re: For once we all seem to agree...
" What I have looked at is shielding and people frequently miss that it is simply the mass of Earth's atmosphere that does most of the shielding and that is not equivalent to all that much solid mass. "
On Earth at sea level it is equal to about 30 ft of water or ice [or liquid/frozen air]. At Denver, Co the mile high city, it's equal to about 25 ft. And if you flying on airline it's equal to less than 15'.