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Overall view of the line (running vertically down from the main fuel valve outlet, then to the left and slightly diagonally downward) supplying fuel to the hypergol manifold.

During engine bootstrap, when the fuel pressure from this high-pressure duct is high enough, it ruptures the hypergol igniter diaphragms and forces pyrophoric fluid (fluid which spontaneously combusts upon contact with oxygen) into the thrust chamber through igniter fuel orifices in the injector.