What are the orders of magnitude of disturbing torques on the ISS itself, preferably split into the following categories, but any numbers (with source) will be useful:

  • Gravity gradient
  • Magnetic
  • Solar Radiation Pressure (SRP)
  • Thrust misalignment
  • Mass movement


Why doesn't the ISS start to spin if people walk inside?

How well and how rapidly can the ISS attitude control system detect periods of astronaut activity?

  • 5
    $\begingroup$ You are missing what I believe is the largest torque outside gravity gradient - drag. Despite being at 400km, the ISS still encounters some atmosphere, which applies torque. I may be able to answer this question in more detail later, but probably not till tomorrow. $\endgroup$ Commented May 11, 2017 at 15:46
  • $\begingroup$ Without sources, I can say with decent confidence that your gravity gradient and drag torques will be the largest (they stabilize each other though), with your next largest being SRP. Thrust misalignment will be difficult to calculate, particularly because it will be very variable. Magnetic is very small, and mass movement again completely depends on what you're moving. What do you need to know this for? That will help a lot to answer this. $\endgroup$ Commented May 11, 2017 at 16:41
  • 2
    $\begingroup$ In addition to what @ArthurDent wrote (with which I totally concur), there are internal disturbances from the very large motors that turn the solar arrays and radiators, and occasionally, from moving the robotic arms. $\endgroup$ Commented May 11, 2017 at 16:44
  • 1
    $\begingroup$ I can produce an arbitrarily large torque with a fixed impulse of arbitrarily short duration, but it won't produce an arbitrarily large change in the motion of the station. It also makes a big difference whether you're interested in effects that would produce a secular trend in the angular velocity vector or only a transient change. Transient changes could, e.g., mess up microgravity experiments, but won't affect the station's ability to stay oriented toward the earth's surface. $\endgroup$
    – user687
    Commented May 11, 2017 at 19:57
  • $\begingroup$ @ArthurDent: I don't know if it's the largest torque. The force is around 0.275N and not much of it transfers into torque. $\endgroup$
    – SF.
    Commented May 12, 2017 at 8:39


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