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Member Since 02 Jul 2006
Offline Last Active Jun 12 2007 03:47 AM

Topics I've Started

Flare formulas

26 October 2006 - 06:36 AM

I was messing around with strontium nitrate, aluminum, and epoxy, and found that the ratio I first used made for a very bright ground flare (it seemed very bright anyways). I didn't weigh this small amount, and wondered if some formula may be around for those 3 chemicals before I try guessing again to make some larger flares.

Can anyone recommend a flare formula using strontium nitrate, Al, and epoxy/binder ratios?

Actually, what I would like to make are some flares which have a very fast burnrate, and a very large light output per size. I do not need extended burntimes.


Ultimate water-proof fuse?

22 July 2006 - 04:10 AM

I have some 2.2mm "waterproof" double-laquered and some 1/8" single-coated visco fuse, which work fine when it's dry.

Neither one of these does good in the rain/water however. Well, the 2.2mm sometimes gets lucky, but 30% are failures when submerged.

What is this thick yellow stuff I see people use? It's not nesseccarily what I need, but curious. Or am I hallucinating? :wacko:

I'm looking for fuse that is able to be handled a bit and bent without its laquer coating breaking so easily and thus rendering it useless in water. Basically the maximum protected fuse available will work. It should be a minimum 1/8" diameter, larger (1/4") would be desireable.

I just don't like the visco stuff, you bend it at sharp angles and you get cracks in the thin laquer coating...

Can anyone give me suggestions/names? Possible online retailers?


Rocket/Missile Formulas and Construction

19 July 2006 - 02:15 AM

I figured this would be a good thread to start, since we currently don't have one like it covering rockets/missiles specifically.

I feel rockets and missiles are some of the most varied pyrotechnic devices in terms of construction/materials used.

So, I encourage all to please post their favorite propellant formulas, as well as construction design techniques for anything that they have made or seen. Any pictures/video available would be an excellent addition to the thread as well.

Please feel no need to keep it short (unless you want to), and elaborate your design for others to understand.

If you can list any other specs such as tubing used, tube diameters/thickness, nozzle dimensions/material, stick size, etc to describe a design - please do so as well. This includes any motor design specifics like cored/coreless and packed/rammed propellant.

(Mention anything that hasn't exactly worked as well. :wacko: )

Ammonium Perchlorate Rockets, and Fuse Ignition...

14 July 2006 - 07:26 PM

Well, after thinking about going the standard route and using a fast burning composition, such as BP for a rocket propellant, I have decided to try and perfect a fuse ignition method for the propellant I have grown to love soo much...ammonium perchlorate. I'm new to the forum and I don't know just how in-depth some of us are with this propellant, so I'm making this long to fully elaborate the details for anyone curious. Bear with me please.

Typically, AP propellants are ignited from the front end, by an ignitor extending up the core of the propellant. When they are fuse lit from the rear or nozzle end, they typically don't build pressure at a quick enough rate due to the heat which has to rise up to the top to fully ignite all the propellant.

As you may know, ammonium perchlorate composite propellants have some of the highest Isp's (specific impulse) of any common solid propellants. It basically doubles the power of BP when comparing equal weights. Not to mention, a variety of flame colors is easily obtainable, my favorite being the blue-lavender yielded from CuO as a catalyst. Most of my amazement comes from the performance, though, which is why I have chose to try and perfect this in a firework design. I'm sure a few of you love those much higher flying rockets as well.

Anyways, I will explain a bit on this since some may be unfamiliar with AP's needs in a motor design. Some of you may be interested in experimenting with this stuff like me as well. First of all, AP propellant is typically run at pressures in the 400-700psi range, and as high as 1000+psi. This requires a slightly sturdier case material...I use 1/16" thickness phenolic tube. It can be run at lower pressures, but at the cost of efficiency. This is probably the most expensive downfall of it's use in a firework design that I can think of.

AP's operational Kn value, or the burning propellant surface area divided by the nozzle throat area, is typically in the range of 180-230, where a model rocket blackpowder motor has a Kn value much lower, around 25. This in part shows that AP reacts less to pressure changes under changing nozzle sizes, or much more forgiving per surface area than blackpowder. This can mainly be attributed to its lower burnrate, though. Due to this simple factor, this does not permit AP to typically be used as an endburning motor design, rather a motor with a core to achieve much more burning surface area. With that being said, comes it's problems in a firework design...it needs a reliable method of front-end ignition.

With the common fast-burning propellants commonly used, ignition is a simple matter...a fuse from the nozzle end ignites the propellant and it burns upward. With a design using a core all the way to the top, this can be much of a problem. I have tried it a few times, some tries work OK, some are complete failures. By failures, I mean the propellant lights, but since it is from the rear end it immediately shoots the fuse out and begins to burn with much too little pressure. Since only the rear of the grain is lit, pressure builds inside, but as gases are trying to escape the rear, the rest of the upper propellant may not be ignited quickly enough. This can look very neat as the rocket begins to slowly liftoff after 2-3 secs like a space shuttle, but for the most part it is unintended as well as dangerous. A rocket needs to leave with enough thrust so that it's path isn't hugely affected by wind/balance, and so that it gets accelerating quickly in the right direction.

Well enough talk about AP and how it works, let's discuss possible ignition methods in a firework design. This is where your pyrotechnic expertise can greatly help out in a possible design that works.

As stated, a sound AP ignition method would simply be a fuse from the front, if only somehow gases could not excape after ignition through this hole. Since this limits the idea out, a method is needed to get the heat quickly to the front of the motor. This could be accomplished a few ways which I can think of.

One method, may be a fuse which is inside of a sheath, or tube, so that the heat is contained through the core until it reaches the upper end. Since a nice quick burst of heat gets the motors going nicely, the fuse could be dipped in pyrogen at the (upper) ignition end. The problem which arises from this method however, is debris existing in the core post ignition, AKA the sheath. Any debris poses a nozzle clog possibility, and should be steered away from, unless it can be certain that it will freely exit the nozzle under pressure 99% of the time. Common electrical ignitors are very slim, and do not pose a clogging threat unless the motor is very long.

My second idea, is a method which to me seems more acceptable. A slower burning fuse is somehow attached to a hot burning fuse with a very fast burnrate. Just before the nozzle is reached, the much faster burning fuse ignites, and shoots up the core quick enough to ignite the entire core before being blown out. This too could use a pyrogen dip at the front for a ensured ignition of the grain. The fuse, being smaller than a fuse which is covered, should easily exit the nozzle without clogging issues after ignition.

This is all I have come up with so far with my experience in rocketry, and not much in pyrotechnics. I'm hoping the pyro experts out there can take these methods and possibly devise a solution which is more reliable. Or, at least methods of assembling the fuses in a reliable manner, as well as recommendations on the fuse which may be desired for this attempt.

Again I apologize for this threads extreme length, hopefully some of you are interested in this idea as much as I am and we can perfect something. :)

Castable rocket nozzle compositions

14 July 2006 - 05:49 PM

I have recently decided to try some rocket designs, but have been faced with the problem of a pourable nozzle substance.

I regularly work with high-power experiental rocket motors, but the nozzle designs I use are graphite and/or a very hard grade of phenolic which is black. These sorts of nozzles are not efficient obviously in firework designs as they are too costly, and also are non-castable materials.

I tried testing the erosion rate of a filled epoxy, and man was that a mistake. It turned epoxy into goo immediately under the heat, but I figured it would have happened without some sort of high-temp filler in the epoxy.

For my firework rocket motor designs (which haven't worked due to no efficient nozzle materials), I cut rings into the inside of the case end for the nozzle to lock into, then I insert a paper plug about 20mm deep. I fill the end with the nozzle material and drill the proper convergence/divergence cones with a countersink bit.

It is a straightforward method so far and would work excellent if the nozzle material I use could hold up to the heat.

Is it possible to get some recommendations from you guys on pourable nozzle substances?

The material needs to be able to withstand very high pressures, 400-600psi, so I would assume this would not permit the use of clay due to its brittleness, but maybe I am wrong.

Thanks a lot.