Coincidentally, I just came across a link someone posted on Reddit to an annotated copy of the so-called "Farm Hall Transcripts."

I had heard of the ALSOS project before. As WWII was winding down in Europe, the Allies attempted to interview as many German nuclear physicists as possible in an effort to learn how far Germany had progressed in their own bomb-making program. But I didn't realize they (we) had essentially captured these scientists and isolated them from contact with the rest of the world, and bugged the building where they were held.

The resulting transcript was declassified in the early 1990s, and it is easily the most fascinating document I've seen all year: http://books.google.com/books?id=pzNjntMMq-oC&printsec=front... You basically get to eavesdrop on Heisenberg, Hahn, and other household names in the physics community as they try to figure out why they're being held, wonder what's going to happen to them, react incredulously to the news of the Hiroshima bombing, blame themselves for it, try to puzzle out how it was done, and try to predict how geopolitics will play out over the coming decades.

Do not click that link if you need to do anything else for the next six hours or so.

This is really cool, is there anything similar for hydrogen bombs? I've always been curious how they are different from fission bombs (although obviously a lot of their true workings are still classified).

This diagram only shows one type of weapon design, and in particular, the type used in the Fat Man bomb. The Little Boy bomb had a different design:

http://en.wikipedia.org/wiki/Gun-type_fission_weapon

[EDIT: Originally had FM and LB reversed. Thanks to droopybuns for pointing this out.]

so the explosives cause the jawbreaker like layers of radioactive materials to compress creating nuclear fission that unleashes ton of energy?

So what stops so many other countries from creating such seemingly simple device? Is it the trouble in acquiring the materials?

tres cool

This is pretty cool.

Here's the funny thing: If you had 6kg of U-235 and through it forcefully on the ground it would most likely explode. This almost happened at Las Alamos. All the machinery in nuclear fission bomb essentially just to protect unintentional explosion and make sure explosion is symmetrical and as vigorous as possible when triggered. The triggering mechanism is essentially firing usual explosives around the sphere of fission material.