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Comment by riffraff | Hacker News Reader

isn't the likelihood of a cascade very low because of the orbit thing? I.e. object X hits Y, they both spin out of control but most likely they will either go towards earth or go away from it, so they chance of them hitting something else is very limited, it's not like billiard balls that would eventually hit each other.

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In 2007, the Chinese tested an anti satellite missile against a weather satellite.

The missile contained no explosives, it relied purely on kinetic energy.

The collision released 2,300 pieces of debris that were large enough to be tracked, so about golfball size or larger, and probably many times that number that are too small to track.

There's also a really, really large amount of space for maneuvering up there. Keep in mind the surface area of the sphere that's at 36,000 km from the ground (approx. average satellite orbit height) is ~22,567,880,697 km - that's entirely disregarding vertical room for maneuvering.

I am sure there are hot spots or rings of higher density corresponding to earth locations. Still, it's big.

I assumed that if object Y hits object X it would result in a huge number of particles from the collision, each with a chance of hitting something else eventually.

Even if a single one of those particles hit one of our precious objects in the next 20 years it could be devastating.

But as it gets cheaper to put new satellites up, cleanup gets cheaper too. And if access gets cheap enough I could easily see an international treaty mandating that all satellites have an EOL burnup system installed. When 20kg costs $2mm a lot of people will balk at the idea. When 20kg costs $200k or $20k it's a lot easier to require people to include it. It could even be a bolt-on kind of thing, separately powered and controlled such that it doesn't have to be re-invented for every new satellite.

Also with access being cheap enough we could start doing active cleanup, beyond just not making the problem worse. Aerogel is supposed to be great for capturing particles because it's basically frozen air. We could build a space-based aerogel factory and ship silicon ingots up which then get turned into aerogel panels to be used as replenishable armor for the factory. And once you have the factory up you just start making the area that the armor sweeps bigger and bigger. Build out sideways to clear a particular orbit faster, build up or down to clear orbits of various heights. It'd be insanely expensive right now, but if launch costs come down to $100/kg or $10/kg it starts to look reasonable.

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