Introductionspace medicine, study of the medical and biological effects of space travel on living organisms. The principal aim is to discover how well and for how long humans can withstand the extreme conditions encountered in space, as well as how well they can readapt to the earth's environment after a space voyage. The medically significant aspects of space travel include weightlessness, strong inertial forces experienced during liftoff and reentry, radiation exposure, absence of the earth's day-and-night cycle, and existence in a closed ecological environment. Less critical factors are the noise, vibration, and heat produced within the spacecraft. On longer space flights, the psychological effects of isolation and living in close quarters have been a concern, especially among multinational crews with inherent differences in language and culture.
A large body of useful medical data on the effects of a prolonged U.S. space flight was obtained during the Skylab program of the early 1970s and from several medical missions of the space shuttles Challenger and Columbia. The Soviet Union's Soyuz program began Russia's experience with long stays in space; the current record of nearly 439 days was set by Russian cosmonaut Valery Polyakov (Jan. 8, 1994–Mar. 22, 1995) on the space station Mir. With the change in the international political climate in the 1990s, the two countries began to cooperate in life-science research that combined the more sophisticated diagnostic and monitoring equipment of the NASA missions with the greater long-term-stay experience of the Russians. In May, 1995, the Spektr module, containing U.S. medical and research equipment, was added to the Mir. A few months later, American physician-astronaut Norman E. Thagard broke the former U.S. record of 84 continuous days in space when he spent 111 days on the Russian space station.
There have been many indirect benefits to medicine from space science. The need to maintain close watch over the physiological conditions of astronauts has spurred the development of improved means for electronically monitoring essential body functions. The development of programmable heart pacemakers, implantable drug administration systems, magnetic resonance imaging (MRI), and computerized axial tomography (CAT) all depended to some extent on knowledge gained from the space program. Studies of how astronauts would walk in the moon's weak gravitational field led to a deeper understanding of human locomotion.
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