Originally Posted by
Dave Therhino
I agree the number is also a good approximation of the per cycle risk because launch and re-entry were by far the most risky phases of flight. There were something like 150 missions (it's been a while since I added them up for a study), and two accidents, one on launch and one on re-entry. I specifically gave a ballpark per hour rate for launch and re-entry, for which I guessed 1 hour of exposure per cycle to those phases of flight. The risk in orbit is much lower, but still quite high theoretically compared to a commercial flight, though the record was good for those 150 or so flights.
I'm not sure I'm grasping everything you were trying to say with the rest of your comment, but my point was the AOA sensor behavior in the max fleet was not a huge outlier failure-rate wise, and it was the system architecture that caused the problem. I think we are probably saying the same thing.
Both accidents were on launch. The final destruction of the second shuttle was delayed until re-entry, but Shuttle Columbia was fatally damaged during its launch for very similar reasons to the fatal damage of Shuttle Challenger; an acceptance of repeated damage due to previously noted defects in the design and a willingness to continue with them unresolved.
I think the launch event, from engine ignition to orbit is about 8-1/2 minutes, with the boosters running slightly more than 2 minutes.
https://www.nasa.gov/mission_pages/s...-leinbach.html