I am reminded of the example Richard Feynman used to show how NASA leadership had pretty much totally misunderstood the concept of safety Factor, leading to the Challenger shuttle tragedy. they noted that the O-rings were typically losing a third of their material during launch, so leadership claimed they had a safety factor of 3. Richard Feynman said that if you had a bridge that was intended to hold 3000 lb, but when you drove a 1000-pound vehicle across it it started to show cracks, your safety Factor wasn't 3, it was Zero.
Edit: someone suggested the context helped, soooo... Here is Richard Feynman's comment on the subject.
For example. in determining if flight 51-L was safe to fly in the face of ring erosion in flight 51-C, it was noted that the erosion depth was only one-third of the radius. It had been noted in an experiment cutting the ring that cutting it as deep as one radius was necessary before the ring failed. Instead of being very concerned that variations of poorly understood conditions might reasonably create a deeper erosion this time, it was asserted, there was "a safety factor of three." This is a strange use of the engineer's term ,"safety factor." If a bridge is built to withstand a certain load without the beams permanently deforming, cracking, or breaking, it may be designed for the materials used to actually stand up under three times the load. This "safety factor" is to allow for uncertain excesses of load, or unknown extra loads, or weaknesses in the material that might have unexpected flaws, etc. If now the expected load comes on to the new bridge and a crack appears in a beam, this is a failure of the design. There was no safety factor at all; even though the bridge did not actually collapse because the crack went only one-third of the way through the beam. The O-rings of the Solid Rocket Boosters were not designed to erode. Erosion was a clue that something was wrong. Erosion was not something from which safety can be inferred.
Grahfzer0 on October 5th, 2018 at 20:30 UTC »
I am reminded of the example Richard Feynman used to show how NASA leadership had pretty much totally misunderstood the concept of safety Factor, leading to the Challenger shuttle tragedy. they noted that the O-rings were typically losing a third of their material during launch, so leadership claimed they had a safety factor of 3. Richard Feynman said that if you had a bridge that was intended to hold 3000 lb, but when you drove a 1000-pound vehicle across it it started to show cracks, your safety Factor wasn't 3, it was Zero.
Edit: someone suggested the context helped, soooo... Here is Richard Feynman's comment on the subject.
For example. in determining if flight 51-L was safe to fly in the face of ring erosion in flight 51-C, it was noted that the erosion depth was only one-third of the radius. It had been noted in an experiment cutting the ring that cutting it as deep as one radius was necessary before the ring failed. Instead of being very concerned that variations of poorly understood conditions might reasonably create a deeper erosion this time, it was asserted, there was "a safety factor of three." This is a strange use of the engineer's term ,"safety factor." If a bridge is built to withstand a certain load without the beams permanently deforming, cracking, or breaking, it may be designed for the materials used to actually stand up under three times the load. This "safety factor" is to allow for uncertain excesses of load, or unknown extra loads, or weaknesses in the material that might have unexpected flaws, etc. If now the expected load comes on to the new bridge and a crack appears in a beam, this is a failure of the design. There was no safety factor at all; even though the bridge did not actually collapse because the crack went only one-third of the way through the beam. The O-rings of the Solid Rocket Boosters were not designed to erode. Erosion was a clue that something was wrong. Erosion was not something from which safety can be inferred.
SanchitoBOC on October 5th, 2018 at 20:44 UTC »
"Holds 1,000 Pounds. No more. No less."
PressTilty on October 5th, 2018 at 21:38 UTC »
How does every home depot have the same handwriting on everything?