Space Medicine


Space medicine is the brand of medicine involved in protecting human beings from the environment of space, at the same time, studying their reactions to that environment. The foundations of space medicine can be traced back to aviation medicine, and the term aerospace medicine has evolved to encompass activity in both areas. Aerospace medicine has been a certified sub specialty of the American Board of Preventive Medicine since 1953. In addition to physicians, however, engineers, veterinarians, dentists, nurses, physiologists, psychologists, bacteriologists, toxicologists, pharmacologists, and biochemists, also work in the field of space medicine. Specialist in space medicine are involved in all aspects of space flight, from spacecraft design and crew selection to flight operations and post flight review.

The early history of spaceflight was characterized by deep concern on the part of many scientists that human would not be able to withstand the rigors of spaceflight especially during lunch and reentry, and might not be able to function usefully in space. As a result of this concern, the United States flew a number of monkeys aboard captured German V-2 rockets between 1948 and 1952. These early flights provided some launch and reentry data on comparable life forms and demonstrated the need for effective and reliable life-support system. Between 1949 and 1956 the Soviet Union flew 15 similar flights using dogs, some flights reaching an altitude of 213 km (132 mi). A dog named Laika was then launched aboard sputnik 2 on Nov. 3, 1957, and orbited the Earth for seven days until she was finally euthanatized. Between 1958 and 1961 the United States flew monkeys in several suborbital and orbital missions. These flights showed that pulse and respiration rates, blood pressure, and performance of specific tasks for which the monkeys had been trained were basically unaffected by spaceflight.
On Apr.  12, 1961, the Soviet cosmonaut Yuri Gagarin demonstrated for the first time that human beings could safely orbit the earth. His flight confirmed a U.S. decision to use human rather than animals on succeeding spaceflights. The U.S. program proceeded cautiously, however, by gradually increasing the exposure time of humans in space and by carefully observing and reviewing the effects of each flight. The six U.S. astronauts who flew on project Mercury between May 1961 and May 1963 returned in good health, and as result, many of earlier medical concern about spaceflight were dispelled. 

The physiological functions of human crews in space have been measured by a variety of means over the years, ranging from simple sensors place on the body to monitor heart rate and respiration, to the use of techniques such as echocardiography and electroencephalography. The many thousands of hours of information thus gained on human activity in a weightless environment have proved that people can perform assigned tasks well and need suffer no permanent postflight physiological changes, even after missions lasting several months. To maintain an acceptable state of health, however, space crew do require an appropriate atmosphere, adequate food and rest periods, and sufficient time to acclimatize to space and also to the return to earth. The atmosphere, pressure, and temperature of spacecraft interiors are always strictly controlled in order to avoid serious or even fatal health hazards such as explosive decompression of the craft, the onset of decompression sickness, carbon dioxide narcosis, hypoxia, and other such problems. All material used in or brought aboard spacecraft are tasted beforehand for the potential release of toxic substances when in the spacecraft environment. As the late 1980s, seven human fatalities could be attributed to errors or malfunctions in life-support systems. 
An important concern is the radiation encountered in space since excessive exposure to such radiation can result in greater likelihood of developing certain kinds of cancer. A crew's exposure to radiation on many factors : 
- The type and length of the mission.
- The amount of shielding on the spacecraft.
- The relative altitude of the craft's orbit.
- The activity on the sun during the period of flight.
The average skin radiation close received on the Apollo missions ranged from 0.16 to 1.14 rads. which is less than the dose received with some diagnostic X-ray procedures. Another environmental concern is that of the natural circadian (24 hour) cycle of human body rhythms. These rhythms are maintained in the U.S.  program by keeping their crew on Houston time, and in the Soviet program by keeping their crew on Moscow time. The Soviet Union has attempted to alter the circadian rhythms of their cosmonauts by having them awaken 20 minutes earlier on each day during a long-term flight, but such efforts have not proved successful and are no longer tried.