Fast Sugar Propellant

[Greg O'Bryant]

Ray thanks for the info on the bates grains. I should be making some fine rockets with my new propellant formula. It casts so easy it is almost like dough when it is still hot but cold enough to touch.

[Dang911]

May I ask what the secret is to having a dough like propellant? I have been making the 33% 65% 1% propellant with the iron oxide, and I cook it up but my results are the following.

Heated till it puddles and stays wet on the bottom and slightly thicker skin on the top. just one step under the point at which it would begin to smoke and eventually catch fire.

Heated so it stays like melted marshmallow sticking to the pan but remaining in soft clumps

Heated till it just comes to together, does not stick to the pan yet, but has barely been cooked.

whenever I handle it, the mix is very hot, and tends to harden real quick. The surface will gets hard and crackly but the inside is still molten lava hot! I never tend to cook it very long, but do stir constantly. I have tried to kneed it but it hardens after one fold.... Do I need to keep it at one of the stages above for a longer time to get workability like clay or dough? I must be doing something wrong because I have to drill out the cores because there is no way I can get a any type of dowel though the material, even a few second after pounding it into the form.

[Greg O'Bryant]

Dang I have noticed that no matter if I am using corn syrup, sucrose or dextrose, if I go by the standard 65/35 ratio it just doesn't cast good. The propellant that was like dough was made out of

44 grams corn syrup (estimated to be roughly 35 grams actual sugar)
65 grams KNO3
1 gram iron oxide
re-crystallize the above then add
10 grams of glycerin.

So the final percentages are 41% sugar (including glycerin) to 59% KNO3
Burn rate is slow, steady and complete. Later today I am going to see what happens if I add even more sugar. I will then add additional KNO3 to get the proper 35/65 ratio, but because it wont be re-crystallized with the original batch I'm hoping it will still retain its casting properties.
I hope this helps

[Greg O'Bryant]

Quick question;

How much does residual moister, in sugar propellants, effect the ISP? I know it will drop the burn rate, but that can be compensated for with a higher KN value. How much does it actually change the efficiency? You have Nakka saying he is getting ISP's of 124, and he really doesn't go into detail if he is using the dextrose monohydrate or not. At the same time James Yawn is getting ISP's of 115 and he is clearly leaving moisture in the propellant. I am asking because it really aids the casting process to leave some moisture in it.

[Greg O'Bryant]

I have been thinking about the end burner and I think I have a potential solution. It doesn't have too much to do with grain geometry or the propellant burn rate, but instead with the inhibitor. Tell me if this has been done before. On James Yawn's web page he uses foil tape to inhibit grains. Well lets say you take some of that tape and you pull off of the backing. Next you place the tape on a table, sticky side up. Take some small strips of paper (say 1/2") and stick them length wise on the tape so that they have a space between them (say 1/4"). Use this tape to inhibit a solid grain so it would have alternating areas of being inhibited and not inhibited. I am hoping that when it burns it will form a cone of burning surface area. The cone would normally deteriorate in an end burner. Now with this configuration just as the cone would begin to taper off a new section of uninhibited propellant would be exposed to start the cone shape all over again. It would probably have some oscillations in pressure but I don't think it should be that bad once you get the details worked out. Tell me what you think. I have posted this messag on the sugpro page and Scott fintells forum. I haven't really gotten much of a response, but I definatley think it should work.

[Ray]

Why not core the grain slightly? Just take an appropriate sized drill bit and drill into the grain some distance.

It'll increase burning surface area. You'll notice a shorter burn time, higher internal pressures and a nice smooth burn. Depending on how deep you drill and what size you drill you'll have a tail off that is large, or small...

[Greg O'Bryant]

You could make one that way, kind of like an estes rocket motor. I just don't like to drop the kn that much, ecspecially with a long tail off. I first thought about having alternating segments of cored and uncored to do the same thing, but i thought it migh just be easier to get the same results with the inhibitor.

[pablo]

i get a good working time with the 100 gr nitrate, 30 gr sugar and 30 gr glucose recipe, you can handle the fuel without gloves and still leaves enough time to make the hole with a stick or something.

pablo