Castle Bravo was supposed to yield 5 megatons but ended up way more powerful than expected at 15 megatons.  So I’m a mental midget when it comes to this stuff but my understanding is that the lithium 6 was the fuel for the secondary and they also added lithium 7 which was basically “filler” and believed to be inert.  It wasn’t, and some people got their hair mused.  Anyway, it was the most powerful portable star ever produced by the United States.

I’m not a science guy so I don’t understand why they added the lithium 7, and if someone explained it to me, I probably wouldn’t understand.  But, along with the Moscow Symphony, narration by Captain Kirk, and some great camera shots, it did produce one of the most ominous yet awesome videos ever made.

They assumed the lithium 7 would be non contributory to the fusion part of the process.  But, it changed into tritium providing 'more fuel' (essentially).

Li7 wasn't "added". Lithium in nature is a mix of 6 and 7. They actually did enrichment to increase the percentage of 6, the thought being it would be reactive whereas 7 was not. They used the enrichment percentage they had because it was what they could reasonably achieve.

If Lithium enrichment would have been easier and it would have been all Li6 they'd have never known what 7 did.

That video is an excerpt from "Trinity and Beyond", the whole video is worth watching if this sort of thing interests you.

The fallout problems weren't because of the yield, it was because of political pressure to conduct the test at a particular time versus waiting for more favorable weather/wind directions. Mil and political bigwigs dismissed the dangers of fallout simply because it hadn't been a problem yet, despite warnings from the scientific folks.

At 15 megatons it wasn't that much larger in practical effects than the 10 megaton Ivy Mike bomb that preceded it, but Ivy Mike's fallout fell on uninhabited ocean away from shipping lanes or commercial fishing areas.

Thanks.  That answered my question.  I don’t know where I got the idea that it was “filler,” like something in dog food…. Added but not needed.  Yes this stuff fascinates me because I did know realize until recently just how much more powerful thermonuclear weapons were than atomic bombs like Fat Man and Little Boy.  Not a few times more powerful, or 10x more powerful, but thousands of times more powerful.

I believe the clip is from: https://en.wikipedia.org/wiki/Trinity_and_Beyond
Edit: Beat bad

Castle Bravo was 750 times more powerful than Trinity/Fat Man.

Device yield became a political grandstanding issue completely disconnected from military usefulness or practical considerations, up to a point. When the Ripple devices were conceived there was thought that such high yield devices might be needed to burst at high altitudes to avoid ABM systems. The Ripple design would have been really the only way to weaponize 10+MT devices that were practical to put on aircraft or ICBMs. As it worked out we never pursued those designs and worked in downsizing and miniaturization. Ripple designs were large in physical size but much lighter in weight than standard design high yield thermonuclear weapons.

The US has some 475kt warheads, most are under 200kt though. There was a 1.2Mt gravity bomb but it's not in the active stockpile anymore. Nothing larger has been available for decades.

This video happened to pop up on youtube for me just a few nights ago.  

Thanks for the videos gents!

Flashback Test Vehicle - The Nuclear Bomb Bigger than the Soviet Tsar Bomba


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A B-52 was also modified to be the carrier of a mysterious “device” code named Flashback.


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Flashback was part of a program created after the signing of the Limited Test Ban Treaty in 1963. It was a way to rapidly build and demonstrate a high yield (50 to 100 megaton) hydrogen bomb in the event the Soviets violated the treaty, as they were likely expected to do. Flashback was a test of such a bomb… but without the actual atomic explosive, testing the associated hardware, ballistics and electronics. The bomb casing and other hardware would be tested and ready to go, with the fission/fusion explosive expected to be plugged in and ready to detonate within 90 days of the Soviet test.

FWIW there are (or were at least) some thermonuclear devices that were roughly the same yield as the Fat Man bomb (20kt), that were designed as "ER" (enhanced radiation) aka a "neutron bomb". The US apparently has an atomic "primary" that's like 2.5kt, so some pretty small thermonuclears could be designed if so inclined.


Almost certainly that would have been a "Ripple" design device, based on the devices tested in Pamlico and Housatonic tests. The whole point of Ripple was high yield devices with reasonable weight and they were about as "clean" as a nuclear device could be, as almost all the yield came from fusion. But they were large in physical size which is just what that device appears to be. The 10mt Housatonic device was derated from a potential design yield of 35 to 50mt due to political restrictions on tests over 15mt.

The Ripple test devices were handbuilt by LRL/LLNL in like a month each, so the idea that this "Flashback" device could be built rapidly is certainly within the realm of reason. And from what is described on that webpage, it sounds like it would be the kind of thing that would be most interested in testing if possible.

If they'd have added stages to a B41 it would have been a longer bomb but not larger diameter like that device.

About all you'll find on "Ripple"...
https://web.archive.org/web/20211030000320/https://muse.jhu.edu/article/794729

Absolute madness.

The evening breeze

blew down the trees

tenderly


Great thread, thanks.

I mean we had the 26MT B41 but it was silly and only B-36 carried it. We are rumored to have some disassembled 9MT W53s in the inactive stockpile for "planetary defense."

RIPPLE... as I originally remember reading the applied concept, it was borne from the need to destroy a very hardened target with a very high burst altitude to avoid point defense ABM... which means you needed an absolutely gargantuan yield, but as a bonus, you could destroy all the nearby targets and a sizeable chunk of the enemy countryside all at once with one warhead It was one of the few ideas more insane than Project Pluto.

M.A.D.

"the rainbow bombs" is also narrated by Shatner and is pretty good. Talks about EMP a tiny bit.

Most powerful ever tested, but not the largest ever produced by the US.  

The Mk 21 bomb had a supposed yield of 18-19 MT, although it obviously was never tested to that level.  The Mk 41 also had a calculated yield of 25 MT; it was also the most efficient nuclear weapon (highest yield to weight ratio) ever deployed by the US, according to the Nuclear Weapons Archive.  It was also the only 3 stage weapon deployed by the US.    https://nuclearweaponarchive.org/Usa/Weapons/B41.html

ABM just didn't turn out to be the threat we thought as it turned out to be hard and expensive, penaids worked, and then the ABM treaty was signed. We made our shit super accurate. All of a sudden, huge yields were not needed.

Inventing Accuracy is a great tech history of this...

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