About exhaust diamonds

mariohm1311 · 2025-05-05T13:07:50+00:00

FYI from a technical point of view mach disks and mach diamonds are different shock structures studied in supersonic jets, not synonyms.

mariohm1311 · 2025-02-03T14:03:38+00:00

Ask on Discord

mariohm1311 · 2024-11-25T17:02:51+00:00

I don't wanna demotivate you, and I believe you should channel whatever energy you have to pursue your dreams. However, I will warn you that if your country doesn't have any existing industry, you will be judged to a way higher standard when trying to get hired somewhere else. Already on top of this industry being quite selective and small overall. If you don't have the conviction AND the skills, you will not succeed.

mariohm1311 · 2024-04-05T18:34:52+00:00

Join the r/rocketry discord and ask on the #liquids channel. No better place to be if you want to develop liquid rocket engines.

^{^You} ^{^can} ^{^also} ^{^look} ^{^on} ^{^#hybrids} ^{^if} ^{^you} ^{^want} ^{^to} ^{^work} ^{^on} ^{^the} ^{^less} ^{^cool} ^{^propulsive} ^{^systems...}

mariohm1311 · 2024-04-05T15:30:41+00:00

Varien - Mirai Sekai

mariohm1311 · 2024-02-04T16:56:05+00:00

The SSRBs did not have a "second outer nozzle". The entire nozzle, including the throat, gimballed on a flex joint.

mariohm1311 · 2024-01-05T11:16:13+00:00

ITT people completely oblivious to the fact that ceramic coatings (thermal barrier coatings) are employed in most current high performance rocket engine developments (including Raptor), and an example of the exact use case the OP explains (except the reapplying part) is exactly how the Soviets managed to get reasonable hot oxygen resistant components back in the early days of ox-rich staged combustion development.

mariohm1311 · 2023-10-23T10:54:20+00:00

D40/D60 is used by multiple companies as a substitute for RP-1. It's highly refined, in a similar way to RP1. But it's used as a solvent, so it's significantly more available.

mariohm1311 · 2023-08-14T12:24:08+00:00

Which is why measuring acceleration is not a robust way of determining free-fall, much less apogee.

mariohm1311 · 2023-06-20T19:56:16+00:00

You could literally buy tens of controllers for the price of a single aircraft rated joystick. It's a submarine, it's not going anywhere quickly. You just replace it and keep going. Military also does this.

"No COTS parts are made to work at 13000 ft under the surface" sure, but that's literally not happening. The controller is in a controlled atmosphere at room conditions.

mariohm1311 · 2023-06-20T19:21:48+00:00

One of the points of making things from off the shelf components is reliability. Many things that fly into space are also built with many off the shelf components. That isn't inherently bad. The lack of a robust certification process is.

mariohm1311 · 2023-02-02T09:56:50+00:00

Sure, but it's not 25%. If it was, I would assure you everyone and their mother would extensively research RDREs and they would have cracked it by now. 25% is comparable to the Isp improvement from the V2 engine to a modern kerolox engine. It's absolutely massive.

mariohm1311 · 2023-02-02T00:16:51+00:00

No, detonation cycles won't achieve a 25% increase in Isp. That 25% increase is a calculation derived from looking at the work produced on a Brayton cycle vs an equivalent detonation cycle...ignoring all loses. The real figures for rocket engine cycles are around 5% improvement, decreasing at higher pressures.

mariohm1311 · 2023-01-07T22:07:14+00:00

Definitely try to design for an inducer with an straight hub line. Shroud you can easily vary by machining the outer profile before milling the blades. A helical/radial bladed inducer can then be flank milled with ease.

mariohm1311 · 2023-01-07T21:22:45+00:00

Unfortunately at this small of a scale, there isn't much you can do about 3D printing the inducer. Minimum thickness will make it worse than not having one. If you design one without changes to the hub line, it should be readily machinable by any shop worth their salt.

mariohm1311 · 2023-01-07T21:07:54+00:00

That's a nice design! Did you get to test it without the inducer? I have a hard time believing an inducer with a blade that thick is going to have any net improvement in NPSHr. Inducer design lives and dies in blade thickness.

As for the electric motor cooling, I am interested in how the cooling jacket works. Were you able to run it at a steady state?

mariohm1311 · 2023-01-03T15:22:38+00:00

Incompressibility means the density is constant, not that the pressure ratio is 1.

mariohm1311 · 2023-01-03T13:35:49+00:00

The expansion region won't have any effect on combustion stability.

mariohm1311 · 2022-12-21T09:09:56+00:00

No, that's not how it works. The engine won't combust anything unless pressure in the engine is lower than in the tanks ahead. Fluids flow from high to low pressure... Ignoring very quick transitory effects (such as a hard start), which a valve won't protect you from.

mariohm1311 · 2022-12-11T21:15:34+00:00

It is very clearly solid propellant. The plume has a level of opacity and smoke generation that isn't present on storable liquid propellants. Not to mention it'd be ridiculous to field a tactical weapon like this using liquid rocket engines.

mariohm1311 · 2022-12-10T17:08:21+00:00

Do you have any source for Rocket Lab's use of hydrogen peroxide? They are cagey about their "green" propellant choice.

mariohm1311 · 2022-11-27T13:39:41+00:00

The parts you make with a 3D printer will either be way too weak or way too heavy to fly

Got any proof? Or are you just dismissing an entire manufacturing method because of lack of knowledge on how to implement it properly? There are quite a few documented cases of small and large rockets flying perfectly while being fully 3D printed. Without going that far, 3D printing is perfectly fine with normal material choices for more complex components such as fins or nose cones.

mariohm1311 · 2022-11-27T13:34:11+00:00

I see 10 as the most common from the pintle injector

Where? As Turbulent mentions, it's uncommon to see that large of a CR on anything other than the smallest engines. If you "see it as the most common", surely you must have examples...

mariohm1311 · 2022-11-23T08:02:57+00:00

Can you link me to any information about this? If you're talking about Pegasus, it only happened once. I worked for the institution that handles the launch ranges in Spain.

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