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Phys.org's NASA's Perseverance Mars rover gets its wheels and air brakes has some interesting photos includes some nice photos and below I've included a cropped section of a photo of one of Perseverance's six 53 cm diameter wheels.

I noticed that the spokes extend radially from the hub, then turn 90 degrees inwards then turn 90 degrees in a spiral direction, connecting 60 degrees later.

That last section in the spiral direction has a cross section that makes it particularly stiff in the radial direction, so I don't think this is a kind of spring, or if it is, it's behavior is more complex than I can figure out.

Question: Why does the Perseverance rover have such complicated shaped spokes in its wheels?

This wheel, and five others just like it, heads to Mars on NASA's Perseverance rover this summer

This wheel, and five others just like it, heads to Mars on NASA's Perseverance rover this summer. Wrapped in a protective antistatic foil that will be removed before launch, the wheel is 20.7 inches (52.6 centimeters) in diameter. The image was taken on March 30, 2020, at NASA's Kennedy Space Center. Credit: NASA

PIA24482: Perseverance Hazcam First Drive, Shamelessly cropped, stretched, contrast and sharpness-modified

Shamelessly cropped, stretched, contrast and sharpness-modified from PIA24482: Perseverance Hazcam First Drive in order to show some detail from the opposite side.

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This NASA page says that the wheels are:

Made of aluminum, with cleats for traction and curved titanium spokes for springy support.

The curved part running ~60 degrees along the rim isn't quite in contact with it. It will act as a spring with a hard stop. Having the spring effect in this direction should allow the wheel to remain reasonably aligned even when the hub is momentarily off-center.

As indicated in the comments, this page about Curiosity's (similar) wheels identifies the spokes as "wheel flexures (spokes)".

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  • $\begingroup$ This page is about Curiosity but the spoke design seems quite similar. They are called "wheel flexures (spokes)" in the text and as annotated in the figure, which supports this conclusion as well. I think you can consider adding that to your answer as well. It's not yet clear which direction of flexure is most important, the cross section appears to be much thinner in the axial direction than the radial direction. Thanks for your answer and Welcome to Space! $\endgroup$
    – uhoh
    Commented Apr 4, 2020 at 21:39
  • $\begingroup$ I don't see further conclusions necessarily but there are some nice images in these: 1, 2, 3, 4, 5 $\endgroup$
    – uhoh
    Commented Apr 4, 2020 at 21:53
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    $\begingroup$ I find compliant mechanics to be extremely satisfying to watch or read about. For lack of a better word, its just sexy. $\endgroup$
    – Stian
    Commented Feb 25, 2021 at 12:13
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    $\begingroup$ I think also that this lets you have something more than a hard stop: it lets you have two spring constants. Until the part running along the rim is in contact with it you'll have quite a low constant, but the moment it is in contact with it you'll be bending the radial part of the spoke, which will have a much higher (but not infinite!) spring constant. This may be what you mean by 'hard stop', in which case sorry. $\endgroup$
    – user21103
    Commented Mar 7, 2021 at 10:49

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