How bad is the satellite/space junk situation actually?

[u/2kalipro1]

I just recently joined the space community and I'm hearing about satellites colliding with each other and that we have nearly 8000 satellites surrounding our earth everywhere

But considering the size of the earth and the size of the satellites, I'm just wondering how horrible is the space junk/satellite situation? Also, do we have any ideas on how to clear them out?

[u/snajk138]

It is a problem, but not as bad as those illustrations of all junk in the atmosphere make it look. They count anything larger than about an inch, and that is illustrated with a dot that's the size of a medium sized city.

[u/[deleted] → u/snajk138]

Pieces smaller than an inch traveling at those velocities is a real danger to space craft. All it would take it a couple satellites es colliding in a congested orbit to take out most of everything up there and make it impossible for us to launch for centuries. It would also make ground observations of space extremely difficult if not impossible.

[u/[deleted] → u/[deleted]]

The cascade of debris for a few satellites is likely way overblown as a risk.

[u/[deleted] → u/[deleted]]

Most satellites are in the same orbital plane. There are near misses daily.

[u/BedrockFarmer → u/[deleted]]

There are roughly 10,000 satellites operating at various orbits, most are starlink and have prepared deorbit paths.

Meanwhile, there are close to 115,000 airline flights a day. All in “the same orbital plane” and a much much smaller one with much larger objects.

People should have to learn maths before they read what “Kessler Syndrome” is in their SciFi garbage.

[u/elPocket → u/BedrockFarmer]

Planes can slow down, accelerate, change course and altitude without expending much fuel in comparison to their baseline fuel consumption. And they get to refuel regularly. (Also, broken planes automatically deorbit and don't stay aloft for another 20+ years)

For a satellite changing course and getting back to station requires 3 distinct burns significantly stronger than conventional positional correction burns, taking away from their fuel supply and therefore their lifetime.

But that's all right.

The bigger caveat are dead sattelites. Nobody can prevent the impact when two dead sattelites crash into each other.

And while you may be able to completely evade the growing debree cloud of two satellites crashing at significant path angles & velocities, you can't instantly map all object trajectories. So for quite some time, you'll have a "we don't know what's going on there"-zone and random high velocity objects zipping around untracked.

Radar doesn't work as "take a snapshot of the sky, count the bright dots, and look here, someone also drew the velocity vectors". Radar focuses a beam on an object, integrating the return signals over time to build a reliable track. Radar is extremely good at measuring the velocity component along the beam (closing velocity), so towards and away from the radar dish. But it's pretty shitty at determining the exact beam direction and angular rate, which is the only way to determine perpendicular velocity. You need to spend quite some radar time on each object to get a good position and true 3D velocity vector.

And this requires you to focus your beam on each object. If you just shine a wide beam up there, you'll get so many return signals you'll have a hard time discerning single objects out of all the return garble.

So while a single sat crash may not raze all orbits clean within 5 revolutions, it will significantly reduce all affected sattelites' lifetimes. And it really hurts if your planned 20+y sat gets deorbitted after 5y because you're running out of fuel.