Raptor is a full flow staged combustion engine [0], that means that the preburner exhaust is fed into the main combustion chamber. This is more efficient than d

Raptor is a full flow staged combustion engine [0], that means that the preburner exhaust is fed into the main combustion chamber. This is more efficient than dumping it separately like it happens on the Falcon 9 engines [1]. The black, sooty smoke on the first image of the Wikipedia article [1] is the (kerosene) fuel-rich preburner exhaust of the Merlin engine. [0] https://en.wikipedia.org/wiki/SpaceX_Raptor https://en.wikipedia.org/wiki/SpaceX_Raptor [1] https://en.wikipedia.org/wiki/SpaceX_Merlin https://en.wikipedia.org/wiki/SpaceX_Merlin