Joe 2, tested at Semipalatinsk on September 24,1951, was an advanced and improved implosion device with an all-U235, probably levitated core. It was smaller and lighter than Joe 1, Sarov's Fat Man copy: at half the diameter, it produced twice the yield. Joe 3, an implosion device with a composite core, was air-dropped on Oaober 18. These two tests led to the design of the first Soviet production atomic bomb, which was not released to the Soviet military until 1953. Yuri Smirnov, personal communication, 2.ix.93.
46
A temperature scale with intervals corresponding to those of the Celsius scale but beginning at absolute zero: 0° Kelvin = –273.15 °Celsius = –459.67° Fahrenheit.
47
Deuterium in 1952 cost about seventy-five cents per gram. — RR.
48
That is, it ignites spontaneously upon exposure to air. — RR.
49
According to Yuli Khariton, Joe 4 derived 15–20 percent of its yield from fusion reactions. Mike derived about 24 percent of its yield from fusion reactions.
50
He changed his mind and requested security clearance on March 26, 1954, three weeks before Oppenheimer's hearing was scheduled to begin; the AEC chose not to expedite the request. Stern (1969), P. 247.
51
A chest-X-ray series is equivalent to about 1 rad. — RR.
52
One hundred million is an extremely conservative estimate; in 1984, the World Health Organization estimated that a ten-thousand-megaton nuclear exchange would account for 1.15 billion dead and 1.1 billion injured. International Committee (1984).
