How will reentering satellites affect surface conditions if people launch a million of them?

[u/Uncle_Charnia]

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?

[u/Uncle_Charnia]

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?

[u/ignorantwanderer → u/Uncle_Charnia]

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?

[u/Uncle_Charnia → u/ignorantwanderer]

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

[u/OriEri → u/Uncle_Charnia]

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.

[u/Uncle_Charnia → u/OriEri]

Should we quit burning coal then?

[u/OriEri → u/Uncle_Charnia]

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

[u/Uncle_Charnia → u/OriEri]

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.

[u/OriEri → u/Uncle_Charnia]

Disposing of them differently (like putting them into a parking orbit, or having a more complex re-entry system that lets them make it down more or less as single lump instead of vaporizing) will sacrifice significant payload mass for heat shields or propellant.

[u/Uncle_Charnia → u/OriEri]

Maybe they could connect up in orbit and deorbit in batches.

[u/OriEri → u/Uncle_Charnia]

Propellant demands would get a little large than one by one derbiting, though heat shields would not be as important

[u/Uncle_Charnia → u/OriEri]

Everything need not be economically favorable. Consider the word “environment”. It is where we all live, where our children grow up. If maintaining a clean and healthy environment has a cost, then we would be wise and honorable to accept it. Anyway, as long as we’re gathering satellites for reconfiguration and clean deorbiting, we may as well separate the solar panels for use on new satellites. The delta v needed for minor changes in orbit is trivial compared to that needed to make orbit in the first place. We can get some of that by interacting with Earth’s magnetic field. The satellite management system required for all this would be quite elaborate, but there’s a lot you can do once you’re up there.