There is a nice little article at IEE Spectrum about the failure of the ISS on-board computers. Here is a quick summary, with my own analysis of information from the article.
Back in June, a new solar power set was added to the International Space Station. Soon after, the three Russian built computers that control the ISS failed. This caused problems like the atmosphere control system locking up, and the autopilot to no longer control the maneuvering thrusters.
Fingers started being pointed back and forth. The Russians blamed the new solar power array and NASA for the computers failing. Then it could have been electromagnetic buildup of the ISS moving through the Earth’s magnetic field. Finally, it was decided that something in the power monitoring and management system must be at fault, and these were bypassed using jumper cables. Ta da! The computers came back up.
Now, the people on board the station began taking the bypassed system apart to see if they could find the problem. It seems that there was condensation on, and in, the system, and that some of the control wires (called command lines) had corroded and the one that is the computer’s version of E-STOP (Emergency STOP) had shorted out, causing the system to immediately shut off. This was designed to keep power spikes from killing the computers. However, it allowed all three to be brought down by a single short.
The source of the humidity and corrosion seems to be a dehumidifier that vented over that control panel. The idea was that the power in the cables, and continuous warm air from the dehumidifier, would keep water from condensing on the cables themselves. However, the dehumidifier doesn’t run continuously, and this caused intermittent bursts of warm, humid air to be blown onto/into the panel where those cables are. Also, it seems another part of the dehumidifier was blowing cold air onto that panel, allow condensation to form in the panel and on the cables.
When the unit was removed water droplets and mold were found and the unit itself had condensate on it. Affected components were replaced and the crew decided to rig a thermal barrier out of a surplus reference book and all-purpose gray tape.
OK, now for my fun.
Jumper Cables – Who says NASA and NASCAR have nothing to do with each other? Jumper Cables! Was this in AAA’s Emergency Road Assistance Kit?
E-STOP on all three computers – So, an E-STOP but no battery backup… is it just me, or is there a problem with this setup? Don’t get me wrong, a good power cutoff is necessary to keep a system from becoming like KFC chicken, but it would be advisable to have some method of indicating what happened, like a relay that flips, an emergency light, a Klaxon or something.
surplus reference book and all-purpose gray tape – So, a manual and duct tape is being used to provide a ‘thermal barrier’ for the system. Why do I feel that we will see the ISS under “emergency manual control” again before too long? I do have a question about this, was that duct tape… sorry, all-purpose gray tape, part of the Car Kit with the Jumper Cables, or was it part of a different emergency repair kit?
Russian space engineers still couldn’t keep unwanted condensation at bay – I would like to know why no one at NASA thought to ask “hey, is having this dehumidifier blowing onto the power management system for the computers a good idea?” Maybe it should have gone along with “maybe we should identify some systems, like those that would be screwed if it got wet, and setup a schedule to look over those?” How about “maybe we could include some of those Silica Gel desiccant packets with the modules?”
drops of humidity and mold were discovered – Was this normal mold, or black mold? Maybe a mold test kit should be sent up. You know, an air-sample kit or two. Let’s also send up some HEPA filters, or at least some ASHREA MERV 13 or higher filters for that place.
What does this make the ISS now?
So, given these things, what is the space station? Quick review:
- Jumper cables to bypass power cutoff
- Power loss when plugging something else in
- A book and duct tape used to seal up leaks
- No one stopping to ask if something really was a good idea or not
- Water leaks and mold
Yep, the ISS has become a trailer in the south. Or, if you wanted to count each module separately, then it is an entire trailer park.
Something witty, part deux 
nice