Tennis racket theorem (Dzhanibekov effect)

What you are seeing: a free rigid body obeying Euler's equations. Spin it about its longest or shortest principal axis and it spins steadily. Spin it about the intermediate axis and the tiniest wobble grows until the body suddenly flips, over and over, even though energy and angular momentum are exactly conserved. This is the tennis-racket / Dzhanibekov instability.

Figure 1. Free rigid-body rotation with I1 < I2 < I3. Method: RK4 on Euler's equations plus quaternion kinematics.

objectT-handle

spin axisintermediate

spin rate6

perturbation0.040

WHAT TO TRY

Vary each control and watch the rail readouts respond.
Compare the diagnostic plot against the live scene.