matters a lot less than the relative velocity to other things you might be nearby - think of it like two cars going in lanes next to each other on the same ‘direction’ of a freeway, vs a free for all demolition derby with no traffic control, lanes, etc.

If everyone is co-ordinated you can have problem free high density. If random stuff is happening, including people potentially trying to hit you - it’s going to be a mess. If everyone just does whatever and never co-ordinates, yeah someone is eventually going to run into someone else - but unless there are a LOT of satellites, the odds are low.

With it being LEO, debris and dead satellites are also going to be a aerobraked pretty quickly.

If it's all so easy peasy and every satellite has zillions of square kilometers at disposal, why do we have collisions and required maneuvering already? And "dead satellites are also going to be a aerobraked pretty quickly" - at 550km this means months. That's definitely not quickly enough.

1) That happens INCREDIBLY rarely right now

2) Many of these incidents are from people are also putting things in Lagrange points and Geosynchronous orbits, and similar 'crowded' areas of space - unlike these constellations. Think jostling for space in downtown Manhattan, vs being fine having a place in Kansas somewhere.

3) Right now it's mostly a demolition derby out there, with only minimal traffic handling/control and the occasional 'haha, I got you' intentional satellite explosion/missile test.

As noted, even with all those factors, it is still incredibly rare. Only a tiny handful of problems have been tracked to orbital collisions with anything man made, and that is with us putting all sorts of things (including 'off the books' military top secret satellites, nuclear reactors, random bits of micro satellites, etc.) up there since the 50's.

Months is pretty quick for this kind of thing - and remember, unless it gets energy from some kind of serious-delta-v impact (or other delta-V adding type of event like a high energy explosion), it will lose velocity and DROP in altitude if the orbit remains circular. If the orbit doesn't remain circular, especially at LEO, it will have to dip significantly into the atmosphere to get to a higher altitude at any point in it's orbit, meaning even faster degradation and burn-up.

The reality is that it's huge up there, and if we do even basic thinking and planning on this to not do something obviously dumb (like tangential, perpendicular, or opposite direction orbits all over the place at the same level), it isn't likely to be a significant problem; just like it hasn't been a real (as in significant probability event) problem so far.

Cosmic rays, high potential static build-up, magnetic storms, micrometeorites, etc. are just as big or more of a problem. They rarely cancel a mission or damage anything notable, but it isn't zero risk there either.

> Why one second and 8km? Satellites are not manually maneuvered.

Satellites are actually manually maneuvered generally. Only the large constellations have somewhat automated systems (SpaceX's system is especially automated because there's too many for humans to monitor).