I don't remember how indepth he went into the radiation theory, I'd have to ask him again. I do remember his main argument was the mathmatics involved in not sending man into space, but sending them to the moon and having them return to earth safely. He claimed that with the technology available at the time, it was mathematically impossible to pull off.

If I get the chance, I'll ask him to divulge deeper next time we speak (and ask him what he meant about the radiation deal), and make another post so we can pick it apart