beige rocks looked the same at night. The three men trudged through the hills for an hour or so, going over the same ground again and again — they thought — as the guardia grew steadily more embarrassed. Finally, the colonel called it quits for the night. The men headed back to the village.
One of Ramirez’s fellow servicemen had more luck that day. A sergeant named Raymond Howe spent the afternoon locating major pieces of aircraft debris and checking them for radioactivity, including a big piece of the tanker fuselage that had fallen near the cemetery, and the B-52’s tail section, which had landed nearly upright in a dry riverbed that led to the sea. Both tested negative.
As dusk fell, Sergeant Howe was still poking around, asking if anyone had seen other major pieces of debris. One of the guardias civiles motioned him back toward the dry riverbed, near the mangled tail section. There, on the bank of the riverbed, about two hundred yards from the sea, lay a bomb.
The bomb was torpedo-shaped and dull silver in color, twelve feet long and twenty inches around. It had a nine-inch gash in its rounded nose, and three of its four tail fins had shorn away. The tail plate, a flat piece of metal that sealed the parachute compartment at the rear end of the bomb, had also torn away, and one of the parachutes lay spilled nearby. The ready/safe switch — part of the arming mechanism — was in the “safe” position. Except for the cosmetic damage, the bomb seemed intact.
Howe checked for radiation and found none. He called some EOD — Explosive Ordnance Disposal — men, who also checked for radiation and rendered the bomb safe. Howe posted some Air Force guards around the weapon. It became known as bomb number one, because it was the first one the Americans found.
The “H” in “H-bomb” stands for hydrogen, the smallest atom in the universe and the simplest of the elements. The hydrogen nucleus consists of one solitary proton, which is circled by one electron — its own tiny, whirring solar system. Hydrogen makes up most of the gas in the universe and most of the mass of stars, and is found in all living things on Earth.
Hydrogen has an isotope — a sort of half sister — called deuterium. Though nearly identical to hydrogen, deuterium has a small but critical difference: its nucleus carries one proton
In 1934, a physicist named Ernest Rutherford and two of his colleagues were working in England and discovered something curious about deuterium. When Rutherford sped up two deuterium atoms and smashed them together, they fused and became a new element: helium. This surprised Rutherford, because the deuterium atoms, each with one positively charged proton in its nucleus, had an immense repulsive force and should have stayed apart. Yet accelerating or heating the atoms gave them enough extra energy to overcome their repulsion and fuse together. Because the reaction required acceleration or heat to fuse the nuclei, Rutherford called it a thermonuclear reaction. He called the whole process hydrogen fusion.
Oddly, the fused helium nucleus weighed slightly less than the two separate deuterium nuclei. The missing mass, Rutherford discovered, had been converted into energy. A lot of energy. Theoretically, each gram of deuterium, when fused, would release energy equivalent to 150 tons of T.N.T. This is about 100 million times as much firepower as a gram of ordinary chemical explosive. To put this into perspective, the firepower of Curtis LeMay’s biggest raid on Japan, involving hundreds of planes and thousands of bombs, would have required only 20 grams of deuterium, about the weight of a robin’s egg. The bomb dropped on Hiroshima: just 100 grams, equivalent to two jumbo chicken eggs. The numbers scale up quickly as the analogy moves on to heavier forms of produce. Twenty-six pounds of deuterium — the weight of about half a sack of potatoes — would yield 1 million tons of T.N.T. That yield — one megaton — is about seventy times the power of the bomb dropped on Hiroshima. It was also close to the yield of bomb number one, which Sergeant Howe had found on the soft bank of the dry Almanzora River.
Back in the 1930s, when Rutherford discovered fusion, however, the idea of a fusion bomb seemed nearly impossible. Rutherford needed a massive amount of energy to fuse just
Atom bombs — the type of bombs dropped on Hiroshima and Nagasaki — work through fission, splitting the atom, rather than fusion. Every atom (except for hydrogen) has a nucleus made up of protons and neutrons, like a ball of marbles stuck together with glue. This nuclear glue has a name: binding energy. Because protons, with their positive charge, want to repel one another, it takes a lot of binding energy to hold a nucleus together, especially a big one. Nuclear fission splits the nucleus of an atom, breaking the marbles apart and releasing the nuclear energy in the form of heat, light, and radiation.
Some elements, namely those with more than 209 protons and neutrons, are so big that no amount of glue can hold their nucleus together. These heavy elements are naturally unstable and regularly shed bits of themselves, or “decay,” to become smaller and more stable. Scientists call these unstable elements “radioactive.” Probably the two most famous radioactive elements are those used in the atomic bombs of World War II, uranium and plutonium (or, more specifically, their highly fissionable isotopes, uranium-235 and plutonium-239). Scientists found that they could speed the disintegration by bombarding the uranium and plutonium nuclei with neutrons. When they did this, the nuclei split and released two or three neutrons and more energy. If additional uranium or plutonium atoms were nearby, the neutrons could blast their nuclei apart as well, releasing more neutrons and causing more fission. This reaction will eventually peter out, unless there is enough radioactive material placed closely enough together to sustain the reaction. If a “critical mass” of uranium or plutonium — about 110 to 130 pounds of uranium-235 or 13 to 22 pounds of plutonium-239—can be piled together, the number of neutrons released will increase in each generation. This leads to a chain reaction of atom splitting and a nuclear explosion.
Plutonium is more radioactive than uranium and more difficult to handle. But during World War II, uranium manufacturing moved slowly. The Manhattan Project scientists would have enough uranium-235 for only one weapon by 1945. If they wanted more bombs, they would have to build them from plutonium.
To build the bomb, metallurgists took a mass of plutonium and cast it into a hollow sphere. Then engineers created a shell of high explosive around the plutonium. In theory, if they detonated the high explosive from many different points at the same time, it would implode, crushing the plutonium into a solid ball. Hopefully, the squeezed plutonium ball would achieve critical mass and lead to a nuclear explosion. Few Manhattan Project scientists believed this design could work. “No one had ever used explosives to assemble something before,” Richard Rhodes explained in
Even before the Trinity test, at least one Manhattan Project physicist was already looking ahead.
Edward Teller had taken charge of the implosion group in January 1944, but increasingly he turned his thoughts to fusion. Maybe, he thought, the immense heat of a fission bomb could ignite a lump of deuterium, making a fusion bomb possible.
Teller, it turns out, was right. Finally, here was a source of energy powerful enough to trigger a fusion reaction. But the engineering problems were daunting, making an imploding beer can seem like child’s play. Engineers had to design a bomb that could contain a fission explosion long enough to trigger fusion, then keep the fusion going long enough to get a good yield before the whole bomb assembly disintegrated. Yet by 1952 they had figured it out. On November 1 of that year, the United States exploded a hydrogen bomb on Eniwetok Atoll, about three thousand miles west of Hawaii.
The test, code-named “Mike,” yielded 10.4 megatons, nearly seven hundred times the power of the Hiroshima bomb. Mike vaporized the island of Elugelab and killed everything on the surrounding islands, leaving a crater more than a mile wide. If it had been dropped on New York City, it would have obliterated all five boroughs. For the physicist Herbert York and many others, the Mike test heralded the beginning of a more dangerous world: “Fission bombs, destructive as they might have been, were thought of [as] being limited in power. Now, it seemed we had learned how to brush even these limits aside and to build bombs whose power was boundless.” The hydrogen bomb lying in the riverbank outside Palomares was called a Mark 28. The Mark 28 could be assembled in five different variants for a range of configurations and yields. This particular Mark 28 was a torpedo-shaped cylinder that weighed about 2,320 pounds. The bomb had entered the arsenal in 1958, and by May 1966, the United States
