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Expanding, And Eventually Replacing, The International Space Station:
Aboard the International Space Station (ISS), humanity has managed to maintain an uninterrupted foothold in low Earth orbit for just shy of 20 years. There are people reading these words who have had the ISS orbiting overhead for their entire lives, the first generation born into a truly spacefaring civilization.
But as the saying goes, what goes up must eventually come down. The ISS is at too low of an altitude to remain in orbit indefinitely, and core modules of the structure are already operating years beyond their original design lifetimes. As difficult a decision as it might be for the countries involved, in the not too distant future the $150 billion orbiting outpost will have to be abandoned.
Naturally there's some debate as to how far off that day is. NASA officially plans to support the Station until at least 2024, and an extension to 2028 or 2030 is considered very likely. Political tensions have made it difficult to get a similar commitment out of the Russian space agency, Roscosmos, but its expected they'll continue crewing and maintaining their segment as long as NASA does the same. Afterwards, it's possible Roscosmos will attempt to salvage some of their modules from the ISS so they can be used on a future station.
(Score: 2) by aiwarrior on Wednesday March 04 2020, @03:24PM (8 children)
What is the DeltaV of air friction and what is the issue in just pushing it to a higher orbit? Is it damaged or something? Cannot stand stresses required for a orbit change?
(Score: 3, Informative) by DannyB on Wednesday March 04 2020, @03:46PM (1 child)
What about on board bacteria that grow?
MIR [wikipedia.org] was de-orbited, in the very same month, March 2001, that Douglas Crockford first specified and popularized the JSON [wikipedia.org] format. Coincidence? There must be a cause and effect at work here!
From the Mir wikipedia article (linked earlier), "On a 1998 visit to Mir, bacteria and larger organisms were found to have proliferated in water globules formed from moisture that had condensed behind service panels".
If Vodka wouldn't kill it, then why would the ISS [wikipedia.org] be immune to the same thing?
From wikipedia ISS article:
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(Score: 0) by Anonymous Coward on Thursday March 05 2020, @07:15AM
If the station is infested, maybe we should nuke it from orbit.
It's the only way to be... oh wait...
(Score: 2) by Immerman on Wednesday March 04 2020, @05:10PM (2 children)
Air friction doesn't really have a delta-V, though I suppose you could calculate the delta-V loss per hour or year for a given orbit.
And really, there shouldn't be any technical issue with pushing the ISS to a higher orbit - other than that it makes it more expensive to get things too and from the station (basically, less payload per launch), and you'd probably want a weak rocket with a huge fuel tank slowly making the transition without risking over-stressing the sprawling space station that was never designed to take high thrust. That's a terribly fuel-inefficient prospect for a chemical rocket, but doable, especially with periodic refueling (which is a major unproven capability). It could be used as a reason to push development of a modust-thrust orbital "tug boat" designed to operate exclusively in orbit. (Perhaps built around a cluster of NASA NEXT ion thrusters powered by a NASA Kilopower reactors?)
The big question is, is it worth the effort? The ISS is basically a proof-of-concept station that's gradually grown over the last 20 years, with the primary mission really being to study the mental and physical health of the inhabitants. Technology has advanced a lot since it started, in a whole lot of different directions, and we're about ready to start building space stations that do something a lot more useful. If the ISS can't be readily upgraded in that direction, then it probably makes a lot more sense to scavenge the useful modules for a new space station, and dispose of the rest. Especially given that a lot of the core modules have now been operating considerably longer than they were originally designed for.
Not to mention the fact that our launch potential is poised to shortly return to payload capacities that we haven't had since the Saturn V last flew in 1973, long before anything on the ISS was launched. Basically, we're about to be able to launch much larger space station modules into orbit than anything on the ISS, far more cheaply than ever before (assuming the SpaceX Starship eventually succeeds). The ongoing value of the ISS itself is very much in doubt. I mean - consider that the passenger Starship is intended to have a greater pressurized volume in the cabin than the entire ISS combined, while likely having the payload capacity to launch the concept design Bigelow B2100 inflatable space station that provides twice that pressurized volume within a thick shell that provides ballistic and radiation defense designed to be superior to the walls of the ISS.
(Score: 2) by DannyB on Wednesday March 04 2020, @05:40PM (1 child)
I had gotten the idea in the 90s that the main purpose of ISS (unofficially) was to have a place for the Shuttle to go. Instead of doing endless circles around the earth.
And the purpose of continuing the expensive (reusable but at what cost) Shuttle was to service the ISS.
Nice, neat circular thinking. Managers like it and refer to it as: no loose ends.
Contractors like it because about four shuttle launches (I think) is roughly enough to buy another shuttle. [In Regan era, replacement shuttle $3 billion, cost of shuttle launch near program end approaching $1 billion; but I could be wrong esp. about the 2nd number]
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(Score: 0) by Anonymous Coward on Thursday March 05 2020, @12:21AM
You're pretty close to correct. Endeavour cost $2.2 billion, but that was mostly assembly, they already had most of the parts. It would probably have been somewhere in the $5-$10 billion range for a new orbiter from scratch, but they didn't need a huge fleet of shuttles, so the per unit cost isn't very important.
As for launch costs, that's about right. It cost about the same, inflation adjusted, to launch a Shuttle as it did to launch Apollo, even though it was much less capable and turned out to be not very reliable either.
(Score: 2) by tangomargarine on Wednesday March 04 2020, @06:03PM (2 children)
I'd have to look this up, but maybe they don't want to boost it to a higher orbit because where it is now gives the occupants some shielding from cosmic rays because it's not fully out of the atmosphere or something? It's not like the walls of the thing are very thick.
"Is that really true?" "I just spent the last hour telling you to think for yourself! Didn't you hear anything I said?"
(Score: 2) by ElizabethGreene on Wednesday March 04 2020, @10:52PM (1 child)
There are a laundry list of reasons that you can't push ISS into a much higher orbit. The hard problems to solve would be significantly increased radiation exposure, comm system link margin, and the power+cooling systems are designed for a ~90 minute day/night cycle.
None of the issues are such that they couldn't be overcome, but it's a lot of work for a station designed when AOL was still on floppies. There would need to be a very compelling reason to do it.
(Score: 0) by Anonymous Coward on Thursday March 05 2020, @02:38PM
So the question is which is more expensive: Retrofit or replacement?
With the newer inflatable hab designs, it is a fair question. Price per cubic foot for those are much lower. As far as utility systems retrofits, I imagine these were all designed to be modular. A few have already been replaced once. And as far as radiation go, Couldn't you just add reflective blankets to the outside of the station?
So first you have to figure out where you want to lift it to, and then do a retrofit feasability study, then do a cost comparison between that and a new station. The retrofit is doable now, the replacement with futuretech that is at least 4 years off. It doesn't matter what the schedule is for SpaceX or Boeing is. Nobody is going to contract the payload builds until they know the price point to fly them, and it takes a long time to build and test a hab. So the lack of parallelism there creates a bump in the schedule.
If you consider the time-cost of money, then retrofit is the way to go. There is interest bearing on the delay. And you can fly most of the retrofit on Falcon 9, which is a known quantity.