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Detail of the first-stage nozzle.

After being admitted to the turbine inlet manifold, the hot gases from the gas generator move in a clockwise direction.

For some reason, when reading about turbopump turbines, I envision the blades on the turbine wheel to be more-or-less flat, like the blades on a fan. On the contrary, the blades on the turbine are cupped, more like a waterwheel (although I was not able to pose a photo which clearly showed this). The vanes on the first-stage nozzle keep the gases moving in a predominantly clockwise direction, where they engage the first-stage turbine wheel.

The second-stage nozzle is visible at the extreme right of this photo.