Eric Schlosser in The Bulletin of the Atomic Scientists:
The Mark 36 was a second-generation hydrogen bomb. It weighed about half as much as the early thermonuclears—but 10 times more than the new, sealed-pit bombs that would soon be mass-produced for SAC [the Strategic Air Command]. It was a transitional weapon, mixing old technologies with new, featuring thermal batteries, a removable core, and a contact fuze for use against underground targets. The nose of the bomb contained piezoelectric crystals, and when the nose hit the ground, the crystals deformed, sending a signal to the X-unit, firing the detonators, and digging a very deep hole. The bomb had a yield of about 10 megatons. It was one of America’s most powerful weapons.
A B-47 bomber was taxiing down the runway at a SAC base in Sidi Slimane, Morocco, on January 31, 1958. The plane was on ground alert, practicing runway maneuvers, cocked but forbidden to take off. It carried a single Mark 36 bomb. To make the drill feel as realistic as possible, a nuclear core had been placed in the bomb’s in-flight insertion mechanism. When the B-47 reached a speed of about 20 miles an hour, one of the rear tires blew out. A fire started in the wheel well and quickly spread to the fuselage. The crew escaped without injury, but the plane split in two, completely engulfed in flames. Firefighters sprayed the burning wreckage for 10 minutes—long past the time factor of the Mark 36—then withdrew. The flames reached the bomb, and the commanding general at Sidi Slimane ordered that the base be evacuated immediately. Cars full of airmen and their families sped into the Moroccan desert, fearing a nuclear disaster.