 Thin Man as a plutonium-based design was therefore abandoned and the weapon was re-designed to use uranium 235. The muzzle velocity required was much lower, reducing the barrel length of the resulting bomb, now code-named Little Boy, to less than 10 feet (3.0 m). This allowed the device to fit into a standard B-29 bomb bay, so the Pullman was modified to its original configuration with the rear bomb bay a standard B-29 design. All subsequent Silverplates were also configured in this manner. The Pullman B-29 was flown to Wendover Army Air Field in Utah in September 1944. It carried out further drop testing with the 216th Army Air Forces Base Unit until it was damaged in a landing accident in December.
