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According to the latest AP report, it's looking like SpaceX will get the contract to decommision the ISS in 2030. Will parts be saved and reused for a new station?

One thing quite objectionable is the idea of 400 tons of mixed metals burning up in a controlled descent into the atmosphere. When defunct satellites burn in the atmosphere, they leave behind chemicals that could damage the ozone layer and affect how much light Earth absorbs. What would it take to send it on a slow path toward the sun instead?

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    $\begingroup$ The Sun is the most difficult place in the solar system for a spacecraft to reach. $\endgroup$
    – John Doty
    Commented Jun 27 at 14:26
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    $\begingroup$ Try to find information about the total mass of the atmosphere of the Earth and compare the value to 400 tons. $\endgroup$
    – Uwe
    Commented Jun 27 at 15:51
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    $\begingroup$ The study that I am referring to is here. Various metals from deorbiting spacecraft such as aluminum, copper and lithium have been found concentrating in the lower stratosphere, especially near the poles. They apparently can remain in the atmosphere indefinitely, so the effect is cumulative. The study predicts that in the coming decades as spaceflight increases the amount of metallic particles from deorbiting spacecraft could eventually equal the amount deposited from meteors, with as of right now unknown environmental effects, if any. $\endgroup$ Commented Jun 27 at 17:50
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    $\begingroup$ It takes more energy (and thus more fuel) to deorbit a mass into the Sun, than to reach escape velocity and thus exit the Solar system. $\endgroup$
    – DrSheldon
    Commented Jun 28 at 3:13
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    $\begingroup$ I would really LIKE to the see ISS on a slow trip to the Oort cloud. $\endgroup$ Commented Jun 28 at 18:08

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Short answer: SpaceX will autonomously dock a spacecraft to the ISS. This spacecraft will then use its thrusters to reduce the speed of the ISS, leading it to "crash" into the ocean, specifically into the spacecraft cemetery which is an uninhabited patch of the Pacific ocean. Parts of the ISS will burn up and vaporize during reentry, and other parts will splash down and sink to the bottom of the ocean.

Longer answer:

You should really read this paper. It answers basically all your questions. That said, as a short summary for your specific questions:

Will parts be saved and reused for a new station?

No. The ISS is very old. The oldest components were designed almost 50 years ago, and are rather outdated and reaching the end of their service life. Neither NASA or any commercial partners think it's worth the effort refurbishing or continuing to use what are, in technology terms, "ancient" modules just to save a bit on launch costs. It is deemed more economical and conducive to mission success to simply send new modules with modern technology up instead for future stations or space activities.

That said, it is possible that select smaller components will be detached from the ISS and safely returned to Earth for historical preservation purposes (museums).

What would it take to send it on a slow path toward the sun instead?

Basically impossible. Due to the way that orbital mechanics work, the Sun is the most difficult and expensive place to reach in the entire solar system. For example, sending something to Mars requires ballpark 15 km/s of delta-v while sending something to the Sun requires maybe 42 km/s of delta-v. Now, consider that all we've been able to put on Mars so far have been things like the 1-ton Perseverance rover. If we wanted to put the ISS into the Sun, we'd need a mission which is something like 1200 times as powerful as the already high-performance mission.

NASA did consider putting it up into a higher orbit for preservation purposes, however this is also not seen as good solution because:

  • Doing so would be rather expensive and require a large amount of fuel
  • The thrust required to do so is not a load the ISS is designed for
  • If unmanned, the station would rapidly fail and become incapable of dodging debris
  • The station would essentially become a debris bomb when it is eventually impacted by something high velocity.

One thing quite objectionable is the idea of 400 tons of mixed metals burning up in a controlled descent into the atmosphere. When defunct satellites burn in the atmosphere, they leave behind chemicals that could damage the ozone layer and affect how much light Earth absorbs.

You personally may find it objectionable, but it's really not a big deal due to how little 400 tons (or any satellite) is. The amount of ozone damage that a single burning up satellite does is probably less than someone in the boonies tossing out their old Freon-filled refrigerator without disposing of the CFCs properly, and while there is a theoretical environmental impact of putting the entire ISS from orbit into the ocean, it's probably less than the cumulative environmental impact caused by the people driving to work at Johnson Space Center in a day or two.

The environmental impact analysis suggests no significant long-term impacts.

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    $\begingroup$ @Bergi Read that as "thrust required to do so in any short period of time". Normal ISS reboosts are on the order of 1-2 m/s delta-V over some 10 minutes. Here we're talking about an impulse some 30000 times larger, so if you want to do it with the same thrust, it's going to take many months (that's a lot of fuel). $\endgroup$
    – TooTea
    Commented Jun 28 at 13:28
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    $\begingroup$ @Bergi deorbiting is a delicate procedure because they want to drop it in the ocean at a certain location. Once deorbit starts, you want to to it really quickly so that when the atmospheric drag force doesn't have much chance to add unpredictability to the area of impact. $\endgroup$
    – uhoh
    Commented Jun 28 at 13:34
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    $\begingroup$ @Bergi I'm afraid that no chemical thrusters capable of continuous firing for half a year have ever been developed, so this would mean developing new hardware one way or the other (even if you decide to go with electric propulsion, you need a whole lot of ion thrusters to get the necessary thrust plus a staggering amount of power to feed them). $\endgroup$
    – TooTea
    Commented Jun 28 at 15:06
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    $\begingroup$ While the ISS isn't near the same scale as satellite constellations, there was a paper from just last month investigating the impact of their eventual deorbiting that concluded over 10% of a deorbiting satellite's mass ends up as aluminum oxide nanoparticles in the stratosphere that would likely persist for decades. NOAA's SABRE study in October also showed a far higher rate of exotic metal-cored sulfuric acid particles in the stratosphere from deobriting than expected. The ISS's impact analysis is almost three decades old; do these more recent studies change anything there? $\endgroup$
    – Idran
    Commented Jun 28 at 20:45
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    $\begingroup$ @uhoh, Can we call that the corundum conundrum? $\endgroup$ Commented Jun 30 at 0:42

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