Re: radiation vs. conduction: safety issue

[brian whatcott <inet@intellisys.net>]

At 12:50 11/21/97 -0500, you wrote:

> > A colleague of mine was asked an interesting question yesterday. His
> > chemistry students were asking about what would happen if someone were
> > released into the vacuum of deep space. He put a water balloon inside a bell
> > jar and evacuated it to suggest that explosion wouldn't be the immediate
> > result. Then someone asked about freezing. He wondered how fast a person
> > would freeze, given that radiation would seem to be the only available
> > mechanism for cooling.
> >
> > What is the best way to understand this? How would I estimate the rate of
> > cooling for a person in a vacuum?
> >
> > - Tim
>
> Keeping your eyes closed should keep them from freezing for a while.
> I'd also try to keep a LITTLE air in my lungs but pinch my nose shut and
> close my mouth.
> A.C. Clarke used this manuever in 2001 so Dave could outfox HAL.
> ...
> Chuck Britton 

I am quite uncomfortable about the "little air in lungs" suggestion.
It was only in the last day or two I recall reading of an accident type
sometimes fatal that is said to lay in wait for beginning aqualung 
divers,  WHEN PRACTISING IN A SWIM_POOL!
 - not breathing out continuously while ascending.
 The comment was that the tender gas exchange tissue of the lung 
ruptures...but this was a net commentary of unknown integrity.

 A swim-pool hardly gets deeper than 20 feet I'd think hence the 
pdelta is perhaps 10 psi ( 690mb, 69kP.)

  Aircrew take explosive decompression training - I don't have the 
numbers but I expect an 8000 ft to 30000 ft change would be 
the largest excursion (753 to 301 mb = 452mb or 45 kP or 6.6psi) and I 
don't hear too much concern about this danger from that direction

 The Navy types have the best grip on the topic and the most need 
for caution, I suppose. An escape from 16 fathoms is a mighty 
pressure change on the lungs.

So I am speculating on admittedly sketchy grounds that a rapid change 
of about 5 psi is the threshold for damage.
And some space environments are held at this pressure...

At any rate, I suggest a sponge half laden with water would be a
more interesting object to evacuate.

Sincerely,

brian whatcott <inet@intellisys.net>
Altus OK