Center for Land Use Interpretation
Places Monument on "Broken Arrow" H-Bomb Impact Site

Event Marker Project Continues With Commemoration of Another Peculiar Detonation

Fran Grayson of the CLUI inspects the new monument soon after installing it at the site where the 15 Megaton H-bomb struck the ground. CLUI photo

Representatives from the CLUI recently installed a monument at the site where a hydrogen bomb accidentally fell out of an airplane and struck the ground, partially exploding on impact. The monument, placed as close to the exact point of impact as could be determined, includes a text that describes the event.

The incident occurred in 1957 when a B-36 Bomber was ferrying the weapon from Biggs Air Force Base, Texas, to Kirtland Air Force Base, at Albuquerque, New Mexico, located a few miles north of the accident site.

As the aircraft approached Kirtland, at an altitude of 1,700 feet, 1st Lt. Robert S. Karp removed the release mechanism locking pin. It was standard procedure to remove the pin prior to takeoff and landing to allow for an emergency jettison of the weapon, if necessary. About 20 seconds after Karp pulled the pin, the unarmed Mk.17 suddenly dropped through the closed bomb bay doors. The abrupt loss of the bomb's weight caused the B-36 to jump up one thousand feet.

Although the weapon's parachute deployed, it failed to fully retard the weapon's fall because of the low altitude. The conventional high explosive components detonated on impact, destroying the weapon, and forming a crater 12 feet deep and 25 feet across. A cow grazing nearby was killed by the blast.

Peter Merlin of the Aerospace Archeology Field Research Team searches for fragments of the Mark 17 bomb. He found several pieces, some of which were still radioactive. CLUI photo

The non-nuclear explosive detonation of the device dispersed some radioactive material, and the area was contaminated by radiation. The plutonium core had been removed from the bomb (as per normal procedure) so the weapon did not undergo a nuclear detonation on impact. Though the site was mostly cleaned-up by the military, some bomb fragments remain at the site and are still slightly radioactive.

The event is characterized by the Department of Defense as a "Broken Arrow", the term for the second most severe accident involving a nuclear weapon (the most severe category of accident is called a "nucflash", a nuclear incident that creates a risk of war). According to Peter Merlin, a military weapons archeologist working with The Center on this project, there have been hundreds of "Broken Arrow" level incidents involving US weapons.

The installation is the third in the Peculiar Detonations Series of the Center's Event Marker Project, a program to install monuments at selected sites of unusual or otherwise significant land use phenomena.

The Mark 17 hydrogen bomb: the largest bomb ever made by the United States. Over 24 feet long, 42,000 pounds, and with an explosive power of 15-20 megatons (equivalent to over 1,000 Hiroshima size bombs). This one is on display at the National Atomic Museum. CLUI photo