To provide a method of forming a cooling system for a rocket engine combustion chamber.

The method comprises steps of providing a plurality of tubes 22 each formed and shaped into a profile of a nozzle with each of the tubes having a constantly expanding cross section in an upper chamber region, providing an inlet manifold 32 and an exit manifold 30 having a plurality of holes for receiving the end of each tube, inserting a brazing preform 31 into each hole, inserting the first end of each tube into the inlet manifold and the second end of each tube into the outlet manifold so that the first end is surrounded by a first brazing preform and the second end is surrounded by a second brazing preform, and brazing inlet and outlet manifolds to the tubes. The brazing step forms a series of brazed joints between the tubes and the manifolds. Further the method includes steps of forming a layer of coating material 34 on exposed portions of the tubes, and forming a single piece jacket construction 36 around the tubes.