Fuel & Reaction

The SSMEs use the cryogenic hydrogen and oxygen contained in the ET as their propellants. The liquid hydrogen is the fuel, while the liquid oxygen acts as the oxidizer.

The hydrogen and oxygen enter the engine through separate fuel lines. Some of the super-cold liquid hydrogen is separated from the rest and flows through the walls of the nozzle and main combustion chamber to cool these parts of the engine.

The rest of the hydrogen is fed into a preburner where it meets up with some of the liquid oxygen. The two cold liquids react with each other and burn to produce an extremely hot gas that drives the engineƕs turbopumps.