Just to add to the other answers: depending on the thickness of the upper atmosphere, the ISS would de-orbit in between 1 and six years if it didn't have periodic reboosts to keep it in orbit..
So if you want to move it permanently somewhere else you'd need to boost it to a much higher orbit. Or do periodic reboosts. Page on nasa.gov
They could boost it to a higher orbit surely. But 1600 km wouldn't be easy to get to with the Soyuz. Before they can boost it so high they'd need a way to get the fuel up there to do the boosting. And would need to be the equivalent of a decade or more of normal boosting to get it that high. And in the process it would take it well out of reach of the Soyuz for taking humans to orbit, I'm not sure what its limit is, but the ISS is not that far from it already.
So - that would be a largely unmanned mission - so would first have to set it up for unmanned operation before they could do that. At present it is designed in such a way that it requires continual human presence.
I suppose they feel it is just not worth the effort to do it and all the extra flights you'd need for the fuel, and adapting it etc - when we have no clear use for the modules? The problem is we don't have manufacturing and repair facilities in orbit, not to do anything as sophisticated as trying to repair or re-use parts of the ISS that are beyond possibilities of easy repair, and not likely to for some time to come I imagine.
But the Russians have ideas to re-use their modules so - that's a possibility that the ISS might be disassembled first and some of its modules used elsewhere - the Russians have suggested that they might withdraw from the partnership in 2024, and build their own space station once more as in the days of MIR and Skylab, and their modules are still usable enough for that apparently.
In any case whatever happens there - I think different parts of the ISS are in different states of repair, so some may be considered beyond easy repair while other parts may be still usable, so that could lead to a situation where parts of it are de-orbited and other parts are re-used for whatever reason. So that seems a quite likely outcome.
Of course it's also possible that by 2024 then the whole situation has changed and it is so much easier to get into orbit, or we have space mining underway already - or telerobotics so much improved that it is easy to repair satellites using telerobotics instead of spacewalks. A lot can happen in a decade. So - I think it is possible (though unlikely) that when it comes to it, that it makes more sense to keep the ISS and boost it to 1600 kms or whatever.
It does seem a shame somehow. Another thing like that - all our spaceships that go to orbit have final stages that also go into orbit. It's done like that because the spaceships themselves haven't got much fuel capacity compared to the final stage - so most of the boost comes from the final stage - so naturally the final stage ends up in a very similar orbit or trajectory to the spacecraft.
Sometimes those final stages, for interplanetary missions - go as far afield as other planets in our solar system such as Mars - just about every mission to Mars is accompanied by a final stage (with the exception of the MOM Indian mission that used gravity boost close to Earth) which also goes all the way to Mars, deliberately "trajectory biased" to miss it.
That's a huge amount of mass, surely thousands of tons of it in total - that we regularly send to orbit - or into interplanetary space - and then just trash it. With the Soyuz, the final stage de-orbits a few days later. Its mass is about a third of the mass of the Soyuz itself. If only we could somehow collect all those final stages and make them into a space station or use the mass in some other way having got it into orbit at such huge expense... But that is way beyond our capabilities and not at all practical or possible so we just have to live with that situation.
So if you want to move it permanently somewhere else you'd need to boost it to a much higher orbit. Or do periodic reboosts. Page on nasa.gov
They could boost it to a higher orbit surely. But 1600 km wouldn't be easy to get to with the Soyuz. Before they can boost it so high they'd need a way to get the fuel up there to do the boosting. And would need to be the equivalent of a decade or more of normal boosting to get it that high. And in the process it would take it well out of reach of the Soyuz for taking humans to orbit, I'm not sure what its limit is, but the ISS is not that far from it already.
So - that would be a largely unmanned mission - so would first have to set it up for unmanned operation before they could do that. At present it is designed in such a way that it requires continual human presence.
I suppose they feel it is just not worth the effort to do it and all the extra flights you'd need for the fuel, and adapting it etc - when we have no clear use for the modules? The problem is we don't have manufacturing and repair facilities in orbit, not to do anything as sophisticated as trying to repair or re-use parts of the ISS that are beyond possibilities of easy repair, and not likely to for some time to come I imagine.
But the Russians have ideas to re-use their modules so - that's a possibility that the ISS might be disassembled first and some of its modules used elsewhere - the Russians have suggested that they might withdraw from the partnership in 2024, and build their own space station once more as in the days of MIR and Skylab, and their modules are still usable enough for that apparently.
In any case whatever happens there - I think different parts of the ISS are in different states of repair, so some may be considered beyond easy repair while other parts may be still usable, so that could lead to a situation where parts of it are de-orbited and other parts are re-used for whatever reason. So that seems a quite likely outcome.
Of course it's also possible that by 2024 then the whole situation has changed and it is so much easier to get into orbit, or we have space mining underway already - or telerobotics so much improved that it is easy to repair satellites using telerobotics instead of spacewalks. A lot can happen in a decade. So - I think it is possible (though unlikely) that when it comes to it, that it makes more sense to keep the ISS and boost it to 1600 kms or whatever.
It does seem a shame somehow. Another thing like that - all our spaceships that go to orbit have final stages that also go into orbit. It's done like that because the spaceships themselves haven't got much fuel capacity compared to the final stage - so most of the boost comes from the final stage - so naturally the final stage ends up in a very similar orbit or trajectory to the spacecraft.
Sometimes those final stages, for interplanetary missions - go as far afield as other planets in our solar system such as Mars - just about every mission to Mars is accompanied by a final stage (with the exception of the MOM Indian mission that used gravity boost close to Earth) which also goes all the way to Mars, deliberately "trajectory biased" to miss it.
That's a huge amount of mass, surely thousands of tons of it in total - that we regularly send to orbit - or into interplanetary space - and then just trash it. With the Soyuz, the final stage de-orbits a few days later. Its mass is about a third of the mass of the Soyuz itself. If only we could somehow collect all those final stages and make them into a space station or use the mass in some other way having got it into orbit at such huge expense... But that is way beyond our capabilities and not at all practical or possible so we just have to live with that situation.
About the Author
Robert Walker
Writer of articles on Mars and Space issues - Software Developer of Tune Smithy, Bounce Metronome etc.Studied at Wolfson College, Oxford
Lives in Isle of Mull
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