I’m curious if they would use the same logic for russian roulette. If you spin the barrel with one bullet, pull the trigger against your head and survive does that mean that the danger wasn’t that serious?
NASA wasn’t saying that they know for certain that the Starliner will have a catastrophe on the way back. What they said is that they cannot be certain that the probability of it having a catastrophe is lower than some decision threshold.
Using the russian roulette as an analogy NASA has a revolver with a barel for a million bullets, and they decided they are fine to pull the trigger against the astronauts heads if there are less than 5 bullets in it. But due to nobody really understanding the mechanism of previous anomalies they don’t know how many bullets there are in the barrel. There might be six or more so they are not willing to pull the trigger. (The number of bullets, and the number of chambers is merelly illustrative. I don’t know what is the real number NASA uses.)
Thank you! It seems wikipedia confirms what you are saying. Sadly the article it references is no longer available, so i can’t dig into it. But it sounds 1/270 is for the requirement for overall mission while the ascent and descent phases have 1/500 apportioned to them each.
Was trying to put this 1/500 number into perspective for myself. It sounds like it is rougly similar to the mortality of having appendicites. [1]
It still had problems during the return flight, i.e. additional unexpected component malfunctions, but not serious enough to prevent a successful return.
Therefore the decision to not use it until the causes for all such malfunctions are understood was completely justified.
Problem: "one of the Starliner’s reaction control system (RCS) thrusters did not function".
Why it was not serious: "there are plenty of backup RCS thrusters".
Even if the redundancy ensured a successful return, the causes must be understood, because otherwise at a future return more than one thruster could malfunction and the redundancy may be insufficient.
How do you know how serious the issue was?