John H. Mauldin has a bachelor's degree in engineering physics (Cornell University, master's in physics (Purdue University), and Ph.D. in science education (University of Texas). He has four books published in science and technology covering mathematical graphics in Perspective Design (1985; second edition now being prepared), physics in Particles in Nature (1986), solar energy in Sunspaces (1987), and optics in Light, Lasers, and Optics (1988). He has taught physics and engineering at several colleges and universities, done education research and development at MIT and University of Texas, and worked at NASA in electronic power engineering on an early phase of the Voyager missions.
Cosmic particles are dangerous, come from all sides, and require at least 2 meters of solid shielding all around living organisms.
Solar (or star) flares of protons, an occasional and severe hazard on the way out of and into planetary systems, can give doses of hundreds to thousands of REM over a few hours at the distance of Earth [b-Lorr]. Such does are fatal and millions of times greater than the permitted dose. Death is likely after 500 REMs in any short time.
The Apollo capsule was not even 1/10 meter thick, the Van Allen Belts have over 100 REM/hour, so the astronauts could not have survived going to the Moon.
http://moontruth.org/