Theoretical Physics Question - firing a cannon under deep water

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[ARCHIVED THREAD] - Theoretical Physics Question - firing a cannon under deep water

Posted: 10/8/2007 6:52:58 PM EDT

Would it be possible to submerge a cannon to great depth [~10,000' feet] and fire it, or would it explode like a bomb due to the water pressure at that depth?

...And i do not know the answer to this

a poll?

Posted: 10/8/2007 7:04:59 PM EDT

[#1]

Quoted:

pretend there's a one-way flapper on the end of the barrel that wont let water in

Here's a flapper but beyond that I got confused...

Posted: 10/8/2007 7:05:45 PM EDT

[#2]

I were gonig to pretend there is a flapper. Then pretend that it will fire also. Pretending is fun!

Posted: 10/8/2007 7:06:08 PM EDT

[#3]

A quick Google search revealed the hydrostratic pressure of 10,000 ft of water is 4500 psi. www.hboi.edu/eng/hydro.html

The pressure generated by the burning of the propellant in a mil-spec 155mm artillery round can be 52,000 psi. findarticles.com/p/articles/mi_qa3738/is_199810/ai_n8815482/pg_9

Therefore I would assume the projectile could safely be fired.

Posted: 10/8/2007 7:06:16 PM EDT

[#4]

Quoted:

Quoted:
arfcom doesn't do physics very well....

So true

[ARFcom guy in the van by the river] The cannon won't fire on a treadmill. No-huh. Cuz of the wheels. They'll be spinning at X-Force speeds and stuff and the gravitation won't work. And it won't fire. Yew can believe me cuz I've been an engineer for a bunch of years. And you can't put a treadmill under water cuz treadmills always float. So a cannon will only fire 10,000 feet under water if you take the wheels off. [/ARFcom guy in the van by the river]

Posted: 10/8/2007 7:08:42 PM EDT

[#5]

Quoted:

Quoted:
arfcom doesn't do physics very well....

So true

[ARFcom guy in the van by the river] The cannon won't fire on a treadmill. No-huh. Cuz of the wheels. They'll be spinning at X-Force speeds and stuff and the gravitation won't work. And it won't fire. Yew can believe me cuz I've been an engineer for a bunch of years. And you can't put a treadmill under water cuz treadmills always float. So a cannon will only fire 10,000 feet under water if you take the wheels off. [/ARFcom guy in the van by the river]

I don't think electronic treadmills work under water, without a flapper!

Posted: 10/8/2007 7:09:52 PM EDT

[#6]

Quoted:
A quick Google search revealed the hydrostatic pressure of 10,000 ft of water is 4500 psi. www.hboi.edu/eng/hydro.html

The pressure generated by the burning of the propellant in a mil-spec 155mm artillery round can be 52,000 psi. findarticles.com/p/articles/mi_qa3738/is_199810/ai_n8815482/pg_9

Therefore I would assume the projectile could safely be fired.

so at the exact moment upon firing the greater pressure exerted from the exploding shell would overcome the water pressure, not allowing water into the breech - 'flapper' or not

wha about at say 20,000' feet? doesn't water pressure exponentially go up

Posted: 10/8/2007 7:10:39 PM EDT

[#7]

Quoted:
Unfortunately, unlike air, the water in the barrel is incompressible, and will not get out of the way in time to prevent overpressure. In fact, just filling the barrel with water at sea level will likely cause enough overpressure to rupture the breach or the barrel.

Assuming this is an old-school iron-tube cannon, it would have an equally great pressure being applied to it at all sides. The bore is still the weakest point. If the cannon were filled with water above sea level I would agree with you.

Posted: 10/8/2007 7:11:53 PM EDT

[#8]

Quoted:
A quick Google search revealed the hydrostratic pressure of 10,000 ft of water is 4500 psi. www.hboi.edu/eng/hydro.html

The pressure generated by the burning of the propellant in a mil-spec 155mm artillery round can be 52,000 psi. findarticles.com/p/articles/mi_qa3738/is_199810/ai_n8815482/pg_9

Therefore I would assume the projectile could safely be fired.

It ain't just the pressure, its the incompressibility of the water. But, given the change in scope to add a flapper, I agree with silence. No range. In fact, the shell will stop pretty much as soon as it clears the muzzle. Water is pretty hard at ballistic velocities.

Where are all the aero-E's who will run a quick spreadsheet calc to determine the range given the ballistic coefficient and the density/pressure at that depth???

[ARCHIVED THREAD] - Theoretical Physics Question - firing a cannon under deep water

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