Space-X makes the Dragon engine block by 3D printing.

It makes sense. Rocket engines are mostly a big single piece with lots of internal voids. The fuel is used as a coolant, so there are channels inside the engine bell and some other sections. It's mostly plumbing.

That's the kind of part where 3D printing is useful. Making a big object with internal plumbing out of multiple parts is a fabrication headache. NASA's engines have vast amounts of welding work in them. High-pressure joints are always a problem. Making something with few or no joints is just better. It still has to be inspected, but that's what industrial-sized CAT scanners are for.

(Most of the real-world problems in both rockets and nuclear power involve plumbing and welding.)

It sounds like an interesting idea, but I'm not sure I buy it.

It makes sense that building single use rockets is expensive, and with only one launch to amortize the construction cost, labor is a huge factor (materials in a rocket are pretty normal: a lot of carbon fiber, aluminum, titanium, etc). But with reusable rockets, you are bringing that cost way down. If you are able to launch and land 5 times on the same rocket, then effectively you've brought the cost of the rocket to 1/5th of what it used to be.

"a handful of the arms can work together to create the rocket’s entire body as a single piece"

Once you get into reusable rockets, I'm not sure that trying to 3d print the whole thing will turn out. Why? Because you need replaceable parts. You need to be able to tear down, inspect, and replace parts as each part of the rocket has a different lifetime. If you make the rocket as one giant piece, and use efficient methods (reduce weight, size, etc), that it would be much less serviceable over its lifetime.

"We want to get to 1,000 moving parts, fewer than a car."

This is why subassemblies of cars are so expensive, even if you only need to replace a small part of one assembly.

They have a fricking PROTOSS[1] logo in their factory (3:22).

That is Awesome! Seeing how the protoss warped in objects from another spot... I guess to them 3D printing is the precursor to that.

[1]http://wiki.teamliquid.net/commons/images/thumb/e/e4/Protoss...

I know very little about rockets and 3D printing, so maybe someone can answer two things for me:

1. Does 3D printing make sense for large projects like rockets, which will be used in extreme conditions? I thought it was more for prototypes.

2. How does this compare to SpaceX, which is attempting to reuse rockets? How important is this fixed cost if you use a rocket 100 times?

After watching https://www.youtube.com/user/AgentJayZ videos (a guy in Canada who works for/owns an industrial/military turbine engine refurbishment shop and publishes great videos on a lot of the details), I've thought about trying to 3d print an inefficient, cold, boring, small jet turbine -- I know GE has already done a reasonable job of it, but making one which can be made at the lowest possible cost and skill level as a learning experience would be interesting. Unfortunately the machines are still a bit too expensive for recreational use.

North Korea now use filament winding machines to make lightweight, long range airframes for it's rockets and ICBMS. It takes large spools of advanced composite filaments as the input and outputs airframes.

Impressive for such an impoverished nation.

http://www.38north.org/2017/08/melleman082517/

http://www.armscontrolwonk.com/archive/1203086/wound-filamen...

http://edition.cnn.com/2017/08/23/asia/north-korea-missile-p...

ARC Engines were one of the companies graduating at the recent TechStars demo day in Adelaide. As another commenter pointed out it seems much of the innovation is the improvements you can make to the internal chamber design through 3D printing. I also gather they’re onto (at least) their second generation of working rocket

http://arc-engines.com

The next step towards Von Neumann Probes!

https://futurism.com/von-neumann-probe/

I wish I could read the article, but there was just too many ads.

the most interesting part of the project is the engine ::: x.co/newlab

Warning: article behind a paywall.