The Buzz

Everything You Need to Know about Finding a Missing Nuke

When a routine Cold War operation went terribly wrong, two planes and seven men died, a village got contaminated and a hydrogen bomb disappeared.

The search and cleanup required 1,400 American and Spanish personnel, a dozen aircraft, 27 U.S. Navy ships and five submarines. It cost more than $120 million and a lot of diplomatic capital.

And it made an obscure 18th-century mathematical theorem a practical solution to finding veritable needles in haystacks.

Around 10 a.m. on Jan. 17, 1966, two B-52Gs of the 31st Bomb Squadron based out of North Carolina approached two KC-135 tankers over the Spanish coast southwest of Cartagena.

The bombers each carried four 1.5-megaton B-28 hydrogen bombs as part of Operation Chrome Dome, a U.S. deterrence mission that placed nuclear-armed bombers on the Soviet Union’s doorsteps.

The resulting breakup destroyed the tanker in a fireball of blazing jet fuel. All four crew on board the tanker died. One hundred tons of flaming wreckage fell upon the arid hamlet of Palomares, near the Mediterranean Sea.

Three of the four H-bombs aboard the bomber fell there, too.

Within 24 hours, a U.S. Air Force disaster team arrived from Torrejon Air Base near Madrid. Specialists from the Los Alamos and Sandia weapons labs — and Air Force logistics units — descended on the tiny rural town.

The search teams found the three H-bombs within a day. One landed on a soft slope, its casing relatively intact. The high explosives within the other two bombs detonated on impact, blowing 100-foot-wide craters in the dry soil and scattering plutonium, uranium and tritium across the landscape.

The region’s long history of human habitation complicated the land search. Almeria, the province where Palomares sits, hosted a mining industry for more than 5,000 years. Countless mine shafts, diggings and depressions pepper its dry landscape made famous by the spaghetti westerns filmed there.

For several weeks, American troops and Spanish police searched the area with radiation detectors, but failed to find the fourth bomb. Eyewitness accounts claimed something on a parachute fell into the sea.

The U.S. Navy moved a fleet tug to the Spanish coast within eight hours of the accident. Five days after the crash, the Air Force officially asked the Navy for help finding the missing bomb. The Navy tapped one of its resident wizards for the task.

Wizard at work

John Piña Craven looked the part and delivered the goods. Handsome, brilliant and accomplished, he studied engineering and hydraulics at the California Institute of Technology and the University of Iowa after his decorated service in World War II.

Upon his return to Navy service as a civilian scientist, he fixed a structural problem with the nuclear-powered USS Nautilus and oversaw the Polaris sub-launched ballistic missile program.

After the loss of submarine USS Thresher in 1963, the Navy put Craven — now head of its Special Projects Office — in charge of deep-sea rescue and salvage research. Three years later he had to find the missing H-bomb … and quickly.

The Soviets would surely hunt for the weapon, and the White House poured on the pressure. Pres. Lyndon Johnson rejected the Navy’s assurances that the bomb was lost at sea forever. But finding an object the size of a kayak in hundreds of square miles of poorly-mapped sea bottom seemed close to impossible.

After weeks of fruitless undersea search by divers and sonar, Craven turned to the wizardly world of mathematics. An obscure 250-year-old probability theory might work.

In an unpublished manuscript dating to the 1760s, the English minister and statistician Thomas Bayes first proposed the idea that bears his name. Bayes’ Theorem mathematically describes how “by updating our initial beliefs with objective new information, we can get a new and improved belief,” according to science writer Sharon Bertsch McGrayne.

Craven realized Bayes’ Theorem could improve the search team’s beliefs about where the missing bomb was. He first ordered up a detailed map of the sea bottom off Palomares, then asked his salvage and search experts to place bets on every possible event that could have occurred during the bomb’s fall.

The bomb had two parachutes — what were the odds that one opened? That both opened? That neither did? What were the odds it fell straight into the water? What if it fell at such-and-such an angle? Craven’s team explored hundreds of possibilities and calculated the probabilities of each one.

Quantified belief

The calculated probabilities put the bomb’s location in many different places off shore. Craven’s mathematicians then calculated the likelihood of each proposed location based on the initial round of bets and assigned probabilities to each location.

Essentially, the mathematicians quantified their beliefs about where they thought the bomb went, based on the scenarios they worked out. They finally mapped their beliefs onto the ocean floor.

This “probability map” indicated the most promising places to search for the lost bomb — but those places lay far from where conventional search techniques said it was. The scientists’ bets indicated the bomb was nowhere near the planes’ wreckage.

The Navy sent down the research subs Alvin and Aluminaut to check the locations, but their searches turned up empty. Craven’s wizards recalculated their odds based on the new search information. More time passed.