On the motion of particles in a plasma and in plasma sheaths in the absence of external forces

'Frictionless' particles have been observed in regions at the edge of plasma in several different plasma reactors. Whilst it is difficult to explain why spheres, even with the right initial boundary conditions, appear 'frictionless', it seems possible for cylinders, given the right 'angle of attack' to surf in the ion stream of the plasma sheath. However, continuous motion of cylinders has also been observed in the main plasma in an experiment in which gravity was compensated by thermophoresis. In general, we conclude that particles of asymmetric shapes may reach high limit velocities independent of the initial boundary conditions. Other 'hollow' shapes which structures of the order of the Debye length have different collection areas for ions and neutrals and may reach even higher limit velocities.