Hills Equations

There's a name for objects in "toroidal orbits" - Hill's equations, in the "Hill's frame."

This paper:

claims the equations below are found here:

but I don't see them in that three equation form.

\ddot x - 2 \omega \dot y - 3 \omega^2 x = f_x ... x is the radial direction

\ddot y + 2 \omega \dot x = f_y ... y is the orbital direction

\ddot z + \omega^2 z f_z ... z is perpendicular to the orbital plane. Right handed triad mentioned in Burns, the equation works with left triad, too.