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Here's an awesome diagram of all tracked space debris from 1959 to 2021 showing the constant cleaning by drag happening at lower orbits. It's the higher ones we

Here's an awesome diagram of all tracked space debris from 1959 to 2021 showing the constant cleaning by drag happening at lower orbits. It's the higher ones we really need to care about. https://www.reddit.com/r/space/comments/ld4vlq/gabbard_diagram_animation_of_space_debris_since/ https://www.reddit.com/r/space/comments/ld4vlq/gabbard_diagr...

lend000 6y ago
That's an amazing visual. Really helps to inform the debate. (Watch on full screen).
hn_throwaway_99 6y ago
Was waiting for that time in the '00s when China conducted an anti-satellite missile test. Did not disappoint. Let's not do that again.
jacquesm 6y ago
Can someone explain the reason for the mirror across the diagonal? Is there some altitude/velocity ratio that causes debris to spiral outward vs inward?
- mutagen 6y ago
  The mirror line would be a circular orbit, this plots each tracked orbiting debris with two dots, the blue dot being the lowest altitude of the orbit and red the highest.
- mjevans 6y ago
  I'm not an expert BUT... I suspect the diagonal line between the colors represents the duration of a stable orbit at that altitude. Anything with a more elliptical orbit will drag when it's in the closer phase and decay. Anything with a lower orbit is already slowing to a tighter orbit (and more drag on the denser atmosphere).
misterkrabs 6y ago
Thank you for showing me the coolest graph I have ever seen.
Waterluvian 6y ago
Wow. Am I interpreting that correctly? Lower orbit stuff falls out of orbit pretty fast while the higher orbit stuff just kind of stays there.
- anonporridge 6y ago
  I think you're interpreting it a little wrong. While it does look like 500km is about where things fall out quickly, it also looks like there's a sweet spot of altitude to orbital period ratio where stuff just stays there. Outside of that sweet spot stuff still falls out fairly quickly.
  - DavidSJ 6y ago
    I'm not 100% sure I'm interpreting your comment correctly, but higher orbits will always decay more slowly, all other things being equal. There's just far less atmosphere to bleed off the energy. Edit: I think I now understand what you mean, but I suspect you're not realizing that every satellite appears twice on the chart: once in blue, for its periapsis (perigee, i.e. low point of its orbit), and once in red, for its apoapsis (apogee, i.e. high point of its orbit). You're probably noticing that some of the red dots, at high altitude, are decaying quickly, but that's because the corresponding blue dots are at low altitude. Note also that orbital period is a monotonic function of altitude. More precisely, the square of orbital period goes with the cube of the semi-major axis (the long axis of the orbital ellipse).
    - anonporridge 6y ago
      I see what you're saying, and you're right, I am mistaken. Thanks!
- MPSimmons 6y ago
  Basically, yes. The atmosphere is a gradient, and the nearer you are, the higher the drag, and the faster you slow down.
BurningFrog 6y ago
So... this means we could theoretically handle the outer orbit space junk problem by putting more gas in those orbits! This would increase the "drag" and deorbit debris in higher orbit much faster. My physics intuition says it would affect smaller things much more than bigger, which is what you'd want. If it can ever be practical, I don't know, but conceptually that works, right?

lend000 6y ago

That's an amazing visual. Really helps to inform the debate. (Watch on full screen).

hn_throwaway_99 6y ago

Was waiting for that time in the '00s when China conducted an anti-satellite missile test. Did not disappoint. Let's not do that again.

jacquesm 6y ago

Can someone explain the reason for the mirror across the diagonal? Is there some altitude/velocity ratio that causes debris to spiral outward vs inward?

mutagen 6y ago
The mirror line would be a circular orbit, this plots each tracked orbiting debris with two dots, the blue dot being the lowest altitude of the orbit and red the highest.
mjevans 6y ago
I'm not an expert BUT... I suspect the diagonal line between the colors represents the duration of a stable orbit at that altitude. Anything with a more elliptical orbit will drag when it's in the closer phase and decay. Anything with a lower orbit is already slowing to a tighter orbit (and more drag on the denser atmosphere).

misterkrabs 6y ago

Thank you for showing me the coolest graph I have ever seen.

Waterluvian 6y ago

Wow. Am I interpreting that correctly? Lower orbit stuff falls out of orbit pretty fast while the higher orbit stuff just kind of stays there.

anonporridge 6y ago
I think you're interpreting it a little wrong. While it does look like 500km is about where things fall out quickly, it also looks like there's a sweet spot of altitude to orbital period ratio where stuff just stays there. Outside of that sweet spot stuff still falls out fairly quickly.
- DavidSJ 6y ago
  I'm not 100% sure I'm interpreting your comment correctly, but higher orbits will always decay more slowly, all other things being equal. There's just far less atmosphere to bleed off the energy. Edit: I think I now understand what you mean, but I suspect you're not realizing that every satellite appears twice on the chart: once in blue, for its periapsis (perigee, i.e. low point of its orbit), and once in red, for its apoapsis (apogee, i.e. high point of its orbit). You're probably noticing that some of the red dots, at high altitude, are decaying quickly, but that's because the corresponding blue dots are at low altitude. Note also that orbital period is a monotonic function of altitude. More precisely, the square of orbital period goes with the cube of the semi-major axis (the long axis of the orbital ellipse).
  - anonporridge 6y ago
    I see what you're saying, and you're right, I am mistaken. Thanks!
MPSimmons 6y ago
Basically, yes. The atmosphere is a gradient, and the nearer you are, the higher the drag, and the faster you slow down.

BurningFrog 6y ago

So... this means we could theoretically handle the outer orbit space junk problem by putting more gas in those orbits! This would increase the "drag" and deorbit debris in higher orbit much faster. My physics intuition says it would affect smaller things much more than bigger, which is what you'd want. If it can ever be practical, I don't know, but conceptually that works, right?