 In August 1945 , the Fat Man was assembled on Tinian by Project Alberta personnel . When the physics package was fully assembled and wired , it was placed inside its ellipsoidal aerodynamic bombshell and wheeled out , where it was signed by nearly 60 people , including Rear Admiral William R. Purnell , Brigadier General Thomas F. Farrell and Captain William S. Parsons . It was then wheeled to the bomb bay of the B @-@ 29 Superfortress named Bockscar after its normally assigned command pilot , Captain Frederick C. Bock , who flew The Great Artiste with his crew on the mission . Bockscar was flown by Major Charles W. Sweeney and his crew , with Commander Frederick L. Ashworth from Project Alberta as the weaponeer in charge of the bomb . 
