Early on in the space race, NASA spent much time and effort seeking a metal robust enough to withstand the heat of reentry and protect the astronauts. The endeavor failed. At some point, a clever person changed the problem. The real problem was to protect the astronauts, and perhaps this could be done without a material that could withstand reentry. The solution, the ablative heat shield, had characteristics just opposite to those originally sought. Rather than withstanding the heat, it slowly burnt away and carried the heat away from the vehicle.
Source: The Mind’s Best Work (Cambridge, Massachusetts: Harvard University Press, 1981), 217
Contributed by: Zaady