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.
- Yellow is bad
- The 60s were awesome
Out of context of the thread, your second point was amusingly interpreted to be about LSD.
Once again people learn the hard way that it's valuable to have tight feedback cycles and embedded knowledge on your team.
Of course, not everything can ever be anticipated, so tight feedback loops are fantastic when you can get them.
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.
Far from a hard lesson, it was one they designed the company around.
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 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.
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
3d printed titanium goes for 300-400 USD/kg, steel is a bit cheaper at ~150 USD/kg for most inconel grades.
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.
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.
But don't forget that the laser sintering of metal powders might result in design constraints not present in plastic printing!
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.
Meaning that instead of thinking "how do I 3D print this?" you should be thinking "how do I manufacture this?"
Something as simple as making a drawing, specifying the material and quantity needed and then going on reddit/r/manufacturing and asking "how would I build 50 of these" can provide very useful answers, even if you have to do a bit of research later to understand what you've been told.
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.
The writer probably was referring to the fact that he was just a regular mechanical engineer and not a Propulsion Engineer.
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.
Keep up great work!
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.
On the site you can see: launch on demand, simple system that can go anywere, tactical launchs.
This is for nukes or similar stuff.
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).
The SDR world is incredible
edit: looks like they took down all the passive radar doppler videos : https://othernet.is/products/kerberossdr-4x-coherent-rtlsdr
lol, engineering humor
