Upper stage plus debris, filmed by Marco Langbroek not long ago:
1) I'd say the RCS are feed from the same set of tanks, so they will also suffer from the "propellant with gas" issue. Depending on the design, they might be able to fire the large engines with a RCS propellant settling burn... but in the end, if the RCS don't burn cleanly, the docking part might be too risky to try.
- Is enough fuel available for a rendezvous via RCS only?
- Is the fuel system safe enough to keep Nauka docked to the rest of the ISS provided it's possible to get it there in the first place?
As far as I know, the MLM is currently not configured to support Progress/Soyuz dockings, it has the wrong docking ports. Both the forward and aft docking ports are of the hybrid SSVP/APAS variety while Soyuz/Progress uses the smaller SSVP docking mechanism. The one other docking port on the spherical docking node compartment is meant for the airlock currently attached to MRM-1 so it won't work either. So it has to get to ISS on its own.The MLM spacecraft carries a total of six 400-liter cylindrical tanks designated 77KM-6127-0. Two of them are used to store high-pressure gas and four others contain fuel and oxidizer under low pressure with a total mass of 2,432 kilograms. This amount is enough for the MLM to make it to the ISS after separation from the third stage of the Proton launch vehicle.
http://www.russianspaceweb.com/iss-fgb2-mlm-2017.html
Did all 4 membranes burst? Is the RCS feed from one set of tanks and the main engines from the other, or is everything connected? This could be the difference between salvaging* the module with a Progress or sending it to the Pacific.
*) It seems the propellant margin is ~30%, so even if they still have a good set of tanks I don't think it can get to the ISS on its own...
It looks like the "Earth-facing" docking port has the capability to dock Progress/Soyuz using an adapter:As far as I know, the MLM is currently not configured to support Progress/Soyuz dockings, it has the wrong docking ports. Both the forward and aft docking ports are of the hybrid SSVP/APAS variety while Soyuz/Progress uses the smaller SSVP docking mechanism. The one other docking port on the spherical docking node compartment is meant for the airlock currently attached to MRM-1 so it won't work either. So it has to get to ISS on its own.
The problem is where to get the adapter from? The only Progress available right now is the one that is scheduled to remove DC-1 from ISS. And you can't just order up an extra Progress, they're made exactly per a schedule, no extras.It looks like the "Earth-facing" docking port has the capability to dock Progress/Soyuz using an adapter:
... so the question is: can they refuel from there? (I'm 99% sure there is no way to dock a 20 tn vessel with the control system of a 7 tn vessel)
Of course, the refueling would only work if they have at least one good set of tanks.
Both Anatoly Zak and Katya Pavluschenko are both excellent and trustworthy when it comes to the details of the Russian space program. Here's a Russian source: https://nplus1.ru/news/2021/07/22/propsfor some reason, the above problems are only on Western English-language resources
the only malfunction I found was a problem with the antenna sensor