Re: Effects of Explosive Decompression

From: GLANDIS@LERC.NASA.GOV (Geoffrey A. Landis)
Newsgroups: rec.arts.sf.science
Subject: Re: Effects of Explosive Decompression
Date: Fri, 12 Aug 1994 16:01:24 -0400

The subject of explosive decompression comes up so often on sci.space.tech 
that I've decided to keep a file on the suject.  In brief, if you keep your 
mouth *wide* open to avoid rupturing your lungs, you can expect to stay 
conscious in complete vacuum for ten to twenty seconds.  If you are 
recompressed within one to two minutes, you will probably survive the 
experience.  In short, Clarke (in _2001_) seens to have gotten it about 
right, since Bowman manages to close the airlock in the ten seconds of 
consciousness he has available..

<snip, snip>

"It is very unlikely that a human suddenly exposed to a vacuum would have 
more than 5 to 10 seconds to help himself.  If immediate help is at hand, 
although one"s appearance and condition will be grave, it is reasonable to 
assume that recompression to a tolerable pressure (200 mm Hg, 3.8 psia) 
within 60 to 90 seconds could result in survival, and possibly in rather 
rapid recovery."

<snip, snip>

Among other things, it has the only published discussion I've ever seen of 
the JSC (well, it was MSC then) suit technician who spent 20 seconds in 
vacuum in Dec 1966 when a suit umbilical came loose during a vacuum- chamber 
test.  The pressure drop was slowed somewhat by the remaining section of 
hose, so it wasn't fast enough to cause lung damage.
He passed out, presumably from anoxia, after 12-15s.  Pressure began to be 
restored at 20s and was well up at 27s, at about which time he regained 
consciousness.  He was apparently uninjured, and aftereffects were minor and 
temporary.


Henry Spencer comments:

>Ebullism (Precious Bodily Fluids vaporize at body temperature):
>	"Small pockets of gas can be detected beneath the skin
>	within two to three seconds after exposure ..."
>	"Gas evolution can also be detected in the abdominal cavity
>	after seven to ten seconds, and within the heart and great
>	vessels after about twenty seconds."

Roth says that vapor bubbles form in the bloodstream essentially 
instantaneously -- delays under 1s -- but initially are not serious enough to 
stop circulation.  Eventually they are.  Worse, these bubbles begin as water 
vapor, but then they start to pick up dissolved gases from the blood... and 
while the water vapor will condense out almost instantaneously on 
repressurization, the gases redissolve much more slowly, and the resulting 
long-lived bubbles are potentially a very serious threat.  There are medical 
countermeasures, which Roth discusses, but most of them unfortunately rely on 
gravity (for example, a well-chosen prone position -- on one side at about a 
30-degree head-down slope -- keeps bubbles in the heart away from the valves 
and gives time for the bubbles to dissolve or be dealt with medically).


Gregory Bennett adds: 

Incidentally, we have had one experience with a suit puncture on the Shuttle 
flights.  On STS-37, during one of my flight experiments, the palm restraint 
in one of the astronaut's gloves came loose and migrated until it punch a 
hole in the pressure bladder between his thumb and forefinger.  It was 
explosive decompression, just a little 1/8 inch hole, but it was exciting 
down here in the swamp because it was the first injury we've ever head from a 
suit incident.  Amazingly, the astronaut in question didn't even know the 
puncture had occured; he was so hopped on adrenalin it wasn't until after he 
got back in that he even noticed there was a painful red mark on his hand.  
He figured his glove was chafing and didn't worry about it.  
     The whole story didn't come out until the suits were back home and a 
suit technician was setting up to clean that glove; he discovered the dried 
blood on the outer TMG (thermal micrometrioid garment) and then found the 
wayward palm restraint bar.  What happened: when the metal bar punctured the 
glove, the skin of the astronaut's hand partially sealed the opening.  He 
bled into space, and at the same time his coagulating blood sealed the 
opening enough that the bar was retained inside the hole. 
     The best estimate we've been able to get from the flight surgeons about 
how long an astronaut might survive a catastrophic suit failure is "several 
tens of seconds to very few minutes" with almost certainty for detectable 
permanent damage.



Geoffrey A. Landis,
Photovoltaics branch, NASA Lewis Research Center
Nyma, Incorporated, Brook Park, OH