History of Nuclear Weapons - The First Thermonuclear Weapons

The First Thermonuclear Weapons

The notion of using a fission weapon to ignite a process of nuclear fusion can be dated back to 1942. At the first major theoretical conference on the development of an atomic bomb hosted by J. Robert Oppenheimer at the University of California, Berkeley, participant Edward Teller directed the majority of the discussion towards Enrico Fermi's idea of a "Super" bomb that would use the same reactions that powered the Sun itself.

It was thought at the time that a fission weapon would be quite simple to develop and that perhaps work on a hydrogen bomb would be possible to complete before the end of the Second World War. However, in reality the problem of a "regular" atomic bomb was large enough to preoccupy the scientists for the next few years, much less the more speculative "Super." Only Teller continued working on the project—against the will of project leaders Oppenheimer and Hans Bethe.

After the atomic bombings of Japan, many scientists at Los Alamos rebelled against the notion of creating a weapon thousands of times more powerful than the first atomic bombs. For the scientists the question was in part technical—the weapon design was still quite uncertain and unworkable—and in part moral: such a weapon, they argued, could only be used against large civilian populations, and could thus only be used as a weapon of genocide.

Many scientists, such as Bethe, urged that the United States should not develop such weapons and set an example towards the Soviet Union. Promoters of the weapon, including Teller, Ernest Lawrence, and Luis Alvarez, argued that such a development was inevitable, and to deny such protection to the people of the United States—especially when the Soviet Union was likely to create such a weapon themselves—was itself an immoral and unwise act.

Oppenheimer, who was now head of the General Advisory Committee of the successor to the Manhattan Project, the Atomic Energy Commission, presided over a recommendation against the development of the weapon. The reasons were in part because the success of the technology seemed limited at the time (and not worth the investment of resources to confirm whether this was so), and because Oppenheimer believed that the atomic forces of the United States would be more effective if they consisted of many large fission weapons (of which multiple bombs could be dropped on the same targets) rather than the large and unwieldy predictions of massive super bombs, for which there were a relatively limited amounts of targets of the size to warrant such a development.

Furthermore, were such weapons developed by both the U.S. and the USSR, they would be more effectively used against the U.S. than by it, as the U.S. had far more regions of dense industrial and civilian activity as targets for large weapons than the Soviet Union.

In the end, President Truman made the final decision, looking for a proper response to the first Soviet atomic bomb test in 1949. On January 31, 1950, Truman announced a crash program to develop the hydrogen (fusion) bomb. At this point, however, the exact mechanism was still not known: the "classical" hydrogen bomb, whereby the heat of the fission bomb would be used to ignite the fusion material, seemed highly unworkable. However, an insight by Los Alamos mathematician Stanislaw Ulam showed that the fission bomb and the fusion fuel could be in separate parts of the bomb, and that radiation of the fission bomb could first work in a way to compress the fusion material before igniting it.

Teller pushed the notion further, and used the results of the boosted-fission "George" test (a boosted-fission device using a small amount of fusion fuel to boost the yield of a fission bomb) to confirm the fusion of heavy hydrogen elements before preparing for their first true multi-stage, Teller-Ulam hydrogen bomb test. Many scientists initially against the weapon, such as Oppenheimer and Bethe, changed their previous opinions, seeing the development as being unstoppable.

The first fusion bomb was tested by the United States in Operation Ivy on November 1, 1952, on Elugelab Island in the Enewetak (or Eniwetok) Atoll of the Marshall Islands, code-named "Mike." "Mike" used liquid deuterium as its fusion fuel and a large fission weapon as its trigger. The device was a prototype design and not a deliverable weapon: standing over 20 ft (6 m) high and weighing at least 140,000 lb (64 t) (its refrigeration equipment added an additional 24,000 lb (11,000 kg) as well), it could not have been dropped from even the largest planes.

Its explosion yielded 10.4 megatons of energy—over 450 times the power of the bomb dropped onto Nagasaki— and obliterated Elugelab, leaving an underwater crater 6240 ft (1.9 km) wide and 164 ft (50 m) deep where the island had once been. Truman had initially tried to create a media blackout about the test—hoping it would not become an issue in the upcoming presidential election—but on January 7, 1953, Truman announced the development of the hydrogen bomb to the world as hints and speculations of it were already beginning to emerge in the press.

Not to be outdone, the Soviet Union exploded its first thermonuclear device, designed by the physicist Andrei Sakharov, on August 12, 1953, labeled "Joe-4" by the West. This created concern within the U.S. government and military, because, unlike "Mike," the Soviet device was a deliverable weapon, which the U.S. did not yet have. This first device though was arguably not a "true" hydrogen bomb, and could only reach explosive yields in the hundreds of kilotons (never reaching the megaton range of a "staged" weapon). Still, it was a powerful propaganda tool for the Soviet Union, and the technical differences were fairly oblique to the American public and politicians.

Following the "Mike" blast by less than a year, "Joe-4" seemed to validate claims that the bombs were inevitable and vindicate those who had supported the development of the fusion program. Coming during the height of McCarthyism, the effect was most pronounced by the security hearings in early 1954, which revoked former Los Alamos director Robert Oppenheimer's security clearance on the grounds that he was unreliable, had not supported the American hydrogen bomb program, and had made long-standing left-wing ties in the 1930s. Edward Teller participated in the hearing as the only major scientist to testify against Oppenheimer, resulting in his virtual expulsion from the physics community.

On February 28, 1954, the U.S. detonated its first deliverable thermonuclear weapon (which used isotopes of lithium as its fusion fuel), known as the "Shrimp" device of the "Castle Bravo" test, at Bikini Atoll, Marshall Islands. The device yielded 15 megatons of energy, three times its expected yield, and became the worst radiological disaster in U.S. history. The combination of the unexpectedly large blast and poor weather conditions caused a cloud of radioactive nuclear fallout to contaminate over 7,000 square miles (18,000 km2), including Marshall Island natives and the crew of a Japanese fishing boat, as a snow-like mist. The contaminated islands were evacuated (and are still uninhabitable), but the natives received enough of a radioactive dose that they suffered far elevated levels of cancer and birth defects in the years to come.

The crew of the Japanese fishing boat, Lucky Dragon 5, returned to port suffering from radiation sickness and skin burns. Their cargo, many tons of contaminated fish, managed to enter into the market before the cause of their illness was determined. When a crew member died from the sickness and the full results of the contamination were made public by the U.S., Japanese concerns were reignited about the hazards of radiation and resulted in a boycott on eating fish (a main staple of the island country) for some weeks.

The hydrogen bomb age had a profound effect on the thoughts of nuclear war in the popular and military mind. With only fission bombs, nuclear war was something that possibly could be "limited." Dropped by planes and only able to destroy the most built up areas of major cities, it was possible for many to look at fission bombs as a technological extension of large-scale conventional bombing—such as the extensive firebombing against Japan and Germany during World War II). Proponents brushed aside as grave exaggeration claims that such weapons could lead to worldwide death or harm.

Even in the decades before fission weapons, there had been speculation about the possibility for human beings to end all life on the planet, either by accident or purposeful maliciousness—but technology had not provided the capacity for such action. The great power of hydrogen bombs made world-wide annihilation possible.

The "Castle Bravo" incident itself raised a number of questions about the survivability of a nuclear war. Government scientists in both the U.S. and the USSR had insisted that fusion weapons, unlike fission weapons, were "cleaner," as fusion reactions did not produce the dangerously radioactive by-products of fission reactions. While technically true, this hid a more gruesome point: the last stage of a multi-staged hydrogen bomb often used the neutrons produced by the fusion reactions to induce fissioning in a jacket of natural uranium, and provided around half of the yield of the device itself.

This fission stage made fusion weapons considerably more "dirty" than they were made out to be. This was evident in the towering cloud of deadly fallout that followed the Bravo test. When the Soviet Union tested its first megaton device in 1955, the possibility of a limited nuclear war seemed even more remote in the public and political mind. Even cities and countries that were not direct targets would suffer fallout contamination. Extremely harmful fission products would disperse via normal weather patterns and embed in soil and water around the planet.

Speculation began to run towards what fallout and dust from a full-scale nuclear exchange would do to the world as a whole, rather than just cities and countries directly involved. In this way, the fate of the world was now tied to the fate of the bomb-wielding superpowers.