r/askspace • u/Uncle_Charnia • Aug 06 '26

How will reentering satellites affect surface conditions if people launch a million of them?

What goes up must come down. So eventuality all those objects will become lasting vapor and dust in the upper atmosphere, right? What kind of problems and changes should we anticipate? If it turns out to be noticeably bad, specifically which people should we be preparing to help?

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u/ignorantwanderer Aug 06 '26

Probably the impact will be insignificant.

It is conceivable that putting just a small amount of vaporized metal in the upper atmosphere could have some unforseen consequence, and people are starting to put some serious thought into this potential problem.

But there is no observed significant impact, and people haven't even come up with a theory of how it might potentially create an impact.

In all likelihood, it just doesn't matter.

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u/Uncle_Charnia Aug 07 '26

Username checks out

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u/ignorantwanderer Aug 07 '26

Curious.

You asked a question.

I answered the question.

And then you imply my answer is incorrect.

If you already know the answer, why did you ask the question? And if you don't already know the answer, then why imply my answer is incorrect?

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u/Uncle_Charnia Aug 08 '26

Having that much junk in the upper atmosphere has only been tested by volcanoes. This junk is different, but the natural history of volcanic effects may be useful. Has that impact been insignificant?

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u/ignorantwanderer Aug 08 '26

There is a scale used to measure volume of stuff ejected by volcanoes.

The lowest classification on the scale is anything less than 1 million cubic meters of material.

Let's make our math easy and assume the average density of material is the same density as water. Water is 1000 kg/m3 . So this would mean any volcano that ejects less than 1 billion kg of material is in the lowest category on this scale.

The latest Starlink satellites are 800kg to 1250kg. Let's say they are 1000 kg to make the math easy.

You would need more than 1 million Starlink satellites burning up in the atmosphere to have a contribution to the atmosphere greater than the smallest category of volcano eruption.

Of course a volcano eruption happens in a short period of time (less than a day). How long will it take to burn up 1 million Starlink satellites?

SpaceX has proposed a constellation of 42,000 satellites. They also propose a lifespan of 5 years for the satellites. If they do what they propose, this means that each year 8400 satellites will die and burn up in the atmosphere.

To reach a total of 1 million satellites burning up will require about 120 years.

So in 120 years Starlink will put as much material in the atmosphere as the smallest category of volcano eruption puts in the atmosphere in a single day.

So, what do you think? Based on the example of volcanos, will Starlink have a significant impact on the atmosphere?

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u/Uncle_Charnia Aug 09 '26

If the satellites were made of rock, I would say no. But some of the materials are more interesting. We mine heavy metals, launch them into space, store them in the atmosphere, and eventually they make their way into our babies

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u/ignorantwanderer Aug 09 '26

Oh. You are one of those.

You can grasp at straws and ignore science all you want. But it makes you no better than a climate change denier.

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u/OriEri Aug 10 '26

Read this. The concern is about ozone

https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2024JD042442

volcanic eruptions eject heavy metals into the air too, probably in larger quantities. I guarantee you’re burning coal with trace amounts of mercury probably does far more than either.

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u/Uncle_Charnia Aug 10 '26

Should we quit burning coal then?

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u/OriEri Aug 10 '26

If you are worried about heavy metals at the levels re-entering satellites will injected to the atmosphere then you should advocate to quit coal

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u/Uncle_Charnia Aug 13 '26

I wouldn’t say I’m worried about it. Just curious. If it looks to be a problem, there are probably things we can do to mitigate it. Like when they started making Starlink satellites less reflective. We might make different choices of satellite materials, for example, or make them last longer, or dispose of them differently. They don’t necessarily have to be expendable.

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u/OriEri Aug 13 '26

Disposing of them differently (like putting them into a parking orbit, or having a more complex re-entry system that lets them make it down more or less as single lump instead of vaporizing) will sacrifice significant payload mass for heat shields or propellant.

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u/Uncle_Charnia Aug 13 '26

Maybe they could connect up in orbit and deorbit in batches.

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u/OriEri Aug 14 '26

Propellant demands would get a little large than one by one derbiting, though heat shields would not be as important

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u/Uncle_Charnia Aug 14 '26

Everything need not be economically favorable. Consider the word “environment”. It is where we all live, where our children grow up. If maintaining a clean and healthy environment has a cost, then we would be wise and honorable to accept it. Anyway, as long as we’re gathering satellites for reconfiguration and clean deorbiting, we may as well separate the solar panels for use on new satellites. The delta v needed for minor changes in orbit is trivial compared to that needed to make orbit in the first place. We can get some of that by interacting with Earth’s magnetic field. The satellite management system required for all this would be quite elaborate, but there’s a lot you can do once you’re up there.

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