R-candy with sulfur

[THEONE]

I have seen that the Isp of the APCP is only a little bit better than than Isp of the ANCP but the AN is much more cheap than AP...

[aeon]

Good luck actually getting that performance out of it. In practice, combustion efficiencies are much lower than theoretical with AN. Once you add the superfine metals (and not Al - you will find it doesn't really help at all; zirconium, boron or magnesium do though) necessary for efficient combustion of AN, you might have well have used AP, if you're looking at it from a cost perspective. I struggle to think of a single mass produced rocket motor that has utilized AN as oxidizer. Even KP has been more popular - GALCIT for example, for JATO bottles, despite poor performance and challenging motor design due to it's horrendous pressure exponent of >0.7. Industry has not had any real success using AN (and believe me, they have tried - AP's dense fog of HCl in the exhaust presents a huge problem for military hardware, which is why no or limited smoke double/triple base propellants along with RDX/HMX/CL-20 modified composites are still the rulers of this field for now) - do you think you will have better luck? By all means try, just be sure to tell the rest of us what the secrets to success are! Edited October 2, 2011 by aeon

[THEONE]

Good luck actually getting that performance out of it. In practice, combustion efficiencies are much lower than theoretical with AN. Once you add the superfine metals (and not Al - you will find it doesn't really help at all; zirconium, boron or magnesium do though) necessary for efficient combustion of AN, you might have well have used AP, if you're looking at it from a cost perspective. I struggle to think of a single mass produced rocket motor that has utilized AN as oxidizer. Even KP has been more popular - GALCIT for example, for JATO bottles, despite poor performance and challenging motor design due to it's horrendous pressure exponent of >0.7. Industry has not had any real success using AN (and believe me, they have tried - AP's dense fog of HCl in the exhaust presents a huge problem for military hardware, which is why no or limited smoke double/triple base propellants along with RDX/HMX/CL-20 modified composites are still the rulers of this field for now) - do you think you will have better luck? By all means try, just be sure to tell the rest of us what the secrets to success are!

 

Ok so better not try cause the AN is also a high explosive... and i afraid a little bit...

But

[Bilbobaker]

Polyurethane or silicone, if you want elastomeric chemically-curing binders...

 

Recipe please...

 

[aeon]

Sure, but I don't expect this to be of much use to anyone, unless you can get HTPB and a diisocyanate curing agent. You could easily just replace the liquid fraction with a different polymer system however - but you will need to do your own research! I have used other polyurethanes (non-HTPB or PBAN), and silicones, and I could give compositions for those too, but it's better that people figure this stuff out on their own rather than blindly copying, I think. (PM me if you REALLY need help, but I expect you to have done some research first)

Anyway, this is one of mine. Ballistic parameters are given below. I don't have all of the data required for a full simulation(such as exhaust gas molecular weight, specific heat, etc), but seeing as the coefficient and exponent are the only ones that have to be experimentally determined, it's actually the most important two parameters. The rest can be calculated from the proportions.

 

This is a formula originally designed for high performance, low smoke endburners, but I have used it for some seriously, seriously fast endburners. The copper oxide is there to increase burn rate sensitivity to pressure (so that with endburners the nozzle throat does not end up too small, and clog on ignition from the ignition material passing through) and to make the flame blue to make it blend in with the sky so it is close to invisible. It also catalyzes a different stage of the decomposition of ammonium perchlorate than iron-based catalysis does, speeding up far beyond what just the addition of iron oxide can achieve.

 

Solid fraction:

 

Ammonium perchlorate, granular, 200 micron - 55%

Ammonium perchlorate, granular, <38 micron - 25%

Aluminium powder, atomised, <20 micron - 1%

Iron (III) oxide, nanoparticles - 2%

Copper (II) oxide, superfine - 1%

 

Liquid/binder/polymer fraction:

 

R45-HTLO HTPB, Sartomer - 9.86%

Isonate 143L - 1.22%

Epoxy resin - 0.48%

Epoxy curative 0.16%

Dioctyl adipate - 4%

6,6'-methylenebis(2-tert-butyl-4-methylphenol) - 0.1%

Tris(4-nonylphenyl) phosphite - 0.1%

Maleic anhydride - 0.05%

 

NCO:OH ratio: 1.0146

 

a=0.014 (in), n=0.55

 

Um, with the epoxy stuff, I forget what it was exactly, but it could be swapped out for any epoxy system with a curative moderately reactive with AP such that some curative reacts with the surface of AP particles,crosslinking them into the polymer network, but some is left over to be incorporated into the polymer network. Obviously, the ratios might need to be changed. Anybody messing with this stuff should know this anyway, of course.

Edited October 4, 2011 by aeon

[donperry]

THEONE,

I see you finally started propep D. One thing you will find with propep is that a given combination may show an nice ISP, but in reality it's not that efficient and some comps wont even light!

 

 

Just one thing about the burnrate.

 

Burn rate alone is not conclusive until ISP is brought into the expression.

 

Remember, a fuel may be burning slow but kicking off heavier particles at higher velocity, which means more thrust <newtons third law>

 

What you will get with a slower burning - higher ISP fuel is more distance for the same mass.

 

<AM i right?>

 

Reminder of the potentials of sugar:

 

26K feet

~ Mach 2

Edited October 9, 2011 by donperry

[aeon]

Yes, burnspeed isn't correlated with ISP. For a dramatic demonstration of this, compare APCP with Zn/S.

You can modify EFFECTIVE burnrate by altering grain GEOMETRY.

 

Yes, it's generally true that a high ISP but slow burning propellant will give you a greater distance than a equivalent ISP fast burning propellant, but this is more down to aerodynamics than anything to do with the propellant itself - drag increases as you go faster (yes, there are exceptions, I know - we're not discussing hyperkinetic projectiles here), which is why slow burning can be better for distance, by minimising velocity and hence drag losses. Note however that a coreburner of slow propellant is usually going to produce a higher Vmax than a endburner of fast propellant. This is why I was stressing geometry before.

 

ISP is pretty much a function of temperature of combustion products and molar mass of products - the latter part is because in general, lower molar mass products are gases at exhaust temperature, not liquids or solids. Liquids and solids are unable to contribute additional exhaust velocity upon expansion because they don't appreciably change volume. The combustion temperature of particular importance because it defines the potential kinetic energy that can be extracted from the propellant -remember, temperature of just a way of describing the average speed of molecules in a mixture, all the atoms are vibrating but not in any particular direction. A deLaval nozzle is a way of ordering that disordered kinetic energy and making it point (mostly) one direction.

[THEONE]

I am trying now to increase the burning time with a slower burning rate propellant, so i have tried a kno3 - nano3 propellant.

The pressure so the thrust can be easily increased with more propellant but the burning rate will be the same... that is why i like - prefer slow burning rate propellants... I believe that slow burning propellants can carry more total impulse than the fast burning rate propellants

Here i have a modified sugar propellant with kno3 and nano3 rocket engine test were the burning time was more than 2 sec when the regular kno3 sugar propellant with the same web thickness had a burning time of 0,5 sec, also nano3 increased the Isp... we have a limit of the pressure so a limit of the thrust, but we haven t any limit in burning time....

The motor surely have a lower average thrust than an another one motor with faster burning rate with the same propellant but you can simply increase the fuel - grains to achieve the same pressure and the same thrust like the faster one fuel - engine, but you can not do this with the faster burning rate propellant cause of the over pressuring causing CATO, so with this way the total impulse will be more....

I do not like to chance the geometry profile cause moon burner or c-slot geometries have not got as good thrust profiles as the bates grains geometry, also bates grains are much more easy to cast...

Edited October 11, 2011 by THEONE