How are rocket nozzles made??
Is it a huge chunk of metal that they cut down or is it a "pipe" that they reshape?
Or something else??
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There are many kinds of nozzles, and many ways to manufacture them. Here is a sampling.
Actively cooled nozzles such as the the SSME and F-1 nozzles were constructed by fabricating the individual tubes that made up the cooling channels (1080 tubes in the case of the SSME) and brazing them together in an autoclave. Nozzle fabrication was one of the pacing items in building an SSME; at one time I was told it took over a year to complete one nozzle.
Modern actively-cooled engine nozzles may be constructed using channel-wall technology pioneered in Russia.
Radiatively cooled nozzles such as the shuttle OMS engines (which have been cannibalized to use on the Orion service module) are formed of high temperature metals such as columbium or niobium. They may be welded or spinformed.
This Merlin vacuum nozzle is clearly welded together.
Nozzles may also be made of composite materials, such as the STS Solid Rocket Booster nozzles. They were built up of phenolic wraps and included a flexible bearing for thrust vector control.
Cold gas thruster nozzles may be manufactured of more common materials (stainless steel) using normal manufacturing techniques.
Your question covers a great deal of territory. I have tried to give you a general idea of the range of materials and techniques used to manufacture nozzles.