[wkat4242]

At those kinds of speeds, the orbital paths have to be really improbably similar to not have "bullet" like destructive effects. The relative velocity will almost aways be in the same order of magnitude as the ground speed and definitely more than bullet speed which is super slow compared to the ground speed.

And calculating the collision speed is pretty complex while the ground speed is static so I can imagine the press just take that.

After all pretty much any speed will be destructive to a satellite that's not designed to be bumped around.

[HPsquared]

Orbital inclination is the big one. A polar orbit intersecting an equatorial orbit would have a very high relative velocity.

On the other hand two orbits in the same inclination, with one being slightly eccentric, their relative velocity is much lower.

[wkat4242]

It doesn't matter though. Even if they hit at 0.01% of their orbital velocities, that's still 100km/hr. So it's like a full highway speed car crash. No way two sats colliding will survive that.

And remember the collision speed can range from 0 to 200% of their ground velocities. Getting that close to zero is extremely unlikely.

[bagels]

Two objects at the same inclination can still have very high relative velocity if on different planes.

[HPsquared]

Ah, so like the "phase" of the inclination? orbital plane being a vector quantity (angle between the Earth's rotational axis and the normal vector of the satellite's orbital plane)

[bagels]

Yes. Find a visualization of starlink orbital shells. They are all in one of just a couple inclinations, lots of crossings

[euroderf]

Thinking about this, and about the big launchers that the three-letter agencies use...

I wonder if US satellites (a) use a lot of Kevlar (or similar), and (b) can see nearby explosions (like, the triggering of a fragmentation weapon) and quickly close semi-armored shutters over their vital bits.

One would defeat this by creating - out of detection range - a fragment cloud that is on an intercept course. But that might be too complex and time-consuming if a war is starting. So what is the threshold for plausible deniability ?

And of course there's also railguns, à la The Expanse.

[wkat4242]

No. Satellites don't use armouring at all. It makes the launch way too expensive. And there's always exposed bits that can't be armoured like solar panels and antennas.

What they do use is... foil! There's a thin layer of foil a bit away of the main body. If a small piece of dust hits it at crazy speed, the impact with the foil will make it (and a bit of the foil) vapourise, and then it won't cause much damage to the main body because it's all vapour.

It's not really like the expanse because a railgun fires tungsen rounds that are meant to penetrate. Most random space crap is just flecks of paint, drops of oil etc.

[euroderf]

I get your point about the utility and appropriateness of foil.

But then what about warfighting ? I'll betcha the US has a railgun up there somewhere.