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I would like to be able to estimate roughly how long it takes for a 1U cubesat using a permanent magnet for passive control to detumble after the deployment at about 550 km.

Assuming there is some flexibility on size and shape of the magnet compatible with a 1U cubesat, can I expect a transition from tumbling to general alignment (with rocking) in a few hours, days, or not for months?

Are other passive damping systems necessary to include along with the permanent magnet?

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  • $\begingroup$ I believe this question is equivalent to "how long will it take for the craft's rotational kinetic energy to drop to zero" which might be a more useful form. $\endgroup$ – Roger Nov 1 '18 at 14:21
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    $\begingroup$ Question as it stands is too broad. How fast is the CubeSat initially tumbling? What orbital inclination is it in? How strong is the permanent magnet? Also, all things being equal a permanent magnet will never fully detumble - it will start rotating the spacecraft twice per orbit to align with magnetic field. Many small satellites have hysteresis rods to help with the dampening of motion. $\endgroup$ – Carlos N Feb 27 at 15:25
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    $\begingroup$ @CarlosN That's not a reasonable reason to close the question. The satellite is not launched yet, they are not going to put a rotation vector from telemetry into a Stack Exchange question. If I ask "how to calculate gravitational quadrupole moment" you don't close because "you didn't tell us the mass". I've made an edit to the question to put it in to a more answerable form. Perhaps it can stand like this now? $\endgroup$ – uhoh Feb 28 at 3:27
  • $\begingroup$ I've made an edit perhaps this doesn't need to be closed now? I've also added a bounty because now I'm really interested in the answer! Damping is certianly necessary, but perhaps the nature of permanent magnet material provides this already? $\endgroup$ – uhoh Feb 28 at 3:53
  • $\begingroup$ See for example Section 2.3.2 in An Attitude Detumbling System for the CubeSTAR Nano Satellite also available here $\endgroup$ – uhoh Feb 28 at 12:37
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For passive magnetic stabilization in CubeSats two things are required. First a permanent magnet must be used to align the spacecraft with a magnetic field. Second, a soft magnetic material must be used to damp out rotational energy. This becomes quite a bit more complicated than it initially looks though because you have to worry about various perturbation torques. If you design it poorly, it may never damp. This can happen if you pick the strengths of magnets and hysteresis material such that you get a resonance with the orbit you are in.

I worked on this problem for a 3U cubesat here is an example simulation. I believe we used a 1 rad/s initial tumbling rate (this is launch provider dependent though and will be in the launch user guide). Based on this simulation and papers I have read, I would be surprised if you could stabilize your satellite in less than one orbit.

De-tumbling and pointing of passive magnetic stabilized system

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