From: bill@bohemia.metronet.org (Bill Dixon)
Subject: Re: Human bodies explode in vacuum?
Organization: Bohemia BBS System
Date: Fri, 6 Nov 1992 08:52:05 GMT



>In article <1992Oct30.110946.1@opie.bgsu.edu> jnigrin@opie.bgsu.edu writes:
>>In article <1cq1urINNe6b@iskut.ucs.ubc.ca>, dkmiller@unixg.ubc.ca (Derek K. Miller) writes:
>>
>>> (Pressure stuff deleted)
>>> 
>>
>>But pressure changes on surfacing are *decreases* to 14.7 PSI, normal 
>>atmostpheric pressure. When you dive, the fluids in your body
>>compress and press back against the pressure (and presumably other 

>Actually, you can't compress liquids.  It's the gases (nitrogen, to
>be exact) that cause 'rapture of the deep' for divers.  The nitrogen
>gets compressed during the decent, and then forms bubbles on the ascent.
>These bubbles block blood vessels, and generally do bad things.  The
>phenominae is called 'Nitrogen Narcosis'.

WHOA!! this may be starting to run pretty far afield but you're confusing two
completely different,(though related) phenomena.
1)Under greater pressures at depth more nitrogen is dissolved in the blood, much like
carbon dioxide is in beer or soda. This nitrogen inhibits the blood's ability to
carry oxygen by combining w/ the oxygen to produce nitrous oxide directly in the
bloodstream. We all know what this does. |-)zzzz This is nitrogen narcosis. Some are
more susceptible than others.

2)The bends occur when a diver rises to the surface to quickly. The nitrogen normally is
outgased under the reducing pressure via the lungs, along w/ carbon dioxide. However, if
the diver rises too quickly (ie the pressure is released too quickly)
the nitrogen doesn't have a chance to outgas and forms bubbles. This is analogous to the
bunch of bubbles you get immediately when you open any fairly carbonated beverage.
The longer and deeper the dive, the more nitrogen dissolved, and the longer one must take to 
outgas the nitro. This is decompression and was standardized by the navy as a series of waits
at specified depths as you surface. The times/depths depend on the times/depth of the current and previous dives.

Both of these problems have been solved by using a helium/oxygen mixture for breathing at
extreme depths. Helium doesn't dissolve as readily and outgases quickly. Nor does it combine
w/ other elements readily. Makes you sound like Donald though. Check out any PBS deep sea
research deal where the guys dive deep, they all talk funny.
Of course the don't use this in bathyscapes (generally) as the internal pressures are
(usually) kept close to 1 atm. Helium can be harsh on mucous membranes.


 In space, you would have the
>same problem, the gases in your blood would expand, and form bubbles,
>which would block vessels to your brain, heart, etc.  Bummer...
>I guess the real question is can the human body withstand the pressure of
>these expanding gases.  (Or does a human make a good balloon?)
>I would say that human skin would make a fairly effective gas-bag.  I
>wonder if surface level blood-vessels would blow open, though.  Maybe
>eyeballs too...  Hmmmm....  >Shudder<  Not a pretty site.  :^)

OK.
Remember that it's not just dissolved gases we're concerned about here. Water boils at
100 degrees C at 1 atm. As pressure drops so does the boiling point. Chemically inclined folks
should investigate vapor pressures. Any way the point is, if we remove all pressure, all that
water (97% ?) at 98.6 F wants to go somewhere fast. I remember a time Time-Life space book
w/ a picture of a guy in a pressure suit holding a beaker of blood (boiling) in a low pressure 
chamber-Scary. BUT-space is a cold place, right?? Well, yes and no. Vacuum makes a pretty good 
insulator (ever use a Thermos?) as there is nothing there for the heat to be transfered through,
so most of the heat lost ina vacuum is lost not by conduction, but by radiation, ie IR radiation.
I find it difficult to believe that one could loose all the heat in their body through IR in less
time than it would take for most of the various water-based fluids to boil out of their body in
near-zero pressure. Most of this would probably occur through the lungs. High-altitude (low-
pressure) moutaineers often suffer from a condition called pulmonary edema. A delicate balance
exists in the lining of the lung which keeps fluid on the right side of the semi-permeable
membrane. If the atmospheric pressure is lowered sufficiently, fluid is forced through this 
and into the lungs. This makes breathing very difficult and one can actualy drown in this fluid.
So IMHO people probably don't explode in space(though I'm fairly certain they would expand)
but instead have most of their bodily fluids boil out through their various orifices. Certainly 
most of the blood coming through the lungs

>>changes I don't understand happen too).  Then things return to normal 
>>when you surface.  But a different situationn applies when the body is 
>>exposed to vacuum. There's no way to *reduce* the internal pressure
>>to zero.
>>

GOOD POINT.
>>~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>>Jon Nigrine                              "A foolish consistency is
>>jnigrin@opie.bgsu.edu                     the hobgoblin of little
>>                                          minds."  -- Emerson


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