# From what material and how are the Merlin engines and nozzles of it (sea level) manufactured?

I am specifically interested in the alloy used to build the engine, also about the nozzle: Is it just in one piece or welded using different sections. If they are welded then which welding techniques are used to withstand such high temperatures, re-entry, etc.

NOTE: I am only asking about the sea-level engines as there are a lot of questions already been asked and answered briefly in this platform regarding the vacuum engine.

• +1 Following this question. Please link to the questions "regarding the vacuum" variant that you mention, however. Jun 6 '20 at 14:52
• I have edited the title. I am asking about both- the nozzle and the engine Jun 6 '20 at 14:58
• This most likely is both ITAR restricted and a SpaceX trade secret. You might not get a good answer. Jun 6 '20 at 20:33

Tl;Dr; Nickel-cobalt with a copper cooling jacket.

Spacenews interviewed Elon Musk where he said

".... The hardest part of the engine to mass produce is the electro-plating of nickel cobalt on the chamber. We create this thick metal jacket that takes the primary stress of the pressure vessel and it’s plated one molecule at a time. Plating is about the slowest way you can make a metal thing. With the Merlin-1D we take a metal jacket that is explosively formed. We take a metal sheet that’s in a cylindrical form and put it in a bucket of water, effectively. Sort of a concrete pool. And you set off an explosive and the jacket just goes “boohmp” and forms to the outer side walls into a jacket shape, so you have a mold, effectively. And then you just put the jacket on the chamber and braise it on. You can do several a day. We have a fully integrated engine and it’s being test-fired right now. There’s really not a lot of question marks remaining about the Merlin-1D. ..."

You can also check out this blog with excellent images of Merlin production from 2006. https://selenianboondocks.com/2006/10/spacex-comstac-briefing/

• +1 apparently rumors of this being a secret have been greatly exaggerated!
– uhoh
Jun 7 '20 at 5:21
• How do you mass-produce an engine so that it doesn't blow up? By blowing it up, apparently! Jun 7 '20 at 9:11
• Blast-forming has been used for manufacturing tank bulkheads since at least the Apollo era. Has it been used for combustion chambers before the Merlin? Jun 7 '20 at 14:41