Extendable divergent tail pipe propulsion unit

A deployable deverging part for a thruster, the diverging part comprising:

• a first portion having an upstream end connected to the end wall of the thruster;
• a second portion in the form of a ring that is moveable between a retracted position in which it surrounds the first portion and a deployed position in which it is connected to the downstream end of the first portion so as to extend it;
• and
• a deployment mechanism comprising at least four hinged arms each having one end connected to the ring, and at least one arm having an arm-driving means enabling the ring to be moved from its retracted position to its deployed position;
• means are provided in distributed manner at the periphery of the downstream end of the first position and at the periphery of the upstream end of the ring so as to enable the ring to be locked onto the downstream end of the first portion when the ring is in its deployed position;
• and
• the at least four hinged arms co-operating with the ring to form a hyperstatic assembly, wherein the at least four hinged arms move in a substantially synchronous manner so that the ring can be moved without significant deformation so as to be brought to the desired position for locking automatically and completely to the first portion when it is deployed.