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View of the liquid propellant gas generator (LPGG).

Picture 4 of 4.

The liquid propellant gas generator is essentially an inefficient rocket engine, consuming high-pressure LOX and RP-1 from the engine's turbopump, whose output gases are used to spin the turbopump's turbine during the engine's maintstage operation. To keep operating temperatures down, the LPGG was run fuel-rich, so the output gases were dark with soot. After spinning the turbine, these gases were routed through the heat exchanger and through the engine's aspirator, where it mixed with exhaust gases from the main thrust chamber.

Visible here is the upper portion of the LPGG and the part which leads to the inlet to the turbine manifold (at right).