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For some first stages and second stages, and some failed launches, their fate is to burn up in the Earth atmosphere. Once the stage has broken into thousands of smaller parts, aerodynamics changes. How? What happens to these pieces?

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Most first stages are jettisoned at a relatively low velocity and will simply fall to Earth. In most cases this means destruction of the first stage by falling in the ocean. In some cases (especially Chinese rockets) the first stage may end up landing on land. https://pauldmaley.com/sd1/

Second stages either burn up or are cast adrift in orbit. Any rocket stage that ends up at high sub orbital velocity is likely to disintegrate due to frictional forces which will reduce much of the stage to particulates comprising of iron and aluminium oxides. Such fine particulate matter will generally end up in the ocean hours or days after the launch.

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    $\begingroup$ Russian booster stages also land on land, where they are often scavenged by scrappers. $\endgroup$
    – ikrase
    Apr 6 at 2:36
  • $\begingroup$ @Slarty and great link reference, +1. This looks right to me though its a bit light on detail given that the question is specifically asking how does the aerodynamics change. it makes sense to me that there will be different regimes, according to the parent object velocity, relating to how much melting/fracturing/oxidation occurs and what the residence time of the smaller objects is. $\endgroup$
    – Puffin
    Apr 6 at 9:46
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    $\begingroup$ Also, just being pernickety but this is a really good example where it really matters that the word "generally" has two meanings one of which is wrong. Its better to say "Such fine particulate matter will typically end up in the ocean ..." as the Earth is 7/10 water. To say "generally" could be interpreted as in the same usage as the general theory of relativity vs the special theory. $\endgroup$
    – Puffin
    Apr 6 at 9:47
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First stages are usually dropped much earlier and don't necessarily 'burn up' when falling back to the planet.

The stuff that does actually burn up, upper stages, satellites and other debris, breaks down into not just smaller parts but right down to fine particles as well.

This Scientific American article "How Much Air Pollution Is Produced by Rockets?" article claims that:

at least 50 percent of a given debris object will end up as RSPs(Re-entry smoke particles) during re-entry.

It further mentions that exact mechanism of this melting-vaporizing-dust creation process is unclear (Not studied). The article is from 2017 and the author of the relevant section in this report might be a good starting point.

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    $\begingroup$ This answers the question as I read it, namely "what happens to the stuff that burns up?". Disappointing to hear it hasn't been studied, but I guess it would be quite hard to do so. $\endgroup$
    – Bear
    Apr 6 at 16:31
  • $\begingroup$ That's a good find. I can think of a lot of follow on questions from the Scientific American article. $\endgroup$
    – Puffin
    Apr 7 at 17:15
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Many spacecraft that are deorbited are aimed for Point Nemo in the South Pacific Ocean.

The area is nowadays known as a "spacecraft cemetery" because hundreds of decommissioned satellites, space stations, and other spacecraft have been deposited there upon re-entering the atmosphere, to lessen the risk of hitting inhabited locations or maritime traffic. The International Space Station (ISS) is planned to crash into Point Nemo in 2031.

It is used because it is the furthest point from any land and relatively lifeless due to a lack of nutrients.

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  • $\begingroup$ Do you have any evidence that this is used for first/second stages of rockets, i.e. things which possibly didn't reach orbit? $\endgroup$ Apr 6 at 19:39
  • $\begingroup$ @PaŭloEbermann This article mentions a SpaceX second stage, but not whether it had reached orbit popsci.com/… $\endgroup$ Apr 7 at 11:59
  • $\begingroup$ This talk more about point nemo than the actual question $\endgroup$ Apr 7 at 14:24

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