Radiation Hazards b. The intensity of radiation in space is significant. Exposure to radiation has a variety of short term and long term effects on the human body based on the type radiation, the intensity and the length of exposure. It is not presently known what all of those effects are. Radiation generating events on the Sun are unpredictable and occur frequently.
Radiation emanating from deep space is also dangerous but it is more constant.
Exposure to high energy galactic cosmic rays is not a serious problem in low Earth orbit. Beyond low Earth orbit, however, shielding against radiation can be bulky and massive, thus making the spacecraft heavier to launch. Additional research on the effects of radiation and protective materials for the crewmembers is needed. The microgravity environment in space is responsible for a number of physical effects and changes on the human body. Some of the effects have immediate impact and others have a long term effect.