There’s a material called FOGBANK…

There’s a material called FOGBANK that’s used by the US Department of Energy that’s so top secret and compartmentalized, that the government once actually “forgot” how to make it due to a lack of actual records and dwindling institutional knowledge. FOGBANK’s precise nature is classified; in the words of former Oak Ridge general manager Dennis Ruddy, “The material is classified. Its composition is classified. Its use in the weapon is classified, and the process itself is classified.”