High temperature composite nozzle extensions, a mature and efficient technology to improve upper stage Liquid Rocket Engine performance.

The need to increase the payload capacity of the current launchers drives rocket engine manufacturers to seek higher thrust level, specific impulse and thrust to weight ratio. An efficient way to do this is to use of increased expansion ratio nozzle extensions for upper stage engines, using high temperature composite materials in order to allow higher temperature material capability, and take benefit of the outstanding thermal, mechanical and fatigue resistance of these materials to decrease mass. Up to the mid 90s, the use of Carbon -Carbon (C-C) or Carbon-Silicon carbide (C-SiC) composite nozzles was limited to solid rocket motors, but challenging performance reqirements led to C -C nozzle extension flight qualification on the RL10B-2 engine of the Delta IV upper stage, in the late 90’s, and both materials are planed for use on the next Ariane 5 ECB upper stage generation powered with the liquid Vinci ® engine. Both engines are equipped with very large extendible composite nozzles developed and produced by Snecma Propulsion Solide, SAFRAN Group. This paper describes the technological background of Snecma Propulsion Solide in the design, materials and manufacturing of high temperature composite nozzles inherited from solid rocket motors and extended to liquid rocket engines. It provides an up-to-date status of the demonstrations already performed on different liquid rocket engines and details all of the recent progress on technical and manufacturing performance. The manufacturing process has also been improved and simplified in order to allow the manufacturing of larger scale nozzles at lower cost.