The combustion chamber is where the propellants mix and chemically react, which causes a rapid increase in temperature and pressure. This pushes the gases towards the nozzle exit. The nozzle is comprised of a converging section, which accelerates the flow velocity to Mach 1 at the throat; and a diverging section, which allows the gases to accelerate to supersonic speeds. Through conservation of momentum, the flow of the gases produces a force in the opposite direction of the flow, called thrust. The combustion chamber is machined out of 1018 cold-rolled steel, chosen for its machinability and low cost. Computer-aided manufacturing techniques will likely be applied to ensure precise geometry. The flame temperature of the chosen propellants will likely exceed 5000°F, so the combustion chamber must be cooled in some way to withstand these temperatures. This is done by transferring heat through the chamber walls to cool water flowing through an outer shell. The water enters the cooling shell near the nozzle throat, where most of the heat is concentrated; absorbs much of this heat, and then exits near the top of the chamber. This system is vital to the success and safety of the entire project. 1020 drawn-over-mandrel steel tube was selected for the cooling shell.
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