Lins wrote:
Would anyone remember the scene in 2001: a space odyssey wherein David
Bowman has to basically bust his way back into the spaceship Discovery?

He's not wearing a helmet and he takes about 5 seconds before he starts
closing the powered door and flooding the room he's blown himself into
with oxygen.So basically he's in orbit above Jupiter,or thereabouts,for
at least 5 seconds without a helmet.

What I am wondering is this: wouldn't his head have been freeze dried
instantly? Or wouldn't the vacuum have done something horrible to it?

The movie got it pretty much right.
In vaccum, you pass out in under 15 seconds or so (the lungs work the
wrong way and becuase of the low pressure of oxygen in the lungs, the
oxygen in the blood streams out).
And the lungs burst if you try to hold your breath.

Essentially nothing irreversable happens in the first minute or so.
Freeze drying is not a very fast process.
In more than a minute, things like brain damage begin to set in,
and you will probably not start breathing again spontaneously without
help.