you are so right, MH. probably the biggest arguement against even attempting to go past the van allen radiation belt, let alone doing it, is exposure to lethal radiation. lead and concrete weigh a lot. there was a window of low radiation from the sun during that late 60s/early 70s time period, but i am not thoroughly convinced that was enough.
maybe we got lucky for a couple of years, but the missions stopped with two more already made and paid for sitting on the pad. no matter how you slice it, we are lied to about it and no one is likely to come clean who has full credibility. if they are able to sheild effectively, we are still going and not telling anyone. the truth is probaly somewhere inbetween.
and for those who dont know, all of our activity in space since that time has been restricted to very low orbit and well within the protection mother earth affords us with her geomagnetic sheild. the moon is an entirely different animal. and mars!?? somebodies nose will probably reach there before any human lands there still breathing and with a pulse.