adapting model rocketry technique

James Yawn describes a method of preparing KNO3-sugar propellant that does not require melting either component, but just heating an aqueous syrup of mixed sugars, separately warming the dry KNO3, and then mixing them off the heat -- a lot like BP blender rockets conceptually. In fact it's JUST like blender rockets except that both the fuel & oxidizer dissolve in hot water instead of just the oxidizer. Mixed sugars such as corn syrup and sucrose are used to inhibit formation of large xtals. The product is said to burn almost as fast as propellant made by cooking the complete mixture.
However, the resulting mixture is not so plastic as to be rammable into a case, or cast as a slurry as with blender rockets. Rather, he rolls it into a cylinder with a core, then primes it inside and out to form a constant-rate grain that he slides into the case. It's not clear from his instructions (or what I've read of them so far) how long after mixing the material remains plastic enough to do this without reheating -- and it's heating the complete mixture that I wanted to avoid -- and then how long it takes to dry and harden in place.
Has anyone used this for firework sky rockets? If I wanted to turn it into a progressive burner with a nozzle (apparently eliminating caseless from consideration), is there another way to inhibit the outside surface while allowing a fit loose enough to get it into the case to begin with, but tight enough to resist the pressure during firing? Or, with a catalyst, might caseless with no nozzle be fast enough to allow it to lift go-getter style?
Robert

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That's really not the method he espouses, unless Jimmy has just in the last month come up with a new one. No; he "cooks" the mixture of oxidizer and sugars and water at a lower temperature than what would have been required to "caramelize" the straight sucrose/KNO3 mixture. The fructose in the corn syrup and the water lower the tendency to begin runaway oxidization, and allow closer control over the final flexibility and performance of the product. He presently uses an electric skillet to do the cooking.
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He covers these issues in great detail. First, it is not correct to say it is not rammable. In fact, I made Jimmy a set of tooling for just that very purpose, and it suits well. It does require slow, continuous pressure, rather than hammer blows. The hot-but-cooked RCandy remains plastic enough to press into a mould for many seconds.
And you obviously missed the treatise of his that states that you can re- heat this material numerous times as necessary to regain the plastic consistency you need. Jimmy uses a toaster oven for this reheating.
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Yep.. with great success. I have.
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He details a simple way of epoxying a layer of manila paper to the outside of the grain. It works well.
If you don't like that, you can always spray-paint the outsides of the finished grains with asphalt-based undercoating spray. That happens to be the way I prefer to do it for fireworks rockets.
LLoyd
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On Mar 3, 8:46 pm, "Lloyd E. Sponenburgh" <lloydspinsidemindspring.com> wrote:
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I have seen webpages describing another similar technique for preparing sugar fuel ,using an oven set at 325 abouts, it melts the mix but is way too low a temp to set it on fire, and the water evaporates easilythis way too, the problem with sugar fuel, and why its not used for fireworks is, storage, It doesn't keep well and absorbs water fast and becomes soupy after just a couple days in humid weather,If I can find that web article, I'll Pm you with a link.

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Jimmy Yawn also has demonstrated a way of preparing finished grains from Rcandy that keep for long periods of time.
It's on his website.
LLoyd

On Mar 3, 8:46 pm, "Lloyd E. Sponenburgh"
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It may not be the one he PREFERS OVERALL, but it is one he DESCRIBES at http://www.jamesyawn.net/syrup/index.html and http://www.jamesyawn.net/syrup/improved/index.html .
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Yes, and he's not the only one doing and explaining so, unless the other person I'm thinking of is also him. At least one person has some very explicit videos online showing the hot plate cooking and working of the dough.
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That's true of that mixture, but he says the syrup method produces a firmer dough.
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And he says that's true of the syrup product too, but remember I want to AVOID heating the complete mixture.
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Wow, I'd've never guessed something that simple would work within a case with nozzle.
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Interesting. Have you also tried the constant-burning grain in a similar application?
Robert

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First... Jimmy tried a number of techniques before he came up with "skillet" Rcandy. It is, believe me, the preferrable method. You _never_ raise the temperature far enough to cause decomposition beyond a slight yellowing of the mix. It does not bubble, it does not smoke, and it does not undergo that rapid "white to brown" transition that plain sucrose/KNO3 does.
Second... The "retempering" of hardening fuel is barely heating. Think of it more as mere "warming".
Last, to your direct question: No, I have not made BATES grains for fireworks rockets. I have made numerous end-burners, one of which developed over 9lb thrust before (gently) blowing out the forward bulkhead -- which was only hot-melt glue.
The entire grain lightly "fluffed" out of the tube in one undamaged piece, and burned quietly on the ground. The tube was completely undamaged (an NEPT thick-walled 1lb tube), and the nozzle was intact.
I've also used the same technique to make BP motors that consistently produce 3-5lb thrust in a 6-second end-burner.
The concept of inhibiting the grain has great implications for our art.
LLoyd

On Mar 4, 2:50 pm, "Lloyd E. Sponenburgh" <lloydspinsidemindspring.com> wrote:
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Lloyd,
I believe Bob is referring to this webpage, http://www.jamesyawn.com/syrup/index.html , in which James goes away from his traidicional recrystilization method, and uses a quick-batch microwave method to make the fuel. Seperately heating the KNO3, and heating the sucrose/corn syrup mix in the microwave, then combining the two.
Bob, I did alot of work with Sucrose based propellant, but it does have quite a few downfalls. Then i found Sorbitol, and its slightly less energy dense as a fuel, but SO much easier to work with; and a joy to make. Check out the process on my website: http://www.doranaerospace.com/Sorbitol.html
Thank you, The Other Bob (haha)

Bob, I did alot of work with Sucrose based propellant, but it does have quite a few downfalls. Then i found Sorbitol, and its slightly less energy dense as a fuel, but SO much easier to work with; and a joy to make. Check out the process on my website: http://www.doranaerospace.com/Sorbitol.html
Thank you, The Other Bob (haha)
I have made and launched many Sorbitol/KNO3 rockets and it probably my favorite "candy" to work with. I get more juice from AP but I don't always want power.
Tom

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Yes, and I'm aware of the work of others with KNO3 and various carbohydrates, including several sugar alcohols. On hygroscopicity grounds alone, if I were willing to cook the mixtures I would prefer them to sucrose. However, I asked one of the workers in that field whether simple recrystalliz'n from sol'n without cooking would make a mixture performing any better than dry mix (of, say, starch and KNO3), and I believe the answer was that it would not.
Robert

On Mar 4, 2:50 pm, "Lloyd E. Sponenburgh" <lloydspinsidemindspring.com> wrote:> First... Jimmy tried a number of techniques before he came up with
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All of which is fine if you have a temperature-controlled hot plate and a place to plug it in outdoors. I mean, you still have a fuel- oxidizer mixture in proximity to heating coils which will be well above the temperature of the temperature-controlled surface, such that a spill and ignition would be possible. Please correct me if I'm wrong about the heating coils. You're corresponding with someone whose stove's enamel is very chipped from cleaning all the spills with Brillo. And even if the coils don't get above ignition temperature this time, an old spill could ignite a subsequent time, and it's a pretty smoky mixture.
Oh, heck, Oster won't even tell me if the jar from this very old blender is tempered, so I'm going to have to try a possibly destructive test before attempting blender rockets. A shattering glass container full of boiling water is no fun. Of course even tempered glass is no guarantee, as I learned with a large flask of nutrient agar fresh from the autoclave.
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Yes, and sometimes it's only a little relative inhibition that's needed. Someone makes pretty good "swimming" star cores by making the layer to the outside of that over-fueled, then spraying on KNO3 sol'n that penetrates only about a hemisphere. I guess dipping could work too.
Robert

On Mar 4, 2:50 pm, "Lloyd E. Sponenburgh" <lloydspinsidemindspring.com> wrote:> The concept of inhibiting the grain has great implications for our art.
And NOT ONLY the fireworks art...check out this --
http://www.youtube.com/watch?v=dLyboeZwg5U
. The placement of the inner layer was such as not to produce xlation by jetting but only a little rotation, but one could easily imagine construction to produce more of either.
Robert

I'm not sure whether I mentioned this other solution -- besides blender rockets, other wet-cast grains, whistle rockets, caseless rockets, end burners, and candy grain. I can just make my own tooling for cored BP rockets out of wood & nails. A nail or spike for a spindle, dowels with drilled cores for rammers. I just don't know if without a taper the suction will crack the grain when I pull the nail out.
Robert

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So, taper the nail. It's a bit of work with a file and sandpaper, but it can be done.
LLoyd