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...
Lots of academic and engineering things from back then are great.
I have an incomplete set of the radlab textbooks. They're still useful even today, and have a really careful pace to them because they were written for a generation for whom electricity was still relatively new.
One of the things that is a real shame is just how artfully bound those old books are. Leather, thick but smooth paper, etc.
"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.
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.
Great post on building extremely complex hardware from scratch.
At the same time I hate to be that business guy, but both this blog post and the abl site are missing a good answer to my first question: Why? Given that SpaceX exists and is quickly approaching feasibility of Starship on top of Falcon, what is the primary goal of this rocket system? How will it compete? Who will its customers be? Is it getting its metric ton payload to orbit faster/cheaper/easier? Is this "from scratch" engine design superior to existing designs in some way? What is its current ISP? Is Jet-A + LOX a better fuel choice given expected mission parameters?
I'd love to see a blog post that tackles these kinds of questions.
From the outside: Diversification is always great. Build a whole ecosystem of small-scale rocket manufacturers instead of one big monopoly. That will foster competition and innovation.
From the investor: SpaceX might fail. Even if there Falcons are pretty much unbeatable now, you don't know what's going to happen with Starship. And even the Falcons could conceivably be grounded for years after some hypothetical flaw is found. More likely: With the price reductions made by SpaceX, the market will grow and there will be more than enough clients.
From the inside: Because it's a fun challenge and literally rocket science, of course.
SpaceX is certainly giving a hard time to its competitors, but it doesn't mean they shouldn't exist. Some of them may actually follow the same route, designing reusable hardware and reducing launch costs. SpaceX took 20 years to become relying on robustly reusable system; maybe some other companies reach a similar state sooner.
IIRC ABL’s specific goal is that you can pack an entire launch setup into a shipping container and set one up anywhere in the world. Also the U.S. government will explicitly buy non SpaceX launch contracts specifically to keep smaller launch companies alive so they don’t get locked into a single supplier.
They can be boxed infrastructure that only require a generator for launch. They can be owned and operated by US gov, allowing them to be launched by land, sea or expeditionary. They can theoretically drop cargo anywhere on the planet in 5 minutes. Which is every military tacticians wet dream.
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?
The material costs (the $300 per kg of titanium suggested in another comment) are only a small part of the overall expense. Electron beam sintering printer time typically costs $100-$200 per hour, and a large build can easily take multiple days.
After the printing itself, one will have to remove to loose powder, which for small cooling channels in the walls of the combustion chamber is very challenging and time consuming.
After that, some post-processing may also be necessary. One process for achieving the greatest strength is hot isostatic pressing, when the part is baked in a furnace in a retort filled with a very high pressure inert gas.
Specifically for rocket engines, it is also desirable to have a layer with the high heat conductivity on the inside, typically made of a copper-based alloy, and the external structure from a higher strength material. This means either bi-metallic printing, which is a rather niche process, or some metal deposition process over the printed part.
In addition to this, there is usually quality control, for example, high resolution industrial computed tomography, to make sure that the invisible internal features have been fabricated and cleaned out correctly.
In addition to the additive steps, it will also be necessary to machine the features which are impractical or impossible to build sufficiently accurately.
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.
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.
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.
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
> You might call me an unlikely candidate to lead an engine program from scratch, but I was hired by ABL in 2018 to do just that. My background was in commercial aircraft interiors, web development, semiconductor fab fluid components, and SpaceX Falcon 9 hydraulic systems.
I don't mean this as an insult, but why did they hire you? It's obvious now that you were a great choice, but from your background story I wouldn't have guessed that to be true.
Seems like from the blogpost that the writer and the founder were part of the same cohort at SpaceX. I would hazard a guess that they became friends, and had planned to do this together, and he joined ("hired") as soon as feasible for him (or the founder gained enough traction to pull him away from SpaceX).
Oh wow, I work for a supplier for ABL and am today in the process of putting some of their stuff into our thermal chamber for cycling. Thats neat.
We work for a lot of launcher companies, but ABL is the most interesting for me (even though we do relatively little for them). The containerised approach to the entire system is a really clever adaptation of existing methods to create a rapid launch system.
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.
The science of pressure chambers have also advanced, we could just pump whatever material, like liquid air into a pressure tank and then load it into the rocket. No mixing or pumping needed just open the valve and let the pressure out and you will have a very cheap and simple rocket.
This is absolutely not true - injector design is the most important aspect of designing a thrust chamber. Poor mixing of propellants leads to severe combustion instability, which often leads to explosions. Even the earliest space programs did significant testing on propellant choices and injector designs (see Ignition! by John D. Clark)
Also, pressure fed rockets have always been a fairly terrible design. Pressure feeding requires heavy tanks, and incurs a big mass fraction (dry mass / wet mass) penalty. Outside of rare cases, it's only used for ground testing.
Since it's 3D printed, I'm guessing from the embedded ports that the nozzle is hollow in parts and Jet A cooled since LOX latent heat of evaporation is orders of magnitude less. Probably one of those ports is for a temperature sensor.
It's not for nukes. We have silos and submarines for those. It's for "responsive launch" and (skeptically) because the DoD has lots of money for space and not much idea what to do with it.
It's the Astra business model, hopefully without the Astra failure model.
(And practically speaking it's because you can't bootstrap a heavy lift launch company on VC funding or even a SPAC - the small sat launcher is a proof-of-concept for your medium/large launch vehicle).
[+] [-] buescher|1 year ago|reply
[+] [-] mhh__|1 year ago|reply
I have an incomplete set of the radlab textbooks. They're still useful even today, and have a really careful pace to them because they were written for a generation for whom electricity was still relatively new.
One of the things that is a real shame is just how artfully bound those old books are. Leather, thick but smooth paper, etc.
[+] [-] duped|1 year ago|reply
- Yellow is bad
- The 60s were awesome
[+] [-] sr-latch|1 year ago|reply
[+] [-] Horffupolde|1 year ago|reply
[+] [-] datadrivenangel|1 year ago|reply
Once again people learn the hard way that it's valuable to have tight feedback cycles and embedded knowledge on your team.
[+] [-] FredPret|1 year ago|reply
Of course, not everything can ever be anticipated, so tight feedback loops are fantastic when you can get them.
[+] [-] cwillu|1 year ago|reply
Far from a hard lesson, it was one they designed the company around.
[+] [-] mdorazio|1 year ago|reply
At the same time I hate to be that business guy, but both this blog post and the abl site are missing a good answer to my first question: Why? Given that SpaceX exists and is quickly approaching feasibility of Starship on top of Falcon, what is the primary goal of this rocket system? How will it compete? Who will its customers be? Is it getting its metric ton payload to orbit faster/cheaper/easier? Is this "from scratch" engine design superior to existing designs in some way? What is its current ISP? Is Jet-A + LOX a better fuel choice given expected mission parameters?
I'd love to see a blog post that tackles these kinds of questions.
[+] [-] choeger|1 year ago|reply
From the investor: SpaceX might fail. Even if there Falcons are pretty much unbeatable now, you don't know what's going to happen with Starship. And even the Falcons could conceivably be grounded for years after some hypothetical flaw is found. More likely: With the price reductions made by SpaceX, the market will grow and there will be more than enough clients.
From the inside: Because it's a fun challenge and literally rocket science, of course.
[+] [-] avmich|1 year ago|reply
[+] [-] Shawnj2|1 year ago|reply
[+] [-] unknown|1 year ago|reply
[deleted]
[+] [-] SCM-Enthusiast|1 year ago|reply
[+] [-] AndriyKunitsyn|1 year ago|reply
[+] [-] generuso|1 year ago|reply
After the printing itself, one will have to remove to loose powder, which for small cooling channels in the walls of the combustion chamber is very challenging and time consuming.
After that, some post-processing may also be necessary. One process for achieving the greatest strength is hot isostatic pressing, when the part is baked in a furnace in a retort filled with a very high pressure inert gas.
Specifically for rocket engines, it is also desirable to have a layer with the high heat conductivity on the inside, typically made of a copper-based alloy, and the external structure from a higher strength material. This means either bi-metallic printing, which is a rather niche process, or some metal deposition process over the printed part.
In addition to this, there is usually quality control, for example, high resolution industrial computed tomography, to make sure that the invisible internal features have been fabricated and cleaned out correctly.
In addition to the additive steps, it will also be necessary to machine the features which are impractical or impossible to build sufficiently accurately.
Together, these steps add to a significant cost.
Some of the above processes can be seen in this video: https://www.youtube.com/watch?v=7pXEf0wHU1Y
[+] [-] WJW|1 year ago|reply
3d printed titanium goes for 300-400 USD/kg, steel is a bit cheaper at ~150 USD/kg for most inconel grades.
[+] [-] avmich|1 year ago|reply
[+] [-] quartesixte|1 year ago|reply
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.
[+] [-] jfoutz|1 year ago|reply
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.
[+] [-] spxneo|1 year ago|reply
[+] [-] criddell|1 year ago|reply
I don't mean this as an insult, but why did they hire you? It's obvious now that you were a great choice, but from your background story I wouldn't have guessed that to be true.
[+] [-] quartesixte|1 year ago|reply
[+] [-] cuSetanta|1 year ago|reply
We work for a lot of launcher companies, but ABL is the most interesting for me (even though we do relatively little for them). The containerised approach to the entire system is a really clever adaptation of existing methods to create a rapid launch system.
[+] [-] philipwhiuk|1 year ago|reply
[+] [-] avmich|1 year ago|reply
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!
[+] [-] z3t4|1 year ago|reply
[+] [-] sr-latch|1 year ago|reply
Also, pressure fed rockets have always been a fairly terrible design. Pressure feeding requires heavy tanks, and incurs a big mass fraction (dry mass / wet mass) penalty. Outside of rare cases, it's only used for ground testing.
[+] [-] hi-v-rocknroll|1 year ago|reply
[+] [-] alfor|1 year ago|reply
On the site you can see: launch on demand, simple system that can go anywere, tactical launchs.
This is for nukes or similar stuff.
[+] [-] philipwhiuk|1 year ago|reply
It's the Astra business model, hopefully without the Astra failure model.
(And practically speaking it's because you can't bootstrap a heavy lift launch company on VC funding or even a SPAC - the small sat launcher is a proof-of-concept for your medium/large launch vehicle).
[+] [-] spxneo|1 year ago|reply
[+] [-] sr-latch|1 year ago|reply
The SDR world is incredible
[+] [-] mrbluecoat|1 year ago|reply
lol, engineering humor
[+] [-] Linda231|1 year ago|reply
[deleted]
[+] [-] brcmthrowaway|1 year ago|reply
[+] [-] WalterBright|1 year ago|reply
[+] [-] trollerator23|1 year ago|reply