Abstract: A diverging ring is displaceable between a retracted position in which it surrounds a first portion of a diverging part and a deployed position in which it is connected to a downstream end of the first portion. A deployment mechanism causes the diverging ring to move from its retracted position to its deployed position under drive from an actuator. A temporary structure, or “insert”, is placed inside the diverging ring so as to transform the diverging section thereof into a non-diverging section, at least over the major portion of the length of the diverging ring, the insert being eliminatable on or after the diverging ring coming into its deployed position.

Abstract: The deployable diverging part comprises a first portion (20) having an upstream end connected to the end wall (14) of the thruster, a ring-shaped second portion (22) that is movable between a retracted position and a deployed position in which it connects to the downstream end of the first portion (20) to extend it, and a deployment mechanism comprising a plurality of hinged arms (30). Means (50, 52) are provided in distributed manner at the periphery of the downstream end of the first portion and at the periphery of the upstream end of the ring to enable the ring (22) to be locked onto the downstream end of the first portion (20) when the ring is in its deployed position, and the deployment mechanism comprises at least four arms (30) co-operating with the ring (22) to form a hyperstatic assembly so that the ring can be displaced without significant deformation so as to be brought into the desired position to lock automatically and completely on the first portion (20) when it is deployed.