Can an explosion outside an airtight tank affect the air pressure inside?

[sohai]

Hi everyone! Here's something that has been bothering me for quite some time now:
If you detonate an explosive device outside a completely airtight tank, what happens to the air pressure inside? Does the shockwave traveling through the wall of the tank have a notable effect on the pressure inside?

 

[DaveC426913]

Depends on how strong the tank is. And how elastic.

The pressure might flucuate a little due to vibration while the tank is being subjected to the insult, but unless the tank is actually deformed by the detonation, it will return to normal in a fraction of a second.

 

[sohai]

So if I sat inside the tank (which would not deform, only vibrate), I wouldn't end up with my eyes and ears bleeding?

 

[russ_watters]

In your question you said completely airtight, implying completely impervious to the explosion. You'd notice nothing.

If the tank were slighly less than completely impervious, you'd get a shock wave traveling through the tank like being inside a big bass drum. Powerful enough and yes, it could rupture your eardrums...and maybe everything else inside your body.

If the tank were not so impervious, it would be crushed, of course.

 

[mgb_phys]

If it can't deform there wouldn't be any change in pressure so your ears would be ok.
Of course if the bang was big enough to throw the tank 100feet up in the air you might feel it!

 

[Danger]

Airtight does not imply great structural integrity. The others have all touched upon what would be my main concern. Even if the container seal remains intact, the whole thing thing could be crushed to the extent that the internal pressure would rise significantly. Think of it as being similar to the pressure spike inside a football at the instance that it's kicked.

 

[DaveC426913]

In your question you said completely airtight, implying completely impervious to the explosion.

How does this follow? What does airtight have to do with impervious?

 

[DaveC426913]

The air pressure rising is not of any concern. For a deformation large enough to change the air pressure, the deformation itself will injure or kill you. What is of concern is the shock wave.

 

[Danger]

For a deformation large enough to change the air pressure, the deformation itself will injure or kill you. What is of concern is the shock wave.

I might be missing something here, but I disagree. If you're not in contact with the deforming material, it shouldn't affect you at all; there wouldn't be any mechanical transfer of energy to your body. As a 'for instance', what about if you're suspended in a hammock or elastic net? If the pressure increase is rapid enough, though, it could still cause damage even it isn't a lot above atmospheric.

 

[Idjot]

I think if the tank is rigid enough and air tight that the shock wave won't do much. However I think the sound waves from the blast may still penetrate the walls of the tank where they could do what they will. Might lose your hearing after all.

 

[mgb_phys]

However I think the sound waves from the blast may still penetrate the walls of the tank where they could do what they will.

If the walls don't deform, ie are infiniely rigid, then no sound can penetrate.

 

[Danger]

The original question didn't mention anything about the walls being even semi-rigid, let alone 'infinitely' rigid.

 

[Idjot]

So if I sat inside the tank (which would not deform, only vibrate), I wouldn't end up with my eyes and ears bleeding?

...,

 

[Idjot]

If the walls don't deform, ie are infiniely rigid, then no sound can penetrate.

First of all, a wall doesn't have to be 'infinitely rigid' to resist deformation.

Secondly, it doesn't take the compression of a shock wave to destroy a person's hearing so where the air might not compress in the tank very much, the noise could still be dangerously loud, especially inside a tank where it will reverberate.

Thirdly, I seriously hope we're not contributing to a dangerous experiment here.

lol​

 

[mgb_phys]

On his second post he said - if the walls can't deform - I was pointing out that if there is no deformation there can be no sound transferred.
To experience no deformation with a finite applied force they have to be infinitely rigid, of course a real wall might suffer not permament plastic deformation from a sound but have some elastic deformation to allow any energy to be transferred.

 

[Danger]

On his second post he said - if the walls can't deform

That one slipped past me. Now that I've read it, though, it's self-contradictory. He says that the walls can't deform, only vibrate. Vibration is deformation.

 

[DaveC426913]

Vibration is deformation.

I think we've been treating deformation as meaning inelastic.

 

[Danger]

I think we've been treating deformation as meaning inelastic.

I thought that any deformation was inelastic. Or does that mean something different here than in a collision?

 

[mgb_phys]

I thought that any deformation was inelastic.

Permanent deformation is inelastic. Elastic would still deform the surface and then it would spring back - like a drum skin

 

[DaveC426913]

i.e.
elastic = springy deformation = vibration
inelastic = permanent deformation = dent

 

[Danger]

My bad; I misinterpreted the terms. My understanding of elastic collision was that there was no loss of kinetic energy. Since a deformation has to convert some of that to heat (if only through intermolecular friction), I figured that it would be inelastic. Thanks for the correction.

 

[russ_watters]

How does this follow? What does airtight have to do with impervious?

Airtight does not imply great structural integrity.

Yes, you guys are right - it doesn't necessarily follow.

 

[sohai]

Sorry for my bad english and wrong way of thinking. By saying that the tank would not deform, only vibrate I meant that the tank would not collapse --> the pressure inside would not increase significally because of a great decrease in volume.

edit: So I think the concept that I mean is elastic or springy deformation or whatever it is called