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Similar articles are on the /Military.htm page at doc pdf URL note: because important websites are frequently "here today but gone tomorrow", the following was archived from https://www.thedrive.com/the-war-zone/32867/fogbank-is-mysterious-material- used-in-nukes-thats-so-secret-nobody-can-say-what-it-is on April 3, 2020. This is NOT an attempt to divert readers from the aforementioned website. Indeed, the reader should only read this back-up copy if it cannot be found at the original author's site.
'Fogbank' Is A Mysterious Material Used In Nukes What we do know is that it's immensely complicated to make and has to be purified using a dangerously volatile chemical. by Joseph Trevithick / The WarZone / April 3, 2020
To this day, details about the weapons in America's nuclear arsenal (especially regarding their warheads) remain some of the most secretive (while still publically known) elements America's nuclear weapons enterprise. There is no better single example of this than a material that the U.S. Department of Energy has used to build thermonuclear warheads (also known as Hydrogen Bombs) that is so secret that no one knows exactly what it does or exactly what it's made of and that is only ever referred to publicly by a codename - 'Fogbank'.
1 'Fogbank' first gained relatively widespread public attention between 2007 and 2008 as it emerged that the material was at the root of technical delays in the life extension program for the W76 warhead. The W76 series is employed on Trident II submarine-launched ballistic missiles (also known as Trident D5s) in service with both the U.S. Navy and U.K. Royal Navy. The National Nuclear Security Administration delivered the last life-extended W76-1 warheads in 2018.
"There is a material that we currently use and it’s in a facility that we built … at Y-12," then-NNSA director Thomas D’Agostino told members of the House of Representatives in 2007,referring to the Y- 12 National Security Complex, a nuclear weapons production facility located near the Oak Ridge National Laboratory in Tennessee. "It’s a very complicated material that ... Call it the 'Fogbank'. That’s not Classified. But it’s a material that’s very important to, you know, our W76 life extension activity."
"There’s another material in the W76... It’s called interstage material, also known as 'Fogbank'. But the chemical details, of course, are Classified," then-NNSA director Tom D’Agostino told senators later that year.
NNSA director Thomas D’Agostino in 2009.
D’Agostino's description of 'Fogbank' as an "interstage material" has led experts to largely conclude that it sits between the primary and secondary stages of a 2-stage thermonuclear weapon. When the first stage (which is a normal fission reaction) goes off, the interstage material would turn into superheated plasma and then trigger a fusion reaction in the second stage.
Experts also believe that 'Fogbank' is an aerogel, a category of ultralight gels in which the traditionally liquid component is instead a gas. Jeffrey Lewis (an expert on missiles and nuclear weapons at the Middlebury Institute of International Studies at Monterey) posted in 2008 that the codename 'Fogbank' might be derived from nicknames for aerogels such as "frozen smoke" and "San Francisco fog". In that same post on the Arms Control Wonk blog, he laid out a number of other known and highly likely details about the material and its production.
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A clay brick weighing 2.5 kilograms sits on top of a block of aerogel weighing just 2 grams.
Lewis noted that in 2007, NNSA's D’Agostino had also told legislators that Fogbank's production included purifying the material in a process that "uses a cleaning agent that is extremely flammable". In a talk that same year at the Woodrow Wilson Center, the NNSA director had also "another material that requires a special solvent to be cleaned" and identified the solvent as "ACN" (the abbreviation for Acetonitrile which is commonly used in aerogel production).
"That solvent is very volatile," D’Agostino said at the time. "It’s very dangerous. It’s explosive."
A 2007 NNSA briefing slide on a program known as the Reliable Replacement Warhead (RRW) [which sought to develop a new warhead design to replace various existing types] further points to Fogbank's potential aerogel composition. Congress de-funded the RRW effort in 2008 and President Barack Obama formally canceled it the following year.
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The NNSA briefing slide from 2007 that offers various details about the interstage and other design features of the then-still-in-development Reliable Replacement Warhead (RRW).
The NNSA slide specifically noted a desire to replace an "expensive 'specialty' material" in the interstage section. This would also have resulted in "eliminating the need for unique facilities".
Y-12 had closed down a Top-Secret and specialized site known as Facility 9404-11 which was used to produce 'Fogbank' following the completion of the final W76 warhead in 1989. The complex established what it called a "Purification Facility" in its place.
"It (i.e., the Purification Facility) reprocesses a material that we’re taking out of weapons so that we can reuse it in refurbished weapons. That’s probably all I can say," Dennis Ruddy (who served for a time as President and General Manager of BWXT Y-12, the division of the Babcock&Wilcox Company that operated Y-12 under contract to the U.S. Government between 2000 and 2014) once said. "The material is Classified. Its composition is Classified. Its use in the weapon is Classified. And the process itself is Classified."
The Middlebury Institute's Jeffery Lewis noted in 2008 that it was public knowledge that the Purification Facility at Y-12 worked with ACN. "On 3 separate occasions in March 2006, workers evacuated the Purification Facility after alarms went off. According to DOE [Department of Energy] documents, the Purification Facility is alarmed to monitor for Acetonitrile (ACN) levels," he explained.
There was also an ACN spill the forced the evacuation of the Purification Facility in December 2014 which thankfully caused no injuries. It took months to get the facility back up and running. An alert about another potential accident in March 2015 turned out to be a false alarm.
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The Purification Facility (also known as Facility 9225-3) at Y-12.
In 2009, an article had also appeared in an issue of Nuclear Weapons Journal [an official publication of the Los Alamos National Laboratory (LANL) ] which disclosed that the decision to re-start manufacturing Fogbank came in 2000 and confirmed that this decision was linked directly to the W76-1 warhead project. It also explained that in the intervening years, NNSA had lost virtually all of its institutional knowledge base regarding 'Fogbank' and how to make it.
"Most personnel involved with the original production process were no longer available," the article said. As such, NNSA personnel had reconstructed the production process from historical records.
In addition, "A new facility had to be constructed. One that met modern health and safety requirements." That facility is very likely the Purification Facility at Y-12.
In a bizarre twist, the new production facility and reverse-engineered production process yielded a version of 'Fogbank' that was of a higher purity than it had been in the past according to the article. The problem, however, was that for 'Fogbank' to work as intended in existing warhead designs, that previous level of impurity was actually essential. NNSA had to revise the process to ensure the final product was just as impure.
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Extremely rudimentary diagrams showing the production process the NNSA initially developed to produce 'Fogbank' in the 2000s (above diagram) and the revised "impure" process (below diagram).
NNSA only succeeded in recertifying the production process in 2008, the better part of a decade after first deciding to restart 'Fogbank' production. The production of life-extended W76-1 warheads began that same year.
It's not clear how many U.S. nuclear warhead types past and present used 'Fogbank'. Jeffery Lewis' has posited that the W78 and W80 used on the U.S. Air Force's LGM-30G Minuteman III InterContinental Ballistic Missile and the AGM-86B Air-Launched Cruise Missile (ALCM), respectively, might have it based on when NNSA designed and produced those warheads.
'Fogbank' (or at the least the story of re-booting its production) has come up more recently amid the broad U.S. efforts to modernize America's nuclear arsenal in recent years. This has included the fielding of a controversial low-yield variant of the W76 which entered service on some U.S. Navy's Trident II submarine-launched ballistic missiles earlier this year and the development of a new warhead (the W93) for those same missiles.
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The official program logo for the W76-2 low-yield variant.
Work on the W93 in particular has raised concerns about whether the Department-of-Energy (which oversees warhead construction) has adequate facilities and other resources to avoid potentially serious delays in the production of large numbers of new nuclear weapons. In March 2020, Allison B. Bawden (a Director on the Natural Resources and Environment team at the Government Accountability Office) highlighted the past difficulties with the production of 'Fogbank' in relation to the production of new nuclear weapons.
"Future weapon programs will require newly-produced explosives including some that NNSA has not produced at scale since 1993," Bawden said during a hearing on Capitol Hill. "As we reported in March 2009, NNSA had to delay first production of the W76-1 from September 2007 to September 2008 when it encountered problems restarting production of a key material known as 'Fogbank'. NNSA is working to reconstitute its high explosives capabilities as we reported in June 2019."
(You can read more about the production of specialized high explosives for nuclear weapons in this past War Zone piece.)
The exact origins of the W93 design are unclear. Senior Department-of-Energy and U.S. Military officials have shied away from calling it all-new. But it is certainly set to be the first new warhead design to enter U.S. Military service since the introduction of the W88 for the Trident II in 1989.
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A non-official diagram showing the general arrangement and features of the W88 warhead.
The W93 is based on “previously nuclear-tested designs. It’s not going to require any nuclear testing," a senior defense official had told reporters in February. However, U.S. Navy Admiral Charles Richard (head of U.S. Strategic Command) told legislators that same month that the W93 itself "hasn’t been designed yet."
The Reliable Replacement Warhead (RRW) program had raised similar questions. NNSA had picked Lawrence Livermore National Laboratory (LLNL) to build the initial production version of the RRW leading to speculation that it might be derived from LLNL's W89. Work on the W89 which was intended to arm the Air Force's air-launched AGM-131A Short Range Attack Missile II (SRAM II) and the Navy's RUM/UUM-125A Sea Lance anti-submarine missile officially ended in 1991. Neither the SRAM II nor the Sea Lance entered service, either.
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W89 warhead.
It is possible that the W93 project will now leverage work from the RRW program regardless of the latter's origins. If the W93 does follow on from that earlier effort, there is also a distinct possibility that it will not use 'Fogbank' in its interstage section.
Whatever happens, 'Fogbank' will continue to be a prime example of both the complexity surrounding the construction of nuclear warheads as well as the immense secrecy surrounding America's nuclear weapon enterprise.
Contact the author: [email protected]
Reader Comments:
1. BraggedMilk That the NNSA was willing to call 'Fogbank' an interstage material is in itself a massive coup for the open-source intelligence available on nuclear weapons. The public knowledge of the so-called 'Teller-Ulam Secret' (i.e., that of how a Hydrogen Bomb works) is based on effectively one data point. The exterior shape of physics package casings that have been released in one-or-two public photographs. We've seen bomb casings. That is everything we know.
The 'knowledge' that a fission primary transmits energy via an interstage to a fusion secondary, the shape of the secondary as cylindrical versus the spherical primary, the use of a fission 'sparkplug' in the secondary -- this was all determined by speculation although a lot of social engineering techniques have been used to trick people into confirming this speculation. The DoE's choice to sue a magazine for publishing this speculation is thought to confirm some details.
Originally, 'Fogbank's purpose was never officially elaborated. As documents said: "The material is Classified. Its composition is Classified. Its use in the weapon is Classified. And the process itself is Classified."... until 2007 when by saying it's the interstage material, the NNSA basically told the global physics community "Yeah, you pretty much figured it out".
9 2. Jason Solomon It can’t be too difficult to figure out. Several other countries have thermonuclear weapons. I imagine it is the specialty designs that they are very concerned with. A report noted that Israeli national labs were technologically equal to or advanced with our nuclear labs.
3. BraggedMilk Your first two sentences play together in an odd way. That only 7 nation states have managed to produce a thermonuclear device should demonstrate how difficult and expensive the process is. Teller was actually intimately involved in the Israeli effort. So I'm not sure noting how advanced Israeli labs are suggests its ease when the original inventor of the process was helping their program along.
4. bad_lightning As is with most engineering, it's the materials science and the production processes thereof that are usually the limiting factor. Just because you have the blueprints of an F35 doesn't mean you can make one that flies as well as the original. Even if you know the exact materials involved, their production technologies are often the limiting factor in achieving success when trying to copy a design.
5. PhilUp Yeah, the actual physics are pretty straightforward. The engineering of getting it efficient-and-small enough to be a deployable weapon is something else entirely. Earlier thermonuclear bombs were enormous. Modern warheads are far smaller. While they usually don't have yields in the megatons (let alone the tens of megatons), they're also far more accurate. (And yes, some of this has to do with the missile. But the warhead takes it the rest of the way there).
Brute-forcing a warhead is mostly a matter of having the materials. If you want something elegant, small, and efficient (and therefore easily deliverable), that takes a lot of work and specific knowledge.
6. BraggedMilk I'm not sure that's completely accurate as the engineering and physics are not strictly separable. Understanding the transfer of energy through the interstage is an extraordinary physics task. Limiting the ability of states to test devices curtails their physical understanding of this process which in turn stops the engineering process of design.
By 'physics', I assume you mean that the architecture is straightforward or the conceptual layout is straightforward. But the physics most definitely is not straightforward. The whole reason that the U.S. and France are working on inertial confinement fusion experiments is to better understand weapons fusion physics despite weapons testing limitations.
7. tweebo colluns I wonder if they made the aerogel with plutonium. From what I remember, a thermonuclear weapon is 2 bombs in one and the outer fission bomb's job is to compress the inner bomb (fusion) into a critical mass.
10 Design-wise, you'd have a chunk of Plutonium wrapped in Plutonium aerogel. The aerogel form would make the mass non-critical and it would be easier for the fission part to compress it. The high purity would be a problem because the yield would be too high.
They could presumably make the fissile material an aerogel as well because it's also going to be easier to compress uniformly if it was in aerogel form. And it'll be easier to shape as well.
8. MrTreason I think that from a physics point of view, something like this makes more sense the\an silica-based aerogels => https://technology.nasa.gov/patent/LEW-TOPS-20
9. bad_lightning The aerogel doesn't need any fissile material in it. It simply needs to be a precisely defined plasma with very consistent properties with respect to pressure, density, specific energy, etc. It needs to conduct the neutrons in a consistent way and compress the secondary in a very consistent and precise way. It needs to compress the secondary fast enough that it achieves maximum density to achieve as much fusion of the secondary fuel as possible before the primary core blows it apart.
So it follows that it would be extremely low density in order to have as little inertia to overcome as possible yet still be maximally radio- and thermally-conductive.
10. AGM69A An aerogel-type substance that can contain the first stage enough for the hydrogen to begin fusing and makes the bomb more powerful.. Can aerogel be made of a fissile material? If possible, it could tell you why it took so long to produce years ago and why they couldn't get it completely pure. PuO2 or similar?
11. Joseph "... the interstage material would turn into superheated plasma and then trigger a fusion reaction in the second stage ..."
That's not actually the point of the interstage material. Typically, a plasma generator is used (such as something like polystyrene). But that's only to control the flow of X-rays from the primary to the secondary. The vast contributor to secondary compression is radiation ablation pressure and not the pressure from the plasma itself.
As for 'Fogbank', it's thought that it is a doped aerogel of some kind that would aid the X-ray flow. Possibly by controlling the peak of the radiation pulse or energy buildup.
12. BillW316 It's properties may be the X-ray equivalent to index-of-refraction helping to shape the radiation into the secondary like a lens to ensure uniformity.
11 13. Spartangreen21 A purposefully added dopant seems... odd to neglect during the first try at remaking this stuff though. Possibly something that was inherent to the raw materials and missed at first. But I can't fathom these guys not properly characterizing what comes in the front end
14. MrHotPants According to legend, impurities from a cleaning agent during the manufacturing process in original 'Fogbank' resulted in improve performance. When the production was restarted, the process was refined and more efficient. But these impurities were removed. By retracing the old process, they were able to discover that the impurities were introduced that resulted in the proper material. The artificially introduce this material in the new process resulting in a more stable and reliable version of 'Fogbank'.
15. Wobbly John I think the problem was something they hadn't purposefully added was having an unexpected positive effect on the reaction. Probably from the use of ACN in the process. When this was removed, it reduced the effectiveness even though what they had was a "better" material.
16. dumpster4 Experts also believe that 'Fogbank' is an aerogel. A category of ultralight gels in which the traditionally liquid component is instead a gas. Aerogels may also be useful on other planets:
"We may be able to survive and live on Mars in regions protected by thin ceilings of silica aerogel, a strong lightweight material that insulates heat and blocks harmful ultraviolet radiation while weighing almost nothing.
Researchers at Harvard University in the U.S., NASA, and the University of Edinburgh in Scotland envision areas of Mars enclosed by 2-to-3 centimetre-thick walls of silica aerogel. The strange material is ghost-like in appearance. Although it’s up to 99.98 per cent air, it’s actually a solid."
See => https://www.theregister.co.uk/2019/07/16/aerogel_mars_shelters/
if on the Internet, Press
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