Aerospace Medicine is the branch of preventive medicine that is concerned with the physiological and on the human body in flight. The study of effects within the earth's atmosphere is also called aviation medicine; beyond this atmosphere the study of effects is also called space medicine.

Aviation Medicine
Specialists in aviation medicine study the of human beings to the of air travel. They are concerned with the proper screening of candidates for flight training, the of efficiency among aircrews, and with clinically into the effects of flight on the body. They also actively with aeronautical engineers in the development of safe aircraft.

History
Aviation medicine is rooted in the early 18th-century physiological studies of balloonists, some of whom were also physicians. In 1784, a year after the first balloon flight by the French physicist Jean Pilâtre de Rozier, a Boston physician, John Jeffries, made the first study of upper-air composition from a balloon. The first studies of health effects in air flight were made by the French physician Paul Bert, who his on the effects of air pressure and composition on humans in 1878 under the title La pression barometrique. In 1894 the Viennese physiologist Herman Von Schrötter an oxygen mask with which the meteorologist Artur Berson set an altitude record of 9,150 m. With the advent of aircraft, the first standards for pilots were in 1912. work in this was directed by the physician Theodore Lyster, an American pioneer in aviation medicine. advances included the first pressurised suit, and worn by the American aviator Wiley Post in 1934, and the first antigravity suit, by W. R. Franks in Great Britain in 1942. In an effort to help better systems for jet aircraft, the United States flight surgeon John Stapp a of tests on a rocket-powered sledge, culminating on December 10, 1954, when Colonel Stapp deceleration from a velocity of 286 m/sec in 1.4 sec.

Physiological Considerations
Aviation medicine is concerned with the effects on human beings of high speed and high altitude, and the study of such as acceleration and deceleration, atmospheric pressure, and decompression. In -aviation medicine, an additional concern is passenger airsickness.

High Speed
In itself, high speed does not produce harmful symptoms. What can be dangerous are high acceleration or deceleration forces; these are expressed as multiples of the earth's gravity at sea level, or gs. In pulling out of a dive, for example, a pilot may be subjected to an inertial force as high as 9 g. If a force of 4 to 6 g is for more than a few seconds, the resulting symptoms from impairment to total blackout. Protection is provided by a specially outfit, called an anti-g suit, which supplies pressure to the abdomen and legs, thus counteracting the tendency for blood to in those . Proper support of the head is essential during extreme deceleration in order to avoid swelling of the sinuses and severe headaches. While facing backwards in a seated position, properly supported human test subjects have been able to tolerate a deceleration force of 50 g without severe .