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Old 08-29-2008, 06:31 PM
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Default The Alvin submarine and effects of pressure

The Alvin submarine is one of only a couple of research subs in the US. It's based at the Woods Hole Oceanographic Institution on Cape Cod, though it doesn't spend much time there. It's due to be rebuilt over the next few years, as it's probably older than some of you!

One of the fun things we do is take ordinary styrofoam coffee cups, and decorate them using Sharpies. We then put them in a mesh bag on the outside of Alvin (or any instrument that's going down to the murky depths). The water pressure crushes the cups - they come back about the size of a thimble! The decorations become really intense in color, as the ink is concentrated. Here are a couple of examples of cups that went down with Alvin. My wife drew some really detailed pictures of the sub on the cups, and it's traditional to put the location and depth of the dive on the cup. There's a penny in the picture for scale...



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Old 08-29-2008, 06:59 PM
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Default Re: The Alvin submarine and effects of pressure

Under pressure... yikes!
Thats quite impressive! thanks for sharing Peter.

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Old 08-29-2008, 08:31 PM
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Default Re: The Alvin submarine and effects of pressure

That's amazing! Thanks Peter.

Last night while walking I was thinking about rigs that descend to great depths and wondering what would happen to various materials. I didn't consider a styrofoam cup and it's very interesting to see the result.

I figured that an uncapped pipe would suffer no damage but what would happen to a hermetically capped hollow steel pipe as it descended to crushing depth?

When it got to the point of failure and air started escaping would the internal pressure rise fast enough to equal the external pressure for the pipe to avoid being crushed? I think not. The pipe would get squeezed flat from the end opposite the leak until it was flattened nearly to the end.

Have you tried that one yet?

Last edited by MichaelKellough; 08-29-2008 at 09:00 PM.
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Old 08-29-2008, 08:34 PM
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Default Re: The Alvin submarine and effects of pressure

Oh yea, how about a close up of that squished drawing?
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Old 08-29-2008, 08:52 PM
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Default Re: The Alvin submarine and effects of pressure

Michael, if you can wait a few days, I'll get you a picture of what happens to a hollow, sealed pipe when it's sent to great depths. In brief: it's expensive!
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Old 08-29-2008, 09:03 PM
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Default Re: The Alvin submarine and effects of pressure

Even if it's cheap pipe?
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Old 08-29-2008, 09:14 PM
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Default Re: The Alvin submarine and effects of pressure

If you sent a Kapex down could you later use it to cut tooth picks, duh
Remember what George on Seinfeld said about cold water
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Old 08-29-2008, 09:18 PM
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Default Re: The Alvin submarine and effects of pressure

Michael, here's a close-up of the Alvin drawings. The cups are also signed by the ship's captain, or the Alvin pilot. Sharon is very good at getting people to do things for her!



No, the pipe itself wouldn't be too expensive. It's what it contained that was $$$. A lot more than a Kapex!
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Old 08-29-2008, 09:29 PM
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Default Re: The Alvin submarine and effects of pressure

Bob,

If you do get your hands on this tiny Kapex, please do not post you have problems with it until you have checked it with an electron microscope, only then could the true tolerances be seen, along with any chip-out...
oh yeah, you would know to use a backer board.. my bad.

Mirko
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Old 08-29-2008, 09:32 PM
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Default Re: The Alvin submarine and effects of pressure

Peter,
this may be a stupid question, but are you using permanent markers?
If so, do they kinda melt the Styrofoam when you rite on em?

Mirko
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