Why was the Sabatier system removed from the ISS USOS?

Question

In 2010 a Sabatier system was added to the Regenerative ECLSS part of the US side of the International Space Station. This system created usable water from hydrogen and carbon dioxide waste gases.

A 2018 presentation about the Robotic External Leak Locator states that the Sabatier was removed from the ISS in 2017.

What happened, why didn't it work out?

Rats, that would have been really useful to get in space experience with. — geoffc, May 21 '20 at 12:57
IIRC, it kept shutting itself off. Parts failed, were replaced, and failed again. It was one of many failed experiments that NASA deemed to be a success but never used again, like tethers. — David Hammen, May 21 '20 at 13:33
Yeah, sounds like Robonaut. Looking for some details though. — Organic Marble, May 21 '20 at 13:47
From a 2019 conference paper titled International Space Station as a Development Testbed for Advanced Environmental Control and Life Support Systems, emphasis mine, "The Sabatier Reactor Assembly (SRA) that was operating on ISS will be upgraded and returned to the ISS for continued operation. The unit was returned to the ground for evaluation in 2017." I however can't find any indication that it has been / will be upgraded and returned to the ISS. — David Hammen, May 21 '20 at 14:53
@DavidHammen the annual "Status of ISS Water Recovery and Management" papers available on ntrs give some insight (including a statement that a new unit is planned) but details are still sketchy. — Organic Marble, May 21 '20 at 14:59
I don't have any insight into the Sabatier reactor, but I know that CDRA was giving them utter fits a couple years ago. I don't know what process that particular piece of hardware used. — Tristan, May 21 '20 at 16:27
There are some references in the ISS On-orbit status reports but I'm gritting my teeth and trying not to answer my own question here :0 — Organic Marble, May 21 '20 at 16:33

Apaiss · Accepted Answer · 2020-05-22T00:55:44.827

Figure 4. Timeline of Recent OGA Events The timeline say the Sabatier was removed and returned at 11/28/2017 for TT&E.

2019 - Advanced Oxygen Generation Assembly for Exploration Missions - Kevin Takada et al source

This below is what I was able to find, with more detailed information.

The performance of the Sabatier reactor degraded over the last several years and was removed from service in October 2017 and returned to ground for a failure investigation. The ISS Program Office is currently planning to build another Sabatier reactor for operation on ISS in 2020. source

11/28/2017 Crew Removing the Sabatier unit from the Oxygen Generation System (OGS) Rack. From on-orbit report

01/27/2017 Sabatier Restart: Last month, the Sabatier system could not be restarted after being in Standby for an extended period of time. During the attempted restarts, the system showed little to no reaction occurring in the reactor and no water being produced. Yesterday, ground teams executed a procedure to warm up the reactor prior to a restart attempt and successfully restarted the Sabatier. The team believes that the higher temperature and additional duration of the heat soak allowed the reaction to kick off. Water continued to be produced overnight. From on-orbit report

Another failure reported, from 2013: (...)The original failure was due to delta pressure fault detected at the inlet to the reactor assembly. The second attempt was unsuccessful when liquid water was detected on both liquid sensors on the Sabatier vent line. After allowing the liquid sensors to dry out, the ground performed a third attempt which was successful. Sabatier was operational overnight before faulting out and shutting down once again. This last shutdown was due to another delta pressure fault. The fault signatures are indicative of moisture in the CO2 accumulator which is partially blocking flow. Sabatier team is concerned with moisture being received from Carbon Dioxide Removal Assembly (CDRA) or condensation that has accumulated in the CO2 accumulator tanks. on-orbit report

I didn't get more details about the failures. It is interesting that the link you used in your question says at the end "Last updated: 7 August 2017". But it seems that it was not, because even the return to TT&E the link/text does not mention. Just 2 months before, they could to add it info.

More info about the subject: A Sabatier reaction based CO2 Reduction Assembly (CRA) is a hardware that interfaces with the Oxygen Generation Assembly (OGA) and Carbon Dioxide Removal Assembly (CDRA), using the Carbon dioxide available from CDRA and the hydrogen that is available from OGA water electrolysisis. When CRA is activated it produces methane and water via the Sabatier reaction CO2 + 4H2 <-> CH4 + 2H2O source

All of that components are part of the ISS Environmental Control and Life Support System (ECLSS)

Can you expand a little bit on the relation between the OGA and the Sabatier for those who might not know? And I'd like some specifics on what was wrong with the Sabatier. If the info is in those links, best to summarize them in the answer. As written, this says when, but not why. — Organic Marble, May 21 '20 at 17:25
yes, sure, I can elaborate this better. Anyway, about the relation between OGA and Sabatier is at your answer in that Q: "How close is the ISS to a closed system, in terms of carbon, hydrogen, and oxygen?" — Apaiss, May 21 '20 at 17:53
Edit greatly improves the answer, thanks! I usually wait a day or so before accepting. — Organic Marble, May 22 '20 at 01:07

Why was the Sabatier system removed from the ISS USOS?

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