One early spring morning back in 1958, a B-47 from Hunter Air Force Base, located outside of Savannah, Georgia took to the skies, bound for bonny England. The mission was part of Operation Snow Flurry, a “Unit Simulated Combat Mission and Special Weapons Exercise.” Making up the flight crew were Capt. Earl Koehler, pilot; Capt. Charles Woodruff, co-pilot; Capt. Bruce Kulka, navigator/bombardier; and crew chief Sgt. Robert Screptock. The ‘special’ weapon, as you might guess, was a nuclear bomb, the Mark 6. The aircraft, along with 3 others from the 375th Bombardment Squadron, was going to carry the weapon with them on the trip to Bruntingthorpe Air Base, England, and conduct a practice bomb run over England before landing to end an 18 hour day. However, the mission did not exactly work out as planned, and the bomb never made it out of the United States. In fact, you might say it became a pemanent fixture in the landscape.
The Mark 6 bomb was a early design, descended from and similar to Fat Man. It used a 32-point implosion system as the trigger explosion to start the nuclear chain reaction. In 1958, the high explosive trigger in the Mark 6 was initiated by concussion, such as contact with the ground. The bombs hung inside the B-47s by a complicated but reliable pneumatically powered catch, operated by the crew, and backed up with a manually inserted steel locking pin. When the locking pin was in place, it was impossible to drop the weapon; but when the the pin was removed, the crew could jettison the weapon very quickly. Due to design limits of the aircraft that made it unable to dump fuel, the only way to lighten the aircraft in an emergency occurring soon after a fully loaded take off was to jettison the load, so the locking pin was to be out for landing and takeoff.
As the ground crew loaded the plane, they had some struggles with the manual pin, and it was massaged in place with a hammer. These types of operational exercises were very high profile within the Strategic Air command, and there was likely some pressure felt by all involved that the mission go off on timeline without a hitch. With the bomb in place, the pre-flight checks were completed and the aircraft took off with its partners and began the climb out. As was normal practice, the co-pilot had actuated the pin release prior to the take-off, allowing for emergency load jettison. Once the plane was safely climbing towards sunny Briton, he discovered that the lever would not re-engage the pin.
The pilot told the bombardier, Captain Kulka, to go into the bomb bay to try to seat the locking pin by hand. This was not a trivial decision; the bomb bay was not pressurized, so the entire plane had to be depressurized. Because the plane was at 15,000 feet, the crew had to go on oxygen. Further complicating matters, the entrance to the bomb bay was so narrow that a parachute could not be worn into it. The task was doomed from the start; later testimony indicated Kulka had no idea where to find the locking pin in the large and complicated bomb-release mechanism. After a tense 12 minutes searching for the pin, the bombardier decided, correctly, that it must be high up in the bomb bay and invisible because of the curvature of the bomb. A short man, he jumped to pull himself up to get a look at where he thought the locking pin should be. Unfortunately, he evidently chose the emergency bomb-release mechanism for his handhold. The weapon dropped from its shackle and rested momentarily on the closed bomb-bay doors with Captain Kulka splayed across it in the manner of Slim Pickens in Dr. Strangelove. Kulka grabbed at a bag that had providentially been stored in the bomb bay, while the more-than-three-ton bomb broke open the bomb-bay doors and fell earthward. The bag Kulka was holding came loose, and he found himself sliding after the bomb without his parachute. He managed to grab something—he wasn’t sure what—and haul himself to safety. Moments later the plane was rocked by the shock wave of the blast when the bomb hit the ground. (americanheritage.com)
The bomb became the first nuclear weapon released over US territory, falling onto Mars Bluff, South Carolina. Luckily, the nuclear core was stored separately from the rest of the bomb inside the B-47, only to be inserted for an actual wartime drop. The explosion from the bomb, while still relatively large, was only the 7,600 pounds of TNT contained in the trigger. It fell in the woods behind the home of the Gregg family, and while the Gregg children, who were playing outside at the time, were injured, and the home heavily damaged, no one was killed. A smoldering crater 50 ft. across and 35 ft. deep remained, and is purportedly still there today.
As soon as the bomb dropped, the crew attempted to notify the Air Force via special coded message, but because the procedure had never actually been used, no one at the base recognized the incoming message. The pilot was forced to make a call in the clear to the Florence, SC, airfield, announcing that they had lost a ‘device’ and requesting that the information be passed to Hunter Air Force Base. Then the aircraft and crew circled for another 2 1/2 hours to burn enough fuel so that they would be light enough to land.
The member of the crew went on to have full careers with the Air Force, and none were ever penalized for being associated with the incident. The Gregg family was offered a relatively paltry settlement from the Air Force (the military used their own claims guideline, treating the family no different than a service member filing a claim). Unhappy with the offer, the family turned to their congressman, who penned a bill allowing private citizens to sue the government. This bill passed, and was signed by President Eisenhower, and so the Greggs retained counsel and filed a suit. Once the lawsuit against the Air Force was complete, the family received the $44,000 they were originally offered, plus $10,000 for legal fees.
As a consequence of this incident, the United States promptly overhauled their atomic arsenal, reformulating the composition of the high explosive used in nuclear-weapon triggers. Instead of the weapons being able to be triggered by concussion, now each required a specific electrical impulse, making them much more stable and less susceptible to shock.
The following newsreel from Universal international News covers the incident briefly, with a look at the house and the crater that remained.