The first field is 272 miles out from Earth. The amount of radiation in the belts actually varies from year to year but every 11 years its at its worst when the sunspot cycle is at its highest. And guess what? 1969 to 1970 was one of the worst times to go as this was the time where the radiation was at its peak.
I have had numerous internet chats with skeptics who say that the radiation would not play a part in the missions because Man would have not been in the radiation belt for too long. My answer to that is, when Dentists or Doctors take X ray pictures they either leave the room or stand behind a sheet of thick lead to shelter from the radiation.
Why did NASA only use a small sheet of aluminium to protect the astronauts when they knew that the radiation levels in Space and on the Moon surface would be many hundreds of times more deadly? And why would they risk their astronauts to such conditions?
In 1959 Bill Kaysing was privy to a study made by the Russians. The Russians discovered that the radiation on the moon would require astronauts to be clothed in four feet of lead to avoid being killed. Why didn't NASA heed their warnings?
Did you know that the US Government tried to blast a hole in the belt 248 miles above Earth in 1962? During Operation Starfish Prime a Megaton Nuclear Bomb was used to try and force an unnatural corridor through the Van Allen Belt. Unfortunately, the radiation levels actually got worse, not better.
What they created was a third belt that was 100 times more intense than the natural belts, and as estimated by Mary Bennett in 'Dark Moon - Apollo and the Whistle-Blowers, by 2002 this artificial zone will still have 25 times more radiation than the other two belts.
There is no agreement to how wide these radiation belts actually are. Dr James Van Allen, the discoverer of the belts estimated that they were at least 64,000 miles deep, but NASA say they are only 24,000 miles deep. Each Apollo craft spent approximately 4 hours within the belts.
So to what lengths did NASA take to shield the astronauts against the radiation? Its accepted that a minimum of 10 cm width of aluminium would be needed at the very least to keep out radiation.
However the walls of the Apollo craft and capsule were made as thin and as light as possible and as a result the craft initially could not carry enough air inside to withstand the equivalent to sea level air pressure. NASA had to reduce air pressure inside the cabin to cope.