THE EFFECTS OF WEIGHTLESSNESS
Muscular deconditioning and loss of bone marrow:
Due to lack of use in microgravity, the skeletal muscles of the astronauts will lose mass, strngth, and endurance. After a long duration flight, the muscles will have atrophied so much that an inability to support the body weight of the astronaut in presence of gravity will result. In addition to this muscular deconditioning, bone marrow loss ca be as high as a 1.5% loss per month in the legs. Although these effects cannot be completely prevented, their severity can be lessened through preventative measures - a regimented exercise program on a space treadmill to fight muscular atrophy and nutritional supplements to lessen bone marrow loss.
Fluid shift:
Due to the absence of gravity, blood from the lower body shifts to the upper body. The heart adapts to this by swelling to accomodate the extra flow of blood. The body adjusts to this by reducing the amount of fluid in the body - astronauts take in less fluid while urine flow is increased. The heart returns to its normal size once the amount of fluid is reduced and balanced. There are no particularly dangerous effects due to this fluid shift, as the cardiovascular system adapts quickly and effectively. For example, the concentration of red blood cells remains the same, despite the obvious reduction of fluid. This implies that the number of red blood cells in the body is decreasing, an effect known as space anemia. Because the astronauts will have a decreased thirst, it is important to monitor the water intake of the crew, as water will help them stay healthy despite the stress of spaceflight and Mars.
Orientation:
In the human body, otolith organs, the inner ear, joints, and touch sensors in the skin detect gravity and keep humans oriented in their surrounds. when weightless in space, however, there is no gravity to stimulate these sensors, resulting in directional disorientation in astronauts. Although the eyes send visual directional signals to the astronaut, the astronaut cannot feel the reality of "up" and "down" and therefore have difficulties maneuvering in their weightless environment. To counteract this, each crew member must be trained for weightlesssness, and "landmarsk", such as handholds and monitors, should all be placed in the same orientation, in order to provide a non-confusing visual reference.
SPACE RADIATION:
Ionizing Radiation
Of the two types of space radiation, only ionizing space radiation poses a serious threat to astronauts travelling through space. Its primary immediate effect is radiation sickness (headache, dizziness, abnormal taste and smell, nausea, vomiting, diarrhea, decreased blood pressure, decreased white blood cells, irritability, insomnia). Its later effects include: lens opafication, cancer induction, impaired fertility, heritable effects, and developmental abnormalities. Trapped Radiation Belts, Galactic Cosmis Rays (GCR), and Solar Particle Events (SPE) are all sources of ionizing radiation in space.
The level of nonionizing radiation in space may vary over a long term mission from low levels to fatally high levels. In order to shield against these various levels of radiation, including the potentially fatal ones, very heavy metal shielding would be required. Instead, the technology exists to generate an electric or magnetic field around the craft, by supercooling superconductors, which creates zero electrical resistance, so a current can be circulated indefinitely.
Nonionizing Radiation
Nonionzing radiation poses much less of a threat for astronauts and equipment. Hypomagnetic conditions and UV radiation from the sun are sources of nonionizing radiation. Generally the effects of nonionizing radiation in space are relatively harmless. Possible more severe effects include loos of memory, decreased perceptual threshholds, and cataract development, although test results and reports on these effects are inconclusive and conflicting.
Extravehicular and Mars suits will be designed to protect the astronaut against dangerous exposure. On the spacecraft and in the equipment.