So-called "cosmic rays" are distinct from high-energy photons (X-rays, gamma rays) because they are ionized atomic nuclei traveling at speeds close to the speed of light and therefore, summing mass energy and kinetic energy, are more than a trillion times more energetic than the photons. No shielding apart from a magnetic field will protect one from such particles. On the contrary: metal (e.g. lead) shielding causes the charged particles to decelerate. As everyone knows, a decelerating charged particle emits electromagnetic radiation -- in this case X-rays in the forward direction. That's bremsstrahlung. Metallic spaceships are like little X-ray ovens for astronauts inside. Cue Gary Owens' Farside cartoon of two polar bears munching on an igloo: crunchy on the outside, chewey on the inside! In other words: the shielding is the problem...

What about the most important organ - the brain? It would be like climbing Mount Everest with all the right clothes except wearing nothing on your head. If only their bodies are protected then their brains will not be and what is the effect of that going to be? I bet they have not tested that on any volunteers on earth - anybody fancy a blast of radiation on their brain? They are hoping everything will be alright based presumably on some dodgy experiments on rats and radiotherapy studies on cancer victims. Well we all know what dubious conclusions are extrapolated from 'scientific' studies.

Apollo flights were about a week and a half long; the walks, only hours. They dodged all but the thin fringe of the Van Allen Belt. Mars is more than 150 times farther away... so more precautions will be needed. No Apollo astronaut took even 1/500th of a lethal dose... Mars will be much tougher.

What'd they use for the Moon walks

Not required by Apollo ??

mars here we come!