but when john glenn was, you know, doing it early on, it's obviously an incredibly risky thing even now, but there was so much still to be learned, so much still kind of unknown. >> yeah. at that time, you know, during those early -- those very early days, it wasn't even clear how the human physiology -- you know, if our hearts would beat the right way and if we would actually be able to survive in a microgravity environment. in addition to the rocket, the risk of the rocket blowing up, which we had a lot of rockets blowing up at that time, there was also the risk of if our physiology would even function and there were just huge unknowns. >> you also look at geopolitical and nuclear proliferation, the cold war, the # race into space, all loomed large in america's consciousness in the 1960s and john glenn had a part in restoring the u.s. confidence, he orbited the earth three times and it's almost impossible to explain what a