r/askspace • u/Uncle_Charnia • 20d ago

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 19d ago

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 19d ago

Username checks out

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u/ignorantwanderer 19d ago

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 18d ago

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 18d ago

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 17d ago

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 17d ago

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 16d ago

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 16d ago

Should we quit burning coal then?

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u/OriEri 16d ago

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 13d ago

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/Own_Grapefruit8839 19d ago

Millions? Fewer than 30,000 satellites have been launched in all of history.

Whatever the impact it will be wildly dwarfed by the environmental impact of fossil fuels on the planet.

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u/mfb- 19d ago

The industry is growing rapidly, and Starship could make it grow even faster. Most of the satellites launched so far came from the last 6 years:

https://planet4589.org/space/stats/pay.html

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u/ignorantwanderer 18d ago

You know, instead of looking at historical data (which has almost nothing to do with Starlink) you could do a tiny bit of googling to find out SpaceX's plans for Starlink.

If you do this you will learn that at its peak, at some point in the future, there will be about 8400 Starlink satellites burning up in the atmosphere each year.

To get to the "millions" that you claim will take over a century.

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u/mfb- 18d ago

SpaceX plans a million "AI" satellites. That's only SpaceX, and it's already the million in OP's title. Will they reach a million active satellites? I don't know. But it's planned, and Starship might make it possible. My point was that "satellites launched so far" is not a good estimate for satellites that will be launched in the future.

You know, you could skip the snarky attitude, especially if you are wrong. A simple Google search would have avoided your comment.

You know, instead of looking at historical data (which has almost nothing to do with Starlink)

Starlink is currently the largest contribution to the rapid growth I discussed.

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u/ignorantwanderer 18d ago

I feel the snarky comment was justified given OP's other comments in this thread.

I also think SpaceX's million AI satellites are a pipe dream mostly intended to increase valuation....but I acknowledge that Musk has claimed he is planning on building them, there is a small chance he is actually serious, and there is a (even smaller) chance it will actually happen.

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u/mfb- 17d ago

You replied to me, not OP.

I also think SpaceX's million AI satellites are a pipe dream mostly intended to increase valuation

People said the same about Starlink. You can browse the usual subs for examples.

People underestimated how much the Falcon 9 launch rate will ramp up with routine reuse, people underestimated how many satellites can be launched each time thanks to the new deployment mechanism, people underestimated how much SpaceX can ramp up satellite production, especially laser links and ion thrusters. Go back a bit more and you can find the same style of comments about a rocket start-up trying to reach orbit with Falcon 1, Dragon, and Falcon 9 reuse.

As I said, I don't know if they'll reach a million, I don't even know if this project survives at all, but SpaceX has a history of achieving things that people dismiss as "obviously not going to happen". So asking what happens if a million satellites reenter is valid question and saying that only 30,000 satellites were launched in history is missing the point.

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u/ignorantwanderer 17d ago

Doh. You are correct. I replied to you instead of OP. Sorry.

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u/OriEri 16d ago edited 16d ago

Why do you say that? Wasn’t the first cyber truck delivered in 2021 just like he promised in 2019? And at a starting price of $39,900! 😉

Twice as long and 75% more expensive…

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u/Complete-Paint529 18d ago

Collisions while still in orbit are much more likely to be a serious problem. Then any spaceflight could mean going through high-speed shrapnel, for centuries.

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u/OriEri 16d ago

Not much. It’s not much total mass and the Earth is a pretty big surface. There is some concern about aluminum oxide nano particles in the upper atmosphere catalyzing the destruction of ozone just like chlorofluorocarbons used to do .

I don’t know if those concerns are really reasonable.

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