deployment charges

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afterburner
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deployment charges

Postby afterburner » Tue Jul 09, 2013 7:12 pm

Could someone please tell me what type of black powder to use for deployment. I have seen FFFFG black powder mentioned on this forum before is this what I ask for or can I use shotgun black powder. I noticed that the powder Scoop uses is granular type used for rifles not the wafer type used in shotguns.
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Re: deployment charges

Postby Scoop1261 » Tue Jul 09, 2013 7:37 pm

The stuff I have is FFFFG or FFFG
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Re: deployment charges

Postby october sky » Tue Jul 09, 2013 7:40 pm

I use FFFg....works well...I have just done charges ready for my OZ Thunder launch for the coming Sunday...just made them ready so no need to do it in panic. There are 3x 8gr and 1x 10gr. Need to blow the laundry out... :P

Hey...Scoop got in just before...well done old mate !

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Re: deployment charges

Postby OverTheTop » Tue Jul 09, 2013 8:48 pm

I use FFFG.
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Re: deployment charges

Postby kopius » Wed Jul 10, 2013 7:20 am

The 'F' rating represents the grain size or coarseness of the BP. The more Fs the finer the granules.

Typically in rocketry, FFFg and FFFFg as the guys have mentioned above are the most common.

Many BP rifles use finer grades too whilst fireworks generally use much coarser grains.

At the end of the day, for most rocketry applications, any grade will work, it is just a case of which is the most efficient for your particular operation. In Saying that, sticking with FFFFg and FFFg works great and is also readily available.
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Re: deployment charges

Postby SpaceManMat » Wed Jul 10, 2013 8:57 am

kopius wrote:The 'F' rating represents the grain size or coarseness of the BP. The more Fs the finer the granules.

Typically in rocketry, FFFg and FFFFg as the guys have mentioned above are the most common.

Many BP rifles use finer grades too whilst fireworks generally use much coarser grains.

At the end of the day, for most rocketry applications, any grade will work, it is just a case of which is the most efficient for your particular operation. In Saying that, sticking with FFFFg and FFFg works great and is also readily available.


Do the finer grains burn faster?
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Re: deployment charges

Postby october sky » Wed Jul 10, 2013 9:23 am

Just wanted to clarify my self here as when reading my post some people might get it wrong : I have 4 small "Glad" resealable bags which are labelled with the amount of BP contained in the bag. I measure the quantity that I need and seal the bag. Then these are stored in and transported in the proper container as per the regulation..... :)

Then the rest of the charges are done at our launch site " Preparation Area"....

I do this mainly because as anyone who has witnessed our public launces knows how easy is to get distracted and that is the last thing I want when launching bigger rockets. :roll:
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Re: deployment charges

Postby ogivemeahome » Wed Jul 10, 2013 2:18 pm

SpaceManMat wrote:Do the finer grains burn faster?

The theory goes that the smaller the particles, the more surface area available to the flame and the faster the burn rate. The powder used in rifle cartridges (smokeless powder) should be avoided as it is formulated to give a faster burn rate (= higher pressures and less margin for error with the required amount). Stick to black powder.
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Re: deployment charges

Postby SpaceManMat » Wed Jul 10, 2013 4:50 pm

ogivemeahome wrote:
SpaceManMat wrote:Do the finer grains burn faster?

The theory goes that the smaller the particles, the more surface area available to the flame and the faster the burn rate. The powder used in rifle cartridges (smokeless powder) should be avoided as it is formulated to give a faster burn rate (= higher pressures and less margin for error with the required amount). Stick to black powder.


Thank, it's good to know why we do these things. Will keep this in mind when the time comes.
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Re: deployment charges

Postby OverTheTop » Wed Jul 10, 2013 4:55 pm

It comes down to the surface area to volume ratio for the burn rate (as a first approximation). That's why something like a wheat silo can explode when the fine dust in there finds an ignition source.

It is also a reason that the rocket fuel ALICE (aluminium and ice) exists. Nanoparticle aluminium powder, stirred into water and then frozen to -30degC. You then set it off with an igniter to launch your rocket.
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Re: deployment charges

Postby rocket_troy » Wed Jul 10, 2013 5:00 pm

ogivemeahome wrote:
SpaceManMat wrote:Do the finer grains burn faster?

The theory goes that the smaller the particles, the more surface area available to the flame and the faster the burn rate. The powder used in rifle cartridges (smokeless powder) should be avoided as it is formulated to give a faster burn rate (= higher pressures and less margin for error with the required amount). Stick to black powder.


Finer grades *with everything being equal* will burn faster due to the explanation provided above; however, "everything being equal" primarily relates to the manufacturing process being implemented to make the BP eg. homemade BP with a finer particle sizing will often burn slower than commercial BP with a courser particle sizing.
Don't take this as gospel, but I think that modern smokeless powers are more nitrocellulose based and rely on it's incredibly high pressure exponent to achieve fast burn rates ie. requires confinement/high pressures to achieve a fast enough burn rate to be useful for mortaring high speed projectiles or deploying recovery gear for a high power (short duration) utilization.

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Re: deployment charges

Postby strud » Wed Jul 10, 2013 6:24 pm

As Troy states the smokeless powders typically have rather slow burn rates at ambient pressure ie slower than BP

However, pistol and shotgun powders have much faster burn rates than rifle powders so it may be possible to find a fast pistol powder to get the job done. Problem may be that without containment you will not achieve reliable performance.

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Re: deployment charges

Postby kopius » Wed Jul 10, 2013 7:58 pm

Also as TP said, a lot of quality of burn rates is manufacturer dependant, even amongst the known manufacturers.

Black powder is typically very inefficient. With the fuel being carbon, its really just burning the charcoal with an oxidiser (Potassium Nitrate) that creates energetic gases with a lot of wasted energy seen as white smoke. Because of this it is great for guns as it has enough energy to push a projectile at relatively high speeds without breaking the barrel.

BP is no longer used in high explosives or war heads because there is far more efficient and cost effective solutions, however much like the gun scenario, with correctly built rockets it is perfect for ejection charges.

So this thread doesn't become too confusing, discussions about other forms of BP or other powders are really for information only. For rockets, simply stick to FFFg and FFFFg and you really can't go wrong.
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