From: eric@ils.nwu.edu (Eric Goldstein)
Subject: Re: Man in space ... 
Organization: The Institute for the Learning Sciences
Date: Thu, 5 Nov 1992 06:26:50 GMT

I showed the guy down the hall the FAQ on "How Long Can A Human Live   
Unprotected In Space" and he sent me the following response, which he
agreed to let me post.  

----------------Letter-From-Eric-Shafto---------------------------------------

>    HOW LONG CAN A HUMAN LIVE UNPROTECTED IN SPACE
>
>    If you *don't* try to hold your breath, exposure to space for half a
>    minute or so is unlikely to produce permanent injury. Holding your
>    breath is likely to damage your lungs, something scuba divers have to
>    watch out for when ascending, and you'll have eardrum trouble if your
>    Eustachian tubes are badly plugged up, but theory predicts -- and animal
>    experiments confirm -- that otherwise, exposure to vacuum causes no
>    immediate injury. You do not explode. Your blood does not boil. You do
>    not freeze. You do not instantly lose consciousness.
>
>    Various minor problems (sunburn, possibly "the bends", certainly some
>    [mild, reversible, painless] swelling of skin and underlying tissue)
>    start after ten seconds or so. At some point you lose consciousness from
>    lack of oxygen. Injuries accumulate. After perhaps one or two minutes,
>    you're dying. The limits are not really known.

I vividly remember a NASA publication entitled "14 seconds of useful
consciousness."  The claim was that, in case of rapid decompression, a
human had 14 seconds to fasten a helmet, close a door, throw a switch, or
whatever.  Not that you were seriously injured in that time, but you would
be incapable of taking whatever actions were necessary to save your life
after 14 seconds.

I wish this article had talked more about that.

As for injuries, while your blood would not boil (at least not for a very
long time) I would think that the fluids in your lungs certainly would. 
This should mean two things, I would think.  One is that I was wrong in
saying that, in a vacuum, you could close your mouth and nose and still
move your chest as though you were breathing.  The boiling mucus should
build up a decent pressure in your lungs and prevent you from doing that. 
In fact, I would imagine that gas would continue to escape from your lungs
the entire time you were in the vacuum*.  The second implication is that
your lungs should get very, very cold, below 0 degrees C, anyway.  You
might survive your exposure, only to asphyxiate after your return to a
pressurized environment, due to frostbite of the lungs.

*Well, for the first few hours, anyway.  After that, I think you would tend
to emit a plume of gas and particles around perihelion.  

***************************************************************************
* Eric Shafto              * Man, unlike any other thing ... in the       *
* Institute for the        * universe, grows beyond his work, walks up the*
*    Learning Sciences     * stairs of his concepts, emerges ahead of his *
* Northwestern University  * accomplishments.  -John Steinbeck            *
***************************************************************************

------------------End-of-Letter---------------------------------------------

Comments anyone?

Has anyone else seen the NASA publication? 

What does happen to the liquid in the lungs?  And ignoring the joke
about the spacefarer looking like a comet, is Eric Shafto wrong about
the danger of freezing?

      -- Eric Goldstein

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