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Comment by djsumdog | Hacker News Reader

I've heard that at least with the SpaceX satellites, they have full plans for decommissioning with these satellites re-entering the atmosphere.

I do agree that this is a real concern though, and we'd hope there's pretty careful consideration, considering the sheer number of satellites being launched. Still, space is big .. really big, even the space just above our planet.

I don't put it past humanity to not fuck up space. After all, look at all the plastics and waste in the oceans. Hopefully all these companies and FCC regulators are thinking far ahead, and require the right designs and safety measures to make sure we don't end up enclosed in a float garbage pile.

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Correct on the decommissioning plans. SpaceX lists out in their FCC filings a number of things including how long it will take them to actively de-orbit satellites, how long for them to de-orbit if they lose contact/control, and also how much of the material will survive re-entry.

I have read conflicting things so don't hold me to this, but on article I read said they delayed adding the laser links to the current batch of Starlink satellites because of concerns over how much would survive the de-orbit maneuver.

What I heard they launched them ASAP because otherwise they would lose spectrum license.

> I've heard that at least with the SpaceX satellites, they have full plans for decommissioning with these satellites re-entering the atmosphere.

It's not just that they have plans to do so, they're low enough that they'll de-orbit fairly quickly on their own without active control (boost from their ion engines). Something pretty strange would have to happen for them not to eventually burn up.

Isn't the Kessler effect partly about creating further junk from a cascade of collisions? Even if the "junk" were to re-enter the atmosphere eventually, how long would that take? How long would access to space be cut off before the junk were to clear?

I'm not an expert (and expect to be corrected on details here), but I think it depends on the orbit altitude - if it's low enough to suffer significant atmospheric drag, then it'll de-orbit fairly quickly. But if they're at high altitude (geostationary and geosynchronous orbits spring to mind - around 22000-26000 miles), then that's much less likely, although there's a much bigger area to cover at that altitude. But given the damage that even a tiny particle can cause at those velocities, I think it's a real concern with such mass launches.

The smaller any given piece of debris is, the greater it's surface area:mass ratio is, and therefore the faster it deorbits due to drag.

Project Kuiper and Starlink both put the very large, thousands-of-satellites constellations low enough that trash gets cleared quickly enough that even a set of multiple catastrophic collisions is very unlikely to threaten most of the network, and even if they all just blow up, the pieces will fall down shortly and clear the orbit for reuse. For Starlink, drag is actually so high that they are using the solar array as a sail for attitude control.

This is relevant: https://www.youtube.com/watch?v=yS1ibDImAYU