How long could I survive in space unprotected?

Assume I’m having to move from one door of a space station to another and I’m (for some reason) just in a pair of shorts and a T-shirt)? How long do I have before permanent damage?

Maybe a few minutes, if you had help:

You’ve got about 30-60 seconds to live. You will lose consciousness in 15-30 seconds. It will take about 30 seconds for your blood to begin to boil as it rapidly loses all of its heat and because of no air pressure to keep it in a liquid state. Depending on whether you are in direct sunlight or in shade you would be exposed to temperatures of 248F or -148F, respectively. Not to mention debris flying around at ludicrous speed.

Makes the notion of astronauts carrying “suicide pills” into space in case of some horrific scenario fairly ridiculous (though at least one Russian cosmonaut reportedly took one up with him); it’s so easy to die out there, it’s almost miraculous that anyone ever comes back.

More like 9-12 seconds, or possibly as little as 5 seconds, depending on how rapidly you decompress.

A couple of links in this post:

This must be a dumb question, but — how is there temperature in a vacuum?

According to Wikipedia, temperature:

In a vacuum, your body isn’t in contact with anything hot or cold, right?

You will gain thermal energy if exposed to sunlight, and lose it if you are in shade. “Space” itself doesn’t really have a temperature (unless you count the Microwave background radiation), but objects in space will become hot or cold depending on the amount of energy they absorb from sunlight.

Electromagnetic radiation travels through a vacuum. e.g. the heat of the sun passes through a vacuum to earth.

So while a vacuum itself doesn’t have a temperature, you would heat up very rapidly in a vacuum if exposed to the sun. You would cool very rapidly otherwise, due to liquids boiling away from all exposed surfaces.

Earth is in a vacuum …

There might a tiny bit of wiggle room. Not much a little.

The problem with unconsciousness and imminent death is the oxygen saturation levels of the blood. It is very balanced. Below a critical level the blood will actually start to scavenge oxygen out of the body. This level isn’t that low. As the partial pressure of oxygen in the gas in the lungs drops the blood saturation level drops, and oxygen is pulled from the blood and from your body. So it isn’t a simply a matter of suffocation. The problem is much more aggressive.

One is warned against holding one’s breath. This is because there isn’t enough strength in the body to hold in one atmosphere of pressure, and you will tear something vital in a nasty manner.

However, the body can exert a non-zero amount of pressure by physical effort. It varies, partly by physical size, and partly by how deep a breath is held. It isn’t much pressure, somewhere between 0.05 and 0.1 atmospheres. That corresponds to exhaling as hard as you can. So, if you were forewarned that you were about to be dropped into vacuum, and inhaled lots of pure oxygen to saturate your blood, and then took a very carefully gauged breath so that you could hold it at maximum exertion, but release any gas past the pressure you could hold (which would take training) you could potentially hold 0.1 atmosphere partial pressure of oxygen in your lungs. You would need to plug your nose, and maybe include some support for the lips. Ears will not be happy. It will hurt. We are basically trying to emulate the effect of a Mechanical counterpressure suit as much as we can with only our body.

But 0.1 atmosphere PP of O2 is 50% of sea level PP of oxygen in air, better than on top of Mt Everest. You won’t be able to hold this for long. But it should give you better than the time available to anyone who is unexpectedly exposed to vacuum and allows the oxygen in their lungs to vanish followed by a precipitous drop on blood oxygen saturation. With training, you might be able to perform useful tasks for a short period, not unlike free divers.

An extremely good summary of the evidence can be found here, by Dr Grant Hutchison.

When in Outer Space, always use protection.
Space Herpes in nothing you want.