...FOGBANK is an aerogel material which acts as an interstage material in a nuclear warhead, i.e. a material designed to become a superheated plasma following the detonation of the weapon's fission stage, the plasma then triggering the fusion-stage detonation. It was originally manufactured in Oak Ridge from 1975 until 1989. The facility was decommissioned in 1993. In 1996, the US government decided that large numbers of its nuclear weapons would require replacement, refurbishing, or decommissioning. It was soon realized that the FOGBANK material was a potential source of problems for the program, as few records of its manufacturing process had been retained when it was originally manufactured in the 1980s, and nearly all staff members who had expertise in its production had either retired or left the agency. The NNSA briefly investigated sourcing a substitute for FOGBANK, but eventually decided that since FOGBANK had been produced previously, they would be able to repeat it.
A brand new production facility was required ($23m). Delays arose during its construction, and in addition, engineers repeatedly encountered failure in their efforts to produce FOGBANK. As one deadline after the other expired, and the schedule was pushed back again and again. In March 2007, engineers finally devised a manufacturing process for FOGBANK. Unfortunately, the material turned out to have problems when tested, and in September 2007 the FOGBANK project was upgraded to "Code Blue" status by the NNSA, making it a major priority. In 2008, following the expenditure of a further $69m, the NNSA finally managed to manufacture FOGBANK.
The experience of reverse engineering FOGBANK produced some improvements in scientific knowledge of the process. The new production scientists noticed that certain problems in production resembled those noted by the original team. These problems were traced to a particular impurity in the final product that was required to meet quality standards. A root cause investigation showed that input materials were subject to cleaning processes that had not existed during the original production run. This cleaning removed a substance that generated the required impurity. With the implicit role of this substance finally understood, the production scientists can control output quality better than during the original run.
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