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Shooting fish

A place to ask general spud cannon related questions.
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Unread postAuthor: john bunsenburner » Fri Mar 13, 2009 3:41 pm

15 psi is what it takes to pop an eardrum and to pop out an eye ball...
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Unread postAuthor: jackssmirkingrevenge » Sat Mar 14, 2009 3:12 am

psycix wrote:If 100 psi comes out of your barrel at a high volume, and the water effectively transfers this pressure wave onto your eardrums, wont that do some serious ear damage?


But unless you're suicidal, isn't that pressure wave directed away from you?
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Unread postAuthor: psycix » Sat Mar 14, 2009 7:05 pm

Waves (sound, light, pressure whatever) don't go straight. They go around corners. For example: look at interference patterns.
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Unread postAuthor: jackssmirkingrevenge » Sun Mar 15, 2009 1:52 am

psycix wrote:Waves (sound, light, pressure whatever) don't go straight. They go around corners. For example: look at interference patterns.


Yes, but if someone is talking to your face, you hear it clearer than if they were talking with their back to you.

Besides, if it didn't make a difference, these weapons would not be in use:

[youtube]http://www.youtube.com/watch?v=x-P578pnctU[/youtube]
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Unread postAuthor: D_Hall » Sun Mar 15, 2009 2:20 am

psycix wrote:
D_Hall wrote:
psycix wrote:Nobody tried it yet. Or survived it....

On the contrary. The military does it on a very large scale every time they launch a missile from a submarine.

I understand that there are indeed some serious pressure waves thrown around in that scenario, however.

But the people in the sub are inside, and not holding the launcher in their hands. In other words: between the muzzle and their ears is not only water, but also air.
I am not worried about damage to the gun, but about damage to the person firing it. If 100 psi comes out of your barrel at a high volume, and the water effectively transfers this pressure wave onto your eardrums, wont that do some serious ear damage?


Well, I was addressing the concept of massive underwater air cannons in general and that much *IS* known about such scenarios. I wasn't directly addressing the effects of such firings on humans.

HOWEVER....

Humans HAVE been exposed to such. During the development of the Polaris missile underwater launches of missile bodies (not live missiles) were performed from a static platform just off the shore of San Clemente Island. Those launches were filmed in about a gazillion different ways...

...Including scuba divers manually handling cameras.

I'm told that it was doable, but painful.

I do not, however, know how close they were to the muzzle.
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Unread postAuthor: THUNDERLORD » Sun Mar 15, 2009 1:43 pm

jackssmirkingrevenge wrote:
psycix wrote:If 100 psi comes out of your barrel at a high volume, and the water effectively transfers this pressure wave onto your eardrums, wont that do some serious ear damage?


But unless you're suicidal, isn't that pressure wave directed away from you?


Good point, that caused me to rethink the long round with internal burst disc, mounted on an aluminum (solid) rod.
It seems there should also probably be another external tube, extending and maybe vented to direct (reversed) muzzle blast away. Thanks!

It seems like lower velocity, heavier round, but with a constant push would work better underwater because the higher the speed the more the water acts solid.
(I played with water and corn starch *edit: or corn syrup?* before...Cool the first times)

My nephews had a torpedo pool toy, it was heavy rubber and I was amazed how far it went and straight underwater with only a light push.
I suppose the external (or internal) dynamics are very important.
That thing would probably clear atleast over 100 meters underwater from an air cannon.
I'll try to find a link to that toy.

I wouldn't be too worried shooting an air cannon underwater, just wear proper potection, ear-plugs, mask and... a cup. :P
Cool aps vid made me wonder is all. But it didn't look much more dangerous than farting in a bathtub. (from the shooter's side of course) :P 8)

EDIT: I think I've found it, scroll to #5Here Looks like the same one! it's 7 or 9$, but maybe with one a mold could be crafted...and maybe a steel tip(?) :twisted: 8)
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Unread postAuthor: jackssmirkingrevenge » Mon Mar 16, 2009 12:50 am

THUNDERLORD wrote: But it didn't look much more dangerous than farting in a bathtub. (from the shooter's side of course) :P


Trust me, on the other side of the muzzle it's very dangerous :shock:

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Unread postAuthor: john bunsenburner » Mon Mar 16, 2009 10:49 am

Did you make that picture?!
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Unread postAuthor: jackssmirkingrevenge » Mon Mar 16, 2009 11:17 am

john bunsenburner wrote:Did you make that picture?!


No, that's actual damage shots from the 5.45mm underwater rounds fired by Russian underwater weapons.
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Unread postAuthor: Sticky_Tape » Mon Mar 16, 2009 11:34 am

That is some great dammage there and is that concrette?
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You can tell how awesome a cannon is by the pressure used.
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Unread postAuthor: jackssmirkingrevenge » Mon Mar 16, 2009 11:47 am

Sticky_Tape wrote:That is some great dammage there and is that concrette?


Yes, not surprising considering the projectile is long and thin therefore whilst it travels slower, it is heavier than a normal bullet while retaining the same cross-sectional area and therefore has an extremely high sectional density which is always good for penetration ;)
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Unread postAuthor: jimmy101 » Mon Mar 16, 2009 3:56 pm

Following up on what D_Hall said...

A torpedo, when it explodes, is essentially identical to the underwater release of a large volume of high pressure gas.

Torpedos are often not intended to actually strike their target. Instead, the torpedo is set to pass beneath the target ship. A metal detecting proximity fuse detonates the torpedo when it is directly under the target (not when it hits the target). The shock wave from the rapid pressure pulse (from the expanding gases) breaks the ship's back.

So, you can indeed do very significant damage to an object underwater with nothing more than a pulse of high pressure gas.
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