re: #50 JC1

This seems like nonsense. These satellites are pretty small. Even 12k of them shouldn’t make a dent.

The study is not embargoed and appeared in the journal Geophysical Research Letters on June 11, 2024. Since I cannot assess the maths in the study (way beyond a high school education), I have to go for the explanatory text.

TL;DR

The study notes that a 250kg satellite generates around 30kg of aluminium oxide as it burns up in the upper atmosphere (this does not include launch vehicles). Aluminium oxide is a known catalyst to create nitrogen oxide and chlorine, both of which break up ozone. Such aluminium compounds stay in the atmosphere for decades.

The limiting factor is that a reëntering satellite cannot be monitored for what sorts of materials are deposited in the atmosphere. Approximations can be made based on the makeup of satellites and rocket bodies. Natural sources (meteors) account for nearly 12,000 tonnes of material every year.

Moreover, the expected number of satellites launched into low Earth orbit is projected to dramatically increase.

The study also summarises studies done in the past showing the same problem.

Not related to this study, it has been suggested in the past that both rocket bodies and satellites at the end of their life be powered out of orbit into deep space or at the Sun, over the same problems regarding both pollution and ozone-depletion. Corporate launch companies oppose this though (extra fuel and weight to dispose of a satellite or rocket body).