Figure 3 from September Inspector General report, annotated to show Zvezda and Poisk locations.

According to information obtained by Anatoly Zak at RussianSpaceWeb.com, the “toxic smell” detected by Russian astronauts immediately after opening the hatch to unload the newly docked Progress at ISS was actually a small but very dangerous amount of hypergolic fuel left over from the previous Progress freighter.

[T]he working hypothesis was that the ground control failed to perform a routine purging of propellant lines between the station and Progress MS-27 before its undocking. As a result, highly toxic residue of hypergolic propellant remaining in the lines could easily spill into the main cavity of the docking mechanism on Poisk, once Progress MS-27 undocked from the module, an industry source told RussianSpaceWeb.com. After the arrival of Progress MS-29, the interior of the docking mechanism between the space station and the cargo ship was re-pressurized trapping the propellant residue and letting it into the station after opening of the hatches. [emphasis mine]

If true, this incident indicates a shocking level of incompetence, sloppiness, or even malice at Russian mission control. How can mission controllers forget to do a “routine purging” of hypergolic fuel, especially when it is known that this very dangerous fuel — which can dissolve skin if you allow yourself to get in contact with it — can “easily spill” into the docking port where people will travel?

The Russian government pays its top-level engineers very little, even as those engineers watch often bungling managers rake in big bucks through legal deal-making as well as bribery and embezzlement (only rarely caught and punished). These circumstances have been suggested as behind the various suspicious leaks in Soyuz and Progress capsules as well as the new Nauka module. In the case of the Soyuz, it was clearly caused by someone drilling a hole on the ground before launch and then fixing it with a makeshift patch that was certain to fail during the mission in space. Both the Progress and Nauka leaks also suggested a similar cause. The Russians told NASA its investigation discovered who drilled that Soyuz hole, but never revealed what it had found. As for the Progress and Nauka leaks, no investigation results were ever even discussed.

There is something distinctly rotten within Roscosmos, a rottenness that it appears Russia is doing little to fix. More likely it can’t really fix it, because the Putin administration in the late 2000s made Russia’s aerospace industry a remake of the Soviet Union, a single government-run corporation that owns everything and blocks all competition. Since then it has shown a steady decline in its ability to accomplish much and the steady growth of problems such as this.

The sooner Americans no longer have to partner with Russia the better. We must hope that NASA can at least get to 2030 and its planned retirement of ISS without a major failure. This leak occurred within the Poisk docking module that is attached to the larger Zvezda module where air is leaking from the station due to serious stress fractures in its hull. Each docking puts more stress on Zvezda, risking a catastrophic failure, so much so that it is now NASA policy to close the hatch between the American and Russian halves of the station whenever such dockings take place.