Kenneth T. Bainbridge, director of the Trinity Project, contracted with the Blaw-Knox Company of Pittsburgh, Pennsylvania, to manufacture a steel tower to his specifications, and Ted Brown's Construction Company of Albuquerque assembled it in New Mexico after it was shipped in sections. The nuclear device detonated at Trinity, nicknamed Gadget, was shaped like a large steel globe and, like the Fat Man bomb dropped on Nagasaki, was a plutonium implosion device. Plutonium implosion devices were more efficient and powerful than gun-type uranium bombs like the Little Boy bomb detonated over Hiroshima. They used conventional explosives around a central plutonium mass to quickly squeeze and consolidate the plutonium, increasing its pressure and density so it could reach critical mass, fire neutrons, and allow the fission chain reaction to proceed. To detonate the device, the explosives were ignited, releasing a shock wave that compressed the inner plutonium and led to its explosion. Norris Bradbury, group leader for bomb assembly, stood next to the assembled Gadget atop the 100 foot test tower and later became director of Los Alamos after the departure of J. Robert Oppenheimer. Bainbridge's purchase request for the bottom 100 feet of a 200-foot Blaw-Knox tower called for a working platform about 100 feet high, an added upper section so sheaves could raise 5 tons of equipment above that level, a minimum 15-foot-square platform with a removable center section providing 6 feet of clearance for hoisting equipment, a stairway with railings and platforms every 25 feet or less, safety railings and headroom, and delivery to Project T siding by June 4 or, at the latest, June 15, along with footing specifications for compacted sandy soil by April 15.
