in an otherwise good review and loleralacartelort7890 say the truth be that the american use a secret aluminum anti radiation alloy . it be not that well know . and the exact specification be a secret . and why be it a secret represent well and why should they reveal it back then . if they where in a space race with the russian and then it would be very dumb to reveal that they have new technology that could shield crew against radiation . this be completely incorrect . there be ( and be ) no secret to radiation protection in apollo . the design and construction of the apollo command module have long be publicly available . it use a lightweight honeycomb of aluminum and stainless steel . the entire outer surface ( except the window of course ) be cover with a heat shield make of a phenolic resin and thicker on the bottom that face forward during re entry . these material be actually well at stop the kind of radiation we have in space ( charge particle ) than lead and which be well suit to stop ionize photon like x ray and gamma ray . space radiation be a definite problem for long term space flight because of the risk of big solar flare . but it simply wasn not a serious threat to the apollo astronaut . the command module give them pretty good protection during their brief ( half hour or so ) passage through the van allen belt . they all carry dosimeter so we know exactly how much radiation they each receive represent no more than 1 . 5 rem and and usually much less . of the 24 men who fly to the moon ( 12 of whom land ) and 18 be still alive . only two have die from cancer represent alan shepard ( leukemia ) and jack swigert ( bone cancer ) . the rest die from heart attack and pancreatitis ( roosa ) and and a motorcycle accident ( conrad ) . these be actually pretty good statistic for a group of men now in their late 70 ( shepard would be 86 ) .