[Andrea Lewis]

Andrea Lewis  asked the Naked Scientists:
   
Greetings from the other side of the world!
 
Love the podcast - completely addicted!
 
My question is when you go up in a plane your ears pop due to changes in pressure, does the same thing happen when you go down in a submarine?
 
Many thanks
 
Andrea
Hobart,  Tasmania  
Australia
 
What do you think?

[Geezer]

The pressure inside an aircraft is not held constant. While it is pressurised to some extent, it does decrease with altitude. This saves fuel and increases the service life of the aircraft, and it's why we experience effects on our ears and sinuses.

However, it seems unlikely that the pressure inside a submarine could be increased very much to help reduce the pressure difference between the inside and the outside of the hull. Because water is so dense (compared to air), during a dive, the rate of change of the internal pressure would be very great if it was to have any benefit to the structure of the submarine. Such a rate of change would not only be very uncomfortable for the crew, it would be very dangerous as it could induce "the bends" when the submarine climbed towards the surface.

In submarines, the air is probably maintained at close to sea level atmospheric pressure, in which case, as submarines change depth the submariners will not experience the same effects we experience in aeroplanes. I think!

[RD]

Some subs have spaces big enough for sailors to run a tight string chest height from one side of the hull to the other (while on the surface).  Deep down, the pressures have compressed the hull all around so much (despite their thickness) that the string will droop down and touch the floor!

That sounds like a practical joke to me: someone replaces the taut string with a longer one when the victim isn't looking.
A chest height string drooping to touch the floor would represent ~10% change in width, I doubt there would even be a 1% change in dimensions at depth.

[Geezer]

Some subs have spaces big enough for sailors to run a tight string chest height from one side of the hull to the other (while on the surface).  Deep down, the pressures have compressed the hull all around so much (despite their thickness) that the string will droop down and touch the floor!

That sounds like a practical joke to me: someone replaces the taut string with a longer one when the victim isn't looking.
A chest height string drooping to touch the floor would represent ~10% change in width, I doubt there would even be a 1% change in dimensions at depth.

I think the string was made of "nautical yarn"

[JimBob]

No - it is true-  my nephew is a submariner. And when he comes back from from sea duty he has problems with his ears - but not while at sea.

[thedoc]

Listen to the answer to this question on our podcast.