[Renee Bonorchis]

Renee Bonorchis asked the Naked Scientists:

Is it true that if a human body had to be injected into the void of space that their blood would boil in their veins within seconds?

What do you think?

[chris]

This was the subject of a question of the week last year. In that instant it was posed as "what would happen if an astronaut took a space walk without a spacesuit?"

The conclusion we reached was based on both fact and fiction. In real life the man who broke the record for the world's highest parachute jump - Joe Kittinger - partially experienced this phenomenon. He jumped from 100,000 feet (three times the height of Everest) having ascended in a gondola slung beneath a giant helium balloon.

At this altitude there is very little atmosphere and it can effectively be considered the edge of space and so he wore a pressure suit to keep him alive.

Unfortunately the seal on one hand failed, exposing the tissue to the ambient near-vacuum. His hand swelled to five times normal size, but did return to normal upon safely reaching the ground! So this proves that blood won't "boil" because the natural elastic pressure of the tissues is probably sufficient to prevent this from occuring; but you would get a lot bigger.

Then we turn to accidental "experiments" in which people have been depressurised and exposed to very low pressures in decompression tanks. The conclusions drawn from these experiments is that when exposed to a vacuum you have about 20 seconds before you go unconscious.

Arthur C. Clarke wrote about this in his book 2001: A Space Odyssey in which the evil computer HAL (interestingly just one letter removed in each case from one of the world's most powerful computer companies - was he trying to suggest something?) locked someone out of the spacecraft. The victim performed a short (< 20s) suitless-spacewalk to re-enter, and survived. The likelihood is that this would indeed be possible.

Chris