My understanding of the Space Shuttle program is that there were a lot of times they knew they probably shouldn't fly, or try to land, and they lucked out and didn't lose the orbiter. It is shocking they only lost two ships out of the 135 Space Shuttle missions.

The safety posture of that whole program, for a US human space program, seemed bad. That they chose to use solid rocket motors shows that they were willing to compromise on human safety from the get-go. There are reasons there hasn't ever been even one other human-rated craft to use solid rocket motors.