Environmental harms from lots of re/entries?

[Phronesis]

Hi all – I recall reading that at a certain frequency atmospheric reentries on Earth accrue to some sort of environmental harm. This would have been a number/frequency somewhat greater than the status quo today.

It came up in the context of asteroid mining, where bringing metals back to earth was held to be potentially harmful, specifically all the entries.

I can't find it now. Is this ringing any bells? I don't think I'm talking about a Hard Rain scenario like in Neal Stephenson's novel Seveneves. This was rather about the scale of maybe a few scores or a few hundred reentries a year from asteroid mining. Maybe a few thousand. I'd be surprised if it was a thermal problem like the Hard Rain.

We obviously have tons of "reentries" of a sort now, or just entries, by natural meteors and bolides. I don't know the number. Do you know of a potential problem with lots of artificial entries?

Thanks.

[b.lorenz]

I also vaguely remember reading about this. If I remember correctly, the problem was nitrous oxide creation from the atmosphere by the high temperatures. But since so many asteroids enter regularly, it really seems a small concern

[speedevil]

Hi all – I recall reading that at a certain frequency atmospheric reentries on Earth accrue to some sort of environmental harm. This would have been a number/frequency somewhat greater than the status quo today.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3306630/ Lists the lifetime of NOX as >100 years, and its activity as an ozone depleting chemical as 1/60th that of CFC-11.
In 1986, ~250ktons of CFC-11 was made in europe, and I'm going to assume a couple of million tons worldwide.
https://www.sciencedirect.com/science/article/pii/0004698176901712 gives ~6% NOX mass made by reentries compared to the reentry mass.
This means that to get to 1986 levels of ozone depletion due to this effect needs ~30Mtons of reentries a year.

Or, hundreds of thousands of 'starship' class reentries.

It's a problem to be concerned about in the distant future. (I have neglected NOX emissions at launch, which I suspect will be rather higher)

[Proponent]

Sounds like it would be a great problem to have.

[Phronesis]

Hi all – I recall reading that at a certain frequency atmospheric reentries on Earth accrue to some sort of environmental harm. This would have been a number/frequency somewhat greater than the status quo today.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3306630/ Lists the lifetime of NOX as >100 years, and its activity as an ozone depleting chemical as 1/60th that of CFC-11.
In 1986, ~250ktons of CFC-11 was made in europe, and I'm going to assume a couple of million tons worldwide.
https://www.sciencedirect.com/science/article/pii/0004698176901712 gives ~6% NOX mass made by reentries compared to the reentry mass.
This means that to get to 1986 levels of ozone depletion due to this effect needs ~30Mtons of reentries a year.

Or, hundreds of thousands of 'starship' class reentries.

It's a problem to be concerned about in the distant future. (I have neglected NOX emissions at launch, which I suspect will be rather higher)

Thanks! Where is the NOX coming from? Is this about fuel burn?

[speedevil]

Hi all – I recall reading that at a certain frequency atmospheric reentries on Earth accrue to some sort of environmental harm. This would have been a number/frequency somewhat greater than the status quo today.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3306630/ Lists the lifetime of NOX as >100 years, and its activity as an ozone depleting chemical as 1/60th that of CFC-11.
In 1986, ~250ktons of CFC-11 was made in europe, and I'm going to assume a couple of million tons worldwide.
https://www.sciencedirect.com/science/article/pii/0004698176901712 gives ~6% NOX mass made by reentries compared to the reentry mass.
This means that to get to 1986 levels of ozone depletion due to this effect needs ~30Mtons of reentries a year.

Or, hundreds of thousands of 'starship' class reentries.

It's a problem to be concerned about in the distant future. (I have neglected NOX emissions at launch, which I suspect will be rather higher)

Thanks! Where is the NOX coming from? Is this about fuel burn?

On reentry, heating air till it glows strips all of the atoms away from their molecules and they reform in random order, some nitrogens bond to oxygens, rather than nitrogens.

Similar processes happen in parts of launch, where very fast moving exhaust molecules hit the atmosphere and split air.

[Eric Hedman]

Hi all – I recall reading that at a certain frequency atmospheric reentries on Earth accrue to some sort of environmental harm. This would have been a number/frequency somewhat greater than the status quo today.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3306630/ Lists the lifetime of NOX as >100 years, and its activity as an ozone depleting chemical as 1/60th that of CFC-11.
In 1986, ~250ktons of CFC-11 was made in europe, and I'm going to assume a couple of million tons worldwide.
https://www.sciencedirect.com/science/article/pii/0004698176901712 gives ~6% NOX mass made by reentries compared to the reentry mass.
This means that to get to 1986 levels of ozone depletion due to this effect needs ~30Mtons of reentries a year.

Or, hundreds of thousands of 'starship' class reentries.

It's a problem to be concerned about in the distant future. (I have neglected NOX emissions at launch, which I suspect will be rather higher)

According to an article in Nature, China is kicking up production of CFC-11 again (so much for countries sticking to international agreements) so NOX from spaceflight may be much less of a concern than other issues in the upper atmosphere.   A couple of key quotes:

"We show that emissions from eastern mainland China are 7.0 ± 3.0 (±1 standard deviation) gigagrams per year higher in 2014–2017 than in 2008–2012, and that the increase in emissions arises primarily around the northeastern provinces of Shandong and Hebei."

"Several considerations suggest that the increase in CFC-11 emissions from eastern mainland China is likely to be the result of new production and use, which is inconsistent with the Montreal Protocol agreement to phase out global chlorofluorocarbon production by 2010."

https://www.nature.com/articles/s41586-019-1193-4

[Zachary888]

Hi all – I recall reading that at a certain frequency atmospheric reentries on Earth accrue to some sort of environmental harm. This would have been a number/frequency somewhat greater than the status quo today.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3306630/MyFedLoan Lists the lifetime of NOX as >100 years, and its activity as an ozone depleting chemical as 1/60th that of CFC-11.
In 1986, ~250ktons of CFC-11 was made in europe, and I'm going to assume a couple of million tons worldwide.
https://www.sciencedirect.com/science/article/pii/0004698176901712 gives ~6% NOX mass made by reentries compared to the reentry mass.
This means that to get to 1986 levels of ozone depletion due to this effect needs ~30Mtons of reentries a year.

Or, hundreds of thousands of 'starship' class reentries.

It's a problem to be concerned about in the distant future. (I have neglected NOX emissions at launch, which I suspect will be rather higher)

Thanks! Where is the NOX coming from? Is this about fuel burn?

It came up in the context of asteroid mining, where bringing metals back to earth was held to be potentially harmful, specifically all the entries.

I can't find it now. Is this ringing any bells? I don't think I'm talking about a Hard Rain scenario like in Neal Stephenson's novel Seveneves. This was rather about the scale of maybe a few scores or a few hundred reentries a year from asteroid mining. Maybe a few thousand. I'd be surprised if it was a thermal problem like the Hard Rain.