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Author: Subject: Ammonium nitrate as propellant
ecos
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[*] posted on 16-2-2015 at 02:16
Ammonium nitrate as propellant


Hi All,

there is a part of the discussion of this topic under a name of "nitrocellulose help" but the initial topic is already different and the name became miss leading. I would prefer to have a separate thread for this topic.

I went through Nakka project : http://www.nakka-rocketry.net/anexp.html#preparation

he stated that the promising mixture is A24 : 68% AN , 4% S , 17% Al , 11% binder (Neoprene)

He also stated in his website regarding the binder :

Quote:

Early experiments performed by the author confirmed that AN mixed solely with typical fuel/binders such as epoxy, sucrose, polyester, polyurethane and silicone would generally not sustain combustion. If a small amount of NaCl were incorporated, sustained burning (smouldering) would occur, however, very slowly, and the resulting low combustion temperature would tend to produce voluminous amounts of carbon-rich ash.


but Nakka never made any tests with those binders in his table.

I also found another formula for Wickman Propellant: http://www.space-rockets.com/prop.html

My problem is with the binders !! specially R45HT binder. it is hard to synthesis.

I found interesting article for optimization over Nakka project : https://www.byui.edu/Documents/physics/Theses/David_NeweyF13...

they used this formula but they didnt state the binder ! : 74.9% AN, 19.8% Al, 6.5% S and the rest is a binder.

I found this equation in the article above , I wonder if he used benzene as a binder?!



do anybody have a successful experiments with AN but with simple binders?

i think this book has many experiments regarding AN and AP : "How To Make Amateur Rockets" but I couldn't find a copy for it.


[Edited on 16-2-2015 by ecos]
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[*] posted on 16-2-2015 at 05:50


Benzene is too volatile and labile to be a binder it must be a typo.
Not counting the carcinogenic and flamability risk involved with its use.




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[*] posted on 16-2-2015 at 06:29


Quote:
My problem is with the binders !! specially R45HT binder. it is hard to synthesis.

You can get it here!

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[*] posted on 16-2-2015 at 17:02


In some countries they use the name benzene to mean white fuel, or coleman fuel. Could they mean that? Just a suggestion...
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[*] posted on 16-2-2015 at 17:25


AN is clean and alright, the problem with it is that its hard to ignite, low OB, and u better have a good catalyst, magnesium works well with AN.
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[*] posted on 17-2-2015 at 02:34


Mg is expensive material thats why Nakka prefered to use Al:


Quote:

The drawbacks to using magnesium as a constituent in a propellant include the safety concerns associated with handling, the high cost of this material (especially when hazmat shipping fees are factored in), and the lack of easy availability.

After much pondering, a rather interesting alternative thermic agent came to light. Aluminum, which has a greater heat of reaction than magnesium, was then tried. The difficulty with combusting particles of aluminum is due to the tough shell of aluminum oxide (alumina) that encases the readily oxidized metal. Initial attempts at simply blending aluminum powder with AN and a binder were fruitless. The aluminum particles did not burn satisfactorily, being well protected by the tough alumina shell. Reference [4] also describes attempts at using powdered aluminum, but the studied formulations failed to burn.



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[*] posted on 17-2-2015 at 23:57


you can try it, but aluminum barely burns because the temperature AN burns at is just not enough to totally utilize Al2O3's high energy out put.
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[*] posted on 18-2-2015 at 00:12


Of course, there are Aluminum-Magnesium alloys. Popular in pyrotechnics, available from suppliers in various ratios and a wide range of particle sizes and shapes.

A 50:50 by weight alloy of Mg-Al poured onto a cold Iron or steel surface shatters like ice. It can be easily reduced in a ball mill to very fine particle size, I recall Dutch amateur pyrotechnists doing this and writing a "how to" article during the 1990's. Key is technique to smelt without setting it on fire, and pouring the alloy at just above melting point to prevent it igniting.

http://m.instructables.com/id/7030-MgAl-Magnalium-Powder-Pro...

[Edited on 18-2-2015 by Bert]




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[*] posted on 18-2-2015 at 01:09


random thought just before bed, so probably a bad one.. but in OP it stated that NaCl helped burn rate/sustainability but not much, and also that benzene was used as/in the binder. perhaps a typo, but made me think of mothballs, or more specifically p-dichlorobenzene. just a thought, prob a poor one
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[*] posted on 18-2-2015 at 01:58


Quote: Originally posted by Bert  
Of course, there are Aluminum-Magnesium alloys. Popular in pyrotechnics, available from suppliers in various ratios and a wide range of particle sizes and shapes.

A 50:50 by weight alloy of Mg-Al poured onto a cold Iron or steel surface shatters like ice. It can be easily reduced in a ball mill to very fine particle size, I recall Dutch amateur pyrotechnists doing this and writing a "how to" article during the 1990's. Key is technique to smelt without setting it on fire, and pouring the alloy at just above melting point to prevent it igniting.

http://m.instructables.com/id/7030-MgAl-Magnalium-Powder-Pro...

[Edited on 18-2-2015 by Bert]


interesting article, i went through it and found the same statement :

Quote:

The hazardous nature of transporting these powders is currently causing shipping costs and restrictions to rise. The recent increase in security within the US and international delivery systems is making it difficult for rocketry hobbyists to purchase these powders at a low cost.


I found it interesting to use S to break the oxide shell of Al, both Al and S are cheap and easily found.

regarding : DubaiAmateurRocketry
Quote:

you can try it, but aluminum barely burns because the temperature AN burns at is just not enough to totally utilize Al2O3's high energy out put.

I am afraid of this point , I was thinking to add some iron oxide on the mixture , this would form Thermit and would increase the temperature in the chamber.
but it seems the articles i showed in my first post stated success with only Al and S and this sounds promising for me.
My problem now is the binder ! , shiping RHHT would be a big problem ! so it wont work.



[Edited on 18-2-2015 by ecos]
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[*] posted on 19-2-2015 at 03:55


do anybody have access to this article : http://www.readcube.com/articles/10.1002%2Fprep.201200159?r3...
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[*] posted on 19-2-2015 at 13:50


AN can form the basis of a very powerful rocket propellant along with aluminum and silicone rubber as a binder. There is a thread here on SM from some years ago about that (this is where I first saw it). The resulting grain is a little difficult to ignite, and gives a quite sedate burn in the open, however, it performs excellently (and smokelessly) in an actual motor. In addition it is very tolerant and works well with a variety of Kn ratios without CATO or "puffing". The original poster felt that this was due to the nature of the binder, giving a quite low n-exponent (in the dependency of burn rate on pressure, IIRC).

I modified the propellant by adding granulated NC/NG and also improved the mixing procedure by utilizing an inert solvent to get a more uniform material that could be processed into a molding powder. Using these modifications I made 12 mm rockets that performed very much like the old gyrojet, though the sound was much more pronounced.
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[*] posted on 20-2-2015 at 06:04


Hi Microtek,

I found the propellant you mentioned but with AP instead of AN : http://youtu.be/TllMf7DzYkA

I would try (AN + S+ Al + Silicone rubber + Fe2O3) but i still think about the percentages I would use.
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[*] posted on 22-2-2015 at 13:16


I was reading about Sulfur and Aluminum and found this on wiki :

Quote:

Aluminium sulfide is readily prepared by ignition of the elements[6]
2 Al + 3 S → Al2S3
This reaction is extremely exothermic and it is not necessary or desirable to heat the whole mass of the sulfur-aluminium mixture; (except possibly for very small amounts of reactants). The product will be created in a fused form; it reaches a temperature greater than 1100 °C and may melt its way through steel. The cooled product is very hard.


for formation A24 : 68% AN , 4% S , 17% Al , 11% binder (Neoprene)

my understanding now , the 4%S would react with 2.2% Al to form very high temperature to disable AN from self-extinguished.
Thats why a high percentage of Sulfur didnt work for Nakka's project, i.e the sulfur reacted with most of Al and this make shortage for Al(fuel) to be reacted with AN(Oxidizer).

I wonder why didnt he use Fe2O3 instead of Sulfur to generate higher temperature to avoid self-extinguished?



[Edited on 23-2-2015 by ecos]
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[*] posted on 22-2-2015 at 23:19


Sulfur is not required if silicone rubber is used as the binder. As I said, it is a little hard to ignite (though not more so than many other propellants), but it exhibits a nice stable burn. At least if well mixed, with very fine Al and AN particles.
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[*] posted on 23-2-2015 at 00:02


By silicone rubber you're talking about window seal or caulk? Never tried it.
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[*] posted on 23-2-2015 at 00:40


Quote: Originally posted by Microtek  
Sulfur is not required if silicone rubber is used as the binder. As I said, it is a little hard to ignite (though not more so than many other propellants), but it exhibits a nice stable burn. At least if well mixed, with very fine Al and AN particles.


I found this mixture :



this means that elastomer binder is silicone rubber?
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[*] posted on 23-2-2015 at 03:15


I doubt that would work. AN mixtures do not burn well without a metallic fuel. Usually said metallic fuel has to be Mg or Mg/Al alloys to sustain the burn, but specifically in the case of siloxane polymers (silicone rubber), pure Al can be used.
Many kinds of caulk contain inert additives which is not good. Look at the MSDS of the product to find out wht is in there.
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[*] posted on 23-2-2015 at 04:30


Clear GE silicone II has been used in other rocket fuel mixtures-



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[*] posted on 23-2-2015 at 06:37


Thx all for the support , I think the improved Nakka formula is my target , very low Sulfur percentage and I would use silicone as binder
the mixture will be like this : 74.9% AN , 0.65% S , 19.8% Al , 4.65% Binder(GE silicone II)

I will try to make a grain and provide my feedback after testing.
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[*] posted on 23-2-2015 at 17:49


AN seems like a fairly terrible oxidizer for a rocket. If it has aluminum (or possibly with magnesium) Any moisture will liberate ammonia and decompose most of the aluminum over time. Boric acid or possible oxalic may help stop this. But you would have to have hardcore storage as well as phase stabilizing it to store it for much time.

Adding some silicon fuel seems like the best solution for keeping the reaction going. The little droplets of red of glass should keep the reaction going. Lol Though, you might as well use AlICE(aluminum Ice) propellent.




"""Blue Strobe Rocket

This is a relatively simple composition to make, but bizarre in its behavior and a mess to formulate. The basic formula is:

Blue Strobe Rocket Formula
Ammonium perchlorate 63%
Copper oxide, black 10%
PVC powder 5%
GE II Silicone #5000 (bathroom caulk) 22%

First, take the three dry ingredients (ammonium perchlorate (ball milled to a fine dust), copper oxide, and PVC powder) and sieve them together three times through a 40-mesh screen. Then, place them in a container on a balance and tare it. Slowly squeeze in the appropriate weight of silicone caulk. This requires some practice to be precise. Go slow and easy so as not to add too much.

Mixing requires some effort. I prefer to use an old plastic container. First I mix it with a fork as thoroughly as possible. Then, I use a wooden dowel, 1.5 inches in diameter by 6 inches long, as a pestle to try to force the strobe rocket mix through a window screen section stretched over a bowl. Not all will go through, but the kneading action will thoroughly mix even the congealed portion, which can later be grated through a wire mesh screen with 1/4-inch squares.

Some folks like to use a plastic bag of the Ziploc variety to manually knead the strobe rocket mix. I prefer not to be holding it! I always wear gloves and safety glasses when working with any pyrotechnic compositions. And, I sure don't want to make a mess of anyone's shop who is gracious enough to allow me to work in their facilities. This composition is so messy that I recommend you set aside a set of tools to use with this and with nothing else.

The composition is highly flammable as soon as it is mixed, so be careful. Use an arbor or hydraulic press, it is best pressed (do NOT hammer or ram this composition!) into strobe rockets BEFORE it has a chance to set and cure. When it cures, it's like working with small pieces of pencil eraser. Try making cut stars before the mix cures. Or, try pressing the soft composition into tubes for strobe pots and letting them cure overnight.

The composition actually burns quite slowly. Try burning some on the ground, outside a tube to see this effect.

There are many types of silicones. Different curing systems are employed. Some may not be compatible with the other chemicals used. I do not recommend any but the most cautious experimentation with any other silicones. Further, if you place a small amount of composition on a steel plate and hit it with a hammer, you will find it is also shock sensitive.""""http://www.skylighter.com/fireworks/How-to-make-sky-rockets/blue-strobe-rocket.asp
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[*] posted on 24-2-2015 at 01:11


Hi Ni3rtap, Thx for the reply.

My problem is with ammonium perchlorate, it needs electrolysis with MMO plates which is a headache for me to find. the electroanalysis process takes around 7 days with a strong power supply.

AP is sensitive and I found many accidents with it. a boy lost his hand when he tried to modify something inside the rocket motor.

I would prefer AN since it is easily found (fertilizer , cold backs, ....) , cheap , low sensitivity.

I didnt search yet about kinds of silicone in nearby markets, I will try to find what is available and then check them online.

anyway , thanks for the info and i would keep this composition in mind :)

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[*] posted on 24-2-2015 at 06:12


ecos, you are in Eastern Europe?

Ammonium perchlorate sensitivity to detonation (and burn speed in a fuel) is closely tied to particle size- AP below a certain mesh size is shipped as a high explosive rather than as an oxidizer in USA. The suppliers to hobby rocket motor builders specify mesh size, and some even tumble the grains to produce rounded, more regular shapes.

See here:

http://www.firefox-fx.com/ChemA.htm




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[*] posted on 24-2-2015 at 07:40


Hi Bert, I am in CE but what is the aim of this question ?

what u stated about AP is the reason why i avoid it.
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[*] posted on 24-2-2015 at 08:23


Where you are located has a lot to do with what chemicals you can easily buy.

CE? No clue.

Have you ever built a rocket motor?




Rapopart’s Rules for critical commentary:

1. Attempt to re-express your target’s position so clearly, vividly and fairly that your target says: “Thanks, I wish I’d thought of putting it that way.”
2. List any points of agreement (especially if they are not matters of general or widespread agreement).
3. Mention anything you have learned from your target.
4. Only then are you permitted to say so much as a word of rebuttal or criticism.

Anatol Rapoport was a Russian-born American mathematical psychologist (1911-2007).

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