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Comment by mrguyorama | Hacker News Reader

How do you do comprehensive QA on a 3D printed part with complex internal structures like that? Can you X-ray copper? What happens to an engine that has a slight void or poor adhesion in a layer, does it have a 1% degradation in performance, or does it fail to cool effectively and melt during the dangerous part of the launch?

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The first several (10s or even 100s) will be run, most likely from test stands, then ripped apart and combed over for hot spots and cracks. Id even expect them to build some with shittier materials specifically to see how it causes them to fail. Rocket engines are a shocking amount of trial and error.

If they had any intention of actually creating something other than a marketing gimmick sure they'd do all that stuff.

Yes you can x-ray metals like copper. CT would be the best choice due to the complex geometry.

Failure modes from any defect would of course depend on the scale and type of the defect, and could lead to nothing or catastrophic failure

X-ray CT is standard. There’s also just borescoping it. You can build witness coupons at the same time and test their strength. No substitute for test firing the engine. Even operationally, you’ll want to acceptance fire the engine before putting it on a vehicle.

This is a huge field in additive manufacturing. One of the most promising solutions is in-situ process monitoring to identify defects that may occur, often using machine learning.

Maybe using ultrasonic testing during the printing process, while the inner parts are still accessible

You can probably build a kind of acoustic signature of the whole at various different points in the boundary and check each build is sufficiently close to that signature.

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