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Old 03-03-2018, 06:05 PM
CuriousAmateur CuriousAmateur is offline
Junior Rocketeer
Join Date: Feb 2018
Posts: 16
Unhappy Newbie failures - sugar rockets


We are new to rocketry, and it shows from our results. I'm wondering if anyone has any advice. We are trying to make a basic (sugar) rocket motor. The results of which have thus far been smoke "bombs." If you have stopped groaning at another failing newbie and are still interested in helping, here are the details:

We're using 33% confectioners sugar and 66% Potassium Nitrate. Our sugar is pure, but I cannot verify the same for my KNO3. We're getting it from Gordon's stump remover, which we know contains a good concentration of KNO3, but we are strangely unable to find the MSDS info in it. We grind it up, and bake it to dry it out before mixing.

We then pack it into a 3/4'' PVC pipe, with a 3/4'' clay plug on each end and drill a 7/32'' nozzle through one plug, set it up, and light it off at the nozzle. It has a nice hot, fast burn, with a good amount of gas output. However, it comes in waves rather than a steady burn. It burns for probably about 20-40 seconds (we never timed) but never lifts off. It also has a small amount of white discharge which comes out liquid and quickly hardens into a hard, crumbly material. As expected, there is also a lot of white smoke. We originally thought that the white discharge might by melted PVC, but it is strange that it is crumbly.

As a couple other notes, we are not crystallizing the KNO3 before use; we don't know if that is needed or not, since we can't find the MSDS info. It does seem to act about right, except there is never enough thrust from rockets. We are packing the powders FIRMLY into the pipe, since it should be oxidized and not much matter. The nozzle is drilled all the way through the white mix to increase surface area though. On the first try, we had 1.5'' of fuel (not sure how many grains that comes to), and on the second attempt, we doubled it to 3'' of fuel, with the same 3/4'' plugs on each end. There is a fair amount of weight to the finished rocket, though we haven't thought to weight the finished product yet. The first one was 3'' long in total, and the second was 4.5''.

Any thought on what we should try? We've thought of perhaps packing it less tightly, but even as it is, some fuel tends to spill out when the nozzle is turned downward, multiple times after the hole is drilled. We've also thought of mixing in a little sulfur to the fuel, and also had it recommended elsewhere that a little iron oxide mixed in could help.

Any thoughts? Does anyone know if Gordon's stump remover is even a pure source? Thank you!

Last edited by CuriousAmateur : 03-03-2018 at 06:09 PM. Reason: grammar fix
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