Question to NASA:
I am curious to know what the effects of solar radiation have on space craft after they leave the protection of the Van Allen belt. How much protection do they need and how long could an astronaut survive in and out of his craft?
NASA's response (extract):
Solar radiation and cosmic radiation are both things to worry about in space.
When the sun flares, it produces x-rays, gamma-rays, and energetic particles. The energetic particles are the worst, but they are delayed compared to the x-rays and gamma-rays, so you have some warning that they are coming. This gives you time to get into a 'storm shelter', a well-shielded area that you can live in for a few days until the particles die down.
A good place for a storm shelter would be in the center of the ship, surrounded by the water tanks. If you don't have a storm shelter (e.g. if you are out moonwalking in just your suit) a bad solar flare can kill you by radiation sickness. Since space is inherently dangerous at the present state of the art, cancer due to cosmic rays is a relatively small additional risk.
Question to NASA:
What do we do when we have to fly through the radiation belts – like when we went to the Moon or send probes to other planets?
NASA's answer (extract):
In the 1960s, NASA asked Oak Ridge National Laboratory to predict how astronauts and other materials would be affected by exposure to both the Earth's Van Allen radiation belts and the Sun's radiation. Oak Ridge biologists sent bacteria and blood samples into space and exposed small animals to radiation.
They concluded that proper shielding would be key to successful flight not only for living organisms, but for electronic instrumentation as well. To develop shielding for the Apollo crews, Oak Ridge researchers recycled the Lab's Tower Shielding Facility, which had hoisted shielding experiments aloft for the 1950s nuclear-plane project.
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