[thedoc (OP)]

David Wintle asked the Naked Scientists:
   In the movie 2001 - A Space Odyssey, astronaut Dave has to reenter the mothership from his pod but he does not have his helmet. Leaving the pod without a helmet, would he freeze first (space being 2.7k), or would his lungs erupt due to relative high pressure of air in his lungs c.f. space (vacuum) or would the cosmic radiation zap him straight away, or could he make it back into the mothership?
What do you think?

[JohnDuffield]

He'd die from lack of air. Cosmic rays wouldn't do much in the time we're talking about. His head wouldn't explode, his blood wouldn't boil, and he wouldn't freeze to death. He'd only harm his lungs if he tried to hold his breath. If he had to jump from one spaceship to another without a spacesuit, he'd be OK provided he wasn't in space for too long. This article gives some details:

http://www.geoffreylandis.com/vacuum.html

It says this:

A slightly more general interest book, Survival in Space by Richard Harding, echoes this conclusion: "At altitudes greater than 45,000 feet (13,716 m), unconsciousness develops in fifteen to twenty seconds with death following four minutes or so later" and later: "monkeys and dogs have successfully recovered from brief (up to two minutes) unprotected exposures..."