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.)
Elon recently noted that Raptor (unlike SuperDraco) won't be fully 3D-printed. It will have 3D-printed parts, but most of the engine will be machined. I guess for a larger engine the things you mentioned have to be more tightly controlled to be able to print the whole engine. Might also be a cost issue as size increases, I guess.
It's definitely possible to use a CNC machine to mill the shape of a rocket engine. You can do some pretty crazy internal milling with a 5-axis machine:
The fuel actually flows through the pipes and voids in the red-hot engine, where it absorbs the heat that would otherwise melt the engine. It then flows back up to be burned.
You'd need an endoscope, not a robot arm, to mill that out!
And neither an endoscope (obviously) nor a robot arm would likely be rigid enough to mill in these materials. Robot arms are typically only used when milling wood, plastic, or soft modeling materials. A CNC mill in metals like the exotic Nobium alloys used in these engines needs incredible rigidity which robot arms just don't have. Consider the hardened tool-steel shafts of the end mills used in the first video - and those are easily broken, while just cutting aluminum!
I think you mean EDM, electrical discharge machining. Typical wire EDM usually needs a hole all the way through the material to start, but sinker EDM would work. Interesting idea, wonder if anyone's tried it.
yeah, i was thinking more of an endoscopic robot arm, it would probably need quite a few entry points, and the those holes would need filling again, you could tap those and put a screw it afterwards.
but maybe it's the coming towards end of subtractive manufacture.
I don't think that would be practical. I assume the volume to be milled out is pretty convoluted if you want yo do it mono-bloc. If you break it down, you're back to welding issues.
I just had an image of a bunch of insect-like robots crawling over and through a giant metal block, chipping away at internal spaces with precision cutting tools to produce the desired shape, carrying away waste material, like an robotic ant colony digging a smooth steel nest.
they wouldn't have to carry anything, you can blow air into the cavity to get the material out. they could have wheels and drive up and down the cramped cavity with a drill on the end. in the end I think additive has won.
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.
My gut feeling about rocket building is that it's not the labor for building parts and putting them together which makes them expensive but the labor for inspecting, reinspecting and then reinspecting once more before putting parts together, only to do some more inspecting on the combined subassembly. The launch is the first true dress rehearsal and the rocket equation leaves little room for "engineering math" (calculate to seven digits, then multiply by two for safety).
My gut feeling about 3D printing is that it just makes it worse. How do you inspect a welding line as long as a rocket's dry mass?
For a liquid fueled rocket you have many opportunities before launch such as firing the engine in a test stand, etc. For the whole rocket you can do a static fire, or even a full duration fire to test the components. Mostly when you are moving you are worried about the mechanical loads on the rocket instead of having to worry if parts were put together correctly. Of course, even this level of testing takes a lot of money, capital, and of course labor.
For a solid fueled rocket, you're right that pretty much you have one shot, and you can't turn it off if something goes wrong.
> My gut feeling about 3D printing is that it just makes it worse. How do you inspect a welding line as long as a rocket's dry mass?
In general, the way you do this is to move it lengthwise through an x-ray scanner, so you can inspect the full length by moving the rocket through. I'm not sure if 3d printing makes this easier (because there's not really welds, it's one piece) or harder (you have to be able to inspect the inside of something), but it is certainly tricky.
I guess you can think of it that way, but it probably depends on the technology used by the printer at that point. My thought was that for the 3d printer, at least it's one consistent piece with no seams or edges that are later welded together. The welds can have imperfections/weaknesses and need to be inspected. Materials can also have weaknesses and imperfections, either on a batch level or individual area level, and need to be tested/inspected. For a printed piece, I would expect the strength to be generally consistent throughout the piece (of course still might be weaknesses based on design shape, thickness), but of course, you'd still want to inspect it.
PS - totally not an expert on 3d printers or materials or welding
I am not an expert on either, but in general 3D printers lay out the material in thin layers (with each layer laid out line by line). Thus you have lots of potential seams everywhere two points laid at different times touch.
I think modern technologies prevent seams forming at most of those points, but the potential (impurities, dirt, etc.) still remains so must be tested.
I could imagine some technology that takes advantage of future layers not being there yet to validate the most recent layer on the same pass, and the one that the current layer will be built upon (as that might have suffered in the time since it has been laid) in a way that is exclusive to this manufacturing method. But as you move to bigger and bigger one-piece parts, you would probably also want your process to support undoing a few layers on failure detection to forego scrapping the whole part.
The printers are going to make the exact same rocket every time.
And you could anneal the rocket after, which would improve the strength.
Also spacex seems to be doing it with their Dragon engine. Is there another rocket part that undergoes more strain? (vocab cringe, not a materials scientist)
The superdraco engines in Dragon have a printed combustion chamber. But these are (relatively) low pressure engines.
Chamber pressure is limited by the fuel injection pressure. The simplest, fastest response time way to provide the fuel pressure is to use a high pressure bottle of gas to push the fuel through. Since those are important features in a launch escape system, that's how superdracos work.
But... chamber pressure is directly correlated with efficiency, so a main engine uses an extremely powerful fuel pump to achieve higher pressures.
That fuel pump is itself, a rocket engine with a gas pressure fuel system like the superdracos.
My actual knowledge of the industry says that it's both. The metalurgy, production prcesses etc. are very very intricate and the inspections are also very very intricate.
A 3d printed rocket would be cheaper right from the start, so they wouldn't need to bother with repairs, they can print another module or whole rocket again. Even a 3d printed rocket is going to be made of parts that can be replaced, because I presume we can't print the whole thing in one piece.
> 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.
I think the idea is to 3D print parts that are currently welded together. I don't see anywhere that they are planning to print as one piece anything that is ever disassembled with current practices.
> I think the idea is to 3D print parts that are currently welded together. I don't see anywhere that they are planning to print as one piece anything that is ever disassembled with current practices.
I would agree that 3d printing smaller parts and putting them together by hand seems more reasonable, but I don't get the impression that is what they're doing (but it's hard to tell from the article).
This is what led me to that conclusion:
"Ellis and Noone say a handful of the arms can work together to create the rocket’s entire body as a single piece, guided by custom software that monitors their speed and the metal’s integrity."
Entire body - single piece. I don't hear any talk of welding or putting it together (which would involve multiple pieces).
Also just as a point of reference, making the bodies or the fuel tank is actually the easier part. It's either metal or carbon fiber. What takes a long time is assembling complex engines, and getting the whole thing together (including wiring).
You won’t be reusing the parts without some refurb work. It’ll be more labor than the initial inspection. For one you’ll be poking around for signs of wear you might not look for on a new part.
Think about how expensive it was to replace the heat shield tiles on the shuttle. The shuttle was “reusable” but the repairs were hell.
In theory, I don't see any reason why 3D printing a reusable rocket is impossible. With advances in 3D, it may become a reality where this company is a complimentary company for SoaceX and not a competitor company.
Open the link in incognito, or just hit enter on the address bar again so the referrer is removed and it's a direct resource request. (refresh won't work).
I think the advantage it gives you is that you can optimize the mechanical structure of the rocket parts.
I speculate that the disadvantage is that a many extreme environments also have hard requirements on the microscopic material structure of the components - and that will also have to be managed at the extruder/nozzle (as well as in the temperature and pressure environment afterward). Getting the materials properties right is much more finicky than the mechanical scale printing. And might change when you change the mechanical design (e.g. do you is there more material on some corner - then that might cool slower, which might give you a microscopic weakness around the corner...). I think you'll need world class materials modeling to do that right - and you'll have to do all sorts of validation that produced parts are ok.
In comparison, the spaceX welding techniques have less to worry about - the weld itself as well as properties the change/arise around the weld - the rocket tube presumably already at it's designed material strength.
I would speculate that their eventual end goal is to be bought out by either SpaceX or Blue Origin. A small space launch startup focusing on one technology isn’t going very far on its own, and few other companies would have an interest in their approach.
Another possible exit scenario is to be acquired by ULA or another cost plus contractor who is grasping at straws to become competitive against SpaceX's reusable vehicles.
1. It matters a lot because you need to optimize the structure and engines for weight and 3D printing lets you make strong, and yet mostly hollow materials.
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.
Shapeways are a printer service, with a whole bunch of materials including metals that are rare on consumer machines. However one of the advantages of 3D printing is you can create rapid prototypes - if you need to order and wait for someone else to make your model you lose that.
I think you can do a crappy jet engine out of boring sintered stainless steel (316L), barely. Particularly if you could throw in some basic stuff from McMaster-Carr (seals/bearings/etc.)
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.
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
It's a bit annoying for pages like Youtube where you do want autoplay to work, so you have to move the timeline cursor a bit, but the upside is worth it.
I'd rather a micropayment system with browser plugin that decrements your account on sites you agree to pay per page view. I don't mind paying $0.02 to read a decent article but I really don't want a bunch of CPU load DOS'ing my machine or malware screwing with it or my privacy.
I wish HN would tag these with a [paywall] label. It is incredibly annoying to find out after the 2nd paragraph that you can’t really read the article you were suggested, turn around and do the google search dance.
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.)