Nuclear

Part 20 - Fusion Bomb

In 1942, at a conference hosted by Robert Oppenheimer on the development of an atomic bomb, at the University of California, Berkeley, Edward Teller spent much of the time discussing Enrico Fermi's idea of a bomb that would fuse hydrogen in a similar reaction to that used in the Sun. 

Teller continued working on the idea, despite objections by the project leaders, Robert Oppenheimer and Hans Bethe who had enough problems developing a "regular" fission bomb.

In 1945, the Trinity fission bomb test yielded the equivalent of 21 kilotons of TNT.  Of this, about 15 kilotons came from fission of the plutonium core, but unexpectedly, about 6 kilotons of TNT equivalent came from fission of the tiny amount of 235-uranium in the natural uranium tamper.

This test convinced Oppenheimer that instead of using the 235-uranium for more gun-type (Hiroshima) bombs, more explosive power could be obtained by using it with plutonium.

After Hiroshima, many Los Alamos scientists were opposed to the idea of more powerful bombs but, Edward Teller, Ernest Lawrence, and Luis Alvarez, argued that it was essential to protect to the people of the United States—especially as the Soviet Union was likely to create such a weapon.

In January 1946, the first General Assembly of the United Nations attempted to prevent uncontrolled development of nuclear weapons, but the Soviet Union did not agree with the U.S. proposal to establish an international authority while the U.S. rejected the Soviet proposal for universal nuclear disarmament.

Immediately after WW-2, the United States had a monopoly of nuclear weapons and, six months after the UN General Assembly, the USA conducted its first post-war nuclear tests at Bikini Atoll in the Pacific.

During WW-2, Soviet efforts to build atomic weapons had been limited by a lack of uranium, so the first Soviet bomb, detonated on August 29, 1949, surprised the world. It was basically a copy of the plutonium bomb dropped on Nagasaki.

As a response to the Soviet atomic bomb test, in January1950, President Truman announced a crash program to develop the hydrogen (fusion) bomb. 

In 1951, Los Alamos mathematician Stanislaw Ulam proposed that radiation from the fission bomb could be used to compress the fusion fuel before ignition. It was therefore not necessary for the fission fuel to be in close proximity to the fusion fuel.

With a contribution from John von Neumann, Teller adopted this idea and in 1951, the USA confirmed that a fusion reaction was feasible by detonating a boosted-fission device (George), that had a small amount of fusion fuel added to a fission bomb. 

On November 1, 1952, a full scale Teller–Ulam fusion bomb test (Ivy Mike, at the Enewetak atoll), yielded 10.4 megatons of TNT; more than 450 times more powerful than the bomb dropped on Nagasaki. The bomb used a large fission bomb to trigger deuterium fusion fuel that was kept in a liquid state by 20 tons of cryogenic equipment. Its total weight, of 80 tons, made impracticable as a weapon.

The first Soviet fusion bomb, developed by engineer Andrei Sakharov and Vitaly Ginzburg, was detonated in 1953. It had a yield equivalent to 400 kilotons of TNT (1,700 TJ). Only 15 to 20% of this came from fusion as the bomb used a hybrid fuel containing alternating layers of fissile material and lithium deuteride spiked with tritium.   

However, it was 20 times more powerful than the first Soviet fission bomb and could be dropped from an aircraft. This was a deliverable weapon, which worried the U.S. government and military as the U.S. did not yet have one.

 Although it was not a "true" hydrogen bomb, it was a powerful propaganda tool for the Soviet Union while also vindicating those who had supported the U.S. fusion program.