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I am thinking of having a reaction wheel cluster set up in a physics lab for educational purposes. I would like to find out what the available options to me are. Here are some more specifics:

  1. I see that there is a commercial, educational option for control moment gyroscopes here. However, the reaction wheels I can find online are mostly space-grade, which is over-kill for my purpose (but more importantly these don't come with gyroscope mountings as they are meant to be sent straight into space). On the other hand, there are several DIY reaction wheel projects, such as those built with Lego, but those are too small scale and wouldn't be able to demonstrate 3 DOF attitude control. Is there an intermediary option available between the two?
  2. How are reaction wheel clusters mounted in a laboratory setting for testing? To simulate attitude control in zero-gravity, I'd imagine that the Center of gravity has to coincide exactly with whatever string is suspending it, which might be mechanically tricky. As such, setups like the Cubli, where there is a constant disturbance torque acting on the setup, would not be ideal (or is this the norm in ground testing of reaction wheels systems?). How is this usually being done? Is there a commercial option out there I can get, instead of having to fabricate gyroscope mountings and the platforms myself? (which I don't know how to)
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  • $\begingroup$ AFAIK, literature which deals with testing of attitude control in a lab setting mostly restrict themselves to 1DOF (air hockey table like setup). Could you find lab test setups where 3dof testing is conducted? $\endgroup$
    – AJN
    Mar 21 at 12:28
  • $\begingroup$ There isn't really any point in testing 3DOF reaction wheel control in the lab (at least in the space industry) - the technique is very well understood and has so much heritage that there isn't any need to do lab testing (and instead is covered by simulation). Individual reaction wheels may tested on their own, but that is about testing how the reaction wheel performs rather than demonstrating attitude control. $\endgroup$
    – Rustony
    Mar 21 at 12:40
  • $\begingroup$ I have a post somewhere (can't find it now) of NASA SPHERES or AstroBees being tested on an air suspension table (like a fancy air-hockey table) but here's something similar youtu.be/sbBQONITclk?t=216 Rather than all fans, you could have one fan for propulsion and at least one reaction wheel to turn. If your test "satellite" was mounted in a gimbal you could also do articulation. If you are really crazy-ambitious, you could consider this, but don't try it at home! Does this kill vehicle contains momentum wheels? Watch how it moves! $\endgroup$
    – uhoh
    Mar 23 at 10:43
  • $\begingroup$ youtu.be/cqFA1yZy7k4?t=38 See also this answer to Which rover(s) didn't have wheels? (Minerva-II) and How does the hopping mechanism of the Minerva II rovers work? and especially The Cubli - a cube that can jump up, balance, and walk $\endgroup$
    – uhoh
    Mar 23 at 10:53

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My approach would be to adapt off-the-shelf components marketed for model jet aircraft . The brushless motors are amazingly torquey. If you remove the fans, you can use them as reaction motors. You could mount wheels on the motor shafts, but I bet the momentum of the rotors themselves would be adequate for demonstration purposes. The speed controllers, batteries and transmitters are plug-and-play.

Make a hollow sphere by part-filling a vinyl beach ball with epoxy resin. Keep the ball tumbling until the epoxy sets (maybe use a modified rock tumbler or 33 1/3 rpm turntable?), then peel the ball off and cut the sphere in half. Mount your reaction wheel-battery-receiver device inside and glue the sphere halves together with silicon. Provide through-hull contacts for charging. The budget would be hundreds, not thousands, of dollars.

Float the device in a bucket of water and fire up the RC controller.

The contraption could also be used as a demonstrator planetary surface exploration rover. Or just have fun chasing your cat.

Similar components (with fans left on the shafts) could be used for a demonstrator reaction control thruster.

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  • $\begingroup$ The hollow sphere floating in water would only work well if the center of mass is located precisely in the center of the sphere. If not the sphere would always turn by itself to an orientation where the center of mass is as low as possible. If all masses are well balanced there is no preferred orientation of the sphere when floating free. $\endgroup$
    – Uwe
    Mar 23 at 21:36
  • $\begingroup$ @Uwe ... yes, the project would require fabrication skills including balancing the device. Adhesive weights used for balancing motorcycle wheels would make quick work of the task. $\endgroup$
    – Woody
    Mar 23 at 23:21

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