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   Compute the wheel speeds for a set of reaction wheels.

   WheelSpeed generates a sun nadir pointing demo.
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   Form:
   wWheel = WheelSpeed( inrSc, wSc, inrWheel, uWheel )
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   Inputs
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   inrSc        (3,3)  Inertia of the spacecraft
   wSc          (3,1)  Wheel speed
   inrWheel     (1,:)  Wheel inertias
   uWheel       (3,:)  Wheel unit vectors

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   Outputs
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   wWheel       (n,:)  Wheel Speed

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