July and August are atomic history months. The two weapons that the Manhattan Project had worked feverishly to build were dropped on Japan on August 6 (Hiroshima) and 9 (Nagasaki). A device of the Nagasaki design was tested at Trinity Site on July 16. The scientists were certain the Hiroshima design (gun-type, enriched uranium) would work. Plutonium implosion was a gamble, but it worked.
There’s a lot more to the story, of course, and others will be telling it on the anniversaries or have told it before. I’ve heard most of it and even contributed a bit to it when I managed environmental cleanup at Two Mile Mesa, where the Manhattan Project scientists tested a number of their ideas.
Dennis Overbye describes his trip to Trinity Site. It’s open twice a year to the general public. Overbye worked for EG&G, who provided support to American nuclear tests when we were doing such things. It’s a very good description and coincides with how I’ve felt when I’ve been there. For me, it’s all that is needed to mark the anniversaries.
At Trinity’s ground zero, hundreds of people were milling around as if at a county fair, but there was little to see. The detonation created a crater eight feet deep, a half-mile wide and lined with glassy pebbles called trinitite: sand that had been swept up in the fireball, vaporized and then fell back down in molten radioactive droplets. But gradually the pebbles were shoveled out and the hole filled with scrubby sand, weeds and rocks. Now display stands sold snacks and souvenirs; at one table, docents were using a Geiger counter to show off mildly radioactive rocks.
The Gadget was detonated atop a 100-foot tower. All that remained was an inch-long stub of metal sticking out of the ground. An obelisk of black rocks, with a plaque commemorating the event, marked the exact point of ground zero; we took turns posing in front of it and a life-size model of Fat Man, which resembled a short, bulbous submarine with enormous tail fins.
At Two Mile Mesa, my team found small models of Jumbo (pictured in a photo from the time) that were tested to determine the specifications for the real thing. So Jumbo is a favorite of mine.