Schematic illustration of the hydrodynamic (left panel) and magnetic (right panel) drag on a moving light sail in a turbulent ISM with a magnetic field, B (green). The tumbling sail is represented by a thin gray sheet with a bumpy surface and a spin axis in the Z direction that precesses around its angular momentum, J, axis. The bombardment of atoms (with open and solid yellow dots representing pre- and post-collision trajectories) and photons (wavy arrows) leads to a force, F_gas (red), which can be decomposed into a drag, F_drag, in the direction of the sail’s velocity, v (gray), and a sideways force, F_drift. The induced currents (blue arrows) conducted away by surrounding charged particles lead to a Lorentz force, F_mag, with components perpendicular to both v and B.