All we need to do is compare the extent to which Man has explored space (and oceans and volcanoes etc.) vs. the extent that robots have been sent on our behalf,

All we need to do is compare the extent to which Man has explored space (and oceans and volcanoes etc.) vs. the extent that robots have been sent on our behalf, with quite resounding success, and the barriers are self-evident. Not to mention the liability and really bad P.R. when human lives are lost in that pursuit.