In 1998, the Space Shuttle flew to one of its highest altitudes ever, three hundred and fifty miles, hundreds of miles below merely the beginning of the Van Allen Radiation Belts. Inside of their shielding, superior to that which the Apollo astronauts possessed, the shuttle astronauts reported being able to "see" the radiation with their eyes closed penetrating their shielding as well as the retinas of their closed eyes. For a dental x-ray on Earth which lasts 1/100th of a second we wear a 1/4 inch lead vest. Imagine what it would be like to endure several hours of radiation that you can see with your eyes closed from hundreds of miles away with 1/8 of an inch of aluminium shielding!