No data to back it up with, but i think during the space race things were new enough that they often didn't know the chances. But the time of the shuttle, NASA

No data to back it up with, but i think during the space race things were new enough that they often didn't know the chances. But the time of the shuttle, NASA had moved from a prestigious project to pork barrel politics. End result was that managers and politicians were endlessly overruling the engineers.