And speaking of the Bikini Atoll.....
So once the US learned how to make atomic weapons, and especially atomic weapon fuel (the really hard part), the only thing left was to make them 'better'. This includes making them smaller in size / weight, larger in output and if possible, cleaner.
The first efforts were to refine the relatively straight- forward weapons developed during WWII of course. But before too long it was time to take the next step and move from fission (where very heavy elements are split into two or more lighter elements) to fusion (where two light elements are fused into one single, heavier element). The theory was developed at the same time the first atomic weapons were being designed but it was considered the proverbial bridge too far and was basically ignored for a few years. But the key person in the development of 'Da Zuper' as Edward Teller called it (he was from Hungary and spoke with a significant accent in English). Together Edward Teller and Adam Ulam conjectured up the Teller- Ulam design for a hydrogen fusion weapon. The first hydrogen or thermonuclear bomb was absolutely huge in size and weight, and used a form of hydrogen called deuterium in liquid form. It was only liquid because it was kept extremely cold. This thing was gigantic and required all kinds of external hardware to allow it to work; in short, it was simply not practical as any kind of deliverable weapon. But it did fuse and that was more than enough at the time. Work continued with the goal of making thermonuclear weapons portable; this meant not requiring any external support equipment as well as reducing the overall size and weight (the first ones were truly massive) and that entailed using different fuels so that the products could be carried in airplanes.
Eventually, a test of a new fusion weapon that was self- contained and unsupported by external devices was built and tested starting with a test- firing of Castle- Bravo, again at the Bikini Atoll. It worked great..... kind of. Mostly. Well, actually a little too good. The designers used the third element, Lithium, as the fuel to allow the bomb to be made with relatively stable parts that would not require extreme cold, extreme pressure or anything else. Now Lithium is usually found in two forms, Lithium 6 and Lithium 7, the difference being L-7 has an additional neutron over L-6. Lithium 6 is fusible while Lithium 7 is not, or so it was thought. So the fusion fuel was a little under 40% L-6 with the balance of the Lithium being -7, an 'inert' type.
As usual, targets were set up, markers placed where the weapon's limits would be, very accurate estimates of output, radiation and so forth calculated and finally someone too Wiley Coyote's job and lit the fuse on the damned thing. It was supposed to have a yield of 6 megatons of TNT, relatively huge compared to earlier fission weapons. But what the scientists did not yet know was that L-7 spits a neutron (technical term) when heated sufficiently and BECOMES Lithium 6. Yep, more fuel. So the yield was not the expected 6 megatons of TNT but 15 megatons of TNT. All the calculations as to yield, damage radius and radiation output were off- way, way off. The radiation swept all the way around Earth eventually and poisoned quite a few people and a vast section of the Pacific and islands there. It also literally vaporized a significant area of the Bikini Atoll, and the resulting crater can be seen to this day. Yep, them managed to leave a divot in the planet we live on. As a result of the Castle Bravo test, the Atoll had to be evacuated of its native population and remains uninhabited, at least continuously, to this day. Opps! This remains the largest nuclear weapon ever detonated by the US, and current nuclear testing bans pretty much guarantee that it will remain the largest.
Of course the Soviets figured out how to make both fission and fusion weapons too. Well, if not figured out, then stolen but at any rate, they eventually had both. US weapons testing reached its heyday (was it really a heyday?) in the 1950's, with the Castle Bravo test being in 1954. The Soviets would plow ahead and eventually design and build a three- stage nuclear device (the US's were all two stage) that they called the Tsar Bomba, or King Bomb. And it really was- dropped from a plane just to prove it was deliverable, it had a nominal yield of 50 megatons of TNT. Detonated above an island in the far north of the Soviet Union in 1961, scientists the world over watched the shock wave circle the Earth three times. If it was not obvious before, this was clear the symbol for M.A.D. or mutually assured destruction in the event of any nuclear exchange by the super powers. Theoretically, one side could 'win' but only at the expense of the reality of both sides losing; no nation would have survived a full- on delivery of our combined stocks of nuclear weapons. And I guess in a sort of left- handed way it worked as there have not been any major wars since WWII.
Brian