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ISS Gyro Fixed Via Spacewalk

Posted by CowboyNeal on from the better-late-than-never dept.

Teahouse writes "After a failed attempt last week, the ISS Astronauts finally got to fix the external gyroscope circut breaker in the station. Tests are being run today, but it looks like the ISS is back to having attitude stability with redundancy. This is particularly significant with the Shuttle being grounded for an extended period because the ISS would have had to use thruster fuel to keep the Station's solar panels pointed in the right direction without the gyroscopes, and no guarantee when more fuel would be arriving."

7 of 143 comments (clear)

  1. Re:Attitude stability? by Xshare · · Score: 5, Informative

    Attitude = The orientation of a spacecraft relative to its direction of motion.

  2. Re:how do gyros work?? by eingram · · Score: 4, Informative

    Maybe this will help? I can't really think of a simple way to explain it. They're a lot of fun to play with, though. :)

  3. Re:Another space station dying of neglect? by RickHunter · · Score: 4, Informative

    Never mind the collossal risk posed by an asteroid strike. Sure, the chances of a species-killer are pretty low, but the downsides are enourmous. Better to start on contingency plans as soon as we can.

  4. Re:Attitude stability? by stuktongue · · Score: 3, Informative

    Disregarding the fact that you're responding seriously to a joke, I'd like to make one minor correction to your thought, just so people understand. A spacecraft's attitude is its orientation relative to some coordinate frame. That frame might be defined such that one axis is inline with the spacecraft's velocity vector, but this is not a requirement, in general. Such a frame would be a local frame. One could easily define the spacecraft's attitude in an inertial frame (or relatively inertial) that had no relationship to the velocity vector.

    Pedantic, yes, but perhaps useful. Or not. :-)

  5. Re:how do gyros work?? by stuktongue · · Score: 2, Informative

    I'll try.

    Gyro is short for gyroscope. Did you ever play with a top as a child? Hopefully, at least once. Conceptually, a gyro is like a top; it is spun up very fast (thousands of RPM, typically), gaining a lot of angular momentum (sorry). Part of the gyro is fixed in the housing in which it resides; the rest is free to move around, typically in two axes, just like a top leans to and fro a little as it moves across a surface. The housing is mounted to the spacecraft in an orientation that aligns the gyro in a known way. When the spacecraft's attitude, or orientation, changes, the housing moves with it BUT the gyro "top" remains fixed inertially, i.e., with respect to things outside the spacecraft. Remember Newton's first law of motion? Paraphrasing, an object in motion stays in motion, maintaining it's orientation, unless something acts on it. The gyro is free to move in the housing, so its orientation remains fixed (inertially) even though the housing its in moves around it.

    Anyway, electronics in the inertial reference unit, the overall package of which the gyro is a part, sense the change in orientation of the gyro with respect to the housing and convert this into rotations about the axes the gyro is aligned with. Actually, IRUs typically put out accelerations, which must be integrated to produce rotations, but the idea is the same.

    Hopefully, that helped a bit. :-)

  6. Reasons for putting it outside by rosbif73 · · Score: 5, Informative
    The reasons were explained recently by a NASA insider on sci.space.station:
    To minimize the number of penetrations through the pressure hull (both the power source and the load are outside, in this case), minimize the number of connections through hatches (lesson learned from Mir), and minimize potential crew exposure to ammonia (used to cool external power components).
  7. A couple of reasons.. by AzrealAO · · Score: 2, Informative

    Mostly because they're integrated in the Z1 Truss Structure on the outside of the station, where it's easier to swap them out with a space shuttle and the robot arm. They're big, they have a lot of mass, they're not the sort of thing you want astronauts to be shoving around inside (where you could smash something important with them) without the help of something like the robotic arms. Putting them somewhere the Crew could reach without a space walk, would mean that they've have to put them inside the station, and they're big (there are four of them), and that's a lot of habitable volume to lose.