Granulated vs. Meal in Rockets

[fireworks]

Is there a difference in power between rocket motors made with meal vs. those with granulated bp? Recently, I've been using bp with 5% ti and have been ricing the propellant and I have also started packing my engines with granulated bp to prevent dust. I have been experiencing much more catos with these endburners since I have made these changes. Edited April 11, 2009 by fireworks

[50AE]

I think that using granulated BP in your engines makes air pockets, which increase the burn rate.

[tentacles]

Lloyd S has been experimenting with using commercial (meal-d?) to make rockets, mostly endburners I think. I believe he's had to spray the inside of the tubes with silicone spray to keep the grains from grabbing the tube and accordian-pleating it.

 

I do know that to use commercial grains (or probably, even corned powder), the pressure needed will be much greater to consolidate properly, or you'll have lots of air pockets and plenty of CATOs. Essentially, you'll be needing to press it hard enough to crush the grains into powder and reconsolidate it as a solid grain.

[fireworks]

What is accordian-pleating?

[scrappy]

Accordian pleating is “ folding forward and backward over itself “ like the air box of a piano accordian

 

Centuries ago the British found that during transport of BP it would settle out in layers and render it useless during battle, so they dampened it down to keep it homogenous.

Upon drying it they found it had increased in power many times, so it was discovered that when it was wetted the Kno3 would migrate into the pores of the charcoal ( instead of it just being mixed with it ) it was now intimate and delivering a faster burn

[fireworks]

So pretty much, its not the air pockets, its just that granulated bp is more powerful whether its in the form of granules or just a powder?

[Pretty green flame]

So pretty much, its not the air pockets, its just that granulated bp is more powerful whether its in the form of granules or just a powder?

 

Granulated powder burns faster, not because the KNO3 migrates into the pores of the charcoal, but because it has a larger surface area as opposed to a fine powder which basicly acts as one solid mass. If you compress hard granules into a tube, there is no guarantee that the granules will crush and form a solid mass, you may be left with cracks or air pockets in the fuel grain, THIS will blow up your rocket, the point is that when the fire hits one of these cracks or air pockets the surface area increases and so does the pressure in the casing, the result is well known....

[scrappy]

Is there a difference in power between rocket motors made with meal vs. those with granulated bp? Recently, I've been using bp with 5% ti and have been ricing the propellant and I have also started packing my engines with granulated bp to prevent dust. I have been experiencing much more catos with these endburners since I have made these changes.

 

How do you pack your motors ? by press or hand, granulated bp will need more pressure to compact than just milled fine powder,

cavities will cause a cato, "whether its fine mill powder or granulated"

 

Kno3 Does migrate in to the pores of charcoal, increasing its performance, but the surface area of the granuals certainly does increase burn rate, due also to the free space between granuals for flame propagation,

[fireworks]

How do you pack your motors ? by press or hand, granulated bp will need more pressure to compact than just milled fine powder,

cavities will cause a cato, "whether its fine mill powder or granulated"

 

Kno3 Does migrate in to the pores of charcoal, increasing its performance, but the surface area of the granuals certainly does increase burn rate, due also to the free space between granuals for flame propagation,

 

 

I pack my motors with a rubber mallet, but my granulated bp is nothing like corned. The granules powder very easily and when I look at the bp when I am done packing it, it looks very solid and there are no visible air spaces. Also, when I scratch the propellant, it is hard and the little bit of propellant that rubs off is like meal.

Edited April 12, 2009 by fireworks

[50AE]

If you put much granulated powder at once, the upper granules will take the most damage and compact, but the lower ones may not. And you will have uncompacted granules on the bottom that accelerate the burning rate. Edited April 12, 2009 by 50AE

[Pyropow3r]

If you are using homemade Bp (granulated) that is made without dextrin it will compress relativity easily without any air pockets.

 

Using granulated Bp is much more easier and cleaner to use as well. You could also use it for reports on the rockets or ejection charge

 

 

Just use granulated Bp it is just more versatile.

[Mumbles]

Without some nice microscopes, it'd be impossible to know if the nitrate absorbs into the charcoal pores. I've personally heard it does not, and this was from a rather reputable authority (Ian von Malitz).

 

As for why they are catoing, it could be many things. The speed does increase somewhat when granulated, but I haven't heard experiences of this transfering over to rockets before. BP does speed up with small amounts of water present, so perhaps your granules arn't as bone dry as the meal. It could be gaps, which most certainly would cause these kind of problems. It could be the Titanium itself. You might want to simply enlarge the nozzle a bit, or add 5 parts extra charcoal. I'd suggest giving the rockets a few extra hammer strikes to ensure it's all packed down.

[scrappy]

Without some nice microscopes, it'd be impossible to know if the nitrate absorbs into the charcoal pores. I've personally heard it does not, and this was from a rather reputable authority (Ian von Malitz).

According to the story of Gunpowder aired on the BBC, wetting Black powder Does migrate the Kno3 in to the pores of the charcal

[Pretty green flame]

According to the story of Gunpowder aired on the BBC, wetting Black powder Does migrate the Kno3 in to the pores of the charcal

 

Ofcourse, the BBC is by far a more reputable source than the man who wrote the book on black powder manufacture

 

Also, look at it from this point, if you are using 10ml of water to wet a 100g batch (7-10% are typical for pressing), your are at best going to disolve ~3.5g (theoretically) of KNO3, not a whole lot. You can't belive everything the TV tells you, if it were so, aerial shells would be filled with rice, some BP and a whole lot of imagination....

Edited April 13, 2009 by Pretty green flame

[scrappy]

Ofcourse, the BBC is by far a more reputable source than the man who wrote the book on black powder manufacture

 

Also, look at it from this point, if you are using 10ml of water to wet a 100g batch (7-10% are typical for pressing), your are at best going to disolve ~3.5g (theoretically) of KNO3, not a whole lot. You can't belive everything the TV tells you, if it were so, aerial shells would be filled with rice, some BP and a whole lot of imagination....

 

 

LOL, thank you, i never looked at it that way, your example is a good one and logical, since when has the tely let that facts get in the way of a good story....

i don't believe everything i see and hear but i did believe that, generaly i am an acute skeptic on everything

 

was that long grain rice or short

[Aquarius]

I have tried both meal straight from my mill as well as granulated powder for BP coreburning rockets. Both with 3 percent Red Gum as the binder and acetone as solvent, just as Sleeter describes in his book. My mix was 60:30:10 BBq charcoal.

Both casings were pressed in a hydraulic press with a fixed pressure. Then I tested my motors on a homemade digital bench hooked to my computer for a readout. (It's a Dataq setup with a loadcell for those interested, have a look at Nakka's site for more info).

 

Both meal and granulated burned roughly 0.5 sec, but with a huge diffrence in thrust: The meal motor reached a peak of avergae 7 Newton, the one with granulated powder a average of 16 Newton! I did the same test agian a few times, thinking I had made a mistake, messed up the settings but with the same results.

 

A while back I had problems with CATOs as well. My hotfix was to use less powder at each pressing to avoid airpockets.

Now they are really great workhorses, and well suited for model rocketry as well as firework drives.

[fireworks]

I have tried both meal straight from my mill as well as granulated powder for BP coreburning rockets. Both with 3 percent Red Gum as the binder and acetone as solvent, just as Sleeter describes in his book. My mix was 60:30:10 BBq charcoal.

 

 

How did you obtain enough thrust to lift a rocket using bbq charcoal bp?

[TheEskimo]

Hi. I just dampen my BP with 70% isopropyl, and send it through a coarse kitchen screen. I then let it dry on newspaper for a couple hours. This keeps down the dust when packing, and might increase, the power; I've never checked. But I ram my 1 pound rockets, I don't press them;, and I've never gotten the accordion pleating so dewscribed; that might be because I ram the BP dry, bot slightly damp, unless I've misread the earlier posts

[scarbelly]

How did you obtain enough thrust to lift a rocket using bbq charcoal bp?

 

He most likely means lumpwood bbq charcoal. It's still used for barbecuing, but it is not mixed with clay and fillers and stuff to form briquettes.

 

 

It's interesting that they burn for the same length...

Edited August 2, 2009 by scarbelly

[drtoivowillmann]

Granulated vs. meal:

 

Industry always uses dry granulates, to make their rocket drivers. Reason: dosage is easier.

Pressed or manually rammed, there are only two secrets:

1st.: To work well you must add 4% of fine graphite powder to your comp. If granulate is quite fine,

you may add it after making your granulate. Dont use less than 4% nor more.

Comps that make your driver explode, suddenly work well, if you add graphite.

2nd.: Your granulate must not be too hard. It must crunch completely when you press or ramm it.

So do not use much water, when you make it. Dont use any binder.

 

This is truely a secret from a professional (me) fireworker.

 

Yours truely:

Toivo

[tentacles]

That's an interesting idea - does the graphite contribute anything to the tail?

[drtoivowillmann]

Dear Tentacles:

 

Absolutely nothing !

 

It only moderates the behaviour during pressing or ramming, the metrial results better compacted,

with less air bubbles.

 

Yours truely: Toivo

[Swede]

Interesting on the graphite. My last BP batch was created as a dedicated rocket fuel using 65:25:10... would the addition of graphite reduce the power too much in this ratio?

[dagabu]

Dear Tentacles:

 

Absolutely nothing !

 

It only moderates the behaviour during pressing or ramming, the metrial results better compacted,

with less air bubbles.

 

Yours truely: Toivo

 

In my experience, the graphite adds nothing to the compaction when pressed. The fuel grain of the same weight is exactly the same length. It makes for easier spindle removal but they become a little harder to light and have an effect on the tail, albeit small.

 

I tried a small amount of baby oil in my last comp to keep the dust down and found that as long as I added 5% Willow to the mix, the thrust remained the same and the tail was just as nice. I just added drop by drop until I saw some clumping and screened it all. I will clump lightly when squeezed.

 

D

Edited October 6, 2009 by dagabu

[Aquarius]

Well, I granulate mostly to keep the dust from floating around. I think it was from one of the Skyligther newsletters I saw it first; a o-ring on the rammer keeps the dust from shooting up when using mill dust in drivers.