Part 7/9:
As the bomb fell, it switched to its internal battery and initiated its timing sequence.
Once the bomb reached about 1,900 feet (580 meters), its radar altimeters activated according to the pre-set parameters.
Upon detection of the correct altitude, the firing sequence was initiated.
This initiated the ignition of the Navy gun primers, followed by the propulsive charge, which launched the uranium projectile at 300 meters per second.
The impact with the target rings led to nuclear fission, producing a chain reaction that resulted in explosive energy release.