Making a SpaceX Engine

A separate building contains the manufacturing flow for the Merlin 1D engines. The shiny nozzle here has channels etched vertically in it for the fuel to run down and back up, keeping the nozzle from melting during use. The nozzles at the far end of the room have those channels and are ready for a metal jacket to cover them. This is much more elegant than the individual brazed tubes used in the earlier Merlin engines, or the RL-10 used on other rockets.