|Fig. 1: The first bomb with intact parachute. (Source: "Wikimedia Commons")|
On the night of January 24th of 1961, disaster nearly struck the town of Goldsboro, North Carolina. Two mark 39 nuclear bombs, each estimated to be from 200-300 times as powerful as the bombs dropped on Hiroshima and Nagasaki, hit the ground just outside of Goldsboro. The B-52 that had been carrying both bombs experienced right wing failure and broke up mid-flight, releasing the two bombs freely into the air. The force of the aircraft's mid-air breakup "initiated the fuzing sequence for both bombs.  The pilot gave his 8-man crew the order to bail out, however only 5 survived.  The parachute on the first bomb successfully opened, and the safing pins that provided power to the weapon from the generator had been pulled, thus rendering the weapon de-armed. The parachute on the second bomb was severed, and it impacted the ground at terminal velocity. 
The first bomb impacted the ground nearly 2 miles from the site of the aircraft's breakup. With the parachute deployed, the bomb drifted into a tree where the parachute became tangled, and the nose embedded 2 feet into the ground (see Fig. 1). In a secret report written eight years after the incident, Parker F jones reports that the arm/safe switch was still in the "safe" position.  Of the seven steps that have to be triggered to detonate this nuclear bomb, the arm/safe switch was the only step left safe.  The second bomb, with no parachute to slow it down, reached speeds close to the speed of sound during its descent. Its plutonium and uranium core was found 18 feet below the surface. Near the core the bomb's arm/safe switch was found. It was switched to "armed". The force of the impact armed the weapon but it failed to detonate.  Historians, military personnel, and scientists have long debated why the weapon failed to detonate, but no definitive conclusion has been reached.
Each of the bombs dropped that day were measured at 3.8 megatons. For comparison, the bomb dropped on Hiroshima was estimated to be about .015 megatons, making just one of the mark 39 bombs about 250 times more powerful. It is estimated that one of the mark 39 bombs would emit thermal radiation around a 15-mile radius. Using the population of North Carolina in 1961, if just one of the bombs had detonated an estimated 28,000 people would be killed. If it were dropped in the present day, that number would rise to 60,000. 
© Harrison Williams. The author warrants that the work is the author's own and that Stanford University provided no input other than typesetting and referencing guidelines. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
 E. Lacey-Bordeaux, "Declassified Report: Two Nuclear Bombs Nearly Detonated in North Carolina," CNN, 12 Jun 14.
 B. Chaffin, "North Carolina Nuclear," Physics 241, Stanford University, Winter 2017.
 E. Pilkington, "US Nearly Detonated Atomic Bomb Over North Carolina - Secret Document," The Guardian, 20 Sep 13.