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Detail of the first injector.

Picture 3 of 4.

Several of the copper rings comprising the face of the injector have been knocked loose, showing the inner structure. The injector face is made up of alternating rings which spray either fuel or oxidizer. The holes in the rings (still visible near closer to the center of the injector) are arranged in "impinging pairs," which spray streams of propellant toward each other, atomizing the propellant to promote combustion.

Two fuel igniter housings (which look a bit like standard screw heads) are visible above and below center of this photo. During engine ignition, a fluid which is pyrophoric (ignites spontaneously in the presence of oxygen) called triethyl aluminum-triethyl borane is sprayed through these igniters. The TEA-TEB mixes with the atomized LOX already present in the combustion chamber, igniting. Fuel soon flows through the injector, igniting and sustaining the combustion.