Movies of Cold War Bomb Tests Hold Nuclear Secrets | Hacker News Reader

Movies of Cold War Bomb Tests Hold Nuclear Secrets

wired.com

46 pointscurtis11 comments

Trinity and Beyond is occasionally available on Netflix and Amazon streaming. If you catch it, watch it. It's a mesmerizing documentary composed entirely of restored atomic test footage with spare narration by William Shatner and an eerie score from the Moscow Symphony Orchestra.

Peter Kuran, the director, worked as a VFX specialist on The Empire Strikes Back and he's done some other nuke-related documentaries too. He's also working for the subject of this article.

https://youtu.be/XsnL6gmGOZA I think you can watch it in 3D.

"100 Suns" is a great book if anybody is interested

http://www.amazon.com/100-Suns-1945-1962-Michael-Light/dp/02...

As far as i remember, there is an easier way to determine bomb yield, which works at least for bombs which are mostly fission: take a sample from a cloud using the aircraft or a balloon, determine a ratio of original fissile material vs some primary fission product, then knowing time passed since explosion calculate fraction of the material that have reacted, and knowing ideal yield per kilo and amount of material in the bomb, calculate precise yield. For boosted fission the fusion portion of yield is insignificant, and also the fusion is nearly 100% complete, so this is easy to factor in, and in some cases even OK to ignore.

Of course if most of the yield was fusion this is a different story.

Not sure this will work for a bomb exploded in 1950 :)

Aren't most bomb designs these days "mostly fission" - with most of the energy in most H-bomb designs coming from fission of the secondary tamper by the neutrons from the fusion stage?

Yes, that's always been the case as I understand. The fusion stage is to get the bomb to do its exploding thing before it propels itself apart and thus just scatters debris everywhere.

Don't you have this backwards?

Fusion is the fusing of two hydrogen atoms into a helium atom - the process of the H-bomb.

Fission is the splitting of a uranium atom which releases neutrons and energy.

The latter reaction produces the energy to start the former reaction.

There are bombs where a fission stage ignites a fusion stage which sends neutrons to start another fission reaction.

From: https://en.wikipedia.org/wiki/Thermonuclear_weapon#Summary

"(3) The fusion fuel of the secondary stage may be surrounded by depleted uranium or natural uranium, whose U-238 is not fissile and cannot sustain a chain reaction, but which is fissionable when bombarded by the high-energy neutrons released by fusion in the secondary stage. This process provides considerable energy yield (as much as half of the total yield in large devices), but is not considered a tertiary "stage". Tertiary stages are further fusion stages (see below), which have been only rarely used, and then only in the most powerful bombs ever made."

Most H-bomb designs have a (fusion) boosted fission primary, then a fusion secondary that has itself a boosted fission "spark-plug", then fusion then fission of the secondary tamper by the neutrons from the secondary fusion stage - with this latter fission stage contributing most of the energy.

Nope. The fusion stages in an H bomb are there mostly to enable further fission stages.

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