Today’s post comes from Michael J. Hancock, an archives technician at the National Archives at College Park, MD.
There was a time when the greatest threat during the Cold War was a nuclear strike by the Soviet Union. But for a moment during those tension-filled years, the United States almost nuked itself.
The U.S. narrowly avoided a catastrophic disaster when two Mark 39 hydrogen bombs were accidentally dropped over Goldsboro, North Carolina, on January 23, 1961. The bombs were released when a B-52 United States Air Force bomber broke apart midair. One of the bombs performed precisely in accordance with its design: its parachute deployed, its trigger mechanisms engaged, and, remarkably, one single low-voltage switch thwarted unimaginable destruction.
“Keep 19,” a Boeing B-52G-95-BW Stratofortress with the 4241st Strategic Wing, was on a 24-hour airborne alert mission off the Atlantic Coast of the United States. At that time, while the U.S. and the Soviet Union were engaged in the Cold War, the Strategic Air Command kept B-52 bombers, armed with nuclear warheads, flying 24 hours a day, seven days a week. The plane was commanded by Maj. Walter S. Tulloch, U.S. Air Force, with pilots Capt. Richard W. Hardin and 1st Lt. Adam C. Mattocks. It was armed with two Mark 39 thermonuclear bombs, each with an explosive yield of 3–4 megatons.
The Mark 39 was a two-stage, radiation-implosion thermonuclear bomb produced from 1957 to 1959, with more than 700 built. It was fully fused, meaning it could be detonated by contact with the ground as an air burst, or “lay down”—a series of parachutes would slow the bomb and it would touch down on its target before detonating allowing the bomber time to get clear of the blast zone.
The Mark 39 was considered a lightweight weapon, weighing 6,500–6,750 pounds, and the bomb measured approximately 12 feet in length, with a diameter of almost 3 feet. The explosive yield of the Mark 39 was 3.8 megatons, 250 times the explosive power of the bomb dropped on Hiroshima and enough to vaporize everyone and everything within a 17-mile radius—roughly the area inside the Capital Beltway around Washington, DC.
Only three days after President John F. Kennedy took office, while the B-52 refueled in flight from an air tanker, the tanker’s crew notified Major Tulloch that the B-52’s right wing was leaking fuel. The leak was severe, with more than 5,400 gallons (37,000 pounds) of jet fuel lost in less than three minutes as the B-52 was directed to return to Seymour Johnson Air Force Base in North Carolina to attempt an emergency landing.
As they descended, the unbalanced condition created by the disproportionate fuel load made the bomber increasingly difficult to maneuver. The bomber went out of control as the right wing was sheared away, and Major Tulloch ordered the crew to abandon the imperiled aircraft. Five crewmen ejected and one climbed out through the top hatch before the B-52 broke apart and exploded. Its wreckage covered a roughly two square mile area and, sadly, three crewmen—Majors Shelton and Richards and Sergeant Barnish—were killed.
As the B-52 broke apart, its two Mark 39 bombs were released. One slammed into a muddy field at over 700 miles per hour and buried itself more than 180 feet deep. The other bomb’s parachute safeguard system operated as intended, and it touched down essentially undamaged, discovered hanging from a tree, the parachute preventing it from hitting the earth.
A mishap like this, involving the loss of nuclear weapons, is known by the military code name “Broken Arrow.” Official statements indicate that there was no danger of the bombs exploding, while others indicate that five of the six steps (or six of seven) required for a thermonuclear detonation did occur.
Recovery of the buried bomb proved to be challenging, but after eight days the ordnance team had recovered most of the bomb, including the 92 detonators and conventional explosive “lenses” of the “primary,” the first stage implosion section. The uranium-235/plutonium-239 “pit”—the very core of the bomb—was recovered on January 29. The “secondary,” however, was never found.
For more information visit the National Security Archive’s Nuclear Documentation Project.