A liquid oxygen/gaseous hydrogen rocket injector assembly built using 3D printing technology is hot-fire tested at NASA Glenn Research Center’s Rocket Combustion Laboratory in Cleveland, Ohio.
Credit: NASA Glenn Research Center

Sometimes people question the strength of 3D printed parts and if it could really replace welding and CNC for the most extreme applications.  Here’s a great article about a 3D printed rocket part that accumulated 46 seconds of total firing time at temperatures nearing 6,000 F while burning liquid oxygen and gaseous hydrogen, showing no difference to standard parts.  Any questions?