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Comment by jeroenhd | Hacker News Reader

With how close to earth Starlink satellites fly, it won't take hundreds of years. Without the occasional boost back into orbit, it'll only take a couple of years for them to fall back to earth. Same with most spy satellites. We can do without space internet for a few decades if we blow up several of these constellations.

As for further-away satellites (Iridium etc.), that's a bigger risk, but there aren't that many that make sense to target in a war.

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Energetic collisions can send debris on higher orbits with significant longer time to decays. It all depends on kinetic energy added

If pieces got bumped into a higher apogee wouldn't their orbit end up with a lower perigee as well? If so I think that might actually be better for deorbiting quickly

Diffuse debris while at higher orbit can take out satellites in those higher orbits (like Iridium, Kuiper, etc..)

As long as it doesn't hit something while it's in apogee.

One collision might be barely statistically possible. Enough collisions to start Kessler takes a lot more than one.

Isn't it the Kessler Syndrome when the debris from the first collision creates the subsequent collisions?

> it won't take hundreds of years

Maybe not for Starlink itself, but its debris may be eccentric enough to hit satellites in higher orbits, thus causing an upward cascade of collisions resulting in debris clouds that do have a real possibility of remaining in orbit for many times the debris of Starlink.

Precisely

Eccentric orbits mean higher apogee but also lower perigee, which for something at Starlink altitude likely means perigee is below the Karman line. Which means they'd deorbit within 90 minutes. So they'd only have one chance to hit something in higher orbit. You won't get enough collisions to start Kessler.

Starlink operational orbits are generally >500KM high (original license "at 525, 530, and 535 km", -Wikipedia).

I think it is not unreasonable to expect any debris clouds from Starlink to impact orbits from 300km to 700km for many months, if not years. Even if the debris with highest eccentricity will quickly burn up in the upper atmosphere, there will likely remain a significant portion in orbits that are eccentric enough to be problematic for higher orbits for years, (slowly?) cascading the debris orbits upward. It doesn't have to happen immediately after impact, but kessler syndrome doesn't have to imply 100% guaranteed loss in a day either.

Debris has a much higher surface to mass ratio than satellites due to their smaller size and irregular shape. Therefore debris deorbits much quicker than satellites do.

300km orbit decays in about a month, so the risk is already reduced significantly.

And there's not much in the 500 - 700km range now. Kuiper will be there soon, but anybody that takes out Starlink is also going to take out Kuiper.

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