[HN Gopher] Building a rocket engine from scratch
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Building a rocket engine from scratch
Author : sr-latch
Score : 84 points
Date : 2024-05-02 19:54 UTC (3 hours ago)
(HTM) web link (blog.ablspacesystems.com)
(TXT) w3m dump (blog.ablspacesystems.com)
| datadrivenangel wrote:
| "At one point, I received a well-deserved earful from our
| machinist about how tightly spaced the turbine blades were. The
| program was taking nearly a month to run and required tiny end
| mills that broke often. We performed a turbine blade count study
| to see if we could use fewer blades with more space between them.
| It turned out the performance impact of running fewer blades was
| minimal, so we cut the number down, allowing our machinist to use
| larger, less fragile tools. Machine time dropped to less than a
| day, which was a significant win for turbine cost and machine
| time. It was also a good lesson in thinking comprehensively about
| a design's manufacturability (those passages between the blades
| looked so big on the computer screen!) in addition to its
| performance. "
|
| Once again people learn the hard way that it's valuable to have
| tight feedback cycles and embedded knowledge on your team.
| FredPret wrote:
| And also the value of a completely obsessed engineer. If the
| mech eng designing the parts is also the type to build things
| in his spare time, this type of machining problem would stand
| out right away.
|
| Of course, not everything can ever be anticipated, so tight
| feedback loops are fantastic when you can get them.
| numpad0 wrote:
| I'd agree with this take more. It's just cheaper and faster
| to just know whys and plan ahead than waiting for failures,
| if you could.
|
| I've been tinkering with 3D printers long enough that I've
| trivially halved print times after seeing long print time
| predictions. Lots of my brackets and parts fits together on
| first try and needs no supports. Rapid turnaround did help in
| _acquiring_ those skills, but now I could just waterfall
| little projects and tight looping is not that important.
| psunavy03 wrote:
| Valuing "completely obsessed" employees is a great way to
| build a company with toxic burnout culture. Some people want
| lives outside of work and are still good at their jobs.
| quartesixte wrote:
| Or some people are so good at their jobs that even while
| being completely obsessed, they still have great work-life
| balance.
|
| I interact with a lot of people like the author in the
| article from this industry. And while yes, their worklife
| balance skews "work", they all have interesting hobbies and
| find time to hang out with friends, go on adventures, and
| live a pretty full life.
|
| Unless you're on the Starship team at SpaceX. Truly, hats
| off to y'all at Boca Chica some intense hours you are
| pulling there.
| guynamedloren wrote:
| This may surprise you, but it's possible to be completely
| obsessed with your work (while you're working!), while also
| maintaining a work-life balance.
| psunavy03 wrote:
| It's also a great excuse for abusing people.
| AndriyKunitsyn wrote:
| Nice read. The fact that it is possible to 3d print metal parts
| that withstand temperatures and pressures of a rocket engine is
| so exciting. How expensive is it?
| jfoutz wrote:
| Stratasys? I'm not sure about pricing, and the website won't
| say.
|
| However, a bunch of places rent out time on those machines.
| Draw up your rocket, and get a quote. Price is generally cc^2
| volume
|
| Metal is not cheap. Make a few out of plastic to verify
| dimensions.
| quartesixte wrote:
| Plastic to verify dimensions is a great approach.
|
| But don't forget that the laser sintering of metal powders
| might result in design constraints not present in plastic
| printing!
| WJW wrote:
| Mostly depends on the volume of the part, or equivalently it's
| weight. Complexity you get mostly "for free" when it comes to
| 3d printing. What type of material you need to "withstand
| temperatures and pressures of a rocket engine" is entirely
| dependent on which part of the rocket engine we're talking
| about. A fuel injector has radically different requirements
| than a supporting strut for example.
|
| 3d printed titanium goes for 300-400 USD/kg, steel is a bit
| cheaper at ~150 USD/kg for most inconel grades.
| spxneo wrote:
| side question to this: where can i design stuff involving metal
| parts (presumably in CAD tools) and have it printed en masse?
| With PCBs? ex) car components
| numpad0 wrote:
| You can draw up mechanical components in Autodesk Fusion,
| OnShape, SOLIDWORKS for Makers, or FreeCAD, and send STEP or
| STL to PCBWay or JLCPCB in China for manufacturing(note that
| export restrictions may apply if it's literal rockets or
| otherwise dual-use/controlled in nature).
|
| PCB mounting outlines can be exported from above 3D CAD and
| imported to EDA tools such as Altium and KiCAD; KiCAD is fine
| unless you're doing DRAM or PCIe. Same PCBWay and JLCPCB
| takes your design, and optionally assemble PCB with parts for
| you.
|
| That should take you to first 2-3 working units at ~$500 and
| up to few dozen beta units with zero initial cost and much
| inflated unit costs, and I guess beyond that involves
| significant human resourcing and networking problems outside
| of PoC hardware scope.
| spxneo wrote:
| thank you so much for this detailed answer. now i just need
| to invest some time into learning CAD and KiCAD
| Robelius wrote:
| You could try a battery powered phone charger since it's
| a "relatively simple" first project. The big hurdle for
| learning these types of tools is usually "What buttons do
| I press to create the output that I want.
|
| For the electrical side, there are plenty of schematics
| online that you can try to copy or use as a starting
| point. And the CAD side can be a simple box with snap
| fits. I'd recommend OnShape if you're just starting out
| since it's the lowest barrier of entry, but Fusion 360 is
| also good. All in, it should be <$150 for the PCBs +
| Components + 3D Prints.
|
| After you get the satisfaction of seeing your device
| charge from something you made, then you'll start getting
| the itch and find more excuses to make things.
| quartesixte wrote:
| Very. Very. Expensive.
|
| Inconel powder is also Not That Great for your health and at
| the particle-size the printers rocket companies use, you need
| full PPE to safely handle the loose powder floating about.
|
| The machines themselves are also expensive. Think in the
| millions of USD. EOS, SLM, and Velo3D are key players in this
| market. They require a fair bit of space, and training to use
| correctly.
|
| You probably need a mechanical engineer who is well-versed in
| materials science and has a tolerance for finicky machines that
| constantly breakdown.
|
| Then you have the metal powders. Which, also potential million
| or two.
|
| And then you have all the associated infrastructure needed.
| High voltage power. Gas (Nitrogen, Helium, Argon, etc etc) in
| the thousands of liters per month. Waste disposal. Safety (some
| alloys are flammable in their powder form). Climate control
| (the powders are sensitive to the environment. Humidity will
| quickly destroy your powder supply). Tooling (the base-plates
| metal printers used are machined from solid blocks of steel).
|
| And last but not least, any of the post-printing work. Heat
| treat. Coatings. Analysis. CNC Machining.
|
| 3D Printing metal on industrial scales is a CAPEX intensive
| endeavor, and not for the faint of heart.
| avmich wrote:
| Paul Breed, from Unreasonable Rocket team -
| https://x.com/unrocket - mentioned, a decade or so ago, that he
| printed some aluminum engines for regenerative cooling by
| hydrogen peroxide for ~$1000 . Another story from
| http://rocketmoonlighting.blogspot.com/2010/ is about a small
| engine cooled with nitrous oxide - and manufactured entirely on
| personal money, also quite some time ago. I think these numbers
| are still indicative of the current prices.
| quartesixte wrote:
| Aluminum is magnitudes cheaper than Inconel. And since volume
| is cubic, and pricing mostly on based on powder weight, you
| are about an order of magnitude or two off for the size of
| engine ABL is producing here.
| avmich wrote:
| That's correct, but it's still interesting that you have
| that opportunity to shave - slash? - costs here.
|
| And also the other engine mentioned isn't an aluminum one.
| spxneo wrote:
| now all that is required is a github for passive radar...for
| educational purposes
| avmich wrote:
| Awesome story, thanks!
|
| It seems the design choices are rather conservative, which is
| entirely justified by the "from scratch" part for the first
| engine. I'm sure subsequent designs will be more bold and
| adventurous.
|
| Keep up great work!
| brcmthrowaway wrote:
| Can you use ChatGPT to build a Saturn V?
| buescher wrote:
| NASA's report server is a national treasure, especially the
| material from the 50s and 60s that he references. Some of the
| most crisp and succinct technical writing you'll find, and you
| can infer a lot about how they ran projects. Declassified NRO
| reports are also very good - you can see the Lockheed Skunk Works
| principles in action. Example:
| https://www.nro.gov/Portals/135/documents/foia/declass/WS117...
| Horffupolde wrote:
| English is great for technical writing.
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