HSF is easily 100x higher tolerances.
Some stuff, you have to live with, some stuff (like the panels and the o-rings) is too far fetched for even NASA to think up beforehand. And if you've ever been to The Cape, you know they will never forgive themselves. They try their very best to think it all up. They really really do. NASA may be full of brains, but damned if they aren't all real heroes there on the ground. Those folk have heart more than anything else.
Per Aspera Ad Astra does not fucking cut it.
Were a known weakness.
Can you break down this calculation? Where did 75% come from? I think your parent poster's point is this: no one really knows where these numbers are coming from.
That was actually explained in the (excellent) comment. Snippet below, but please re read the comment or example how resistors are actually tested in batches to give real failure rates.
>Each resistor on a PCB, each explosive bolt, each screw and panel. All of it has a lifetime curve, typically a Bathtub plot, to an extreme degree