Amid heavy competition, Relativity Space secures $140M in funding | Hacker News Reader

Amid heavy competition, Relativity Space secures $140M in funding

arstechnica.com

33 pointsrbanffy14 comments

Wondering if a complex machine like an orbital rocket could be 3D printed as a whole and not just the components separately...

Sintering (the most popular industrial 3D printing process) typically involves a substantial manual/machining component after the print. Also any precision elements or bearings rule out 3D printing. So, no.

Not only that, but sintering is also (generally) a lot less sturdy than a completely machined part.

The new sintering processes and alloys have gotten amazingly close for most purposes to be indistinguishable in application. Like any additive process, it still often requires machine work where precision is important.

Tht said... I am sad to see that lately, casting being overlooked often when it is still the best choice in many projects just because '3d printed' sounds better in the marketing. I have in front of me a 1960s magnesium alloy casting from the early 60s and the quality would make most sinterig operaters beyond jealous. Not to mention the material properties.

Yes, diecast components can be very precise. At the same time diescast process is cheap enough that 3D printing has no edge there.

Where 3d printing really helps is replacing wax or investment casting necessary for high melting point materials. You end up having quicker turnaround, better part quality and sometimes even lower price.

Rocket Lab uses an engine that is mostly made by 3d printing: https://en.wikipedia.org/wiki/Rutherford_(rocket_engine) (Not as one piece though)

SpaceX also 3D prints the SuperDracos [0].

[0] https://en.wikipedia.org/wiki/SuperDraco#Manufacturing

I think it's important to print different things at different scales because smaller printers are more precise.

If we are just looking at whether it could be 3D printed, I think the answer is that eventually anything could be 3D printed.

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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