MadSci Network: Physics |
Because of the utmost concern for saving weight, spacecraft are not shielded to protect the astronauts from the ionizing radiation in space. There are three sources of ionizing radiation out there: galactic cosmic rays, energetic particles from the sun, and the radiation trapped in the Van Allen belts. The latter two are not constant, but can vary through wide ranges over relatively short times, such as hours or even minutes. So, to protect the astronauts, the radiation levels in space are constantly monitored, and spacewalks (when the astronauts are liable to pick up the most radiation exposure) are scheduled to keep the exposures as low as possible. In any case, the radiation exposure limits for the astronauts are up to a factor of ten higher than they are for us ordinary mortals here on Earth. That is just a recognition of the fact that they will get a lot more exposure in the course of their normal duties than we do. The spacecraft are shielded against the effects of heat or "infrared" radiation so that the interior does not bake on the side nearest the sun while it is subzero on the side facing away. For information on that, check this article on the NASA website: http://science.nasa.gov/headlines/y2001//ast21mar_1.htm?lis t14388.
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