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Solid fuel revisit

Post questions and info about combustion (flammable vapor) powered cannons here. This includes discussion about fuels, ratios, ignition systems, safety, and anything else relevant.
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Unread postAuthor: Biopyro » Thu May 28, 2009 3:09 pm

I don't think aluminium would be particularly good at all. In the same way that thermite is useless, because it has no gaseous products, aluminium wouldn't be very good either. There might be some gaseous Al2O3, but I don't think it's be as good as MAPP.
It would also be the ultimate pain to mix nicely, and would have to be fired seconds after mixing.
A lot of the heat would be retained by the oxide, which would settle in the chamber and potentially cause a problem by melting the chamber, or at least causing heat damage.

It might work using pure oxygen, but then the hot residue problem would be even worse.
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Unread postAuthor: spencetron » Fri May 29, 2009 10:48 pm

I have thought about this before, staring at my stash of 2-3um aluminum powder and then my cannons. I was thinking if you could make an aluminum powder laden burst disk, then pressurize with air until bursting pressure (aerosolizing the aluminum), and have the burst disk burst into a chamber containing a continuous spark... you could probably pull it off.

But measuring the correct amount of aluminum, finding the right burst disk, finding a suitable ignition source, and dealing with the resulting mega pressure would prove to be rather difficult.
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Unread postAuthor: LGM » Mon Jun 01, 2009 5:54 pm

I started a thread on solid fuels over at APC a while ago with the intent on making a charcoal powder fueled cannon from steel tube. The exact design I was going to use is a little beyond what forum rules permits, but it involved igniting the charcoal in the same step as dispersing it.

Aluminum would work as a fuel, but as was said before, you would need pipes capable of handling rather excessive pressures. Thermobaric bombs used by the military to take out caves work on the same principal, using aluminum powder to create a fuel air explosion. The powder takes longer to burn than standard high explosives, so the shock wave is far more sustained in thermobarics.

I'm pretty sure it would take rather fine flake aluminum to work in these cannons, not something you could make on your own, unless you happen to have a stamp mill lying around. I'd rather not use $20/lb dark aluminum powder in a cannon on a regular basis, but if I ever get around to making that cannon I might give it a try. Actually, this might be just the reminder I needed to get up and finish that thing.
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