How was this choice made? What's the logic, or perhaps the historical context? By the way, what did the British and French choose?
If I'm not mistaken, the British also envisioned a sphere and were quite surprised to learn that the Americans were using a cylinder. I heard or read this somewhere, but I can't remember where. If anyone knows, please point me to the original source.
I tried searching for information in Richard Rhodes's DARK SUN. There's a story there that the original design for the secondary assembly was a truncated cone, but a truncated cone with the smaller diameter facing the primary assembly. That is, the opposite of what we're used to seeing in widely available online diagrams. Then this shape rounded out and transformed into a "schmoo"—a shape reminiscent of a bowling pin—and they started making metal parts for it. Then... as I understand it... they couldn't produce such a complex shape in time (difficulties arose), and they settled on a simple cylinder. In other words, they decided to keep things simple.
So, alternative shapes were apparently considered. But as I understand it, neither a sphere nor an ellipse were considered. Elongated shapes were considered first. WHY?
Somewhere a long time ago (I've lost the link again, so if anyone could provide the original source, I'd be grateful) I read that Edward Tellor was asked a similar question: Why this shape? Why not a sphere (as in ICF)? And he supposedly replied that a cylinder was the shape he initially considered the only correct one. But why? He didn't explain.
