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What would happen if the astronauts on the ISS stopped maintaining it, and no further vehicles or remote control commands were sent up from the ground? I'd like to know what systems would stop working, what would burn out, fail, jam, freeze, overflow, etc, at what point the astronauts would die, and in what order the station would break down into a heap of unrecoverable junk.

To prolong this experiment, let's assume it was in a much higher orbit so orbital decay wouldn't become terminal for hundreds of years. I am just interested in the process of decay, and if/when a steady state eventually gets reached, what would be salvageable and what would be ruined.

If you can, please format an answer as a rough timeline or chain of events, with guesses as to the durations, and comments on interesting events where appropriate. Answer should include much info on the main life support failures, but also cover the other subsystems, and can span hundreds of years if necessary. Please include: power generation, truss bearings, cooling, stations attitude, pressure, water and o2 content, long term viability of electrical systems should power ever be restored.. What is no longer salvageable and repairable after 10years, 20, 50..

Innovine
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    Related: https://space.stackexchange.com/q/17196/58 – called2voyage Aug 31 '17 at 12:10
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    Everyone is welcome to assemble resources to answer the question in this meta discussion: https://space.meta.stackexchange.com/q/906/58 – called2voyage Aug 31 '17 at 12:55
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    Related: How long would ISS stay in orbit if it didn't get reboosts? – armatita Aug 31 '17 at 15:31
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    @armatita Given that information, the setup of this question ("To prolong this experiment, let's ignore atmospheric drag which could de-orbit the station.") would require that the station somehow continue to perform station-keeping. Innovine, should we consider the impact of that station-keeping on the ISS as it ages, or should we just presume that the ISS is magically held in orbit and that station-keeping has ceased? – called2voyage Aug 31 '17 at 20:32
  • The effects on its ability to station keep would be interesting. Just ignore the atmospheric drag. – Innovine Aug 31 '17 at 21:10
  • But station-keeping is an essential part of maintenance. – Uwe Aug 31 '17 at 21:36
  • @called2voyage Yes, you're right. I've linked the question because I didn't read the description carefully. I don't have the know how to provide the OP with the kind of detail s/he hoping for, but it seems to me that for the ISS to avoid quickly falling into earth it would need to be in a very high orbit. Far away from the protection of the Earth's magnetic field. My first concern would be radiation, and as so I doubt the electronics would be reliable for long (see this). – armatita Aug 31 '17 at 23:00
  • @uwe True, but I already know the effects of atmospheric drag. Also, the reason I am asking is that this is background research for a video game, where the player will encounter an abandoned space station in a very different location. Knowing the way the mechanical and chemical systems on the ISS would fail over a long period is extremely useful data.. but the atmospheric drag is utterly irrelevant. I didn't think it was relevant to go into this much background explanation in the question. – Innovine Sep 01 '17 at 07:50
  • @armatita radiation damage is extremely interesting, and not something I'd considered when writing the question – Innovine Sep 01 '17 at 07:51
  • But its quite relevant. Radiation related phenomena is likely the main cause of degradation in space vehicles. And there is branch of space sciences named Space Weather that is well worth exploring in order to obtain some of the estimates you're looking for. For example have a look at this article. – armatita Sep 01 '17 at 10:06
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    @armatita It's interesting, but the slow degradation must already be accounted for in the planned lifetime of the station anyway. The rate of decay due to radiation damage is not going to change just because the maintenance stops, I guess. – Innovine Sep 01 '17 at 10:38
  • Well its not so much the planned lifetime of the station, but of the mission. Multiple components are changed regularly. Also there tends to be at least one big crisis per year. This is the good scenario where people are there to take care of it and its mostly protected from solar and cosmic radiation (due to a low orbit). In a bad scenario my guess is that it would become inhabitable in under a year. – armatita Sep 01 '17 at 13:49
  • Is there an easy to digest summary of the repairs done on the station throughout its lifespan? And which parts are designed to wear out and be replaced? Something like this list for cars, but for ISS: http://www.aa1car.com/library/car_parts_replaced.htm – Innovine Jan 24 '18 at 08:56
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    @Innovine the major spares currently at the station (Orbital Replacement Units) are listed in this article https://en.wikipedia.org/wiki/Orbital_replacement_unit These ORUs were selected to be placed on the station based on predicted likelihood of failure and size (no planned replacement for shuttle can carry the larger parts). – Organic Marble Feb 02 '18 at 01:44

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It would slowly come down into the atmosphere and burn up. There is also the possibility that pieces of it will reach the surface of the earth. But probably before that, the ISS will be hit by space debris, as no one will control it to maneuver the ISS away from the junk. Once the amount of junk is big enough, it will keep smashing into each other and create a whole lot of space junk. This is why it will be de-orbited to point Nemo in the pacific, the place that is the furthest from any inhabited land, after the final mission. Water and oxygen probably will not run out since it's not used as extensively. For the power: as long as the systems aren't damaged, it will be available. The main solar panel gimbal system is fully automatic. I think it'll be over for the ISS once completely left alone in about 15 years. But the space debris issue is the most important one, the ISS doesn't automatically move out of the way, but once upcoming debris is detected it can be moved from Earth, to avoid collision. I can't seem to find anything about how often this happens, though.

Edlothiad
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Simon V.
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