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Comment by Robotbeat | Hacker News Reader

This is probably the most expensive way to make a rocket body I can think of.

Furthermore, it will give inferior material properties and potentially have more quality/repeatability issues.

They must believe that more complex designs can more than make up for the disadvantages of 3d printing. That is hard to fathom for a thin walled pressure vessel like a rocket body, but I'm sure they know things that I don't.

The main advantage of additive is automation. You can 3D print a lunar habitat with a Fresnel lens, a remotely operated robot, and sunlight well before humans install and inflate an internal pressure vessel. If you could do that with metals on the moon or, better, on an asteroid, you'd have a lot of parts that'd need minimal human intervention before being used.

Even if not as practical, or high quality, or light, it means huge savings.

That's the "freshman's dream" of additive manufacturing. In reality, additive manufacturing is often more labor intensive than conventional manufacturing, particularly if you're building multiple items or are using the process where it doesn't make sense.

The "minimal human intervention" thing is just not true.

It's nice to not have to make tooling. But post-processing is super labor-intensive. Often post-machining is also needed. And certification of additive parts for aerospace is a nightmare.

These are all limitations of the process itself, but we can design around them. If the printed material is not rigid enough, we make it thicker or add support structures. If the surface is not as smooth as we need, we can machine it or use a thicker gasket. A lot of our tech and tooling is built around subtractive processes and their characteristics, but that's not a hard boundary of the design and process space.

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