NASA 1960s rocket motor case failures

High-strength thin-wall steel cases shattered like glass; the failure that brought fracture mechanics into NASA practice. Critical flaw sizes on order of 1 mm.

They knew the cutting tools broke, but they just replaced them with another one. One of the reasons cutting tools improved over the last thirty or forty years — actually from the 1950s to the 1980s — was improvement in fracture mechanics. NASA used fracture mechanics on some of the 1960s missiles. They had some major failures: rocket motor cases, very high-strength steel, very thin wall, and they loaded them up with things and they just broke to smithereens, like shattered glass. There were big studies that NASA did.