MadSci Network: Physics
Query:

Re: What shielding is needed to protect an astronaut from the Van Allen belts?

Date: Fri Mar 30 09:44:54 2001
Posted By: David North, Staff, Medical Physics, Rhode Island Hospital
Area of science: Physics
ID: 985233206.Ph
Message:

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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