What happens to your body while you are orbiting earth? Firstly, your heart will have enlarged, your face looks puffy and you will feel nauseous.
As a result of fluid re-distribution in the body, the face will swell, as legs appear skinnier. The space traveller's nose will feel blocked, as though he is getting a cold. He will also lose at least one litre of urine.
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The lack of gravity will confuse the person's sense of balance, causing him to feel nauseous, dizzy and lose his appetite. His heart will begin to enlarge and his heart rate will slow down. His body will also not have to work as hard as on earth to move around, so his muscles will begin to shrink while his bone density will start to decrease.
His body will start to produce fewer red and white blood cells as a result of his lower body fluid levels, and so his immune system will begin to weaken. He might also struggle to get enough sleep due the different light cycles experienced in space.
During lift-off Cosmonauts experience a force of between three to five times the force of gravity during lift-off. The space shuttle accelerates within minutes to more then 27 000km/h.
The cosmonauts are strapped into their seats in a supine position during lift-off, so the incredible acceleration, which usually lasts almost 20 minutes, does not cause them any harm. They merely feel heavier, and may struggle to lift their arms.
If the cosmonauts sat or stood upright during this phase of the journey, they would black out due to their blood pooling in the lower half of their bodies.
At zero gravity Once the space shuttle has left the earth's atmosphere and is orbiting the earth, the cosmonauts begin to float. They are able to walk up walls and ceilings and pick up heavy objects with their fingertips.
Organs drifting in space In zero gravity, the organs of the body are weightless. The chest expands due to less pressure on it, the organs shift and float in the abdominal cavity.
Losing fluid Due to the lack of gravity, the body's fluids do not concentrate in the lower half of the body, but shift to the head and chest area. This is why cosmonauts' faces puff up while their legs shrink.
The fluid shift also causes the body to eliminate what it thinks is an overabundance of fluid by increasing its urine output. Crew members wear a type of nappy during lift-off to store the urine for removal to the waste system in the shuttle later on.
The blood Because the overall fluid level in the body decreases, blood volume also decreases. The body starts reducing its output of red and white blood cells to compensate.
Although this change will not affect the cosmonauts much in space, they will feel the affects on earth when they return.
The heart The shift of blood and fluid to the chest causes the heart to pump harder and the heart starts to enlarge to handle this extra blood.
Cosmonauts have to adhere to strict physical fitness training programmes before take-off, and this will be maintained in space. They will spend at least two hours a day exercising to prevent heart problems.
Space sickness
In space, there is no up or down. The body becomes confused and disorientated. It becomes difficult for the cosmonaut to tell where his arms and legs are. These changes cause a feeling similar to that of seasickness. It is common for a cosmonaut to suffer from nausea, headaches, to lose his appetite and struggle to maintain an efficient work rate aboard the shuttle.
Bones and skeleton Weakening of the skeleton is one of the most serious effects of space travel. The bones lose so much density – similar to that of accelerated osteoporosis – that the risk of fracture is five times greater.
This can seriously affect the success of a mission.
A cosmonaut can lose up to one percent of his bone mass a month. A trip between three and six months can cause bone loss that can take between three to six years to replace. Some researchers believe that the bone density can never fully be recovered.
Exercise is the best way to prevent bone loss, but this can be difficult in space. Cosmonauts have to be strapped to equipment, otherwise they might go bouncing off against walls of the shuttle.
Fertility One of the surprising effects of zero gravity, is that sperm swims faster than on earth.
Immune system A space traveller's immune system is affected by space. Fewer of the body's T-cells, which fight infection, are produced, and those that are, are less effective than here on earth.
It is hardly surprising that the saliva of cosmonauts contains more bacteria and viruses than it would on earth.
This reduction in T-cells, coupled with the fact that cosmonauts often do not get enough sleep in space, weakens the immune system, making it more likely that the crew members will get sick.
Cosmonauts have to be extremely conscious of hygiene and cleanliness. The water is heated and treated with iodine to kill bacteria. The air is filtered through ventilators and humidity is kept as low as possible. Food is irradiated to kill any germs which may be present.
Muscles Cosmonauts can lose 10 to 20 percent of their muscle mass during a space trip. Muscle fibres can even change their type to adapt to motion in space.
The greatest loss of muscle occurs in the spine and leg muscles. This already starts happening on the first day in space. Exercise is essential to prevent muscles from atrophying.
Internal clock Cosmonauts sleep roughly six hours per day. The spacecraft orbits the earth every 90 minutes, so the crew is exposed to 45 minutes of light followed by 45 minutes of darkness. This causes sleep disruptions, which is why almost half the medication used on board the space shuttle is used to help cosmonauts sleep. (Health24, updated November 2008)
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