[Retric]

They are 0.8 ton each and last ~5 years. 10,000 / 5 * 0.8 = 1,600 tons per year at 10k satellites, and their goal of 40k satellites would put it well above the amount of asteroid debris impacting each year. Further asteroids contain very different materials and don’t all impact at the very low angles you see from de-orbiting in satellites. Thus, I don’t think you can presume this is meaningless without actually modeling it.

Space dust on the other hand behaves very differently on reentry because of the high surface area to volume ratio.

[mikkupikku]

They last 5 years if they're dead in orbit. These satellites have electric thrusters and boost themselves regularly to maintain orbit, so your estimate is wildly off.

As for presuming them to be safe, there's fuck all evidence to the contrary. Whining with baseless speculations about the effect of satellites burning up is motivated by the base reflex to shit on any technological progress as an environmental disaster in the making, but nobody can come up with a story about how dolphins might choke on satellites so instead we get this "muh aluminum" narrative.

[Retric]

“A Starlink satellite has a lifespan of approximately five years” https://www.space.com/spacex-starlink-satellites.html

A 5 years useful lifespan sets the replacement rate and thus the average number burning up each year. In steady state the delta between end of life and reentry is irrelevant, instead the average number of satellites launched each year = average number that burn up each year.

As to harm. Aluminum is mildly toxic, you don’t eat your bike but vaporized aluminum from a satellite is way more likely to cause harm than if the things were made of steel. The plastic bits are likely fine though.

Saying let’s study something ahead of time rather than contaminating all the world’s farmland with and then seeing what happens seems like a perfectly reasonable standard. Technology has generally been wonderful, but that doesn’t mean everything is equivalent. We want to phase out leaded aviation fuel in the US even though it’s ‘only’ 2,000 tons of lead per year, that’s still enough to be problematic. Perhaps ramping up to ~5k tons/y of vaporized aluminum worldwide is a complete non issue, but if it’s not insisting on some other material isn’t the same as a ban.