Enhancing the tail of the BP rocket

[Alex1101]

Enhancing the tail of the BP rocket

Hello,
This is my first post to the forum, so I apologize right away if the issue I bring up is too trivial or of no interest at all. Now, let’s get to my question (yes, as any novice I start with the question :) )

Some time ago while browsing Internet for the BP rockets articles (sorry, could not find the link any more) I came across a suggestion that adding 2-3% (by weight) of atomized aluminum to the propellant enhances visibility and overall appearance of the BP rocket tail by adding sparks etc. Prior to trying this recipe I did some additional research (including research on the forum) to make sure that this is safe – I am doing rocket “experiments” together with my 10-year old son, so safety is a paramount concern not like when I was 12 years old and was doing it on my own :) . This research brought me to the following questions:

1. Is this practical at all? Will addition of Al enhance the tail?
2. Adding Al to the BP propellant puts it into a close proximity to KNO3, which are known to react in the presence of water – do I need to add boric acid to the composition to counteract possibility of this reaction? If so, how much boric acid might be required?
3. When and how to add Al to BP composition – usually I put together BP components, then wet them with water and then mix the paste in the mortar. Would it be safe to follow the same process with Al added to the mix?
4. Is it safe to use ramming to load the rocket with BP that also contains some Al – together with KNO3 aluminum is a component of the flash powder which is generally not recommended for ramming :)

Thank you very much for the answers!

[ShadowMyGeekSpace]

1. Possibly, but at the same time not really. The Al isn't that noticable in something going way up into the sky unless you've got a huge engine and 2-3% is a signifigant ammount of Al, but what IS going to happen is your engine will burn slightly hotter and slightly faster - although not enough to matter.

2. What does adding Al to the mixture have to do with water? I don't see the need for adding any, but maybe someone with more experiance can chime in here.

3) The Al will oxidize(beyond the usual oxide layer) if you allow it to get wet, rendering it somewhat useless in this hobby... although that might not be the case with this mixture, since the BP will burn plenty hot.

4) There is no increased danger in this case, Al isn't sensitive to pressure itself. Treat it like you would when pressing any normal BP charge.

[sparkchaser]

If the particle size is fairly large, the sparks will be fairly visible. If visibility is what you're going for, I would use magnesium. Particles made by filing a magnesium block with a fairly coarse file will make nice sparks!

Other options would be magnalium or titanium, which are both a little less sensitive to boot.

[Smoakie]

You might want to check out rec.pyrotechnics for all the rocket info you can handle.

1) It depends on the size of the aluminum. Fine aluminum will be consumed quickly and all you will do is make the exhaust flame brighter. If you add some course aluminum it will hang in the air as it is burning giving you a nicer tail. An easier and cheaper way would be to add course charcoal but you can also add steel and titanium.

2) Al and KNO3 will react with water present but it takes a lot of aluminum. You will be fine with a couple percent AL without boric acid. If you start to add like 20% AL then you might consider the boric acid.

3) Since you are not milling the mix, you can add the AL whenever you want. If you are serious about rockets you might want to build a ball mill so you can make some hot BP. Not putting anything down, but if you're using a mortar and pestle your BP is not hot.

4) Since you are not using hot BP I'm pretty sure you are making cored engines. Are you drilling the core or do you have tooling? You should be ok with AL, but if you start adding titanium or steel you will want to press them and not ram them.

Good luck and let us know if you have any more questions.

[Alex1101]

Thank you for your replies and suggestions!

Now couple more points:

1. My aluminum came from Skylighter as a 80-325 mesh; I sifted it through the coffee filter into fine and coarse batches. I believe my coarse aluminum is in the 80-150 mesh range – is it coarse enough to make visible sparks?

2. Should I compensate (with some extra KNO3) for adding 2-3% aluminum to maintain the same properties of the propellant?

3. I have some Mg turnings – I may add them to the propellant (as Sparkchaser suggested) instead of Al, but probably would have to grind them in the mortar before use as they are rather large… Anything special I should know before adding Mg to BP propellant?

4. “Chicago Tools” manufactures and sells VERY inexpensive 3-lb and dual-drum rotational and 5-lb vibration rock tumblers (http://search.harborfreight.com/cpisearch/web/search.do?keyword=tumbler); however at this stage I opted for the all-plastic toy rock tumbler – until I get experience with ball milling I want my tumbler small and plastic – Chicago’s one has too many metal pieces for my taste – as I mentioned before, safety is a paramount concern :) However I would greatly appreciate comments from somebody more experienced on Chicago's tumblers for use in pyrotechnic.

So if I decide to use wet ball milling for the propellant – when should I add Al and/or Mg to the mix? My guess would be to add metals to the BP granules right before loading instead of ball milling everything together. Advise on this issue will be greatly appreciated!

5. I do 2 types of rockets – 3/4 inch using the 3 inch long tubes and 1/2 inch by reloading spent Estes engines (which I have quite a few). For the 3/4 rockets I use a Stinger Missile Kit I bought from Skylighter (p/n TL1630 at Skylighter.com). The Estes engines I reload using a half-inch aluminum ram (from Home Depot) and then make core with the awl.

[deadman]

Yes the addition of "large" aluminum will enhance the tail with bright white sparks. By large I mean 200 mesh. It also depends on the size of your motor. I'm guessing either a 1/2" x 5" or a 1/4" x 2.5".

If you are looking for a long silver tail, atomized aluminum will work. If you are just looking for a more brilliant tail that hangs longer I would suggest some course charcoal added to your rocket powder. When I first started making rockets my BP was actually too hot for even a small core and the added charcoal cooled it down and left a long tail in the night sky.

KNO3 + atomized aluminum would make horrible flash, so do respect it, but don't sweat too much worrying about it if you ever decide to mix those. Also such a small amount of aluminum would not make a flash-like comp. Ramming your rocket with this amount of aluminum should be fine, but be careful and never fist your rocket tube.

[nbk2000]

Assuming that the noise of a possible tumbler explosion wouldn't be a problem, a safe way of using it would be to build a U-shaped sandbag enclosure outdoors and start/stop it by plugging in a looong extension cord. :)

[deadman]

Thank you for your replies and suggestions!

Now couple more points:

1. My aluminum came from Skylighter as a 80-325 mesh; I sifted it through the coffee filter into fine and coarse batches. I believe my coarse aluminum is in the 80-150 mesh range – is it coarse enough to make visible sparks?

2. Should I compensate (with some extra KNO3) for adding 2-3% aluminum to maintain the same properties of the propellant?

3. I have some Mg turnings – I may add them to the propellant (as Sparkchaser suggested) instead of Al, but probably would have to grind them in the mortar before use as they are rather large… Anything special I should know before adding Mg to BP propellant?

4. “Chicago Tools” manufactures and sells VERY inexpensive 3-lb and dual-drum rotational and 5-lb vibration rock tumblers (http://search.harborfreight.com/cpisearch/web/search.do?keyword=tumbler); however at this stage I opted for the all-plastic toy rock tumbler – until I get experience with ball milling I want my tumbler small and plastic – Chicago’s one has too many metal pieces for my taste – as I mentioned before, safety is a paramount concern :) However I would greatly appreciate comments from somebody more experienced on Chicago's tumblers for use in pyrotechnic.

So if I decide to use wet ball milling for the propellant – when should I add Al and/or Mg to the mix? My guess would be to add metals to the BP granules right before loading instead of ball milling everything together. Advise on this issue will be greatly appreciated!

5. I do 2 types of rockets – 3/4 inch using the 3 inch long tubes and 1/2 inch by reloading spent Estes engines (which I have quite a few). For the 3/4 rockets I use a Stinger Missile Kit I bought from Skylighter (p/n TL1630 at Skylighter.com). The Estes engines I reload using a half-inch aluminum ram (from Home Depot) and then make core with the awl.

First off let me say I have no idea why I didn't see this last night. And I'll answer these right now.

1: Yes.

2: No. You want it to burn in the air to give the effect of a white spark. Your rocket powder will ignite it and it will burn brightly as the trail. Same with course charcoal.

3: Honestly, if they are large it's ok. I use large pieces quite often. What to watch out for.... since you said you were milling wet, water and Mg react exothermically so it would heat up if your BP is still wet when you add the Mg. I'm not sure if ignition is possible, but even if it doesn't much of your magnesium will have oxidized and not burn that brilliant white you want.

4: Harbor Freights tumblers would be a great choice for you. I have pushed on to do 500g of BP at once. Bad idea. I needed a new one. Also don't take it apart. I think 100g-200g can be done efficiently in an overnight milling session and results in BP worthy for lift, break, rocket (maybe too hot), and even salutes. If you take the precautions you won't have to worry about catostrophes, but be aware they DO happen. And yes diaper the metal into the BP after it has been milled.

5: Well it's not a question but I have a few suggestions. I have never tried a stinger so I'll ignore it. With your Estes remakes I would change two things about your process. When you ram your clay (you do use clay right?) use a rammer with a rounded end. If you have a drill chuck that accepts 1/2" stick your rammer in there and put a file to the end to round it off. This will help the gasses flow out the rocket motor better. Do you use the awl to punch a hole or as a spindle for your own tooling? If you punch it then I'd suggest drilling the core over punching as it wouldn't be as likely to crumble your end plug. But awls are tapered so that is good.


Last note: I just realized you core your rockets. End burners give much better tails and travel higher. A cored rocket is for lifting a heavier payload.

[Alex1101]

Great suggestions!

For ball milling I will probably make a large wooden box with the sand bags inside. By the way here on the forum I saw a recommendation to wet the BP composition with about 5-6% of water before starting ball milling and then check every hour and add water if the mixture becomes too dry. If I leave it overnight wouldn’t it get too dry and increase the chance of spontaneous explosion?

Thus far I have limited my Estes remakes to those engines that still have their clay nozzle intact; I used awl to make a core in the compressed BP for the fuse. I may now give a try to those that do not have the nozzle.

Deadman, should I use the rounded rammer just to form the clay plug or for ramming propellant as well? It looks like the rounded rammer will exert more pressure on the tube during ramming…

The end burners do not have the core, but do they need the clay plug with the nozzle or the exhaust end can be left wide open?

[deadman]

For ball milling blackpowder, wetting it makes it hotter because of the recrystillisation of the KNO3 in the pores of the charcoal. It's hard to know for sure, but at a microscopic level it is happening. I have honestly never milled wet black powder because I know the mess of sticky blackpowder on my balls would suck. I don't think you have to worry to much about spontaneous ignition, but go ahead and spray some static guard in your barrel if it helps you sleep better.

I see how you do your remakes now. Actually that is a great way to make use of awesome nozzles. I've never checked, are the nozzles slopen in commercial rockets on the inside to help direct gasses? I believe for a nice tail, you should try a very shallow core. Enough to jump off the launch site, but not enough to burn through in under 2 seconds. Experemint.

After you've gotten the nozzle rammed, I would switch out to a normal flat ended rammer. The incline will increase pressure on the walls slightly. It shouldn't be a problem, but if you have a problem with walls bursting make a support sleeve by slicing a pvc tube with the same inner diameter as your tube and clamp it with those round clamps that you screw to tighten.

With an endburner you will definitley need a nozzle. Even whistle mix fueled rockets can't fly as an endburner with a wide open exaust. They would topple from insufficient initial thrust, and the whiz off in who knows what direction.

[hst45]

Alex, try milling the mix dry. Adding water to the material to be milled is o.k. to make regular BP, but if you have any residual water in the compound when you ram the motor it will likely crack when drying, resulting in a CATO (boom).

You can produce orange sparks by replacing a portion of your charcoal with a coarser charcoal. These should give a long burning hanging tail effect. This will be at the expense of burn rate though, so some trial and error is required. Aproximatly 5 to 10% coarse hardwood charcoal should be a good place to start.

Good luck to you and your son. Stay safe, have fun.

[Alex1101]

My thanks to everyone for providing suggestions and advise! I will do my next try when I get back from my long-awaited vacation early next year and report the result.

As for now, I wish everybody a very Happy New Year!!!

++++++++

You advise someone when you give them advice.

NBK