Operation Castle
The "Ivy Mike" test was the world's first "hydrogen bomb", producing a full-scale thermonuclear or fusion explosion. The "Ivy Mike" device used liquid deuterium, an isotope of hydrogen, making it a "wet" bomb. The complex dewar mechanisms needed to store the liquid deuterium at cryogenic temperatures made the device three stories tall and 82 tons in total weight, far too heavy and bulky to be a usable weapon. With the success of "Ivy Mike" as proof of the Teller-Ulam bomb concept, research began on using a "dry" fuel to make a practical fusion weapon so that the United States could begin production and deployment of thermonuclear weapons in quantity. The final result incorporated lithium deuteride as the fusion fuel in the Teller-Ulam design, vastly reducing size and weight and simplifying the overall design. "Operation Castle" was charted to test four dry fuel designs, two wet bombs, and one smaller device. The approval for "Operation Castle" was issued to JTF-7 by Major General Kenneth D. Nichols, the General Manager of the AEC, on January 21, 1954.