Are the Russians no longer going to dock to its leaking Zvezda module on ISS?
The Zvezda module, with aft PrK section indicated
where the cracks have been found.
In a report today at Ars Technica, Eric Berger cites two anonymous NASA officials as saying that the Russians have decided to decommission the aft PrK section of its Zvezda module where it has found numerous cracks and air leaks in the hull, apparently caused by the stress of the many dockings to Zvezda since it was launched almost thirty years ago.
Berger’s report was aimed at providing more information about the kerfuffle between NASA and Roscosmos on June 5, 2026,, when NASA had the astronauts on its half of the station shelter inside their Dragon capsule because Roscosmos was going to have its Russian astronauts cut off a structural bracket in Zvezda as part of the first phase of a new leak patch effort. NASA objected strongly to this action, fearing justifiably that the work could cause a catastrophic failure in Zvezda.
The Russians eventually backed off, merely doing measurements of the module’s new crack, which appearantly appeared after a Progress docking in April
Berger doesn’t really add any significant new details to this June 5 story, but he ends his report with this tidbit:
In the days since, there has been some additional back-and-forth, but Russia has now told NASA it will decommission the PrK module. Effectively, this means cosmonauts will no longer enter the PrK module or attempt to pressurize it. Progress vehicles will still be able to use the docking port to transfer fluids or perform other functions, but Russia will need to use other ports to move supplies on board the space station. [emphasis mine]
This quote however doesn’t tell us anything, and actually raises more questions. The Russians have already been keeping the hatch to Zvezda closed as much as possible, opening it only to unload Progress cargo. And if Progress freighters are still going to dock to Zvezda to “transfer fluids or perform other functions”, the module isn’t decommissioned. Nor is the risk reduced. One of the reasons Zvezda has been stressed over the years is that this port is along the station’s main axis, which makes it ideal for engine burns to raise the station’s orbit. Progresses have been doing this repeatedly from Zvezda for three decades. If they intend to dock with Zvezda to “transfer” fluids”, that also suggests they also plan to continue to use that port for those burns.
It also makes no sense to say other ports will be used to “move supplies” from freighters. Russia isn’t going to dock to Zvezda to transfer fluids, do engine burns, and then move Progress to a different port to transfer cargo.
Thus, we really at this moment do not know what the Russians intent. Nor do we know if they plan to continue to dock with Zvezda. And it appears that each time they do, the chances of a catastrophic failure Zvezda increases.
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I agree. But I think the biggest takeaway is just how much NASA and Roscosmos were at odds over this, and just how little the Russians were telling them. I know that the working relationship has never been free of bumps, but the picture painted by Eric’s sources, if he is accurately representing them (and they are accurately representing what really happened) looks like an almost total breakdown in cooperation.
In a way, that’s more dangerous to the ISS future than a leaky transfer module.
It would be a pain, but I don’t see the practical obstacles to doing so. Roscosmos has moved Soyuz and Progress vehicles between ports before, just as we have done with Dragons (I believe this last occurred with Progress 78 in October 2021). I expect what this could look like is that a new Progress would dock at Pirs/Nauka, transfer all supplies and take on trash, then undock and move over to PrK, dock for just purposes of doing a burn or simply transferring propellant for Zvezda to do the burn, then depart for a disposal reentry. Maybe I’m missing something here, but they have done this sort of thing before.
Now, it could be that the Russians have not made up their minds, or worse, made up their minds to do something risky and misled NASA about that intent. But that wouldn’t make Berger or his sources liars. It would just make them dupes.
The biggest question I have is this: if indeed the PrK module catastrophically failed and “unzipped,” what do NASA and Roscosmos models suggest this would do to the station’s spin and orbit, and what capability does the station and potential docked vehicles have to correct that? Because you know both agencies have to have studied such a possibility at some length.
The second biggest question I have is: What is NASA’s “breaking point” on Russian actions? But it could be that this hasn’t really been decided yet — that there’s active disagreement at top levels of the agency on what would constitute a scenario or scenarios where it’s time to give it up.
Thanks for doing a writeup on this.
Docking elsewhere for cargo and at Zvezda just the burns is absurd. It fixes nothing. It is the dockings and burns that are stressing the module and causing stress fractures.
As for a breaking point, there really isn’t any. When Clinton signed us up for this partnership, it was a deal with the devil. Until we replace ISS we are stuck with the Russians.
Also, this recent friction with the Russians is nothing new. It has been this way on and off for the past decade or so.
So does this mean they are going to depress the module to vacuum? If so, in the case of a progress burn, is there sufficient structural strength to support such a burn without pressure? Not an engineer, honest question.
All of Robert Z’s questions are valid and don’t appear to have especially encouraging answers. About the only seemingly unalloyed positive to this “decommissioning” is that the rest of the station volume will be permanently closed off from the leaking module. That doesn’t make a sudden major structural failure of said module any walk-in-the-park to deal with, but at least the crew won’t have to be scrambling to get into IVA suits if the thing finally blows out. If it was me, I’d probably be sleeping with my arms wrapped around mine and towing it around on a tether the rest of the time.
More broadly, it seems this new procedure of routine dock-move-dock of Progress could have been initiated at any time over the past several years. That it has not suggests simple bloody-minded stubbornness on the part of the Russians.
Jared needs to have a Tiger Team working on what needs to be done to operate the station without any Russian personnel or vehicles if it becomes necessary to evict them prior to ISS decommissioning. Then all preparations should be made and the Russians quietly informed of this fact. Perhaps if they knew they no longer had any leverage, the Russians would straighten up and fly right. Failing that, we could just toss them out and be done with them.
Given the growing amount of damage Ukraine is inflicting on Russia, I think there’s a real possibility the Russians may be forced to abandon ISS on their own for loss of ability to any longer participate well before decommissioning in any case.
I bet they are actually physically unable to undock the module?
What fluids do they need to transfer? Lox, LN, or water.
Doesn’t America ship that stuff up also?
As for the module popping open and moving the station. It just does not have enough gas mass to make this happen.
Hi Bob,
(I’m not nesting my replies because for some reason my phone’s browser refuses to include the authenticator on nested replies.)
I would say that I don’t know what the stresses are from just docking and undocking, or doing altitude raising burns, versus opening and closing the PrK airlock hatches. I don’t think any of that has been published. The *implication* of the article seems to be that the latter creates more stress than the former, and presumably also that the former are somehow small enough to be considered (by Roscosmos, and perhaps NASA, too?) safe enough. That being the case, that’s what informed what I wrote.
If that is not the case — if using the PrK port at all really is that high of a stressing event — then that strikes me as a grave problem, because the alternatives available for altitude raising burns are all considerably inferior to Zvezda/Progress, as things stand even now. Correction: Quick research reveals that the new Crew Dragon “boost kit” provides a total reboost impulse of 9 m/s, that is, about as much as provided by one-and-a-half Russian Progress cargo vehicles. So it actually can replace the Russian reboost’s delta-v; its disadvantages (as I understand it, I stand happy to be corrected) are that a) it is not steerable, b) can only be used when a Dragon is docked (whereas Zvezda can do a burn all by itself), and c) the Dragon would actually have to have a boost kit installed, and so far, NASA is only willing to have SpaceX install them on cargo Dragons (for safety reasons, I assume).
That said, if the risk is that high from just docking or doing burns at Zvezda’s aft end, then this may still be a safer, if more awkward, way to reboost the station. Unless the Russians refuse to agree, in which case the ISS may well become untenable.
Pzatchok,
The PrK is actually not a separate module; it is integral to Zvezda.
And Zvezda is pretty thoroughly connected to Zarya, and after 25 years in space there’s a question of how easy it would be to disconnect, due to material degradation. Anyway, it is the central node of the Russian side.
“”part of the first phase of a new leak patch””
This entire phrase above just unnerves me. Space is very unforgiving.
Richard M wrote:
“”I’m not nesting my replies because for some reason my phone’s browser refuses to include the authenticator on nested replies.””
Same here. I tried different phones, same thing. I will try my laptop and see what happens. This belongs in the category of First World Problems. Not too worried, just wanted to let you know.