[perihelions]

It's postulated that the high aluminum content of satellites (for perspective, Bennu samples are only 1% Al), as oxidized Al2O3 particles in the stratosphere, catalyze chemistry that destroys ozone. But that's far from a quantitatively meaningful problem, at the current scale.

This source[0] says satellite reentries are about about 12% of the space industry's contribution to ozone depletion (the big one is chlorine from solid rockets), which in turn is 0.1% of the entire anthropogenic contribution; i.e. satellite reentries are ~0.01% of the total.

https://www.space.com/spacex-starlink-reentry-pollution-dama...

[schiffern]

  >0.01% of anthropogenic ozone depletion

The sheer percentage increase in stratospheric AlO is still alarming.[0]

Satellite reentries in 2022 (ie mostly pre-megaconstellation) were already raising stratospheric AlO levels by 29.5% above normal levels (with satellites adding 'only' 17 t/year), but megaconstellations could raise that to ~480% above natural levels (360 t/year).

This isn't a rounding error, it's a non-trivial change in chemical composition across the entire globe, and effecting a complex and poorly-understood part of the climate system. What could go wrong?

What else can this effect (as usual, discovered belatedly) beyond ozone? Hopefully it's nothing! But I guess we're gonna find out...

[0] https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2024GL10...

[perihelions]

That's still much less than the aluminum from solid rockets, which have been ongoing since the 1970's. Per your own link,

> "In situ measurements showed evidence of a 1,000% increase in stratospheric aluminum levels from 1976 to 1984 (Zolensky et al., 1989), which was associated with the emission of hundreds of tons of such particles from solid rocket motors (SRM) during atmospheric ascent (Brady et al., 1994)"

If you follow Brady et al. (1994)[0], you'll read that every Space Shuttle launch (Table 1) deposited 112 tons of Al2O3 into the stratosphere (>15 km).

[0] https://apps.dtic.mil/sti/pdfs/ADA289852.pdf

This isn't a new phenomenon at all; in fact the peak alumina pollution from in the past (112 tons per STS launch) exceeds the worst-case future estimates from academic research (360 tons per year from satellite reentries).

(/meta Coincidentally, I once linked that exact Brady paper on HN, three years ago[1]. Actually, long before the current social media fad for being concerned about satellites. At the time I wrote, and this has truly aged well, "No one ever gave a shit").

[1] https://news.ycombinator.com/item?id=34812863

[schiffern]

As I understand it, the concern is not just AlO but specifically nanoparticles with high reaction surface area and long lofting lifespans.

The importance of this distinction is acknowledged in Brady et al (1994):

  >The exact chemical nature, as well as size distribution (and total surface area) of particles formed in rocket exhaust in the stratosphere is currently unknown. Preliminary experiments at Aerospace by L. R. Martin indicate that plausible particle compositions give highly variable rates of direct ozone destruction.

The 17 t/year and 360 t/year figures are specifically for AlO nanoparticles (formed by hypersonic ablation), whereas Brady et al gives numbers for all AlO particles, regardless of size.

Nice username btw.

[JumpCrisscross]

> Satellite reentries in 2022 (mostly pre-megaconstellation) were already raising stratospheric AlO levels by 29.5% above normal levels

Those findings are simulated, not observed. Hence "potential."

> it's a non-trivial change in chemical composition over the entire globe, and effecting a complex and poorly-understood part of the climate system. What could go wrong?

Perhaps a lot. Perhaps not much. It's a good question to study. But if this is an issue, it's solvable--carbon composite satellite structures could use a boost in demand and funding.

[schiffern]

Interesting. Incidentally SpaceX is probably the most likely to preemptively adopt those measures.

Of all the megaconstellations, SpaceX has historically been the best at being a "good neighbor," with low orbits for debris and lots of engineering to reduce brightness.[0] But hype around SpaceX gives the real bad actors a pass, for example AST is much worse on brightness,[1] and OneWeb and Qianfan are much worse on debris risk.[2]

[0] https://www.youtube.com/watch?v=MNc5yCYth5E&t=1717s

[1] https://spacenews.com/astronomers-raise-interference-concern...

[2] https://spacenews.com/chinas-megaconstellation-launches-coul...

[tehjoker]

i still don’t understand why we need huge constellations of satellites at all

[HanClinto]

Because providing infrastructure to remote regions is incredibly difficult through other mechanisms. I don't believe it's hyperbole to say that -- for the goal of improving infrastructure access in some of the most remote and challenging places in the world -- Starlink in particular is one of the most successful pro-humanitarian engineering projects that I can think of in maybe the last 20 years.

Starlink is easily one of my favorite engineering projects. I don't believe anybody has done it cheaper, better, or at wider scale than Starlink has.

[tehjoker]

I believe Starlink was used to guide Ukranian drones. I think this has nothing to do with poor people in rural areas and everything to do with ensuring deployed military devices work. Modulo of course the egotistical whims of an insane American billionaire hailing from aparteid south african descent.

https://www.reuters.com/investigations/musk-ordered-shutdown...

[gambiting]

>>Starlink in particular is one of the most successful pro-humanitarian engineering projects that I can think of in maybe the last 20 years.

Better than gates' effort to eradicate malaria?

Sorry to be snarky, but to me Starlink is something rich people in rural England have, because it's slightly easier than paying OpenReach to connect them to proper network. And it's hard to imagine anyone else being their clients, at the prices that they charge.

[robotresearcher]

> one of the most successful pro-humanitarian engineering projects

That claim does not exclude Gate’s projects or any other as being superior. You’re looking for conflict that isn’t there.

Starlink is used all over the world, by regional governments, NGOs and companies where it’s too expensive for individuals.

You might well find that rich English people are subsidizing the project for poorer people elsewhere.

[elcritch]

Access to information has historically been a great equalizer.

Not to diminish Gates’ malaria efforts, but remote villages having access to information about malaria and prevention methods could be helpful. Along with techniques for filtering water, etc. Access to telehealth.

[HanClinto]

> Sorry to be snarky, but to me Starlink is something rich people in rural England have

Yeah, so our perspectives may differ a bit. My personal focus has primarily been with Africa, where Starlink is truly transformative. Demand for Starlink may be underwhelming in developed countries (such as your "rural England" example), while in underdeveloped countries, the demand regularly outstrips the supply [0]. I love that it's affordable enough for my African colleagues to use. In the last couple of weeks, I've had more than one full-motion screen-sharing video call to northern Nigeria (I.E., not the capital city) to do collaborative engineering. Even just a handful of years ago, this would not have been possible before Starlink was available.

I'm not casting any shade on malaria eradication -- that is awesome as well. I can love both things, but the subject here is Starlink, and I want to underscore how truly impressive and effective Starlink has been for advancing infrastructure in a quantum leap.

Improving African infrastructure has been an extremely difficult problem for a very long time (for a quagmire of reasons -- regulatory, power, cost, distribution, etc etc etc). I think most people in the developed world simply don't understand how challenging it is to live day-to-day without solid and reliable infrastructure, or how effective Starlink has been in improving that. Very few other projects have been THIS successful at THIS scale. I think more people should be aware of the good that it does.

It has been a disruptive technology in so many of the best ways.

* [0] https://news.ycombinator.com/item?id=42408457

[marcus_holmes]

Come to Australia, see the remote communities that were abandoned by NBN (well, gaslit and then completely screwed by Murdoch manipulating Abbot to sabotage the NBN). Starlink is literally a lifesaver for them.

[Tuna-Fish]

Because it's a way to provide communications from space with acceptable total throughput and latency.