Comment by elzbardico
10 hours ago
I'd bet lots of telemetry, comprehensive design and change documentation, along with engineers tacit knowledge.
Something like:
telemetry shows dramatic drop of temperature on this, that given the location of the sensor could only be caused by a specific LOX line leak, and vibration sensors show data compatible with friction as the ignition event and not a short circuit because the relevant telemetry doesn't show any electrical abnormality, so, by exclusion, given no other anomalies, give that computer simulations show it is a feasible scenario, followed by lab work with a physical model, this must be the cause of the accident.
Yeah, but at the end of the day you can't be sure right? That doubt would eat away at me
The doubt is supposed to stay with you! You need to make sure there aren't other causes or contributing factors hiding behind 'the obvious'. There have been notorious cases in spaceflight where the issue was 'identified' and 'fixed', only for the same thing issue to happen in the next mission.