Starlink generated pollution

[Robotbeat]

Current Gen Starlink has a lifetime of around 5-7 years. If we assume the larger satellites last a little longer, say 10 years, then that puts the amount of alumina generated per year for the full 30,000 constellation as similar to Shuttle’s peak year of 1985, including the LWT burned up mass. (Not counting shuttle’s payloads burning up.)

That’s assuming SpaceX doesn’t implement servicing or active capture.

[meekGee]

Still waiting for these concern arguments to either link to studies or provide falsifiable, quantifiable (ie number-containing) statements.

…rather than handwaving and rhetoric.

The paper that's been reported on in SpaceNews and other outlets is behind a paywall, but here's the link if you want to spend $32 on it.

In addition I linked a PhD dissertation on alumina catalysts up-thread.  This paper is oriented more around making Space Shuttle ozone depletion models more accurate, and comes to the conclusion that the alumina is a significant activator of ODSes, and needs to be included in the modeling--as does what little I can read of the Shutler paper.

The only numbers I'm fooling with are the ones comparing aluminum entering the atmosphere from orbital debris with the natural rate of aluminum from meteoroids/cosmic dust, and noting that, if Starlink really winds up with 30,000 birds, then the reentry aluminum mass is likely at least as large as the natural mass.  Contrary to what you're insinuating here, those numbers are up-thread.

My position is that this doesn't require regulation right now, and may never require regulation, but that we ought to be really sure that we haven't created yet another significant ozone depletion pathway.  If you'd like to characterize that as concern-trolling, go right ahead.

Yup interestingly 30,000 satellite, 3 year life span, and 2 tons per satellite, you arrive at about 50 tons/day which is the same as the estimated meteor mass input.  Coincidence?  I smell a rat.  Clearly Musk wants to replace meteors.

30,000 birds, 5 year lifetime.  33t/day.  Pick some percentage that you think will be aluminum.  25%?  1500t/year.

The Spencer dissertation used 1.6E4t of meteoroid dust, and didn't distinguish between silicates, Fe, Ni, Al, Mg, and Ti oxides.¹  That would make the new stuff a 9.4% increase.  If you do an apples-to-apples comparison with just Al, which is, according to another reference, 1.4% of the meteoroid mass,  the Starlink aluminum would be 670% more.

However, my "orders of magnitude" comment was about industry and volcanoes (millions or billions of tons) compared with the aforementioned 20,000 tons.  Sure they're emitted at lower altitudes, but so were CFCs and we know how that went.

So your argument is that, because we emitted lots of CFCs and then took action to drastically reduce their emission, that we shouldn't worry about adding new sources that can enhance the conversion of chlorine from its reservoirs?

And yes, there are natural sources of ozone depleting substances.  But those natural sources are why the ozone layer has roughly the concentration that it has.  The question is whether we're going to add substances that force it away from that equilibrium.

And I'd mention the Space Shuttle not because it created more pollution, but because the same characters that propagate the "Starlink Pollution" meme were not concerned one bit about Shuttle pollution.  Just like "Electric cars use Coal" and "immensely complex and high risk", you sometimes just need to look where the memes are coming from.

The "same characters" did a fair amount of work looking a Space Shuttle SRBs and concluded that the effect was significant but nothing like the effects of CFCs.  I suspect that this will be the ultimate answer to the orbital debris question.  But at this point, we don't know. 

Are your suspicions that some secret cabal of scientists is out to get us so great that you'd actively suppress their work?  And if you're not that paranoid, then isn't this just a perfectly legitimate piece of atmospheric science that you can expect to turn out to be nothing?

__________________
¹Spencer also asserts that there are other substrates beside alumina that can catalyze free chlorine production, which I assume is his rationale for comparing things to all meteoroid dust, not just the aluminum in the dust.  However, he only measured the reactivity of alumina and silicate glasses.

Nope, that was not my argument at all...

I said industrial sources of Alumina and other contaminants are many orders of magnitude higher, and you can't wave that off as "itst only low altitude pollution" because for example CFCs did a lot of damage from that low altitude.

As for numbers  30,000 sats are mostly VLEO, so 3 years.  10,000 reentries per year  times 2 tons, divided by 365, gets you 55 tons of stuff per day.

Some fraction of which is Alumina

[TheRadicalModerate]

Nope, that was not my argument at all...

I said industrial sources of Alumina and other contaminants are many orders of magnitude higher, and you can't wave that off as "itst only low altitude pollution" because for example CFCs did a lot of damage from that low altitude.

As for numbers  30,000 sats are mostly VLEO, so 3 years.  10,000 reentries per year  times 2 tons, divided by 365, gets you 55 tons of stuff per day.

Some fraction of which is Alumina

[Edit:  Most] CFC's are gases at STP, and don't condense as they get higher in the atmosphere.  They're not water-soluble, and they can't nucleate water droplets.  So as winds loft them through the troposphere, there are very few mechanisms to remove them.  And once they reach the stratosphere, they photo-dissociate into free chlorine, which is what causes all the problems.

Alumina is a particulate.  It will nucleate water droplets, which precipitate the particles back to the ground.

Alumina from space will also eventually fall through the topopause and get carried down to Earth by water.  But it's falling through the stratosphere from the top, where it persists as an aerosol for quite awhile.

This is another area where I'd like to know the size distribution of various alumina particles.  I would expect industrial alumina to be fairly coarse-grained.  I would expect meteoroid alumina to be fine-grained.  And I'd expect orbital debris to be somewhere in between.  The size of the particles will be critically important in estimating the lifetime in the stratosphere, and therefore how many chlorine-freeing reactions they can enable.

BTW:  CFCs don't do damage at low altitude.  They have to be lofted into the stratosphere before the mischief starts.  But that's a pure atmospheric mixing problem.  The tropopause isn't a hard boundary.

[meekGee]

Nope, that was not my argument at all...

I said industrial sources of Alumina and other contaminants are many orders of magnitude higher, and you can't wave that off as "itst only low altitude pollution" because for example CFCs did a lot of damage from that low altitude.

As for numbers  30,000 sats are mostly VLEO, so 3 years.  10,000 reentries per year  times 2 tons, divided by 365, gets you 55 tons of stuff per day.

Some fraction of which is Alumina

[Edit:  Most] CFC's are gases at STP, and don't condense as they get higher in the atmosphere.  They're not water-soluble, and they can't nucleate water droplets.  So as winds loft them through the troposphere, there are very few mechanisms to remove them.  And once they reach the stratosphere, they photo-dissociate into free chlorine, which is what causes all the problems.

Alumina is a particulate.  It will nucleate water droplets, which precipitate the particles back to the ground.

Alumina from space will also eventually fall through the topopause and get carried down to Earth by water.  But it's falling through the stratosphere from the top, where it persists as an aerosol for quite awhile.

This is another area where I'd like to know the size distribution of various alumina particles.  I would expect industrial alumina to be fairly coarse-grained.  I would expect meteoroid alumina to be fine-grained.  And I'd expect orbital debris to be somewhere in between.  The size of the particles will be critically important in estimating the lifetime in the stratosphere, and therefore how many chlorine-freeing reactions they can enable.

BTW:  CFCs don't do damage at low altitude.  They have to be lofted into the stratosphere before the mischief starts.  But that's a pure atmospheric mixing problem.  The tropopause isn't a hard boundary.

This exchange shows how impossible it is to argue against vague assertions.

You're saying:  Starlink satellites can harm the ozone via production of Alumina particles.

I'm saying:  There's 50 tons per day (under worst case assumption), some fraction of which is Aluminum, some fraction of which becomes Alumina, some of which may linger in the upper atmosphere.  That's all we know. There's nothing else I can directly counter, except provide context.

For example, other pollution mechanisms that are vastly larger.  Except for each one, you'll find differences, and the conversation now shifts to whether I've proven beyond a shadow of a doubt that your assertion is wrong.  Which I can't, since it's too vague.

So I give up.

Apparently other agencies looked at this and arrived at the same conclusion I did, for pretty much the same reasons.

You can argue with them.

I'm going to go party today as if I still have a job

[LouScheffer]

This could be studied, if required.  Build a test satellite enriched in ²⁶Al, an aluminum isotope uncommon in nature.  Have it re-enter at a known time and place, then sample the upper-atmosphere plume using NASA's U2s, weather balloons, and sounding rockets.  From these samples, deduce the size distribution of the aluminum (and other) particles, and what fraction of the particles come from the satellite.  From this the impact of the satellite entry on the ozone layer can be estimated.

[novo2044]

This could be studied, if required.  Build a test satellite enriched in ²⁶Al, an aluminum isotope uncommon in nature.  Have it re-enter at a known time and place, then sample the upper-atmosphere plume using NASA's U2s, weather balloons, and sounding rockets.  From these samples, deduce the size distribution of the aluminum (and other) particles, and what fraction of the particles come from the satellite.  From this the impact of the satellite entry on the ozone layer can be estimated.

Well the missing element is to what extent do such alumina particles actually degrade the ozone layer?  There's some literature here but it mostly seems to be studying the alumina that's ejected by SRB's, which is tricky because the same boosters also apparently release Hcl at the same time.  That said, what little I could glean suggests attempts at observing any measurable change in the ozone layer caused by boosters ejecting a nontrivial amount of alumina and chlorine at high altitudes found little or no observable effect.  Most of these studies seemed quite old, perhaps with modern imaging more subtle effects might be detectable.

[whitelancer64]

Full PDF (80 pages) attached:

Large Constellations of Satellites:
Mitigating Environmental and Other Effects

GAO-22-105166
Published: Sep 29, 2022. Publicly Released: Sep 29, 2022.

https://www.gao.gov/products/gao-22-105166

"Enabled by declines in the costs of satellites and rocket launches, commercial enterprises are deploying large constellations of satellites into low Earth orbit. Satellites provide important data and services, such as communications, internet access, Earth observation, and technologies like GPS that provide positioning, navigation, and timing. However, the launch, operation, and disposal of an increasing number of satellites could cause or increase several potential effects.

This report discusses (1) the potential environmental or other effects of large constellations of satellites; (2) the current or emerging technologies and approaches to evaluate or mitigate these effects, along with challenges to developing or implementing these technologies and approaches; and (3) policy options that might help address these challenges.

To conduct this technology assessment, GAO reviewed technical studies, agency documents, and other key reports; interviewed government officials, industry representatives, and researchers; and convened a 2-day meeting of 15 experts from government, industry, academia, and a federally funded research and development center. GAO is identifying policy options in this report."