ISS News and Discussion

[JB47394]

Understood we are just speculating, but if that is the situation it seems potentially very serious.

Nah. They're not on a submarine. It's a 1 bar pressure differential. It's not that different from an airliner which runs at about a 0.5 bar differential, and those constantly leak cabin air without blowing out a panel or anything dramatic. Airliners have a single wall hull of 3mm while the Destiny module has a double wall hull of 3mm each (with a thick layer of insulation between). I couldn't find information on Zvezda.

 

[ecarfan]

Here’s an article at Smithsonian.com dated today, with more information. This is an ongoing leak:

While the leak used to be releasing about a pound of air each day, that rate increased to a little over two pounds a day in early February, roughly a week before the unpiloted Progress 87 cargo mission launched to the ISS on February 14 and docked on February 17.The leak is in Russia’s Zvezda service module, in a vestibule between the port where the Progress spacecraft docks and the rest of the module, writes Space News’ Jeff Foust. The area can be sealed off to mitigate air loss from the rest of the station. The area of the module where the leak is now occurring is about three feet long. “We’ve been watching this for a while,” Montalbano said. “This area has had some leaks. In fact, we’ve repaired a couple cracks in that module part, and we’ve done some other areas of interest, so we’re continuing to watch that.”

So the general area of the leak is a known problem area.

There have been other leaks on the Russian side in recent years:

Russia first reported a leak in the Zvezda module in August 2020 and tried to seal it temporarily. Then, the nation reported a leak in a different part of its section of the ISS in November 2021, per the AP. Roscosmos had said in January 2022 that it identified the “last air leak” in the module and would fix it.

Well, not the “last”.

The Zveda module was launched and connected to the ISS in 2000 but the structural frame of the module was built in the mid 1980s according to Wikipedia https://en.wikipedia.org/wiki/Zvezda_(ISS_module)

 

[TunaBug]

Here's the article that I read yesterday: NASA monitoring increased leak in Russian ISS module

While the article does say "Joel Montalbano, NASA ISS program manager, said the leak in the Zvezda service module...", it later clarifies that...

The leak is in a vestibule known as PrK between the docking port and the rest of the module. That section can be sealed off to minimize the loss of air from the rest of the station.

Montalbano said that, once the hatch was opened after the Progress docking, it was kept open for about five days to allow crews to unload the spacecraft, then it was closed. The hatch will remain closed until early April. “We’re working with our Russian colleagues on the next steps,” he said, including future plans to access the vestibule and ways to study the leak.

The PrK leak was first detected in 2019 and has been extensively aanlyzed by Roscosmos and NASA. That included apply Kapton tape to try to plug the leak, as well as installing gauges to measure stresses on the module that could be causing cracks.

I think the "PrK" is the small spherical submodule on one end that has three docking ports. It sounds like there is a hatch separating it from the rest of Zvezda so that would minimize risk, and greatly reduce the volume of air subject to leaking.

I'll withdraw my previous comments about micrometeorite damage and Keppler syndrome as well. I would expect that the submodules that have docking ports to have more stress on them than the rest of the station, and maybe it's succumbing to fatigue?

 

[ecarfan]

would expect that the submodules that have docking ports to have more stress on them than the rest of the station, and maybe it's succumbing to fatigue?

Well…the amount of force the ports experience during docking/undocking when the spacecraft is moving at just a fraction of 1m/s would be very low. As I noted above the structural frame of the Zvezda module is now almost 40 years old. Maybe this is an age-related issue.

 

[JB47394]

I think the "PrK" is the small spherical submodule on one end that has three docking ports. It sounds like there is a hatch separating it from the rest of Zvezda so that would minimize risk, and greatly reduce the volume of air subject to leaking.

I believe it's at the other end. It's a cylinder that allows a Soyuz or Progress vehicle to dock there. Because it's on the end of an arm of the station, they can close it off without interfering with station operations. If they closed off the spherical thingie, they wouldn't be able to get into the Zvezda module.

 

[ecarfan]

It's a cylinder that allows a Soyuz or Progress vehicle to dock there. Because it's on the end of an arm of the station, they can close it off without interfering with station operations.

For reference, this is a photo (from Wikipedia) of the Zvezda module with a Soyuz docked to it.

 

[scaesare]

Nah. They're not on a submarine. It's a 1 bar pressure differential. It's not that different from an airliner which runs at about a 0.5 bar differential, and those constantly leak cabin air without blowing out a panel or anything dramatic. Airliners have a single wall hull of 3mm while the Destiny module has a double wall hull of 3mm each (with a thick layer of insulation between). I couldn't find information on Zvezda.

The difference being that a jet airliner is within the atmosphere and can re-supply the breathable oxygen to the cabin via compressor stage bleed-off... and flights are a duration on the order of hours. The ISS has a limited oxygen supply that needs to last for a duration of days/weeks.

A small leak on the latter would seem more serious than the former.

 

[JB47394]

A small leak on the latter would seem more serious than the former.

Clearly, but my point was to emphasize that there's no fear of anything as dramatic as explosive decompression. Nobody mentioned that as a possibility, but I was trying to bring the scope down in case anyone was leaning in that direction.

NASA monitoring increased leak in Russian ISS module

NASA says it is studying a long-running air leak on a Russian ISS module that recently doubled in magnitude but is not a safety risk.

spacenews.com

Montalbano said later that the leak has increased to a rate of more than 0.9 kilograms of air lost per day, double the previous rate detected in that part of Zvezda. When Progress docked to the station, he said they kept the hatch closed for about 24 hours “to let everything dampen out” and see if that affected the leak. “Nothing changed.”

So they're losing 0.9 kg of air per day.

The oxygen generator on the ISS can generate up to 9 kg of oxygen per day. It relies on the water recovery system to provide water to an electrolysis system.

There are reserves of nitrogen gas onboard specifically to account for losses associated with leakage and operations (spacewalks).

The total mass of air in the ISS is roughly 1200 kg.

I think this is why they're not worried.

 

[scaesare]

Appreciate the numbers...

Just pointing out that the comparison to a jet losing air is a substantially different scenario.

While there's not an immediate emergency threat... being like the 3rd leak in a row, and this one a crack doubled in magnitude, and venting 10% of my genrated air... is more than a tad concerning when I'm in space and not landing in an hour...

 

[ecarfan]

In his latest Deep Space Updates video, Scott Manley used this graphic of the Zvezda module, saying the link was in the “vestibule” which is between the docking adaptor and the “crew area”. Unfortunately the graphic has no label called “vestibule”. I’m still not clear where it is exactly. We’ve been told the vestibule can be sealed off without effect operations. Since the module controls and the “laptops” (labeled in the graphic) that control everything on the Russian side are all located in the smaller diameter part of the module where the solar panels attach, that clearly is not the “vestibule” area. So is it a relatively small area attached to the docking adaptor that is not clearly shown in this graphic?

 

[JB47394]

In his latest Deep Space Updates video, Scott Manley used this graphic of the Zvezda module, saying the link was in the “vestibule” which is between the docking adaptor and the “crew area”.

Look for the bulkhead just to the right of the "Crew Quarter Windows". Connected to that bulkhead is a big brown boxy structure and a white cylinder. That's the PrK, Scott's "vestibule", the thing that has the leak. It looks like it's just a tunnel that connects the docking port on the right end of the module with the rest of the module. It can be closed off to provide a double seal to the outside.

I also beat my head against this, trying to reconcile all the different names used for the area in question.

 

[ecarfan]

Now I’ve got it! Thanks. So in the Wikipedia photo that I posted upthread it is where the Soyuz is docked at the lower left of the image. Now I see why it can be closed off and not affect operations in that module.

 

[ecarfan]

Trash from the International Space Station may have hit a house in Florida​

At the time of the March 8 reentry, a NASA spokesperson at the Johnson Space Center in Houston said the space agency "conducted a thorough debris analysis assessment on the pallet and has determined it will harmlessly reenter the Earth’s atmosphere." This was, by far, the most massive object ever tossed overboard from the International Space Station. "We do not expect any portion to have survived reentry," NASA said.

Oops. It appears that statement was incorrect.

Interesting article that goes beyond just the one incident to discuss the issues involved when space debris, from rockets to very small objects come back to the surface of the Earth after an uncontrolled reentry.

Which makes me think about how difficult it is going to be to safely deorbit the ISS someday. Its huge irregular shape would seem to make it impossible to accurately predict how it will behave during reentry.

 

[JB47394]

Which makes me think about how difficult it is going to be to safely deorbit the ISS someday. Its huge irregular shape would seem to make it impossible to accurately predict how it will behave during reentry.

The greatest danger comes from stuff that has a slowly decaying orbit. Such objects pick up a bit of atmosphere in increments, and it's not clear at what point they'll begin their plunge. If the ISS was treated like that, then yes, it would be an issue of concern. Instead, they're going to do what they did with Mir, which is to attach a vehicle with braking thrusters that will ensure that the station will plunge into the atmosphere instead of just incrementally graze it.

My greatest concern would be what I assume is a relatively weak structure. They can't slap a Starship on there and fire full thrust. Copilot claims that they stick to milli-g's of acceleration when boosting its orbit. They'd have more control by deorbiting individual modules, trusses and such, but they'd never spend the money for that. It'll be interesting to see if they do anything to try to stabilize the structure for higher accelerations.

When Mir came down (deorbited by a Progress module), the debris was scattered through a 3000x200 km patch of the Pacific.

At full thrust, the Progress vehicle would have applied 0.002 g of acceleration to Mir. That's the same order of magnitude as an ISS orbital adjustment maneuver. So NASA may be planning to go through such an adjustment, but keep firing until the orbit has been decayed enough to ensure that it hits the atmosphere at a relatively aggressive rate of descent. That is, they'll want to avoid a grazing reentry as much as possible.

Note that the ISS masses ~450 tons, while Mir massed ~140 tons.

Starship 28 massed ~200 tons (including remaining propellant).

 

[fhteagle]

Is there anything they could do with the old ISS structure(s) to up cycle it? Boost it into a much higher orbit, connect the solar panels to some electronics and make it a massive unmanned communication / sensing platform?

 

[JB47394]

Is there anything they could do with the old ISS structure(s) to up cycle it? Boost it into a much higher orbit, connect the solar panels to some electronics and make it a massive unmanned communication / sensing platform?

I understand the desire to use the mass that's up there, but there is no synergy between what you're after and what you're starting from. You've got a 400 ton manned research laboratory in LEO, and you want a communications platform at some higher orbit. Perhaps GEO. The station would have to be refitted for communications and sensing, then moved. When moved, we'd be moving 400 tons to that higher orbit, most of which is devoted to being a manned research laboratory. Then there's the fact that the structure is old, and requires regular maintenance.

Of course, the real question is who wants the platform at that higher orbit? What's the cost benefit for the owner?

I've suggested similarly ambitious notions such as gathering up all the unused junk in various orbits and breaking it down for materials so that other stuff could be built from it. But even if there's 1000 tons of technology and raw materials up there, it's old, often bespoke, and we can expect Starship to launch 100-200 tons to LEO at relatively low cost in the next few years. The only reason to gather up all the unused junk is probably so that it's located in one place. Sometime in the future, perhaps somebody will want to move it all to someplace that would be happy to have any materials like that. Such as a Moon station or a Moon colony. But that's probably a pipe dream as well. We're not much on cleaning up after ourselves.