[Namel (OP)]

I love to read and watch science fiction. Quite common plot is someone being put out of airlock without space suit for various reasons. However science fiction writers sure can't agree what happens. Sometimes they explode, sometimes they freeze, sometimes they fry.

Does anyone know what really happens if someone is put to space without space suit? And would having just breathing apparatus keep astronaut alive while longer or is full suit mandatory to survive at all?

What would zero pressure do? I guess all moisture outside skin would boil out but what happens inside? I take human body would still hold some pressure so our blood would not boil? What other effects do zero pressure have to human? And could just using breathing apparatus help? I also wonder how heat would work? Space is near absolute zero temperature. But would that make human freeze very fast? After all there is almost no matter so heat could not be conducted via air like in earth. Heat could only be radiated out from astronaut. Wouldn't it act like thermos and keep all the heat inside human and human would actually become very hot?

[graham.d]

Good question Namel and welcome to the forum. I don't know the answer to this for sure (not my field) but I do know that much of the SciFi examples in movies is complete rubbish. I am sure it is known to a high degree of accuracy what would happen though.

My guess is that you would not die immediately and could recover if not exposed too long. One atmosphere of pressure is not very much. Postive pressures of many atmospheres are experienced by divers so I don't see that one atmosphere of negative pressure would be disastrous. The body is mostly liquid and solid, apart from the lungs and any trapped wind in the intestines. I suppose you would have to exhale a bit and, probably want to evacuate (actually there are other reasons why you may do that given the circumstances). Surface blood vessels would be damaged, especially in the eyes, but I don't think eyeballs pop out as happened in one scifi movie I saw. My guess is that the cause of death would be suffocation before other effect come into play. I reckon, like many other things, they got it right in 2001.

Any experts around? Anyone whose tried it?

[syhprum]

I think that after a few minutes they would die from lack of Oxygen, nothing very spectacular would happen.
Assuming they were mostly on the Sunlit side of the Earth they would slowly freeze as the radiative balance temperature is about -18°C at this distance from the sun 

[GlentoranMark]

As an added question, could you inhale in space?

[LeeE]

Hmm... I'm not an expert, but there have been documented cases of people being accidentally exposed to a near vacuum for short periods without any lasting injury.

The primary problem with being put into space without a space suit is lack of oxygen, without which you die.  The very low external pressure also causes problems, resulting in the rupture of blood vessels near the surface of the skin, the low temperature vacuum boiling of surface fluids, for example on the eyes and in the lungs and the ejection of the contents of body orifii(?) i.e. anus, ears, nose & lungs.  It's not a good idea to try to hold your breath in this situation as it could lead to the rupture of your lungs.  Finally, there's also a radiation risk too, especially from hard UV if in direct sunlight, which would very quickly induce bad 'sun' burn of exposed skin.

Like graham.d says, they seem to have got it just about right in 2001.

Once the pressure has equalised I see no reason why you couldn't continue to operate your ribcage and diaphragm, provided you haven't damaged your lungs by trying to hold your breath and haven't panicked, which would be a reasonable response under the circumstances.

[graham.d]

No. You would have to create a lower pressure inside yourself. With zero outside, you can't.

[Namel (OP)]

Assuming they were mostly on the Sunlit side of the Earth they would slowly freeze as the radiative balance temperature is about -18°C at this distance from the sun 

I don't think it is nearly as simple. As long as astronaut lives he is generating more heat. Is that heat more or less than he can radiate away? Secondly if astronaut has head directly to sun only his head and shoulders absorb sun's heat which is maybe quarter area of what astronaut absorbs if his stomach is facing sun. Same time he radiates heat out from whole body in both cases. It seems there is lot of variables.

What I am very interested is how long could naked astronaut survive heat and cold if other things would not kill him first and would astronaut get fast frostbites or would vacuum prevent that?

[LeeE]

Vacuum is a very good insulator; heat and cold would be the last of a naked astronaut's worries.

[flr]

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