What is happening to Mark Shuttleworth's body now that he is orbiting earth? Firstly, his heart will have enlarged, his face will look puffy and he will feel nauseous.
As a result of fluid re-distribution in his body, Shuttleworth's face will swell, as his legs appear skinnier. His nose will feel blocked, as though he is getting a cold and he will also lose at least one litre of urine.
The lack of gravity will trick Mark'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.
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 in to their seats in a supine position during lift-off, so the incredible acceleration, which lasted almost 20 minutes, did 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 on their fingertips.
Organs drifting in space
In zero gravity, the organs of the body are weightless, as and the chest expands due to less pressure on it, the organs shift and float in the abdominal cavity.
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. Shuttleworth and his fellow crewmembers wear a type of nappy during lift-off to store the urine for removal to the waste system in the shuttle later on.
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 shift of blood and fluid to the chest makes causes the heart to pump harder and the heart starts to enlarge to handle this extra blood and
Mark's resting pulse rate before his departure was roughly 45 beats per minute – indicating that he is quite fit. His pulse rate will slowly drop as his heart enlarges.
Mark and his fellow crewmembers have adhered to strict physical fitness training programmes, and this will be maintained in space. They will spend at least two hours a day exercising to prevent losing heart condition.
In space, there is no up or down. The body becomes confused and cannot tell its orientation or even where the arms and legs are. These changes cause a feeling similar to that of seasickness. Mark will probably suffer from nausea, headaches, 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.
Although Mark will only stay in space for a few days, he will already have started to lose bone. Exercise 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.
One of the surprising effects of zero gravity, is that Mark's sperm will swim faster than on easrth.
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 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 crewmembers 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.
The cramped confinement of the 19 square metre large space shuttle and the tension and anxiety of each crewmember can also cause problems.
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 will already have started in Mark's body.
Exercise is essential to prevent muscles from atrophying.
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, April 2002)