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Detail of an igniter poppet on the injector face.

Picture 2 of 2.

The igniter fuel, from the engine's hypergol container, entered the combustion chamber via six of these igniter poppets. The igniter fuel, triethylaluminum (TEA), is a clear, colorless liquid used by the engine's hypergolic ignition system. TEA is pyrophoric, igniting spontaneously in the presence of any source of oxygen, and reacts violently with water, alcohol, acetone.

These poppets were later replaced by igniter buttons, which looked much like flat-head screw heads (and which looked similar to those used on the F-1 injector). The igniter buttons were more reliable, fouling less than the poppets. On the baffled version of the injector, there was an igniter button in each compartment, including the circular center compartment (the igniter button being located in the injector's center hole).