from Hacker News

A truck driver uncovers secrets about the first nuclear bombs

by 3eto on 3/6/21, 10:45 AM with 36 comments

• by creato on 3/8/21, 12:19 AM

  > In the standard historical accounts, the way that the bomb’s gun mechanism worked was by shooting a cylindrical “male” uranium projectile into a concave, stationary uranium target. This act of atomic coitus created a mass sufficient to produce a critical reaction. The mass of the projectile was said to be 38.5 kilograms, and the mass of the target was said to be 25.6 kilograms. But no matter how many times Coster-Mullen did the math the numbers never quite worked out in a way that allowed the projectile and the target to fit inside the gun barrel while remaining subcritical.

  > The source of the error, Coster-Mullen recognized, was an assumption that every (male) researcher who studied the subject had made about the relation between projectile and target. These scholars had apparently been unable to conceive of an arrangement other than a “missionary position” bomb, in which a solid male projectile penetrated a vessel-like female target. But Coster-Mullen realized that a female-superior arrangement—in which a hollow projectile slammed down on top of a stationary cylinder of highly enriched uranium—yielded the correct size and mass.

  Does anyone understand what point is being made here? I don't understand how which piece is the projectile would make a difference in the overall size/geometry. All else equal, I would think it would be easier if the lighter, simpler piece were the projectile. Accelerating a cone/cylinder without breaking/damaging it seems a lot easier than accelerating the complementary shape.

  Then again, I'm male, so I guess I'm just not capable of imagining the "female superior" design...

• by ChuckMcM on 3/8/21, 3:40 AM

  I got this guy's "book" off Amazon back when he was taking them to Kinko's to be printed up. His is a fairly remarkable story of curiosity which I have always enjoyed. He even signed it for me.

  What is not often pointed out is that he managed to reason his way into understanding to various points, and the process of doing so revealed information that is otherwise still classified.

  As a teen in Las Vegas in the 70's we could "feel" the underground tests, and I was always fascinated by the test site. I even managed to snag a summer internship there (inadvertently[1]) when I was in college.

  I know folks who worked at Sandia and Lawrence Livermore who found the book fairly remarkable.

  [1] The job offer was for the contractor facility in Las Vegas but my clearance had not come through so they bused me to an unclassified facility at the test site to do the work.

• by cuspycode on 3/7/21, 8:24 PM

  If you don't like nagging subscription popups, here is a popup-free summary of the truck driver's story:

  https://www.atomicheritage.org/profile/john-coster-mullen

• by akavel on 3/7/21, 10:41 PM

  The "simplicity of the Bomb" phrase reminded me of the story of the Demon Core:

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

  For me, it shows how hard it is to internalize dangers of a technology one is working with daily. How hard it is to trade convenience for security.

• by bombcar on 3/7/21, 8:18 PM

  Direct link to the spiral bound copy on Amazon: https://smile.amazon.com/dp/B0006S2AJ0

  He binds and ships them himself as far as I can tell.

• by phkahler on 3/7/21, 11:04 PM

  >> Fat Man used explosives to squeeze together two hemispheres of plutonium.

  I thought the plutonium core was one piece and the explosives compressed it, making the same mass critical due to increased density.

• by macintux on 3/7/21, 8:23 PM

  (2008)

• by hoten on 3/8/21, 12:49 AM

  Can anyone locate the photo from Gene Smith he mentioned towards the end?

• by Animats on 3/7/21, 9:12 PM

  (2008)