I Can Fix The Space Station With A Metronome, A Metronome, A Metronome


If the space station were left to its own devices, the living quarters would get incredibly hot. There are computers, hardware, and six crew members, all generating heat that must be gotten rid of. To do this, there are two heat exchangers inside the station that take warm water, dump that heat to ammonia, and send that ammonia out to panels outside the station. On December 11, 2013, Loop A of the thermal control system shut down, putting the station one failure away from evacuation. Plans for a spacewalk were tabled, but the ground crew managed to fix this hardware failure by telling the astronauts to push buttons, a metronome, and a software patch.

The problem with Loop A of the Internal Thermal Control System was a flow control valve that regulated the amount of ammonia flowing through the heat exchange. Too much ammonia, and the station would be far too cold. Too little, and it would be too hot. This valve is electronically controlled and takes exactly 13 seconds to move from open to closed. The first attempt at fixing the problem was having ground crew send the command to open the valve and cut the power halfway through. This involved using a metronome app on a phone to send two commands 6.5 seconds apart. It worked, but not quite well enough.

The failure of the metronome technique led [Todd Quasny] to write a script to turn the ‘on’ and ‘off’ commands from the ground to the ISS with millisecond resolution. This meant the commands to control the valve could be sent with the right delay, but they weren’t received with the right delay. This is a problem that had to be fixed from the station’s computers.

To finally solve the problem, ISS software engineer [Steve Joiner] was called in to write a software patch for the thermal control system. This is spaceflight and writing software is a long a laborious process of testing and code reviews. Nevertheless, the team managed to write and upload a patch in just two days.

This patch gave controllers the ability to control the valve with a resolution of 100 milliseconds, good enough for very fine control of the thermal system, and all without requiring the massive amount of planning that goes into a spacewalk or resupply mission.

Ups to [Ed Van Cise] for this tip. If you’re curious about the headline….

42 thoughts on “I Can Fix The Space Station With A Metronome, A Metronome, A Metronome

  1. (The page is down so I can’t read the actual article.. but…)
    WTF?? Are you kidding me? Timing sending commands to one of the most advanced things ever built by man, by a person counting pulses from the speaker of their phone??? Is this NASA or Soviet Russia?

  2. Its like a fire on board a submarine thats hundreds of feet down. One mistake and you could kill people that have no where to escape to. For a government org, 2 days is crazy fast to get anything done with peer review too boot!

  3. This has got me wondering… are there life boats? It sounds silly, but it seems like they should have something that could reenter like the Apollo Command Module, but something tells me they don’t. Off to research!

          1. Yes! The bus had to speed around the city, keeping its speed over fifty, and if its speed dropped, the bus would explode, it was called The Bus That Couldn’t Slow Down.

      1. Gravity. The inertia keep the movement going for a long time but without the gravity to act on it, it will stop. This is because most metronomes are just simple pendulums with calibrated weights on both ends. It is possible to build a spring based metronome that will work in space however. Anyone know if Hadfield had one up there for doing music?

    1. They used a mobile application to emulate a metronome. I guess mobile apps will work on low g.
      And a metronome needs gravity to work, there must be some force driving the mass left and right…

        1. I don’t know this, but I suspect this video is not showing a platform moving in order to get some metronomes synchronised. It is showing a platform moving as a result of the movement of the metronomes. Have you seen ‘the wobbly bridge’ in London? This started shaking because some of the footfalls of the people on it happened to be in step, this made it shake a bit and more people fell into step, until everyone on it *had* to walk in step. Of course it didn’t necessarily help that the pace of a human walking happened to match up with a resonant frequency of the structure… but I believe the point stands.

  4. Reminder to all, that we (no disrespect to non CONUS readers), the United States of America – do NOT now have MANNED space flight capability ! We (thanks to the liberal social welfare tree huggers), have to “hitch” a ride (at $70 million/per astronaut) onboard Soviet spacecraft if we want to visit the ISS.

    Of course this discounts, the “black” (military) manned space flight programs
    alluded to by many on Coast to Coast AM.

    1. I imagine the astronauts like to play Angry Birds or whatnot, there aren’t a lot of entertainment options up there. Actually, the article said she had the phone specifically for the metronome app, which she used in church handbell choir practices that the crew would have.

    2. What the hackaday summary didn’t make clear was that the phone was on Earth, used by a director at Ground Control. The ISS computers could only do 1.0 second accuracy from the astronaut’s controls, but would immediately do whatever commands they received from Ground control.
      So they tried using the metronome to time sending of commands from Earth to ISS at 6.5 seconds apart. Accuracy sucked, so they refined transmission timing in software on the ground, then new software to do this sub-second control directly on the ISS, and eventually got the cooling loop operating “well enough” until the broken part could be replaced.

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