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Nasa is making plans to de-orbit the ISS safely over the pacific ocean, this eventually leads to the question of whether or not an ISS module can survive reentry (survive meaning it is recognizable upon being retreived)

Guest2204
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2 Answers2

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“Aluminum, rather than steel, comprises most of the outer shell of the modules” https://science.nasa.gov/science-news/science-at-nasa/2001/ast14mar_1 . Aluminum has low melting point and softens significantly before it melts. Aluminum and Titanium are major components of the modules. Both are combustible. Titanium will burn in nitrogen, in the absence of oxygen. https://umdearborn.edu/offices/environmental-health-and-safety/lab-safety/chemical-safety/combustible-metals , https://umdearborn.edu/offices/environmental-health-and-safety/lab-safety/chemical-safety/combustible-metals Kevlar melts at an even lower temperature (500*C). A module is unlikely to survive re-entry intact. Try burning a beer can with a propane soldering torch for a good visual. The steel components of the module have a much better chance of landing as debris.

A component that is much more likely to survive than modules are the four NORS oxygen and nitrogen cylinders. They are 1m long and weigh about 100kg. https://www.nasa.gov/content/air-supply-high-pressure-tanks-ready-for-space-station . Their operational pressure is 6000 psi, about twice that of SCUBA or welding tanks. They are seriously beefy components. I couldn’t source their construction, but they are likely Type IV Composite Overwrapped Pressure Vessels

Woody
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  • +1 aluminum readily reacts with oxygen to form a protective aluminum oxide barrier so I don't think "oxidized readily" has much significance. – uhoh Nov 09 '21 at 07:15
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    @uhoh But that only works below the melting point of the metal. There's no stable oxide layer on hot aluminium droplets. – TooTea Nov 09 '21 at 08:50
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    @TooTea at which point the oxide continues to be irrelevant. I'm saying that "I don't think 'oxidizes readily' has much significance." Do you disagree? Do you think oxidation has some relevance here? – uhoh Nov 09 '21 at 09:31
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    @uhoh: Well, yes. Once it has turned into aluminum oxide dust floating in the upper atmosphere, it's no longer "recognizable upon being retrieved" as specified by the OP. I suspect you may have understood the phrase "oxidizes readily" somewhat differently than the rest of us. Maybe phrasing it in simpler words, such as "burns easily in air", would make the answer more understandable? – Ilmari Karonen Nov 09 '21 at 12:25
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    @IlmariKaronen that's IF rather than "once". I'd predict a mix of big and small chunks and a spray of droplets rather than dust, but a good authoritative source would be better than speculation. Related: How many kilograms of nickel particles will be dispersed in Earth's atmosphere by dumping old ISS batteries overboard? remains unanswered. – uhoh Nov 09 '21 at 13:05
  • @CuteKItty_pleaseStopBArking evidence of aluminium moving through an oxygen atmosphere at mach 25, exposed to plasma that is well above the vaporization temperature of aluminium burn(ing). Very, very brightly..." Does this happen only in gedankenexperiments (one's imagination) or can sources for this be cited? I'm ready to be convinced with facts, but not with sarchasm. – uhoh Nov 10 '21 at 21:04
  • @CuteKItty_pleaseStopBArking it doesn't make sense to leave a comment asking me to take a look at satellite debris, I can't. If you can link to a careful and authoritative analysis that presents information on aluminum melting upon reentry in the way you describe, please do! – uhoh Nov 11 '21 at 09:02
  • The structural components of the ISS modules are made of aluminum, titanium and steel. All three metals are reduced from oxidized ores. All three will re-oxidize exothermically (burn) in the presence of heat and oxygen. Like on re-entry. Aluminum, titanium and the chromium in stainless steel all form surface oxide layers which protect against bulk corrosion but not melting or combustion. – Woody Nov 11 '21 at 22:09
  • Sumitomo (a Japanese firm) and Kyoto University are designing a satellite whose structural components are made of wood https://www.economist.com/science-and-technology/2021/01/13/a-japanese-forestry-firm-wants-to-put-wooden-satellites-into-orbit . Not so nutty. Depending on the wood, it can have lower thermal expansion, higher hardness, higher specific strength and higher specific modulus than aluminum. Wood is transparent to radio waves. Carbon neutral. And there is no argument that it burns up on de-orbit. – Woody Nov 11 '21 at 22:32
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This (not so new) article says it can:

"NASA estimates that 16 percent of the ISS would likely survive the burn and stresses of reentry, between 53,500 and 173,250 pounds falling to earth. "

Rodo
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    The parts will not be recognizable. 16% of the mass might make it in solid form to splash-down, but approximately 0% of it will be functional parts in the milisecond before metal meets wave. – dotancohen Nov 09 '21 at 07:47