Human reactions during flight to acceleration preceded by or followed by weightlessness.

D U R I N G the past quarter of a century, aeromedical investigators have succeeded with great ingenuity in simulating on the ground nearly all the conditions and stresses to which the pilot of an aircraft or of a space vehicle could be exposed. Gigantic human centrifuges and rocket sleds have been created to produce high accelerations at controlled rates of onset and decay. Elaborate low pressure chambers now simulate any desired condition of temperatu,re, humidity, and altitude, including even explosive decompression. This makes possible a thorough and more comfortable observation of the subject's physiologic reactions than has been 9ossi'ble in actual flight. However for studying weightlessness, one of the most challenging problems of