Human Adaptability to Space

Human biological nature has evolved over millions of years on the surface of the Earth. Gravity has shaped our bones and muscles. An oxygen-rich atmosphere has nourished our bodies and shielded us from harmful radiation. Our psychological cycles of sleep, heartbeat, and aging have reflected the rhythm of earthly time.1 In the last hundred years scientific achievements have allowed us to leave this surface environment and travel into space. Airplanes carrying people to the upper reaches of the atmosphere are a common means of transportation. Astronauts in the Apollo spacecraft have traveled to the moon and back. Today, the National Aeronautics and Space Administration (NASA) is building the International Space Station with Russia and other European countries. This will allow humans in space to orbit the Earth for months at a time. In the planning stage, there is a more aggressive and high risk three-year manned trip to the planet Mars.2 This trip will test human adaptability to space.

Scientific concern is high over human ability to go to such extremes. In the three-day 1972 Apollo mission, astronaut Eugene Cernan, fatigued and filthy with rock dust on the moon, barely made it back to the spacecraft for a return to Earth. A trip to Mars will multiply the hazards of space travel. Scientist Michael Long suggests a troubling scenario.3 He says, "Imagine a radiation-sick, sleep-deprived astronaut stepping onto Mars. Challenged by a different gravity and with his bones, muscles, and immune system weakened by the long trip; he falls and breaks his leg. How would NASA respond?" Today NASA is concentrating on known environmental problems in space and experimenting to find methods to solve them. These issues range from physical problems of weightlessness and radiation, to psychological problems of isolation, sleep deprivation, disorientation, depression, and time changes.4 These problems are serious and affect many parts of the human body. For these reasons, only the major ones will be examined.

Weightlessness

Weightlessness is a constant problem in space but hard to simulate on Earth. In a cosmonaut training center in Moscow, there is a special airplane that flies astronauts in maneuvers simulating weightlessness. This helps astronauts prepare for adaptation to the zero-gravity conditions of space. During zero-gravity periods, people bounce off the ceiling, do airborne gymnastics, and are thrilled by the sensation of weightlessness. Others are not amused, but sick. This free motion causes many to be nauseous. Motion sickness affects two-thirds of all astronauts.