0347: Bock's Car takes off from Tinian, the target of choice is Kokura Arsenal. Charles Sweeney is pilot. Soon after takeoff he discovers that the fuel system will not pump from the 600 gallon reserve tank. 1044: Bock's Car arrives at Kokura but finds it covered by haze, the aim point cannot be seen. Flak and fighters appear, forcing the plane to stop searching for it. Sweeney turns toward Nagasaki, the only secondary target in range. Upon arriving at Nagasaki, Bock's Car has enough fuel for only one pass over the city even with an emergency landing at Okinawa. Nagasaki is covered with clouds, but one gap allows a drop several miles from the intended aim point. 1102 (Nagasaki time): Fat Man explodes at 1950 feet near the perimeter of the city, scoring a direct hit on the Mitsubishi Steel and Arms Works. Yield is 19-23 Kt (best estimate is 21 Kt). Meanwhile, J. Robert Oppenheimer cables General Leslie Groves with the following shipping schedule: 11 Aug. first quality HE unit; 12 Aug. next plutonium core; 14 Aug. another first quality HE unit.