In the early morning hours of Jan. 24, 1961 (59 years ago), a B-52 bomber flew a routine route along the East Coast. The plane broke apart midair and spun out, forcing most of the crew to bail as the plane fell. The vessel spiraled and lost more and more of its pieces, including its payload, scattering debris across two square miles of farmland in North Carolina. The death toll of the event was limited to three of the crew members.
It could have been 28,000 more.
The aforementioned payload included two Mark 39 thermonuclear bombs, each with a 3.8 megaton yield (260 times more powerful than the bomb that ravaged Hiroshima). The parachute on one of them opened, allowing it to land safely intact and untriggered. The second, however, was damaged by the breakup and landed with full force.
Nuclear weapons, especially those in years more recent than the ‘60s, have several safeguards that prevent accidental detonation. Only by setting very particular conditions in different types of switches are the mechanisms of a bomb primed to trigger the detonation of the warhead. The Mark 39 had only four. One of these was not set up and effective while in the air. Two of them were destroyed by the breakup and collision. When the bomb hit the ground, the switch flipped to “armed” and a firing signal was relayed to the core. Only the last safety mechanism — what a senior engineer for Sandia Labs described as “one simple, dynamo-technology, low voltage switch” — prevented a blast that would have covered a massive area.
To put a Mark 39 bomb into perspective, let’s imagine a surface detonation centered on the home plate of Sahlen Field, in downtown Buffalo. Immediately, the force renders everything within a third of a mile to a crater that falls just short of Niagara Square to the northwest and the Buffalo River to the southwest. Then the nuclear fireball expands, covering a 1.3-mile radius and effectively vaporizing everything from Allentown to Silo City. A shockwave expands so powerful that solid concrete buildings on the intersection of Utica and Main St. are demolished entirely (this radius also extending to Tifft Nature Preserve). Canisius College is caught in the range of “medium damage,” in which the buildings from Parkside to South Park are enough for massive outbreaks of fire to be almost certain. Injuries are universal, and fatalities are widespread. The heat from the blast is powerful enough to cause a 100% chance of third-degree burns as far out as North Tonawanda, Hamburg, Lancaster, Orchard Park and half of Grand Island.
Not including the consequences of fallout, a Mark 39 detonation in Buffalo this year would end in an estimated 187,000 deaths and 258,000 injuries. If that second bomb had exploded near Goldsboro in 1961, it would likely have killed 28,000 and injured an additional 26,000.
The Pentagon claims that the number of “Broken Arrows,” or incidents involving the accidental launching, firing, detonating, theft or loss of nuclear weaponry, is a mere 32. Recently declassified documents raise that number into the hundreds, with the severity ranging from busted sprinkler heads in the bomb bay to a warhead burning for four hours.
Despite the stresses that nuclear materials have gone through in the U.S., there has never been an inadvertent nuclear detonation. Any incidents in which blasts took place were simply conventional explosives.