Sciencemadness Discussion Board

additional AL (negative OB) for better velocity

underground - 3-1-2014 at 08:51

Ok i believe that almost everybody knows tha the additional of AL powder does increase the velocity of explosive and it will be burned with atmospheric air. But is that true ?

So lets say an example for better explanation

3 moles of ETN and 2 moles of NM has a zero OB

3 C4H6N4O12 + 2 CH3NO2 = 14CO2 + 12H20 + 7N2

Now with the additional of AL powder, doest it will be burned with the atmospheric air, or it will absorb any mole of oxygen from the above reaction ending with negative OB ?





[Edited on 3-1-2014 by underground]

Turner - 3-1-2014 at 08:58

Al decreases velocity in explosives like ETN.

VladimirLem - 3-1-2014 at 09:40

Quote: Originally posted by Turner  
Al decreases velocity in explosives like ETN.


yep...at less powerfull explosives like ANNM it may increase the power -a bit- (maybe with a better OB) but normally AL is crap...i read a few PDFs and all they said was, it decreased the performace of explosives...especially if they are not used to become a "around zero" OB

underground - 3-1-2014 at 10:46

So it would be better to leave the metalic fuel aside as long as the OB is zero... i didnt know that... i thought that AL has almost the same properties in propellants and explosives.

[Edited on 3-1-2014 by underground]

Dornier 335A - 3-1-2014 at 11:02

The key to a detonation is that the whole decomposition reaction takes place in a small zone just behind the shock wave in the explosive. This is possible when the fuel and oxidizer are in the same molecule. Aluminium particles are enormous compared to a single molecule of say ETN, so only the outermost layer has time to react in the primary reaction zone. The rest will burn later on, but only the first fraction will contribute to the shock wave. So it acts almost like a completely inert material, and will therefore lower the detonation velocity.

Ral123 - 3-1-2014 at 11:34

Aluminium gives extreme velocity gain to rocks, silicon dioxide and wide range of phosphates.

underground - 3-1-2014 at 11:35

Quote: Originally posted by Dornier 335A  
The key to a detonation is that the whole decomposition reaction takes place in a small zone just behind the shock wave in the explosive. This is possible when the fuel and oxidizer are in the same molecule. Aluminium particles are enormous compared to a single molecule of say ETN, so only the outermost layer has time to react in the primary reaction zone. The rest will burn later on, but only the first fraction will contribute to the shock wave. So it acts almost like a completely inert material, and will therefore lower the detonation velocity.


I understand, really helpfull. That is why mixed explosives are not so powerfull... and sometimes smoke can be seen, unreactive material.

DubaiAmateurRocketry - 3-1-2014 at 12:32

Quote: Originally posted by underground  
Quote: Originally posted by Dornier 335A  
The key to a detonation is that the whole decomposition reaction takes place in a small zone just behind the shock wave in the explosive. This is possible when the fuel and oxidizer are in the same molecule. Aluminium particles are enormous compared to a single molecule of say ETN, so only the outermost layer has time to react in the primary reaction zone. The rest will burn later on, but only the first fraction will contribute to the shock wave. So it acts almost like a completely inert material, and will therefore lower the detonation velocity.


I understand, really helpfull. That is why mixed explosives are not so powerfull... and sometimes smoke can be seen, unreactive material.


Well if you really want to take it to the next level, you could try ultra fine nano aluminum, where the biggest particle is no more than a handful of aluminum atoms. However those are extremely reactive with air and such.

underground - 3-1-2014 at 12:38

Quote: Originally posted by DubaiAmateurRocketry  

Well if you really want to take it to the next level, you could try ultra fine nano aluminum, where the biggest particle is no more than a handful of aluminum atoms. However those are extremely reactive with air and such.


Well i have no idea how can i make that.
Except that, i actually use homemade magnilium, it is really fine.

DubaiAmateurRocketry - 3-1-2014 at 13:00

They're not fine enough for this purpose. nano aluminum is produced on industrial scale with special methods, Im not sure exactly how, they're expensive. However your homemade magnalium would be some good rocket fuel additive. I wonder if magnalium powder can achieve higher density when alloyed ? Magnesium give slightly higher specific impulse and use less oxygen than aluminum, the only reason aluminum is used is because its so much denser than magnesium.

[Edited on 3-1-2014 by DubaiAmateurRocketry]