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View of the turbopump's second-stage turbine wheel.

Picture 2 of 2.

Note the black soot covering the turbine wheel; the wheel is naturally a shinier metal color. The gases which drive the turbine wheels are fuel-rich (to keep the temperatures lower), and so contains unburned fuel which exhibits as soot (not unlike an 18-wheeler when it starts to accelerate).

When I photographed the turbine the previous year, the turbine exhaust hood was still bolted to the turbine.