What is really happening when Satellites “burn up during re-entry”? Is there any debris left? Is it toxic? Can anyone get hurt?

Question

Apparently instead of once in a while at a predictable time/path, now satellites are going to be dropping from the sky all the time?

https://gizmodo.com/spacexs-next-gen-starlink-satellites-have-started-falli-1850299668

Has anyone verified that is safe for the planet and people below?

Almost seems like someone throwing toxic sludge into the ocean and saying “well the ocean is huge and it’s only a little toxic so no big deal” until it’s done thousands of times over and over and it’s only trivial to them because they can’t see the final damage?

In: 5

Answer 1

tl;dr they pose essentially zero risk to the ground.

First off, the satellites here are in low earth orbit – they’re a LOT closer than most satellites traditionally have been. In the past, satellites have been extremely expensive to put into orbit so typically they are large and designed for as long of a lifespan as possible. The downside of being so high up and lasting so long is that when they eventually die, it takes centuries for them/any debris to eventually re-enter the atmosphere which means hazards for any other satellites out there.

These Starlink satellites are as I mentioned, in low earth orbit – rather than centuries, once they run out of fuel or otherwise stop working, it will take more like a year for them to hit the upper atmosphere. They are also quite a bit smaller than most older satellites.

When that happens, they will literally disintegrate. Satellites are moving really fast – as in like 17,000MPH fast. When they go from the near-vacuum of low earth orbit they start hitting denser and denser pockets of air which causes them to heat up more and more and more. While larger objects are likely to have small pieces that might survive re-entry, these satellites are a lot smaller. So while it’s **possible** some tiny chunks of debris might not heat up to the point of disintegration and re-enter earth’s atmosphere, think tiny flecks of metal, not big chunks.

And by the time they reach the ground, air resistance will have slowed them to terminal velocity. Think of a large grain of sand being dropped off a skyscraper – it’s not going to do much of anything.