this post was submitted on 17 Jun 2024
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Abstract from the paper in the article:

https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2024GL109280

Large constellations of small satellites will significantly increase the number of objects orbiting the Earth. Satellites burn up at the end of service life during reentry, generating aluminum oxides as the main byproduct. These are known catalysts for chlorine activation that depletes ozone in the stratosphere. We present the first atomic-scale molecular dynamics simulation study to resolve the oxidation process of the satellite's aluminum structure during mesospheric reentry, and investigate the ozone depletion potential from aluminum oxides. We find that the demise of a typical 250-kg satellite can generate around 30 kg of aluminum oxide nanoparticles, which may endure for decades in the atmosphere. Aluminum oxide compounds generated by the entire population of satellites reentering the atmosphere in 2022 are estimated at around 17 metric tons. Reentry scenarios involving mega-constellations point to over 360 metric tons of aluminum oxide compounds per year, which can lead to significant ozone depletion.

PS: wooden satellites can help mitigate this https://www.nature.com/articles/d41586-024-01456-z

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[–] [email protected] 113 points 5 months ago* (last edited 5 months ago) (7 children)

SpaceX has been receptive to design changes to starlink in the past to minimize impact, like decreasing reflectivity and reflection angles for astronomers. They might be receptive to moving to different alloy for the body construction.

Magnesium comes to mind that would be light but expensive. Steel alloys might be cheap and heavy options for later when starship is operational. Would those have similar effects on ozone, or is it only the aluminum oxides?

[–] Gsus4 55 points 5 months ago* (last edited 5 months ago) (1 children)

Magnesium oxides can also serve as a catalyst for lots of reactions, but I'm not sure if it will have the same effect in this specific context, I'd guess it would.

That's why I added the link to the wooden satallites, that also reduces the metal debris somewhat and reduces other effects like radio interference.

[–] [email protected] 21 points 5 months ago (1 children)

Wood is interesting, but the article doesn't address off gassing at all, which is a huge problem for communication satellites. Is there a way to keep the wood from off gassing? For 3d prints in vacuum, they metal coat them to keep the gas inside. Or maybe you could resin soak them? With hopefully an extremely UV stable resin. But I didn't know what the weight trade looks like then, resin is heavy.

But if you're looking composites anyway, carbon fiber would be another great option. Lightweight but with a few manufacturing constraints. But should burn up to carbon dioxide on reentry.

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[–] [email protected] 82 points 5 months ago (2 children)

So... Let me get this straight... The satellites burning up are essentially creating aluminum chemtrails that my mother-in-law keeps going on about?

[–] [email protected] 8 points 5 months ago

Well yeah ever since you guys forced us to stop doing the airplane chemtrails, we’ve been out of business.

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[–] [email protected] 70 points 5 months ago (11 children)

Before anyone jumps on the Anti-Musk train, read the article, please. They admit that they don't understand the complications that could arise and that they don't have any hard figures for the damage being caused. I'll be the first to jump in and say that it's probably a bad thing to just let metals burn in in atmo, but let's make sure we discuss the facts, and not just the politics of the potential polluter.

[–] [email protected] 49 points 5 months ago (28 children)

Ah yes, the usual method of waiting until the issue becomes confirmed and also way too severe to fix instead of acting on precaution and harming profits of private companies. What could go wrong?

[–] [email protected] 36 points 5 months ago (1 children)

Yeah, PFAS comes to mind. It took decades to confirm it's harmful to humans but at this point it is everywhere and hard to get rid of. Worst part is they try to use other chemicals to replace PFAS, but again how harmful they are we don't know and we will learn that decades later too because companies don't want to make long term research before releasing the product. Enviroment shouldn't be a billionaire's testing ground.

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[–] [email protected] 68 points 5 months ago (2 children)

Another thing Elon is screwing up on

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[–] [email protected] 68 points 5 months ago (2 children)

Quite possible. Let's fix our ISPs so that all of humanity has access to bandwidth priced to a value that they can afford for their area. A huge project that means lots of union jobs and an economic payoff for decades. If we pull this off Starlink won't have any customers except very marginal cases.

Fix the problem directly instead of fixing the solution unintended side effects

[–] [email protected] 44 points 5 months ago (3 children)

Gee, where are the boatload of billions that the US congress passed for nationwide broadband?

Fucking ripoff telecon companies.

[–] [email protected] 11 points 5 months ago (1 children)

They should just pay people to lay the cable directly instead of awarding it programmatically to companies.

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[–] [email protected] 9 points 5 months ago (2 children)

I got fiber in the middle of nowhere from it. ¯\_(ツ)_/¯

[–] [email protected] 9 points 5 months ago (2 children)

Whereas we are smack dab in the middle of cities, but just far enough out of reach to be stuck with 20Mb DSL that will never improve.

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[–] [email protected] 44 points 5 months ago (5 children)

You would think space engineers would‘ve run those numbers before sending tens of thousands of them in orbit. It‘s really annoying that we can only hope for the best at this point.

[–] [email protected] 33 points 5 months ago

I fully expect they did. I think this is partly why Elon went from "there's no planet B" to a Saudi simp. Way to much money to be made to waste time on the concerns of scientists and the welfare of the planet.

[–] Gsus4 29 points 5 months ago (1 children)

I was just worried about Kessler syndrome and just felt relaxed that their orbits were low enough to naturally decay and never become a permanent problem. What this research seems to show is that the aluminum oxide dust does not settle in days/weeks, but it is fine enough to stay there for decades :/

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[–] [email protected] 24 points 5 months ago

Why would you think that?

When I fire up the grill, I don't do calculations on how much weight in CO2 I'm putting into the air and then extrapolate that to find the total mass of CO2 that grills generate globally. I usually just make burgers.

That space engineer made sure that they were on the right side of the rocket equation and they made it to orbit (which is hard on its own).

I agree that thorough environmental studies really ought to be happening, but I'm not surprised that aspects got missed.

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[–] [email protected] 41 points 5 months ago (6 children)

About 48 tons of meteorites enter the atmosphere every day. I couldn't find the elemental distribution, but I'd guess there is some aluminum in there. How much of an increase is 14 tons aluminum per year over the many tons of aluminum entering the atmosphere already? That might be good to get a rough estimate of how impactful this is.

[–] [email protected] 41 points 5 months ago* (last edited 5 months ago) (5 children)

Even assuming the meteorites are 100% aluminum it's a 30% increase which is quite significant.

From a short google search apparently only ~8% of asteroids in our solar system are metal rich which is mostly iron nickel. Rarer metals can be as rare as 100 grams per ton.

Which means of the 48 tons only 4.8 kilos could be aluminum. Compared to that the 14 tons would be a whopping ~3000% increase.

[–] [email protected] 17 points 5 months ago (1 children)

The asteroid weights are given per day while the sats per year.

[–] [email protected] 9 points 5 months ago (3 children)

Still only 1752 kg per year

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[–] [email protected] 8 points 5 months ago

Isn't it 48 tons of meteorites per day vs 14 tones of satellites per year?

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[–] [email protected] 39 points 5 months ago (1 children)

damn, starlink is my only way to access the internet. I wish there were an alternative that's usable. Traditional access providers don't work and cell data is extremely slow and there's no coverage where I live. I pay for Starlink with a bitter taste

[–] [email protected] 21 points 5 months ago (30 children)

Might I enquire as to where this remote location might be?

Like on a general basis, no need for addresses.

As a Finn I'm forever spoiled in terms of wireless coverage. We got tons of solitary forests. But you can get an internet connection in literally all of them.

97% of the country gets 4g. And not of the people. The country.

[–] [email protected] 16 points 5 months ago

I live in rural California. We only just this year are able to pick up a faint LTE signal. I think it might get us a very unstable 1-2 Mbps if we hold the phone just right. We have no cable, DSL or other land-based options and because of the topography can't pick up the local wireless provider, which is very expensive anyway - like $175/month for 50/5

So without Starlink our only options are crappy regular satellite providers like Hughesnet which impose very low quotas - 10 GB monthly for day time usage - and have insane latency.

It bugs the shit out of me I have to give money to that fuckwit but without it we live in the dark ages.

[–] [email protected] 11 points 5 months ago

We're in Mayotte. Two undersea cables connect us to nearby continents (cf submarinecablemap.com) but they're down most of the time. We haven't had a connection in the last six months so we finally subbed to Starlink. Well, strictly speaking there was a connection but it would take anywhere between 5mn to 15mn to load the text of a static webpage, no images or anything else... forget about sending data, using forums... I had to get out and walk uphill for a minute or two to use my phone's cell data

[–] [email protected] 9 points 5 months ago (1 children)

My family has Starlink, they live in mountainous rural. Cell towers aren't too far away, but mountains get in the way of decent signal. No one is running any cables their way, despite a local telco taking money explicitly for providing internet service.

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[–] [email protected] 25 points 5 months ago (3 children)

burned wood in the upper atmosphere also catalyzes ozone depletion That's why it was bad putting CFCs up there in the first place, almost everything catalyzes these reactions

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[–] [email protected] 18 points 5 months ago* (last edited 5 months ago) (1 children)

So they take 17 tons of emissions (from all satellites, not just starlink), which are basically nothing on an atmospheric scale, then extrapolate that to 360 and start freaking out. Peak quality journalism.

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[–] [email protected] 18 points 5 months ago

Thanks Elon

[–] [email protected] 15 points 5 months ago (1 children)

I hate Elon, but he ain't the only one trashing the LEO

[–] [email protected] 12 points 5 months ago (2 children)

Okay, but he's trashing it the fastest and for the dumbest reasons.

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