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