The Magazine

The Fog of War

Forgetting what we once knew.

May 18, 2009, Vol. 14, No. 33 • By JONATHAN V. LAST
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On February 17, the Navy took delivery of its first refurbished W76 warhead. The W76 is a nuclear payload that sits atop the Trident II missiles carried by America's Ohio-class submarines. As such, it represents an important part of the country's nuclear arsenal. The refurbishment of the aging W76s has taken much longer than was originally anticipated because once the engineers cracked open the old warheads they encountered a substance codenamed "Fogbank." And they had no idea how to replicate it.

The mystery of Fogbank begins in the late 1970s, in a building called Facility 9404-11 on the grounds of the Y-12 complex in Oak Ridge, Tennessee. The Oak Ridge site sprang from the original Manhattan Project and became one of the seven facilities making up America's nuclear weapons complex (an ominous-sounding phrase coined by the government, and gleefully seized on by the antinuclear left).

Most everything about Fogbank is classified, but we know from unclassified official sources that Fogbank was manufactured in Facility 9404-11 from 1975 until 1989, when the final batch of W76s were completed. After that, the building went dormant. By 1993 it was slated for decommissioning, leaving behind only a pilot plant which had been used to produce small batches of Fogbank for test purposes.

But warheads, like other materiel, have operational lifespans. In 1996, the government realized that large parts of its nuclear arsenal would need to be replaced, refurbished, or pulled from service. In response, the Department of Energy initiated a refurbishing program with the goal of extending the lives of old weapons. In 2000, the National Nuclear Security Administration (NNSA), the branch of the DoE responsible for nuclear weapons, settled on a life-extension plan for the W76s that would keep them in service until at least 2040.

Straight away, the NNSA realized that Fogbank could be a problem because, as the GAO would later report, they had "kept few records of the process when the material was made in the 1980s and almost all the staff with expertise on production had retired or left the agency." The NNSA briefly considered creating a substitute for Fogbank, but ultimately decided that since they had made it before, they would be able to make it again.

But Fogbank proved to be quite tricky. With Facility 9404-11 gone, a new production house was required. There were delays with the construction, and frustrated engineers kept failing to produce a usable version of the mysterious substance. As deadlines passed and the schedule was pushed back again and again, the NNSA eventually decided that, come to think of it, they would invest $23 million in an attempt to find a Fogbank alternative.

As it happens, in March 2007, the engineers found some success and came up with a tentative process for making Fogbank. But when the final tests were run, the material had problems. In September 2007, the NNSA upped the Fogbank project to "Code Blue" status, making it a major priority of the agency. That effort failed, too.

A year later--and with an additional $69 million spent--the NNSA finally rediscovered a workable way to manufacture Fogbank. And seven months after that, the first refurbed warhead was finally handed over to the Navy, nearly a decade after the government began the life-extension program. The NNSA charmingly refers to the ordeal as an example of "lost knowledge."

So what is Fogbank, anyway? As Dennis Ruddy, the former general manager at Oak Ridge, once told reporters, "The material is classified. Its composition is classified. Its use in the weapon is classified, and the process itself is classified." That said, the conventional wisdom among arms experts is that Fogbank is an aerogel--a highly rigid yet incredibly low-density material. Aerogels look like fog or smoke, but are solid, like a piece of Styrofoam. Because Fogbank was manufactured at Oak Ridge, it most likely functions as an "interstage" in the warhead: a substance that surrounds the fission and fusion portions of the weapon and channels energy from one to the other. After the fission-stage detonation, the aerogel becomes a superheated plasma, which triggers the larger, fusion-stage detonation.

But all of that hardly matters because Fogbank is just a MacGuffin, a useful reminder that technology is not eternal.

Knowledge can be lost. Sometimes this is perfectly reasonable: No one knows how to kill and skin a mastodon anymore, for obvious reasons. And cultures frequently lose knowledge as they evolve past it--you'd be hard pressed to find anyone who could write a computer program on punch-cards today. But there is something worrisome about misplacing knowledge that is only a generation or two old. And this happens more often than you might think.