I've been re-reading Kim Stanley Robinson's "Red Mars". Robinson's cable was ten meters in diameter. It weighed six billion tons. Its anchor point in orbit was an asteroid named "Clarke", which weighed seven and a half billion tons.

Clarke would have been outside the asynchronous orbital altitude of 17,049 Km, measured from the surface. My calculator bashing suggests that Clarke is very roughly 2944 Km beyond the asynchronous orbit, at an altitude of 19,993 Km.

The system can be treated as a single mechanical unit with its centre of gravity at the asynchronous altitude.

When the terrorists pulled the cable out of Clarke, the cable suddendly became a separate unit with a cen