> It appears that there are enormous differences of opinion as to the probability of a failure with loss of vehicle and of human life. The estimates range from roughly 1 in 100 to 1 in 100,000. The higher figures come from the working engineers, and the very low figures from management.<p>Am in business with someone many years older than me. It has always struck me how little tolerance he has for risks to my safety. The natural reaction is to have more lenience for situations that wont directly impact your personal safety. Wheras this guy will do potentially dangerous tasks that would otherwise be my responsibility. His kids are grown up, mine are young.<p>It is the kind of attitude that would be near impossible to enshrine in a larger organisation (like NASA) but refreshing to see all the same.
Feynman argues for unit tests:<p>> For example, cracks have been found in the turbine blades of the high pressure oxygen turbopump. Are they caused by flaws in the material, the effect of the oxygen atmosphere on the properties of the material, the thermal stresses of startup or shutdown, the vibration and stresses of steady running, or mainly at some resonance at certain speeds, etc.? How long can we run from crack initiation to crack failure, and how does this depend on power level? Using the completed engine as a test bed to resolve such questions is extremely expensive. One does not wish to lose an entire engine in order to find out where and how failure occurs. Yet, an accurate knowledge of this information is essential to acquire a confidence in the engine reliability in use. Without detailed understanding, confidence can not be attained.