# Tag Info

9

HTP will sustain a combustion reaction without a catalyst once ignited, but it's not clear to me if the reaction proceeds quickly and smoothly enough to be a good idea for rocket combustion chambers. As MSalters comments above, hydrogen peroxide "will undergo potentially explosive thermal decomposition" before reaching its theoretical boiling point,...

6

Partial answer because based on a simulation doesn't address the secondary question about changes with throttling The paper CFD SIMULATION OF A LIQUID ROCKET PROPELLANT (LH2 /LOx) COMBUSTION CHAMBER shows a "flame front" in the sense that majority of the combustion reactions take place in a relatively small area of the combustion chamber. (zero ...

5

Combustion requires a fuel (hydrogen), an ignition source (your enormous explosive), and an oxidizer. There's a very small amount of oxygen in the atmospheres of the gas giants, almost all of it already bound up in water -- i.e. all the oxygen has already combusted with some of the hydrogen. Without the introduction of a lot more oxygen or other oxidizer, ...

4

From my (probably) similarily rough understanding of L*, it's a minimum size required for propellants to stay long enough in the chamber to mix properly. If the distance is shorter than that, you will experience problems with combustion instability. As such, having a length that's too large is certainly not as bad as too short, although the engine is then ...

4

The reason you can't finish your calculations is that you are missing half of the engine. You are going to have to make some decisions about the nozzle in order to get exhaust velocity. I'll make some decisions for you and show you how to work through it. Your engine's design altitude is going to be 11.8 km. This means that your nozzle exit plane pressure is ...

4

Partial answer In broad terms, about what velocity do the propellants come out of the injector plate? For the instrumented 50 klbf LOX/LH2 engine used in this study they varied the LH2 injection velocity from ~300 to ~700 ft/s. LO2 injection velocity was about 1/6th of that. For the other part of the question, it seems what you are asking is, what ...

3

tl;dr: I see that comments below the question by the OP argue against this being a deal-breaker problem but I'm going to point it out anyway as a partial answer. Any engine using "sand" as a reaction mass will have to avoid any significant production of silica nanoparticles so large that they are not accelerated in the nozzle. Assuming a perfect, ...

3

There are different numbers on this NASA page about Saturn V: Finally, the fuel squirted through 3 700 orifices into the combustion chamber to mix with the oxidizer, which entered through 2 600 other orifices in the injector face If the hole numbers of the question are correct, (1428 Oxidizer holes and (approximately) 1404 Fuel (RP1) holes) the explanation ...

2

The equation that you really want to look at is called the Area-Mach Relation. It’s an equation derived from 1D isentropic flow assumptions with varying cross-sectional area. Without going through the entire derivation, we can skip to the end result and interpret its implications. Area-Mach Relation: $\frac{dA}{A} = (M^2-1)\frac{du}{u}$ This one equation ...

1

It's not very scientifical, but for candy fuel engines I built when I was younger, I used simple formula to compute area of the nozzle (An) from area of engine (internal diameter) (Ae): An = Ae / K or for radiuses: Rn = sqrt(Re^2 / K) or for diameters: Dn = 2 * sqrt((De/2)^2 / K) for candy fuels, K of around 100 worked for me. So for example if you have ...

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