# What would happen to the ISS if the Russians undocked their part?

So... RIA Novosti (Russian media agency) made a video, where they show the Russians ostensibly undocking the Zarya module and the US part of the station falls into the atmosphere (someone was playing with Kerbal Space Program since the US part wouldn't fall immediately as it does in the video). It's unlikely that the Russians on the ISS would endanger their own lives like this, but we live in strange times.

Obviously bad things would happen eventually, but what would happen in the short-term? Would the US crew immediately have to abandon their part? Could any sort of fix be applied?

• It would take EVA, maybe multiple EVAs to detach the two segments. Look at all the external cables that cross the interface in this rendering. Also, as @DavidHammen points out, the US owns Zarya. i.imgur.com/ZYcztgi.png Mar 9, 2022 at 20:25
• Strange, eh? Like that one time two humans shook hands in space and ended the Cold War? It's unlikely that anyone on the ISS would endanger their own life's work or anyone else's involved, country of origin notwithstanding. Fatalities are not even in question. They are literally above that. Mar 10, 2022 at 1:27

The US Orbital Segment maintains ISS attitude, so tumbling is not an immediate problem. The need to desaturate the control moment gyros used to maintain attitude and the need to reboost the ISS to maintain altitude will eventually be a solvable problem.

If Russia did undock the Zarya module, I suspect a near immediate response would be the US would withdrawing over \$200 million from the Russian assets the US has frozen. Zarya was financed by the US. That money would pay for some resupply missions. • Probably not that simple. It would depend on weither the detaching of Zarya can be considered a breach of a commercial contract, an act of war, or an act of piracy. Lawyers alone may get more than$200M. Mar 10, 2022 at 8:47
• @fraxinus You are correct in that it is not as simple as I presented. Should Russia detach the Russian Orbital Segment from the USOS that would pretty much spell the end of the primary rationale for the ISS's existence. The ISS was built largely due to the promise of Russian cooperation. President Clinton was this close to canceling the previous incarnation of the ISS, Space Station Alpha, until diplomacy mechanisms got Russia involved. Mar 10, 2022 at 14:04
• @Graham if the US and Russia go to war, what happens to the ISS and how we pay for it will be the least of our problems. Mar 11, 2022 at 6:35
• @fraxinus I'm not sure why you put "Russian segment" in scare quotes. The ISS comprises two main segments that in English are officially called the Russian Orbital Segment and the US Orbital Segment. A Visiting Vehicle that docks with the ISS at one of the seven ROS docking ports needs to work with Roscosmos to satisfy ROS interface requirements. A VV that docks with the ISS at one of the five USOS docking ports needs to work with NASA to satisfy USOS interface requirements. Mar 11, 2022 at 7:15
• @fraxinus Would that make the Russian cosmonauts space pirates? Mar 11, 2022 at 12:52

Spacecraft such as Cygnus has previously been used to boost the ISS and might be used again, although with some difficulty with finding an appropriate launch booster. https://en.wikipedia.org/wiki/Cygnus_(spacecraft)

Dragon resupply craft might also be used, although it would be far from optimal due to the positioning of the thrusters among other things.

There are many other complicating factors such as the availability and position of docking ports and the time frame. One further complicating factor is the US astronaut Mark Vande Hei who is scheduled to land in Soyuz-MS 19 on the 28th of March. Other arrangements could be made but nothing is straight forward.

https://forum.nasaspaceflight.com/index.php?topic=55602.160

Not a good day for sure. However boosting into higher orbit is most often done by attached visiting spacecraft that also can take over the attitude control if needed. And American Cygnus seems docked right now. It can dock automatically same as Progress that once took attitude control over Mir so likely has comparable capabilities.

Hence very immediate catastrophic reentry is unlikely. Also USA part does have life support systems on its own that may pull out. The "Electron" oxygen generator in Zvezda is long dead anyway, as well as its main computer (three laptops are running as replacement). Zarya is also now little more than optional storage space.

Russians could also fight, and if they win, destroy the station. This looks mad enough to consider unlikely even if such an order would be given. They are skilled, bright-minded experts with the mind set for friendly co-operation.

I think the scenario would just require launching more supply ships than planned, and companies like Space X would be happy to arrange this.