In the first seconds of a nuclear explosion, a fireball of radioactive debris will rise to the ground followed by an overpressure shock wave that can destroy or damage built structures up to several kilometres out from the epicentre. This will be followed by radiation fallout that can contaminate everything within a few hours, if not days. Immediate actions, such as hunkering down in an indoor shelter and covering your eyes could mitigate the effects of radiation exposure.
The decision to develop the h bomb was not taken lightly. Scientists like Hans Bethe and J Robert Oppenheimer had spent a good deal of the Manhattan Project on fission research, and it seemed that a weapon based on this process would give the United States a considerable advantage over its adversaries in any future thermonuclear war.
But after the Manhattan Project ended, many scientists became obsessed with pursuing the far more powerful thermonuclear H-bomb.
One of the biggest barriers was figuring out how to get the fission and fusion stages to work together. At Los Alamos, Teller and Stanislaw Ulam developed a design that separated the fission trigger stage from the fusion fuse, allowing them to detonate at different times.
The physics behind this was complicated, but the result was a remarkably simple device that exploded with the equivalence of a quarter million tons of TNT. Another obstacle was the immense pressures and temperatures that atomic reactions generate. The uranium fuel used in the fission bomb had to be cooled to extremely low temperatures. A similar approach would be required to power the fusion reactor.
