The human factors involved in manned space flight, according to Strughold, the province of space medicine. Thus, space medicine includes the study of conditions on other celestial bodies and their effect on explorers in terms of human physiology. It overlaps astrobiology, the study of the possibilities of indigenous life on other celestial bodies.
Space medicine belongs in the category of industrial medicine, specifically environmental medicine.
In the area between space medicine and traditional aviation medicine, there are certain overlappings, such as the tolerability of high g-forces and rapid decompression. In the early 1950's Strughold and his coworkers suggested that the atmosphere ceases and space begins at different altitudes for different physiological functions. This altitude was designated the region of space equivalence, or the functional border of space. While it is not the purpose of the present study to discuss the physiological problems facing maid in space flight which have been ably discussed elsewhere they should be kept in mind by the reader, because in 1958 and in the year following the answers had not yet been found. Only actual flight into space could answer these questions.