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Conical burst discs?

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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potential?

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Conical burst discs?

Unread postAuthor: sputnick » Thu May 07, 2009 4:56 pm

Hey everyone, been a while since I posted anything here, (been over at The Canadian airgun forums) But here's a little something I was wondering about,

I was watching future weapons, an old rerun of the shape charge episode.

[youtube]http://www.youtube.com/watch?v=mXp5czdufoQ[/youtube]


And just for a split second I was wondering if this principle of a conical explosion face could work in the burst disc of a spudgun, my logic being that it would form a concentrated jet of hot gasses that could maybe propel it better than just a straight blast could...

What do you guys think? Does the idea have any potential? will it just blow apart a spud, or is it just a waste of time :roll:

anyone with a large-ass cannon willing to do some testing? I could make up a cutout form to specify whatever barrel width you have, if you're interested.
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Re: Conical burst discs?

Unread postAuthor: Technician1002 » Thu May 07, 2009 5:21 pm

sputnick wrote:Hey everyone, been a while since I posted anything here, (been over at The Canadian airgun forums) But here's a little something I was wondering about,

I was watching future weapons, an old rerun of the shape charge episode.

Note, embedded players are disabled for the video. The link will be needed to view it.

And just for a split second I was wondering if this principle of a conical explosion face could work in the burst disc of a spudgun, my logic being that it would form a concentrated jet of hot gasses that could maybe propel it better than just a straight blast could...

What do you guys think? Does the idea have any potential? will it just blow apart a spud, or is it just a waste of time :roll:

anyone with a large-ass cannon willing to do some testing? I could make up a cutout form to specify whatever barrel width you have, if you're interested.


To work this requires very high energies. This with an air cannon would work about as well as replacing the flush valve in your john to bust out the drain trap. The high energy is missing in my opinion.

If someone had a 20 bar or larger cannon, then supersonic compression may start to work, but spuds don't hold up at that pressure.

In a combustion at normal pressure, I don't think it has potential. unless you were working with an oxygen acetylene hybrid, but we should not discuss something that off topic here for the moderators wrath is to be avoided.

Am I off base? :?:
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Unread postAuthor: psycix » Thu May 07, 2009 5:55 pm

I once had that thought too. But it was more like: could I replace the C4 by a 200x mix?

Note that the copper cone does not just get deformed, it melts and flies away at a high mach number. It will need a lot of energy. Note that the energy efficiency of this is probably lower then a cannon so attaching a barrel and using a projectile on it (and changing the jar into a massive steel chamber) may give you an even more powerful result.

I also had this idea: If your burst disk is so devastating (look at larda's) by itself, then you will no longer need a projectile!

Conclusion, I do not think it is profitable to use gases to propel a krakatoa cone, use it to fire a sabot round and pierce just as much.
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Unread postAuthor: KineticAmbitions » Thu May 07, 2009 6:05 pm

Conical shaped charges work by inverting a metal cone with pressures that are momentarily in the >100kBar range, and a shock wave propagating at 7km/s or more. This inverted cone is then propelled as a jet by the shock of the detonation wave, probably outrunning the expanding gases (~10kBar and a few thousand Kelvin) behind it.

Hybrid cannons work on pressure of <2kBar (so far, at least :wink: ), and produce no shock wave to speak of, unless something goes horribly wrong (combustion in the chamber propagates at under 100m/s even in a high mix hybrid, if I remember correctly).

If the jet could be made to work at all with gases, well...
I'd imagine that it would require mixes of oxy/hydrogen in the kX range, being intentionally detonated. And even then, if my limited knowledge of CSCs is anything to go on, a proper, coherent jet may not be formed. Needless to say, I don't think a potato would stand much of a chance. In fact, considering the amount of steel those charges can cut, and the speeds at which the loose particles of the cone are projected, I'd imagine that one would have a hard time building a barrel that could be used more than once in this function, regardless of resources available.

I have read about a member's work on a launcher powered by certain, err... "energetic substances", but that wasn't producing jets of hot metal at 8km/s, slicing through whatever got in their way.

So, in a nutshell, it probably won't work, and if it could be made to work, it probably wouldn't work well or easily.
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Unread postAuthor: psycix » Thu May 07, 2009 6:15 pm

DDT may be a must for this to work with a gas mixture. That way a gas mixture does create a supersonic shock wave.
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