Comment by Gud

14 days ago

If someone starts blowing up satellites it’s pretty much game over for space based communications.

https://en.m.wikipedia.org/wiki/Kessler_syndrome

Kessler is often overplayed. Kessler trashes a low orbit and you wouldn't want to launch more birds into the trashed orbit. But, loads of com sats live in MEO or GEO, which is far too high for the numbers to work. They're all fine.

You will even see Kessler cited as some sort of barrier to leaving, which is nonsense.

Imagine there's a 1x1m spot where on average once per week, entirely at random and without warning a giant boulder falls from the sky and if you're there you will be crushed under the boulder. Clearly living on that spot is a terrible idea, you'd die. But merely running through it is basically fine, there's a tiny chance the boulder hits you by coincidentally arriving as you do, but we live with risks that big all the time. If you're an American commuter for example that's the sort of risk you shrug off.

Likewise, Kessler isn't a barrier to leaving, humans won't be leaving because there's nowhere to go. The only habitable planet is this one, and we're already here.

  • GEO is very cramped. It's just a circle, not a sphere.

    Edit: I guess I was assuming geostationary. There's a whole sphere of geosynchronous orbits to play with.

    Edit2: I was right the first time, GEO (geosynchronous equatoral orbit) / GSO (geosynchronous orbit), apparently. Now my head hurts.

    • > GEO is very cramped. It's just a circle, not a sphere.

      "cramped" the way that like, Alaska is cramped on account of how everybody has to live on the surface, not evenly distributed through the volume of the planet?

      Like yeah, it's "just a circle" but did you check the radius of that circle?

      Remember if there's debris, the debris isn't stuck in the circle, but, any time it's not in the circle it's harmless. This has the effect of significantly defusing the problem, so in total it's too low risk to be worth considering.

  • LEO is where starlink is stationed. Really, there is no good scenario where LEO is unusable due to some dumb reason, like blowing up junk in space. I'm not sure our "world leaders" appreciate this.

The military is shifting toward LEO constellations for communications such as SpaceX Starshield. Kessler syndrome isn't a serious concern for those because the orbits decay fairly quickly anyway.

  • That "quickly" is on the order of years (as opposed to decades, centuries, etc). If the Starlink constellation goes boom, you can't start launching new ones for several years -- and then the build-up would take years, from there.

    • Nah. In any major future conflict, the combatants will go ahead and launch replacement satellites immediately regardless of the risks or long-term consequences (or they'll do it at least as long as their manufacturing and launch facilities survive). A constellation of hundreds of satellites can't go "boom" all at once. Even with a bunch of orbital debris floating around the hazards will be sparse and some satellites will live long enough to be operationally useful.

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Could they place a giant electromagnet in space to collect debris?

  • Space is too big, and the field of even the world's strongest electromagnets are too small for this to be practical. And even if it did work, you'd only collect ferromagnetic material.

  • A large enough electromagnet could actually increase effective drag in conductive materials, which may help. All the non-conductive materials would still be there, and paint chips can be brutal at orbital speeds.