[ot] blood in space

[NoOneofConsequence]

Joe Haldeman's "The Forever War" sums up exposure to hard vacuum rather elegantly....

"Once your exposed it's a split second race between the vacuum and the cold to see whether your blood boils before your body flash freezes."

Pleasant.

Also, just for the sake of being pedantic, in the case of the film Event Horizon, the ship Event Horizon is in fact in the upper atmosphere of the planet (Uranus, IIRC) and so the character does not get exposed to hard vacuum, but rather to an extremely thin atmosphere, which is why the character manages to survive in spite of about thirty seconds exposure. This point was made by the director in an interview with Starlog magazine around the time of the film's release.

 

[JacktheRabbit]

Actually the first thing that will kill a person exposed to the vacuum of space will be suffocation. This will be accelerated by the lack of pressure which will make it nearly impossible for a person to keep whatever breath he has in his lungs from forcing its way out.

Okay, my Outer Space Physics and Human Biology are a little rusty, so anyone who knows better should feel free to step in any time.

First, let's talk about zero-g, or "microgravity" as it's referred to while in orbit. Liquids exposed to microgravity environments do tend to collect in spheroid shapes and float around, as film showing astronauts having fun with their Tang (or whatever ) proves. We don't fully understand the ramifications of spending extended periods in microgravity, but we have a number of good guesses.

http://spacelink.nasa.gov/products/Space.Food.and.Nutrition/microgravity.html (the text, not the pic)
http://www.space.edu/projects/book/chapter31.html

Second, blood takes its color from the oxygen incorporated into it; the level of atmospheric oxygen doesn't change the color of blood. Blood changes color to "crusty brown" as it *dries.*

http://www.madsci.org/posts/archives/dec96/839903302.An.r.html
http://www.seps.org/oracle/oracle.archive/Life_Science.Anatomy/2001.02/000981693349.24712.html

Third, the primary hazard to an exposed human body in outer space is the zero atmospheric pressure ("hard vacuum"), after which follows the ultra-cold {EDIT - extreme} temperature and, if the unfortunate soul somehow survives *those* two hazards, there's often a hefty dose of hard radiation to deal with.

http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/970603.html

So to answer the question we leave aside the fact that a spacesuited character in hard vacuum is facing a serious and quickly lethal emergency if the suit is punctured (venting the suit's air and pressure into space) and the character is bleeding (venting blood into space).

So the color of the blood will vary between dark red, venous blood and bright red, arterial blood depending on what's been punctured. Assuming our poor victim is in a hard vacuum + microgravity environment, the blood will most likely spray forth from the suit (remember, blood is under pressure) and collect in large droplets. If we now assume our hapless astronaut is in the cold of outer space, I'm inclined to guess the droplets will freeze rather quickly, but that may {EDIT - does} depend on how much radiant heat is available from the nearest star.

 

[JacktheRabbit]

Unfortunately it is wrong. In a vacuum your body only freezes as quickly as it radiates the heat from your body. This means it will take a while for your body to freeze, much much longer than it will take to suffocate.

Remember a person freezes in cold weather because they are continually in contact with molecules in the air and other substances that are colder than the person and thus steal heat from the body. In a vacuum there is very litter matter around you to rub against your body and steal heat. So most of the heat only leaves you as fast as your body radiates it.

Joe Haldeman's "The Forever War" sums up exposure to hard vacuum rather elegantly....

"Once your exposed it's a split second race between the vacuum and the cold to see whether your blood boils before your body flash freezes."

 

[Mark]

Actually the first thing that will kill a person exposed to the vacuum of space will be suffocation. This will be accelerated by the lack of pressure which will make it nearly impossible for a person to keep whatever breath he has in his lungs from forcing its way out.

Is it possible that heart failure while being "spaced" kills the person even more quickly...?

 

[JacktheRabbit]

Assuming you have a heart condition of course the shock may kill you. This will only happen though to someone with a weak heart.

It is pretty much a work of fiction that you can scare a person to death.

Is it possible that heart failure while being "spaced" kills the person even more quickly...?

 

[Hygric]

It's been a while since I have had to dust of this part of my brain, but from memory boiling points are closely tied to pressure (hence why the inner core of Earth is a solid instead of a liquid), so in a vacuum, it should pretty much boil of quite quickly, if not explosively.

And O2 is only lightly held bay hemoglobin, so in a pO2 of 0 mm Hg, hemoglobin will hold on to no O2 whatsoever, even in temperatures approaching 0 degrees kelvin.

I guess that this would mean that our poor astronaut would have a jet of gas and dust flying from his space suit, instead of globs of blood or frozen pellets.

 

[Hygric]

About the heart failure:

Thermal shock can induce heart failure in even the most healthy individual, and I can't imagine of too many greater thermal shocks than either being exposed to extremely low or extremely high (depending on solar radiation) temperatures.

 

[JacktheRabbit]

A vacuum does not have that much of a thermal shock. As I said, you only lose heat as fast as you can radiate it since there is little matter in space to drain heat from you.

Remember when you "feel" cold you are in fact feeling particles of matter that are colder than you colliding with your body. Since a vacuum has few particles to it you would in fact not feel that cold. Certainly there are many places on Earth that feel much colder than even the most remote sections of space.

About the heart failure:

Thermal shock can induce heart failure in even the most healthy individual, and I can't imagine of too many greater thermal shocks than either being exposed to extremely low or extremely high (depending on solar radiation) temperatures.

 

[Wolf72]

given any of the events above (shock, suffocation, blood freezing what have you ...)

exactly how much time is there? ... as in ... is there that much of a difference?

 

[JacktheRabbit]

Not really. Though it does tell you which movies are crap and which movies are not. Mission to Mars with the man freezing the instant he opened his helmet was crap. 2001 when Bozeman jumped across the vacuum in a second without a helmet and survived was actually possible and realistic.

given any of the events above (shock, suffocation, blood freezing what have you ...)

exactly how much time is there? ... as in ... is there that much of a difference?