There are several posts and comments about the parts of the ISS striking Earth on re-entry. Here is one example

Would the ISS actually burn up completely? It's pretty big.

No, the Mir was much smaller and about 40 tons of debris ended up in the seas somewhere when it was decommissioned. Source

There are also a number of posts that talk about ISS re-entry, either planned or not, some examples:

But I don't find anything that talks about what parts would survive, and what real danger those parts would pose.


Worst case scenario, with the current ISS configuration which parts would not burn up on re-entry and would survive to strike Earth. If one or more of those impacted a major city what would the likely outcome be?

  • $\begingroup$ When you say "potentially harmful energy," do you mean radiation? $\endgroup$ – Bob516 Feb 28 at 17:18
  • $\begingroup$ there's liquid oxygen and hydrogen, which could be hazardous if the tanks weren't emptied before reentry. The ISS probably has some parts on it that are toxic to sea life. Human waste is occasionally discharged, so there might be a bit left on board. And any experiments that are hazardous $\endgroup$ – Mohammad Athar Feb 28 at 17:40
  • $\begingroup$ @Bob516 LEO orbital speed is 7.8 km/s (28,000 km/h; 17,000 mph), that is a LOT of energy. Some of that will be shed on re-entry. Any large pieces moving fast and hitting say a building or a car, will impart all that energy to what they hit. That is what I mean by "potentially harmful energy" $\endgroup$ – James Jenkins Feb 28 at 17:54
  • 2
    $\begingroup$ @MohammadAthar there is no liquid hydrogen and very little if any liquid oxygen on the ISS. $\endgroup$ – Organic Marble Feb 28 at 18:19
  • $\begingroup$ @JamesJenkins So you mean a substantial amount of kinetic energy? $\endgroup$ – Bob516 Feb 28 at 19:56

Partial answer, addressing "which parts would not burn up on reentry"

For clues we can look at what pieces of Skylab survived and for a lesser degree of applicability what pieces of Columbia survived.

In both cases it appears that the debris that made it to the ground was characterized by either very high ballistic coefficent (dense debris such as hatch mechanisms, SSME turbopumps, landing gear) or very low ballistic coefficent (tanks, usually composite overwrap type tanks).

The ISS has some of both - tanks such as the NORS tanks and the HPGT tanks; dense components such as the Solar Alpha Rotary Joint bearings and the already-mentioned hatch mechanisms. These are the types of debris that I would expect to have the best chance of surviving reentry.

The part about potential damage I cannot answer.

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