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Comment by beefman | Hacker News Reader

I want to believe but my B.S. detector is pegged at 11 with this company.

> The Symphony engine will be designed from scratch by Boom’s partners: Florida Turbine Technologies (a subsidiary of Kratos) will do the engine design proper, GE Additive will consult on manufacturing, and StandardAero will be on maintenance duty. (FTA)

They're (Boom) not the ones designing it. Kratos Turbine Technologies has made turbopumps for liquid rockets so they're well placed to do this work.

The hard part is making the rotors which I bet is why GE is involved.

Interestingly, it's not GE Aviation (the GE division who make engines) but GE Additive, a division of GE who specialise in Additive manufacturing (aka 3D printing) metal parts.

So it's going to have 3d printed rotors and probally other , which is super cool.

GE Additive have previously made 3d printed turbine parts for GE Aviation[1], so they do have some experience. Also, this appears to be Kratos' second jet engine [2]

[1] https://www.ge.com/news/reports/mad-props-3d-printed-airplan...

[2] https://www.janes.com/defence-news/news-detail/kratos-comple...

Turbine blades are the bits that whizz around really fast and are subject to extremes of temperature and force. Established engine manufacturers go to interesting lengths to make turbine blades made of interesting materials like single crystal metal alloys just so that they can cope with the conditions. In a jet engine, a small increase in working temperature gives a significant improvement in efficiency and performance. I can't see how 3D-printed turbine blades could possibly be a good idea.

It doesn’t look like they printed the rotors. It’s hard to find real concrete info but it looks like they added cavities to other parts of the engine for active cooling and/or increased strength to weight, which is more of a well explored topic (I remember watching a rocket engine test in Mojave with a hollow cryocooled aluminum nozzle in the late 2000s).

The rotors are still made using those fancy 5-axis CNCs - I think either Boeing or GE still have a shop in LA that makes them.

> Kratos Turbine Technologies has made turbopumps for liquid rockets so they're well placed to do this work.

Liquid rocket turbopumps and jet engines are completely different things.

And FTT was a designer of missile and UAV engines, according to Kratos' website they're developing 300lb thrust turbojets and 900lb thrust turbofans: https://www.kratosdefense.com/products/uav/air/turbines. Their KTT is 200lbf, targeted towards "cheap cruise missiles" and "attritable" (aka expendable) UAVs, and was developed in 18 months.

But apparently they'll be able to develop an airliner engine with 175 times more thrust (without afterburner), in 2 years?

Hell, the linked page boasts of their newly commissioned "X-58 test facility", able to accomodate engines "up to 3000-lb thrust".

I'm not panning KTT here, I don't know if they were even involved in the press release, but things don't really make any sense.

And remember, this is a project Rolls-Royce fucked away from 3 months ago, after two years of collaboration. So in 3 months Boom has supposedly found a company which is able to design an engine type which has basically never existed from scratch with no experience.

That conceptual render is so laughably bad that it reeks of a designer copying a turbine schematic from Wikipedia, but they don’t even know how an axial turbine works or what a stator is. The schematic is similar to a turbine engine in the same way Fred Flintstone’s car resembles a modern automobile. This is looking theranos bad.

I am even wondering if it's an AI-generated picture?

- Look at the top of the last two stages of the "low-pressure compressor", you can see like some "phantom" blade airfoils? And yeah, no stators at all...

- The "high-pressure compressor" is even more bizarre: each stage seems to have a slightly different, random chord length, the first stages' airfoils have alternating pitch/curvature resembling rotor-stator stages but in the last ones they forget about this...

- In the turbine casing they have included some grooves that resemble cooling channels or labyrinth seals but the shapes seem random?

- The primary and secondary dilution air holes in the combustion chamber are huge, like those of small RC gas turbine? No fuel injectors at all?

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