  We investigate the effects of disorder on the propagation of one-dimensional
polariton condensates in semiconductor microcavities. We observe a strong
suppression of the backscattering produced by the imperfections of the
structure when increasing the condensate density. This suppression occurs in
the supersonic regime and is simultaneous to the onset of parametric
instabilities which enable the "hopping" of the condensate through the
disorder. Our results evidence a new mechanism for the frictionless flow of
polaritons at high speeds.
