(New York Times) In space, heads swell.
A typical human being is about 60 percent water, and in the free fall of space, the body’s fluids float upward, into the chest and the head. Legs atrophy, faces puff, and pressure inside the skull rises.
“Your head actually feels bloated,” said Mark E. Kelly, a retired NASA astronaut who flew on four space shuttle missions. “It kind of feels like you would feel if you hung upside down for a couple of minutes.”
How that alien environment changes the body is not a simple problem, nor is it easily solved.