Why only combustion?

[pat123]

I am just curious if any one else has made a cannon using a different type of chemical reaction. I got the idea because my chemistry teacher showed us a video of hydrogen and chlorine mixed in a test tube with a cork in the end and as soon as a bright light was apllied the cork flew out. think this would work for a cannon? I think that was a synthesis reaction. anyone tried this?

Pat

[sandman]

lol, no because we would die

you do know that chlorine is ungodly toxic, like disassociate the cell membranes in you lungs toxic

and it produces Hydrochloric acid and thats not stuff to be playing with

so do not do this reaction

[BigGrib]

Yeah completly agree that is horrible, imagine firing your spud gun a few times doing that and going to blow out your chamber and after about 5 shots you pass out because of the lack of air in your lungs because there is chlorine in there and then dying because you were stupid

[boilingleadbath]

Besides the properties of the reactants and products, and the difficulty of acquiring them, propane-oxygen outperforms the hydrogen-chlorine.

Post-reaction pressures, starting at 1 atm and 300 k, stoichiometric mixtures, per Gaseq:

H2-Cl2: 10.3 atm
C3H8-O2: 18.2 atm

Or for that matter. . .
C3H8-air: 9.3 atm

So your exotic reaction scarcely does better than an ordinary combustion as far as chamber pressure.

[MikeNice]

Yeah, and . . . nevermind, that about does it.

[williamfeldmann]

However, on a brighter note, there are lots of various reactions that could potentially be harnessed for propulsion.

I have seen the coke and mentos and the old classic baking soda and vinegar both used to propel model cars and 2 liter rockets. However, they produce very limited amounts of gas for the amount of material required.

Sodium and water makes for one hell of a release of energy but requires time in a sealed environment so it would only work in burst disk or ball valve situations, similar to hybrids.

Basically, there are lots of choices out there, combustion of aeresoled fuel is just cheap and easily contained, not to mention has pretty significant power.

[Fnord]

I've tried dumping a large amount of current through a thin wire, so that it (basically) explodes. I then tried containing this explosion in a barrel to propel a bb outward, but sadly, it didn't move very much.

This could potentially be a new type of propulsion, but an ungodly inefficient one.



<<Edit: I've just earned my first "post whore" star.

[pat123]

I know chlorine is toxic. I didn't mean everyone using chlorine in their cannons i was just wandering if other types of chemical reactions were used. there are thousands of different chemicals you could use that aren't toxic. any way it is not that hard to get chlorine and hydrogen,

[Novacastrian]

A dry ice burst disc cannon would be cool. Use a 500psi burst disc.. BOOOOOM. Are there any dry ice cannons on the forum?

[pat123]

I tried making one with my friend a few years ago. he bought all the parts so I helped him put it together. it was my first cannon so I didn't know anything about them. he bought cell core pvc. we let the glue dry for like 30 minutes, then wedged a potato in the end, unscrewed the cap and put in a coke bottle with dry ice in it into the gun. about 30 seconds later there was a huge boom, a shard of pvc in my leg, and there is a 2 inch deep hole in the wall of my garage.

anyway the only way to do it would be in a steel gun or something i doubt sch 80 pvc would hold it

[benstern]

The French sometimes build and use chemical reaction spudguns (patators) and in typical French fashion, it sucks.

[pat123]

what type of reaction do they use

[Ragnarok]

anyway the only way to do it would be in a steel gun or something i doubt sch 80 pvc would hold it

That may not be a good choice. Steel can become relatively very brittle at low temperatures - I don't know if dry ice is cold enough it's below that point, but I wouldn't want to take that gamble.
Some brass mixes might be suitable, but I can't give any solid assurance of that.

I think dry ice cannons are a pretty bad idea. It's an extra safety risk, and storing it would be an absolute bitch.
If people want to make a high pressure burst disc cannon, why not use a CO2 tank instead and pipe in the gas that way? It's safer, and the performance would be better as the gas temperature would be higher.

[sandman]

well, technically isnt dry ice against the rules as it is a solid (even thought it does sublimate) propellant

[Ragnarok]

That sounds like an over literal interpretation - my guess is that in this case, solid propellant will refer to materials like gunpowder, and other materials or mixtures that contain their own oxidiser, so can burn in the absence of oxygen.

Or rather, that is the definition I would apply to solid propellant.