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Shock-Compression Light-Gas Gun (Concept)

Post questions and info about hybrid (compressed gas with fuel) powered cannons here. This includes discussion about fuels, ratios, ignition systems, build types, safety, and anything else relevant.
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Shock-Compression Light-Gas Gun (Concept)

Unread postAuthor: sudpuzzer » Tue Jan 28, 2014 9:57 am

Hey all,

Found a particularly interesting article for those so inclined:
http://history.nasa.gov/SP-4302/ch2.11.htm

The article is about the history of wind tunnels and testing at NASA, but there's a bit near the middle about shock-tunnels and a shock-compression light-gas gun. It's basically a hybrid with an additional intermediate compressed gas shock tube between the chamber and launch tube. Chamber pressure drives a piston which in turn compresses intermediate gas, which ruptures burst disk, and launches projectile.

Thought it was an interesting concept, and might be worth looking into, perhaps adapted to spud gun use? Thoughts?

Obviously there would be some new math involved, I may try to look up the analysis on the original gun and work through it myself.

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Re: Shock-Compression Light-Gas Gun (Concept)

Unread postAuthor: jackssmirkingrevenge » Tue Jan 28, 2014 10:02 am

The concept has often been discussed but I don't remember one being built - mostly because in practical terms you can get the same performance out of a high mix hybrid with a much simpler setup.

Hybrid style concepts are also being used in industry: http://www.utroninc.com/tech.html
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Re: Shock-Compression Light-Gas Gun (Concept)

Unread postAuthor: Gun Freak » Tue Feb 04, 2014 8:32 am

Why is there primer/powder?
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Re: Shock-Compression Light-Gas Gun (Concept)

Unread postAuthor: jackssmirkingrevenge » Tue Feb 04, 2014 9:05 am

Gun Freak wrote:Why is there primer/powder?


Because only gregarious sodomites of some repute use purely pneumatic devices :D

The explosive charge drives the piston which compresses the gas.
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Re: Shock-Compression Light-Gas Gun (Concept)

Unread postAuthor: sagthegreat » Tue Feb 04, 2014 5:44 pm

this technically isnt against forum rules?

It doesnt use explosives to propel the projectile, it uses the explosion to propel a piston which creates air pressure that propels the projectile
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Re: Shock-Compression Light-Gas Gun (Concept)

Unread postAuthor: sudpuzzer » Tue Feb 04, 2014 9:12 pm

I posted this with the intention of adapting it to spudgun use, i.e. propane/air mixture in the primary chamber, and a light gas like helium in the intermediate chamber. But, as it was pointed out, there probably isn't much of a performance gain to be found over a standard hybrid.
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Re: Shock-Compression Light-Gas Gun (Concept)

Unread postAuthor: jackssmirkingrevenge » Wed Feb 05, 2014 9:57 am

sagthegreat wrote:this technically isnt against forum rules?


If someone replicated the NASA version, yes, but in this case it was just illustrating the principle.
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Re: Shock-Compression Light-Gas Gun (Concept)

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Re: Shock-Compression Light-Gas Gun (Concept)

Unread postAuthor: Gun Freak » Wed Feb 05, 2014 9:22 pm

Ahhhh. I have missed that the powder was in the rear of the cannon; by breech, I thought it meant the beginning of the barrel. Makes sense now...
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