Relativistic Rotational Speed?

## Question:

What is the highest rotational speed ever achieved? If a theoretical substance had infinite strength and was molded into a fly wheel, say with a .5 meter radius, could the angular motion in theory approach the speed of light, if given enough rpm? Such a disk would be magnetically suspended in a vacuum using a linear motor to provide the angular acceleration.

The fastest rotational speed I am aware of is a few hundred thousand rpm in devices designed to store energy in the form of rotational inertia. Theoretically there is no upper limit on the amount of energy stored in a rotating object. As the tangential speed increases the relativistic mass will increase increasing the moment of inertia so that any further increase in speed requires incrementally more energy. The difficulty of course is in the strength of the material. The force resulting from the centripetal acceleration goes up as the rotational speed increases. Real objects fly apart at velocities well below those where relativistic effects become noticeable.

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