Effects on a protected human body in space
On Earth, the heart is programmed to distribute blood evenly throughout the body. The
heart must do more work to supply the upper body, because blood is naturally drawn
downward by the force of gravity. The lower limbs do not have this problem, as the
blood coming to them is gravity-assisted.
In space, bodily fluids no longer flow back down naturally by gravity. The heart is still
programmed the way it was on Earth. So, under the pressure of the heart and the veins
and arteries, the blood rushes to the person’s torso and head, and they then
experience “puffy face syndrome.” The veins of the neck and face stand out more than
usual; the eyes become red and swollen. This effect is often accompanied by nasal
congestion and sometimes even headaches. Astronaut’s legs also grow thinner,
because instead of dropping effortlessly down to the lower limbs, the blood has to be
pumped there by the heart.
Particularly because of physiological changes such as these, astronauts suffer from
space sickness or space adaptation syndrome (the space version of what we call
motion sickness on Earth). About 40% of those who have gone into space have had
dizziness or nausea. Both generally wear off after 2 or 3 days, as soon as the
astronaut’s body has had time to adapt.
Influence on the bone and muscle structure
In space, the musculoskeletal system
continuously deteriorates.The muscles, in particular the leg muscles, which are underused, become flabby and lose tone and mass. The astronauts are then subject to muscular atrophy. The bones, too, become weaker because of a loss of minerals (calcium, potassium and sodium). This bone degradation can reduce bone in the lower limbs by up to 10%. Astronauts try to mitigate these changes by taking medication and, especially, by exercising as often as possible.Did you know that your body gets taller in space? Because the spine is no longer compressed by the force of gravity, the vertebrae separate slightly from one another and the person’s body lengthens. Astronauts often have backaches, which, it is thought, are caused by relaxation of the muscles and ligaments of the back.Back on Earth, the force of gravity will influence the astronaut’s spine, which will return. Influence on balance and the sense of orientation
Balance and orientation are also disturbed, for in space the body lacks its normal points of reference. Whatever medium the human body finds itself in, the brain receives information from its environment through the eyes (the visual cues), the muscles and tendons (the proprioceptive apparatus) and a set of sensors that detect liquid movement and are located in the semicircular canals of the inner ear (the vestibular apparatus). Even after the astronaut leaves Earth, his or her brain continues to believe that its points of reference are terrestrial ones. Thus, because the information being received is chaotic, the astronaut has trouble adapting to this new microgravity environment. He or she is disoriented because the sensors of the inner ear and the muscular apparatus cannot orient themselves in zero g. The only useful information reaching the astronaut’s brain is through the eyes.o its normal size.
Effects on an unprotected human body in space
The short answer!
The complete lack of atmosphere means that all of the air in your lungs tries to escape since there is a pressure difference between the inside and outside. The effects can be similar to the bends, where gases dissolved in the blood can expand and accumulate in joints. There can be some slight swelling (mostly painless and reversible) of the skin. Tests on animals and accidents have shown that people will lose consciousness after 10-15 seconds. Interestingly, on 1 occasion, the subject reported that the saliva boiled off his tongue.For prolonged exposure (the time it takes to starve the brain of oxygen) there is death.
What won't happen?
Your blood won't boil away out of your veins!
Blood is a fluid and as such does not change volume (by much) with changes in pressure with changing state (into a gas). Since blood is contained inside the body and not exposed directly to the vacuum you can expect not to boil.You won't instantly freeze.To freeze, you need to have all of the heat in your body to be drawn away. If you think back to your science lessons in school, you'll know that there are only 2 ways to transfer heat away from a body, conduction and radiation. Space is cold, but there is also nothing there so you wouldn't lose any heat from conduction (as you would in an atmosphere). You would lose heat by radiation, but in practice this isn't very much when you look at the amount of time you're actually going to care about it!No, your eyes do not pop out of your head.Once more, this is to do with fluids not expanding.
You could get severe sunburn!
Ok, perhaps this should be in a different section. In space, you are pretty much naked to the sun without the atmosphere to protect you. If you are in direct sunlight, the intense UV radiation will give you something to think about!
Has anyone ever been exposed to a vacuum?
Yes. When doing some tests in a vacuum, the suit worn by the subject sprung a leak and he was exposed to (near)vacuum. He lost consciousness after 14 seconds. The suit probably did not reach total vacuum since the test chamber was repressurised very quickly.
Another incident involved Joe Kittinger on his historic balloon ascent. He lost pressurisation to his right hand where it became painful and useless. It returned to normal as he returned to earth and air pressure became gradually normal.