The invention relates to a propulsion nozzle (21) for the expansion of a supersonic gas jet (25), that comprises a divergent skirt (27) in which the combustion gases (25) are expanded before being ejected into a surrounding medium (55) outside said skirt (27) substantially along the axis (X) of the nozzle (21). The nozzle of the invention is characterised in that the skirt (27) includes at least one channel (29) for supplying a fluid in the vicinity of the free end (32) thereof, means (33, 37, 39) for the annular collection of said fluid around said skirt (27), said at least one channel (29) opening into said collecting means, and means (51, 41, 47, 49) for discharging said collected fluid in the form of an accelerated secondary flow in a direction substantially following the axis (X) of the nozzle (21), and means ensuring a supersonic secondary flow.