In 1957, a B-36 nuclear bomber accidentally dropped a Mark 17 hydrogen bomb while landing at Kirtland Air Force Base just outside of Albuquerque NM.
"Hidden History" is a diary series that explores forgotten and little-known areas of history.
Mark 17 hydrogen bomb, on display at the National Museum of Nuclear Science and History, Albuquerque
In January 1950, President Harry Truman announced that the United States would begin a crash program to develop and deploy a weapon that was still
entirely theoretical — the hydrogen bomb.
In contrast to the uranium and plutonium atomic bombs which depend for their energy on nuclear fission, in which heavy nuclei are broken into lighter components, the hydrogen bomb depends on the energy released during nuclear fusion, in which small light nuclei are fused together to produce larger heavier nuclei. Physicists had known for decades that the fusion process releases an enormous amount of energy, and that nuclear fusion of hydrogen to make helium was the process that fueled the cores of stars. Since nuclear fusion required fantastically high temperatures, it was presumed that no earthly process would be able to produce it.
During their work on the Manhattan Project, though, Enrico Fermi happened to remark to Edward Teller, somewhat offhandedly, that he wondered if the temperatures produced by a fission bomb would be high enough to produce nuclear fusion. It sparked an idea, and Teller became interested in the possibility of a “Super Bomb”–using the temperatures produced by a fission bomb to set off a thermonuclear reaction and producing a fusion bomb potentially 1,000 times as powerful as the 20-kiloton plutonium Gadget. The extremely complex mathematical calculations were virtually impossible to do by hand, though, so most theoreticians dropped the matter.
After the Soviet A-bomb test in 1949, however, Teller once again took up the cause of championing the Super, and the Atomic Energy Commission’s General Advisory Committee, made up of Manhattan Project veterans, was asked to prepare a report on whether a crash program should begin to produce a Super Bomb. Most Committee members were opposed to the idea. President Truman, however, decided to fund development of a workable thermonuclear weapon as rapidly as possible.
By 1950, when President Truman ordered full-scale work on the hydrogen bomb, computer power had reached the point where the necessary calculations could finally be done. Oddly, though, the computers were beaten to the punch by mathematician Stanislaus Ulam, who devised a simpler method of doing the calculations by hand–and discovered that the original ideas for a hydrogen bomb would require unrealistic amounts of fusion fuel.
After finishing his mathematical calculations, Ulam turned his attention to improving the efficiency of fission weapons. In January 1951, he came up with the idea of placing a hollow tube of uranium or plutonium inside the bomb casing but outside the explosive lens assembly. The intense radiation produced by the implosion trigger might, he thought, flood the bomb casing and momentarily produce enough pressure to squeeze the hollow tube into a solid rod, in effect imploding it into a supercritical mass which would then add to the yield.
When Ulam told Teller about the idea, Teller put two and two together. If he were to replace Ulam’s plutonium tube with a separate container of fusion fuel, he realized, the same radiation pressure from the trigger explosion would compress and heat it, setting off a thermonuclear reaction. A few weeks later, Teller added the idea of placing Ulam’s hollow plutonium tube (now known as the “spark plug”) inside the fusion fuel, where it would be imploded by the radiation pressure and explode, increasing the efficiency of the thermonuclear fuel. This “staged radiation implosion” concept was adopted as the main theoretical method of H-bomb assembly. It became known as the Ulam-Teller design.
Plans were quickly made for a full-scale test of the Ulam-Teller concept, codenamed Ivy Mike. The Mike device contained two stages. The primary stage was a modified Mark 5 plutonium implosion bomb with a yield of about 45 kilotons. The secondary stage was next to it, separated by a hollow radiation channel. On November 1, 1952, the Mike device was detonated at Eniwetok atoll in the Pacific, producing a total yield of 10.4 megatons. It produced a fireball three miles wide, and left a crater 6240 feet wide and 164 feet deep.
The Ulam-Teller configuration was now finalized. The exploding primary trigger would flood the plastic foam-filled radiation channels at the sides of the bomb with x-rays, which were re-radiated and reflected to the secondary. The resulting pressure crushed the entire “pusher” assembly inwards, compressing the thermonuclear fuel and imploding the plutonium spark plug. The spark plug detonated, igniting fusion in the lithium-deuteride fuel. Finally the uranium-238 in the pusher underwent fission from the fast neutrons released by the fusion. The whole process took just a few millionths of a second.
The Ulam-Teller design
When sufficient quantities of lithium-deuteride compound became available, the liquid-fueled Mike device was replaced by a smaller solid-fueled test device called the Runt. This was the final modification to the Ulam-Teller configuration, and became the basis for every American thermonuclear weapon since.
The first American thermonuclear weapon to be deployed in large numbers was the Mark 17, which was based on the Runt test model. It measured 5 feet
wide, 24 feet long, and weighed 21 tons, with a plutonium-fission primary and a lithium deuteride fusion secondary. The yield was 15 megatons—around 1,000 Hiroshimas. The bomb was so big and heavy that it could only be delivered by specially modified B-36 bombers, and was provided with a parachute to slow its descent long enough to give the bomber enough time to get out of range. Some 200 Mark 17s were produced in 1954 and 1955. They were, at the time, the most powerful nuclear bombs in the American arsenal.
B-36 nuclear bomber, on display at the Pima Air and Space Museum in Tucson AZ
On May 22, 1957, a B-36J bomber (serial number 52-2816) from the 334th Bombardment Squadron took off from Biggs Air Force Base near El Paso TX. Commanded by Major Donald Heran and piloted by Captain Richard Meyer (a 15-year veteran who had flown bombers during the Second World War), the aircraft had 20 people aboard. Ten of these were the regular crew complement, and the other ten were along for the ride, most of them because they needed the flight hours to keep current, and some because they were just hitching a ride.
Also aboard, nestled in the rear bomb bay, was a Mark 17 hydrogen bomb. The mission was routine—the bomb was being shuttled to Kirtland Air Force Base outside of Albuquerque NM to have its fusing system replaced at the nearby Los Alamos weapons lab as part of a planned upgrade to the Mod 2 version. For safety, the Mark 17’s plutonium core had been removed from the bomb’s primary stage and was stored separately in the airplane.
The flight was uneventful, and shortly before noon the B-36 arrived at Kirtland and began its landing approach. About five miles away from the runway, as the big bomber descended to 1700 feet, navigator/bombardier First Lieutenant Robert Carp opened a hatch and crawled into the cavernous bomb bay.
The Mark 17 was secured to the airplane by a Type U-2 pneumatic bomb-release mechanism, which could be triggered from the bombardier station or, in the event of a failure, could be manually opened by pulling a release cable. As a safety precaution during flight, the bombardier would manually insert a metal locking pin into the mechanism, which would physically prevent the bomb from being released even if the mechanism were tripped. During takeoffs and landings, however, which were always potentially hazardous in the big bomber, this pin would be removed, allowing the pilot or bombardier to quickly jettison the bomb in the event of an engine failure, fire, or an abort.
As the B-36 made its approach to Kirtland, Carp’s job was to crawl into the bomb bay and pull out the locking pin for the landing. To do that, he had to stand on a narrow catwalk above the bomb bay doors and reach over the bomb. At 11:50am, he pulled out the pin.
Then something went wrong.
There are several versions of what happened next. Carp’s report indicated that he thought an exposed section of the cockpit bomb release cable had become entangled in some of the equipment that he wore on his belt. Some Air Force investigators concluded that Carp had stumbled when the plane jolted, reached out for something to grab on to, and accidentally pulled the manual release cable. Some other investigators have concluded that the flexing of the metal aircraft body during the flight had taken in all the slack in one of the cables, and now it had accidentally opened the release.
Whatever had happened, the end result was immediately apparent. As Carp watched in horror, the immense Mark 17, now without its locking pin, fell free from the bomb-release shackle, rested for a few seconds on top of the closed bomb bay doors, then broke its way through, tearing off most of the doors and dropping out of the airplane.
In the cockpit, Heran felt the bomber, now 21 tons lighter, suddenly lurch several hundred feet upwards. At the same time, one of the crewmen, seeing the Mark 17 tearing through the bottom of the airplane, yelled the warning “Bombs away!”, while Carp shouted to Heran over the intercom, “Bomb Bay to AC, we just dropped the blivet!” Another crewman hastily checked to see if Carp had fallen out of the plane along with the bomb, and found the bombardier pulling himself up out of the bomb bay yelling, “I didn’t touch anything!”
Decades later pilot Meyer recalled to a newspaper reporter, “Someone yelled, ‘SHIT’!” Then he added, “It might have been me.”
The Mark 17 plummeted towards Albuquerque. Although the parachute deployed, the plane was too low for it to open, and the bomb hit the desert sand at speed. Without its plutonium core there was no danger of a nuclear explosion, but the bomb still contained three hundred pounds of conventional explosives in its primary trigger, and the impact detonated this mass. The resulting explosion blew out a crater that was 25 feet wide and 12 feet deep. Fortunately, the impact area, owned by the University of New Mexico, was empty except for a herd of grazing cattle, so the only casualty was one of the cows.
At Kirtland’s control tower, one of the air traffic officers saw the billowing cloud of smoke from the explosion and, immediately thinking of the nuclear weapon, radioed to the pilot, “Do you have hot cargo aboard?” Meyer’s laconic response was, “Not anymore”. At the same time, the plane’s radio operator sent a distress message, informing the tower, “We’ve dropped a hydrogen bomb.”
As luck would have it, Kirtland AFB was the command center for the Armed Forces Special Weapons Project, which had responsibility for dealing with nuclear weapons accidents. With the help of the 2700th Explosive Ordnance Disposal Squadron, based in Utah, the Air Force teams quickly reached the impact site. They found pieces of the bomb (and presumably of the cow) scattered over a mile away, and detected radiation levels inside the crater of half a milli-roentgen per hour. Over the next few days, they cleaned up the site as best they could.
The incident was promptly classified, and the Air Force put out a cover story that the accidental explosion had been a conventional “service bomb”. The truth didn’t come to light until 1986, when the reports were declassified. The impact site is accessible to the public, but it is located in empty desert and is not marked or identified, so it’s only the hardcore Cold War fans and YouTubers who can find it.
A small piece of the Albuquerque bomb
As it turns out, I have a small piece of the Mark 17 bomb that was dropped at Albuquerque, though I didn’t visit the location myself. The impact site is located at Mesa del Sol, in an empty roadless plot of land just a mile away from the Albuquerque Airport. Although the Air Force did a cleanup at the accident site and removed most of the contaminated soil, there are still small bits and pieces of the bomb scattered around a large area, which are still being gathered up by enterprising collectors. One such “nuclear archaeologist” is one of our fellow Kossacks who, when he heard that I would be visiting Albuquerque, offered to accompany me to the Nuclear History Museum. Afterwards, he gifted me a bit of charred polystyrene plastic, about the size of a nickel—part of the plastic foam that once filled the Mark 17’s radiation channels and held the secondary core in place. It is still radioactive.
The Mark 17 bombs in the Air Force’s arsenal were phased out of the nuclear arsenal by the end of 1957, after the B-36 bomber was replaced by the B-52 and smaller H-bombs became available.
Today, a Mark 17 bomb casing is on exhibit at the Museum of Nuclear History and Science in Albuquerque, just a few miles away from the accident site. There are also Mk17 displays at the Castle Air Museum in California, the US Air Force Museum in Dayton OH, the Strategic Air Command Museum in Nebraska, and the Strategic Air Command Memorial at Carswell Field in Ft Worth TX.
NOTE: As some of you already know, all of my diaries here are draft chapters for a number of books I am working on. So I welcome any corrections you may have, whether it's typos or places that are unclear or factual errors. I think of y'all as my pre-publication editors and proofreaders. ;)
