Best Position For...

[Kerbal7]

What is the best position for an Inline Reaction Wheel? Top, middle, or bottom of a rocket/object?

[OhioBob]

Doesn't matter.

[Starman4308]

Assuming a perfectly rigid vehicle, it doesn't matter.

If your vehicle is a bit wobbly, the center of mass is probably the best place to minimize torque-induced wobbling, but usually you can just stick them wherever they fit.

[Superfluous J]

I like to put them near the command module, for similar reasons to why @Starman4308 likes to put them near the center of mass.

But really it doesn't matter except on large, spindly, wobbly craft like a space station, that will likely wobble anyway.

[Kerbal7]

Thanks for the answer!

[FrostedShoe]

I usually try for the centre of mass or the middle of the stage that will be using the reaction wheels for pointing the nose because the craft will try and rotate around the reaction wheel - its not a big issue of you don't but it seems more responsive than chucking them at one end.

With really long craft, the reaction wheels controlled by the SAS system will react according the movement of the pod that is in control, not their own movement. This usually results in the top part of my rockets wobbling a little, but the bottom bit with reaction wheels flailing all over the place and getting worse as time goes on. The only solution I find is to turn off SAS and let it settle down on its own.

[GoSlash27]

25 minutes ago, FrostedShoe said:

With really long craft, the reaction wheels controlled by the SAS system will react according the movement of the pod that is in control, not their own movement. This usually results in the top part of my rockets wobbling a little, but the bottom bit with reaction wheels flailing all over the place and getting worse as time goes on. The only solution I find is to turn off SAS and let it settle down on its own.

^ This is why I keep any reaction wheels as close as possible to the controller.

Best,
-Slashy

[Plusck]

The other reason to put reaction wheels close to the controller is that they increase the amount of wobble in the craft, since they increase the number of joints. Unless you autostrut, putting a 2.5m module in the middle of the stack between 2.5m tanks can be very bad for wobble: the joints simply aren't strong enough.

[Aegolius13]

Was anyone else slightly apprehensive about what they were going to find when clicking on this post title?