Analysis of a star

[Swede]

This is the formula posted by CrazyBoy from the compositions area for a red star; thanks CrazyBoy.

 

Strontium nitrate...............50

Potassium perchlorate.........8

Parlon..............................18

Magnalium (-325 mesh).....12

Charcoal (airfloat)...............5

Sulfur................................5

Red gum...........................2

Dextrin..............................5

 

I would like to truly understand what the ingredients in this particular case actually do. My uderstanding of it...

 

Strontium nitrate............... Red spectra electron transitions; oxidizer

Potassium perchlorate.........Oxidizer

Parlon..............................Chlorine donor

Magnalium (-325 mesh).....increases burn temp, brighter colors, fuel

Charcoal (airfloat)...............ignition, fuel?

Sulfur................................ignition, fuel

Red gum...........................binder, fuel

Dextrin..............................binder, fuel

 

What is the purpose of the charcoal in this particular comp? I also understand we have two basic classes of stars, organic, and metallic, with the metallic stars tending to be brighter and better. This is due, I assume, to the temperature of the burn? All else being equal, higher temps create a more brilliant display. Is there a method to measure the temperature of a burning star outside of special lab equipment?

 

Thank you.

[psyco_1322]

With the metal fuels being burned the luminous output is much higher, making the colors a lot brighter also. The more light your eyes take in the better it will look obviously.

 

The red gum is more than likely just an accessory fuel, it burns great in combination with the KClO4. Since there is dextrin in there that is more likey to be the binder since its not often used for a accessory fuel. If you have a color star that has problems lighting up just add a few percent charcoal and it will make a world of difference. You will not notice the charcoal in the star burning though.

 

You will see a lot of color comps with charcoal in them. The charcoal aids greatly in the stars ignition

[Mumbles]

More specifically charcoal is added to smooth out the burn of the star. It helps keep it going once it gets started. There is also some talk of it eating up any extra oxygen, which improves flame color.

[psyco_1322]

I read something about it in the BAFNs but I cant find it and I dont really remeber how it was explained. But yah it keeps them from being blown blind real easy.

[Swede]

Thanks guys. The red gum and dex are binders that use different solvents, water for the dex, and alcohol or other non-aqueous solvents for the gum. So the gum is in there as yet another type of fuel?

 

That is interesting on the charcoal. I've never heard that one of its functions would be to scavenge stray O2. As far as easing ignition, Yes I can see that.

[psyco_1322]

Yah. I personally think when stars are bound using red gum, especially in high amounts, it causes them to burn considerably slower to what they would be if using dextrin. Like if you where to bind that star using the red gum and basically just let the dextrin set and do nothing, but that star doesnt really have that much in it so it may not effect it as much. Im talking with 10% or more red gum.

[Niter]

When a star burns, there is always energy directed outward (lost to the surroundings) and energy directed inward (available for burning the star).

 

Carbon, being black, greatly increases the amount of combustion energy absorbed by the star, which is put to work in the burning of the star. Less energy is "lost" as heat output.

 

In addition to that a grain of charcoal acts as an ignition source to the surrounding composition.

 

Here's a simple example:

 

Try to light a lump of sugar. You will find it is hard to near impossible to do so. Now cover the surface of the cube with a tiny bit of ash, for instance cigarette or paper ash. Now light it. You will find the sugar cube not only keeps burning, but the carbon aids in its further combustion, like a wick in a candle.

 

A pyrotechnical experiment to the same effect:

 

Make a 7 : 3 mixture of KNO3 and sugar, and observe its speed of combustion. Now make the same mixture again, but with +2% of finely divided charcoal thrown in the mix. You will find that the combustion speed is significantly enhanced.

 

Its not the +2% of charcoal's extra heat that makes it happen, its because the carbon draws more of the compositions heat into the powder itself by being black (as opposed to the white mix) and because it adds ignition points, making the sugar more readily combustible.

 

This trick works with most lightly colored compositions: adding +2% of very fine carbon usually enhances speed of combustion and like Mumbles says, smoothens it out.

[ST1DinOH]

When a star burns, there is always energy directed outward (lost to the surroundings) and energy directed inward (available for burning the star).

 

Carbon, being black, greatly increases the amount of combustion energy absorbed by the star, which is put to work in the burning of the star. Less energy is "lost" as heat output.

 

In addition to that a grain of charcoal acts as an ignition source to the surrounding composition.

 

Here's a simple example:

 

Try to light a lump of sugar. You will find it is hard to near impossible to do so. Now cover the surface of the cube with a tiny bit of ash, for instance cigarette or paper ash. Now light it. You will find the sugar cube not only keeps burning, but the carbon aids in its further combustion, like a wick in a candle.

 

A pyrotechnical experiment to the same effect:

 

Make a 7 : 3 mixture of KNO3 and sugar, and observe its speed of combustion. Now make the same mixture again, but with +2% of finely divided charcoal thrown in the mix. You will find that the combustion speed is significantly enhanced.

 

Its not the +2% of charcoal's extra heat that makes it happen, its because the carbon draws more of the compositions heat into the powder itself by being black (as opposed to the white mix) and because it adds ignition points, making the sugar more readily combustible.

 

This trick works with most lightly colored compositions: adding +2% of very fine carbon usually enhances speed of combustion and like Mumbles says, smoothens it out.

 

awesome explanation.

 

will lamp black will work the same, better, or worse than charcoal in these situations?

Edited August 20, 2008 by ST1DinOH

[psyco_1322]

Can anyone confirm that the color of the composition increases its burning properties? This sounds very strange and I would not think that the darker the comp is the more energy its going to keep in. I can see charcoal increasing burn rates and an aid to ignition through the mixture but making it dark in color is kinda fishy sounding. I may be completely wrong but I have never heard this refered to before.

[FrankRizzo]

He is correct. The darker color increases the amount of infrared energy absorbed back into the composition. In fact, that guy with the crazy whistle motors, Gerald, has been experimenting with additives along those lines that both increase the thermal absorption by conduction as well as absorbing infrared energy.

[tentacles]

Frank: Now imagine if he took his whistle mix and riced it with RG like your last batch. I'm not sure those carbon fiber reinforced tubes would be able to take it. Lifting a 5" shell with a 3/8" motor, maybe?

[psyco_1322]

Ok now I think of it in terms of infrared light and energy it makes a bit more since.

 

Hmmm he never said anything about that to me. We talked quite a bit this year about things. Every time I see that guy I learn a little bit more. I think people are starting to slowly add up to what he has been doing. I keep seeing things that are close to what he is doing but not quite there and not all in the same place.

 

Frank just what is the purpose for the red gum? The Vaseline is for lowering friction sensitivity and helping the fuel stick together. The red gum seems to just aid in working messes. If you really wanted a hot fuel just leave out the binder and make the formula straight. It might be kinda scary to press but you are already leaving out the Vaseline. So I wouldnt say that the red gum is directly related to your good success. You did leave out a major burn rate suppressor. I bet if you rice that fuel with lacquer thinner you would even a hotter fuel. Gerald was explaining to me why using lacquer thinner will aid in a hotter fuel. Its about the same concept behind why red gum bp is hotter than the water bound stuff.

 

If anyone has Gerald Muths email please send it to me off board.

[FrankRizzo]

The reg gum is there strictly to aid in the granulation process and make loading less messy. I was running short of time, and using a binder that would dissolve in a (cheap) fast-evaporating solvent was an attractive idea. It does have a bit of fuel value, and that's why I chose to stay with the 76:23 ratio. Without additional fuel (vaseline, mineral oil, red gum, etc.), a more ideal ratio is 70:30. I've found whistle mix to be quite insensitive to friction by itself (no titanium).