The medical speciality concentrating on the alleviation of the physiological effects encountered by astronauts in the microgravity atmosphere of space. Branches include space sickness, radiation, and changes in bone and muscle and the cardiovascular immunology systems. Psychological problems, such as coping with isolation in space, are also addressed.

NASA has a medical science division that supports missions and conducts research, a medical operations branch responsible for operational space medicine (OSM) for crews, and a flight medicine clinic (FMC) for astronauts and former astronauts.