Humans lose concrete recipe for 1300 years!
Humans lose critical heat-shielding recipe for re-entry to Earth!
NASA looks for heat shields in Smithsonian museum
"...according to the Orion program executive the Orion project originally intended to use the heat shield from the Apollo program
as a fallback technology for the Orion thermal protection system, but was unable to recreate the Apollo material."
NASA has trouble with Newton's Law -- as contrasted with better analysis at
Chernobyl nuclear experiment (no accident?)