The Mystery of Fogbank (2009) | Hacker News Reader

The Mystery of Fogbank (2009)

weeklystandard.com

35 pointsareoform17 comments

One thing the article doesn't say was that early attempts to recreate Fogbank failed because the materials used to make it were too pure. They had to put back in the impurities to get the same product.

(I read about this in a Navy magazine when my son and I slept on this ship

https://en.wikipedia.org/wiki/USS_Little_Rock_(CL-92)

as a Cub Scout activity.)

My guess about Fogbank is that it might not do much at all from a weapons physics standpoint, but it is highly rigid so that the weapon maintains its dimensions throughout the process of launch and atmospheric reentry, never mind the long time of sitting in the launch tube.

Aerogels are fun materials to play with since they are amazingly light and rigid; drop a piece on the floor and you hear a very high pitching ring thanks to that.

At the risk of ending up at a black site. A literature review suggests that when it is used as an interstage material - FOGBANK acts as a lens i.e. it directs and focuses the neutron flux from the primary device and does something with the X-Rays produced to help trigger the secondary.

Whatever it does, it is an extremely critical component worth spending god knows how much money on.

You may be right.

But my understanding is that there is a U238 shell that focuses the X-Rays like a mirror. If you've got reflection you don't necessarily need refraction. Also my understanding is that the X-Rays from the primary cause adiabatic compression (as much as possible) of the primary.

The fogbank turns to plasma but I think the action is long done by the time the plasma gets to do anything.

If there was an empty space where the fogbank was and the geometry of the weapon changed during storage and delivery, that definitely would prevent the secondary from firing correctly.

IIRC, according to Richard Rhodes in 'Dark Sun', the key insight (with Teller and Ulam disputing who had it first) needed to make a true fusion bomb (as opposed to a boosted fission bomb) is that the fusion part has to be far enough separated, from the fission bomb that starts it, that it can do its thing before it is blasted apart by the shock wave from the fission bomb. That raises the problem of how to transfer energy from the fission bomb to the fusion part, and the solution is to surround the latter with something that will absorb some of the X-rays and vaporize, thus applying a very uniform compression of the fusion part. Wikipedia says that polystyrene foam was used in early bombs [1], and apparently polyethylene was used in the original Ivy Mike device. I have no idea whether this is actually the purpose of fogbank.

One problem with re-creating or replacing any special material critical to the weapons' functioning is that test-ban treaties forbid an end-to-end test of bombs using the new stuff.

Update: see also 'Speculation on Fogbank' [2]

[1] https://en.wikipedia.org/wiki/Thermonuclear_weapon

[2] https://www.armscontrolwonk.com/archive/201814/fogbank/

Thank you to yourself and the person you're replying to for an interesting thread (with links!).

Wikipedia on Fogbank:

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."

https://en.wikipedia.org/wiki/FOGBANK

Interestingly...the first portion of the weekly standard article seems to pretty clearly match wikipedia.

I'm wondering who is plagiarizing whom?

See the references in the wikipedia article. Article came first it appears.

I am pretty sure it is not aerogel. The material has to be transparent for neutrons, lightweight, and immediately vaporizable to create radiation and/or ablation pressure. Styrofoam fits the bill; usual aerogels do not.

From what I know about the Stockpile Stewardship program, they had difficulties in recreating the exact composition (including impurities) of many weapon components, probably including the interstage — because the only way to make sure that new weapons and their replacement parts will work without tests (which are now banned) is to recreate everything to the smallest detail. So the problem is not manufacturing some exotic material, but recreating the exact composition and impurities.

This is a good point- imagine having to recreate, exactly, plastic foam manufacturing processes from decades earlier. How much shop tradition- "oh, yeah, the official design says we do this, but Bob over there figured out a clever trick that saves a lot of time and now we all do it instead"- might you have to track down or rediscover?

Related from 2017 and 2010:

https://news.ycombinator.com/item?id=15331731

https://news.ycombinator.com/item?id=1928233

shame they didn't stockpile but I guess once you start stockpiling, its admitting you didn't mean to do START after all.

> So what is Fogbank, anyway?...

>...But all of that hardly matters

Considering I felt compelled to read most of the article to find out what it is, I disagree. Just tell us upfront already.

Well, they did right before that quote... and then they go on to draw broader conclusions. I'm not sure what else you would want, other than the highly-classified details?

Its a 0/2 flying wall that can't take or deal combat damage. What more do you need to know?

I signed up for an HN login to tell you how much I enjoyed this comment, brother.

Recalls Steven Wright:

"He told me that he had spent most of his life working on a research project for the government trying to find out

who financed the Pyramids.

He worked on it for 30 years, and they paid him an incredible amount of money. He told me he was pretty sure it was a guy named Eddie."

https://jjkentala.typepad.com/blog/2010/01/steven-wrights-19...

Reply on news.ycombinator.com