Function flip_angular_momentum 

pub fn flip_angular_momentum(
    mass_kg: f64,
    radius_m: f64,
    angular_rate_rad_s: f64,
) -> f64

Angular momentum for a flip maneuver (kg·m²/s).

Given ship mass (kg), characteristic radius (m, distance from center of mass to thrust point), and flip angular rate (rad/s), returns the angular momentum about the rotation axis.

Approximates the ship as a cylinder: I ≈ 0.5 * m * r²